Participants list The New Era of Multi-Messenger Astrophysics

Abstracts for the The New Era of Multi-Messenger Astrophysics

Name Key theme / Title / Authors / Abstract
Mark Allen Key theme: Multi-messenger technology and interoperability
Title: All-sky astrophysics enabled by innovative systems for indexing the sky.
Authors: M. Allen, P. Fernique, T. Boch, C. Bot, A. Nebot, S. Derriere, M. Baumann, K. Lutz, F. Genova
The Hierarchical Progressive Survey (HiPS) scheme is a multi-resolution representation of astronomy data sets based on the HEALPix tessellation of the sphere. HiPS facilitates the publication of very large astronomical image surveys, 3-d data cubes, and catalogue data sets, so that these data can be accessed and visualised in a fast and interactive way. HiPS is complemented by the Multi-Order coverage maps (MOC) which supports the description and manipulation of complex sky regions. Together HiPS and MOC enable an all-sky approach to the use of very large data sets that is stimulating new ways of using the data, as will be necessary for the ESFRI projects participating in ASTERICS DADI. HiPS and MOC have been standardised by the IVOA and there is a growing network of global astronomy data centres providing HiPS-nodes, making hundreds of all sky surveys available for interactive visualisation and interoperability within the Virtual Observatory framework. We describe recent developments and improvements to the tools in the context of the ASTERICS DADI activities, including publication of HiPS data sets, and tutorials for implementation and scientific use of HiPS in Aladin and Aladin Lite. We highlight the capabilities for complex queries involving large surveys, complex sky regions and catalogues, and we also describe other potential innovations and applications relevant to big multi-messenger data sets.
Gemma Anderson Key theme: Alert mechanism systems and fast response of facilities
Title: Rapid-response radio telescopes in the era of multi-messenger astrophysics
Authors: Dr Gemma Anderson
Only recently have radio telescopes been capable of automatically responding to transient alerts and multi-messenger events through the use of a rapid-response observing system. Such systems enable telescope to automatically repoint and begin observing an event within minutes of its discovery, responding to VOEvents broadcast by dedicated telescopes or multi-messenger facilities. Many transients and multi-messenger events are known or predicted to produce early-time radio emission. One prime target is merging neutron stars (or a neutron star and black hole), detected as short gamma-ray bursts (SGRBs) and/or gravitational wave events, which are predicted to produce prompt, fast-radio burst (FRB) like signals and longer-lived synchrotron afterglow emission. Using SGRBs as an example, I will discuss Australia’s effects towards the roboticisation and automation of Australian radio telescopes for transient studies through the use of rapid-response observing systems, These telescopes include the Murchison Widefield Array (MWA) and the Australia Telescope Compact Array (ATCA). I will provide a comparison between the performances of different radio telescopes with rapid-response observing modes and their strengths for different multi-messenger science. I will then discuss the challenges associated with running an interruptible observing system and will include some recommendations on how to deal with scheduling conflicts.
Igor Andreoni Key theme: Alert mechanism systems and fast response of facilities
Title: Discovering electromagnetic counterparts with ZTF, DECam, and GROWTH facilities
Authors: Igor Andreoni
Sensitive wide-field imagers can be used to search for electromagnetic counterparts to gravitational wave events. Our team combines the discovery potential of the Zwicky Transient Facility (ZTF, 47 square degrees, g<20.5) in the US with the unique capabilities of the Dark Energy Camera (DECam, 3 square degrees, g<24) in Chile to rapidly discover transients generated during neutron star mergers. Facilities part of the Global Relay of Observatories Watching Transients Happen (GROWTH, PI Kasliwal) participate the quest and characterize ZTF and DECam transient candidates with photometric and spectroscopic follow-up observations.
Hugo Ayala Key theme: Alert mechanism systems and fast response of facilities
Title: AMON: Multimessenger alerts from high-energy gamma rays and neutrinos
Authors: Hugo Ayala
The Astrophysical Multimessenger Observatory Network (AMON) has been built with the purpose of binding the world’s high-energy and multimessenger observatories into a single network, with the purpose of discovering multimessenger sources, and exploit these sources for purposes of astrophysics, fundamental physics, and cosmology, and to explore project datasets for evidence of multimessenger source populations. We are planning to commission multiple multimessenger alert streams, including gravitational wave + gamma-ray and high energy neutrino + gamma-ray coincidence alerts. In this case, I’ll show one of the neutrino + gamma-ray coincidence alerts, using data from the High-Water Altitude Cherenkov (HAWC) and the IceCube Neutrino Observatory. These alerts will be distributed to AMON follow-up partners with a median anticipated delay of six hours due to the HAWC transit. The alerts will be well-suited for deep electromagnetic follow-up observations.
Ulisses Barres de Almeida Key theme: Multi-messenger technology and interoperability
Title: Science with the Cherenkov Telescope Array: MWL & Multi-messenger scene
Authors: Ulisses Barres de Almeida, for the CTA Consortium
CTA will be the major global observatory for VHE gamma-ray astronomy over the next decade and beyond. The scientific potential of CTA is extremely broad: from understanding the role of relativistic cosmic particles, to the search for dark matter. CTA is an explorer of the extreme universe. Covering photon energies from 20 GeV to 300 TeV, CTA will improve on all aspects with respect to current instruments, surveying the high-energy sky hundreds of times faster than previous TeV telescopes. The angular resolution of CTA will approach 1 arc-minute -- the best resolution of any instrument above the X-ray band -- allowing detailed imaging of a large number of gamma-ray sources. With over an order-of-magnitude collection area improvement, CTA will be a powerful instrument for time-domain astrophysics, being three orders of magnitude more sensitive on hour timescales than Fermi-LAT. Furthermore, the observatory will operate arrays on sites in both hemispheres to provide full sky coverage and hence maximize its discovery potential of rare phenomena such as nearby supernovae, GRBs or gravitational wave transients. The first CTA telescope has been inaugurated in the Canary Islands in 2018, and as more telescopes are added in the coming years, flexible operation will be possible, with sub-arrays available for performing specific tasks. All this considered, CTA will have important synergies with many of the new generation of major astronomical and astroparticle observatories. Multi-wavelength and multi-messenger approaches combining CTA data with those from other instruments will lead to a deeper understanding of the broad-band non-thermal properties of target sources, elucidating the nature, environment, and distance of gamma-ray emitters. In this talk I will introduce the broad scope of CTA science, and present in detail the synergies and potential for cooperation with CTA from all wavebands and astronomical messengers.
Michal Bejger Key theme: Gravitational Wave Sources in multi-messenger signals
Title: Machine learning classification for gravitational-wave triggers in single-detector periods
Authors: Michal Bejger, Agata Trovato, Eric Chassande-Mottin
Current paradigm for the multi-messenger gravitational-wave detections requires observations of a network of detectors.
A single detector such as LIGO or Virgo makes scientific observation ('science mode') typically for 70-80% of the time. This implies that a pair of detectors is in science mode for at most 40% of the time, while the duty cycle is 30% for a network of three detectors. Here we show an implementation of a proof-of-concept single-detector low-latency classifier for astrophysical signals (binary black holes) and local detector artifacts (glitches) based on deep learning, using minimally-processed data (time series), that takes into account additional information in the form of auxiliary detector channels as well as possible multi-messenger triggers.
Suryarao Bethapudi Key theme: Alert mechanism systems and fast response of facilities
Title: VLITE-Fast: VLA's commensal FRB search engine
Authors: Suryarao Bethapudi, Matthew Kerr, Namir Kassim, Fredrick Jenet, Paul Ray, Tracy Clarke
The VLITE (VLA Low Band Ionosphere and Transient Experiment) program commensally collects data at 320-384 MHz on 16 antennas during all Very Large Array (VLA) observations, VLITE-Fast is a GPU-based backend, operating alongside the CPU-based correlator, capable of detecting short (<1s) transients in real time and triggering recording of baseband voltage for offline imaging. In the A and B configurations of the VLA, the 1 to 10 arcsecond resolution is sufficient to uniquely identify FRB host galaxies. Recent results from the bright ASKAP sample suggest VLITE-Fast should detect at least 1 FRB every 3 weeks. In addition to the heimdall-based candidate detector, we are developing a software suite, dubbed Asgard, for real-time analysis, visualization, and assessment of FRB candidates. We anticipate further extension to machine learning-based candidate classification. Here we present the development status of VLITE-Fast and recent results from FRB searches.
Sudip Bhattacharyya Key theme: Electromagnetic transients in multi-messenger signals
Title: Do some millisecond pulsars emit gravitational waves?
Authors: Sudip Bhattacharyya
We will discuss our new result that the transient accretion could spin up some neutron stars to rates much higher than the observed spin rates of millisecond pulsars. This suggests that the spin rates of some millisecond pulsars could be limited by the spin-down torque due to gravitational waves emitted by them continuously. Note that a millisecond pulsar with a structural ellipticity should emit such continuous gravitational waves. We will also discuss the application of our new method to study the possibility of gravitational waves from an accreting millisecond pulsar Aql X-1. (References: S. Bhattacharyya, D. Chakrabarty, ApJ, 835, 4, 2017; S. Bhattacharyya, ApJ, 847, 2, 2017).
Catherine Boisson Key theme: The principles of Open Science
Title: Archiving data from a software telescope
Authors: C. Boissson, M. Servillat,K. Kosack, M.Louys, F. Bonnarel
The landscape of ground-based gamma-ray astronomy is drastically changing with the perspective of the Cherenkov Telescope Array (CTA). For the first time in this energy domain, CTA will be operated as an observatory open to the astronomy community and produce data that will be publicly released to a large community of scientists. In the context of Cherenkov astronomy, the data processing stages imply both assumptions and comparison to dedicated simulations. As a consequence, « Provenance » information is crucial to the end user in order to interpret the high level data products and there are thus strong requirements to ensure data quality, reliability and trustworthiness. Among those requirements, traceability and reproducibility of the data products can be answered by structuring and storing the provenance information for each data product. We are partners in ASTERICS DADI and developed several pieces of software to enable the tracking of provenance information for the large-scale complex astronomical observatory CTA and a web-based data diffusion prototype , in close relation with the International Virtual Observatory Alliance (IVOA).

Paul Boven Key theme: Multi-messenger technology and interoperability
Title: Dwingeloo telescope VLBI with a remote maser
Authors: P. Boven, C. van Tour, R. Smets, P. Maat, J.C.J. Koelemeij, A. Szomoru
The dissemination of time and frequency signals with high stability and accuracy is a common challenge in multi-messenger observatories. Using an enhanced implementation of the White Rabbit optical time and frequency transport protocol, we demonstrate transporting the hydrogen maser reference signal from the Westerbork Synthesis Radio Telescope (WSRT) over a production fiber network to the Dwingeloo radio telescope over a link of 169 km. A further extension to this network also carries the time and frequency reference to the core of the LOFAR radio telescope.

We demonstrate that the achieved frequency stability is sufficient to obtain interferometric (VLBI) fringes between the Dwingeloo telescope, the WSRT, and other telescopes in the European VLBI Network. We use these VLBI observations to measure the performance and accuracy of the time and frequency transfer link. Demonstrating a White Rabbit link over fiber that is already in use in an existing DWDM network (the SURFnet network), and with sufficient stability to perform VLBI, are two significant improvements on the current state of the art.

Digitization and timestamping of the received radio astronomy signals at the Dwingeloo radio telescope is carried out using an off-the-shelf software-defined radio. Converting the sampled voltages into a datastream compliant with the VDIF standard is performed using the open source GNU Radio signal processing suite. This marks the first VLBI back-end implemented using only open source hardware and software.
Cristiano Bozza Key theme: Sources of high-energy particles (neutrinos, CRs, VHE gamma-rays)
Title: pLISA: a parallel Library for Identification and Study of Astroparticles and its application to KM3NeT
Authors: Cristiano Bozza, Chiara De Sio
INFN has produced a Machine Learning library in Python that applies Convolutional Neural Networks to various common problems in the field of astroparticle identification and study in suitable detectors. The library itself makes few assumptions and has few requirements that are easily met in most astroparticle detectors, such as the presence of the basic concepts of "event" and discrete and regularly arranged sensing elements producing "hits" that may have integral or real weights. The Parallel Library for Identification and Study of Astroparticles (pLISA) has been tested against simulated events for the ARCA detector of the KM3NeT Collaboration, seeking high-energy neutrinos from galactic and extragalactic sources. Interesting preliminary results have been obtained for up/down-going particle classification, muon/electron neutrino classification, Z component of the direction and energy estimation. Already with very little optimization work and using limited hardware resources (one NVidia GTX GPU), pLISA was shown to yield results that can compete with traditional algorithms. Considering the amount of work done and the resources used, it is safe to say that the approach chosen allows room for improvement and also portability to other detectors fulfilling the same requirements. pLISA is based on TensorFlow and Keras, two commonly used open source frameworks used in Machine Learning, which helps ensuring portability and scalability.
Silke Britzen Key theme: Sources of high-energy particles (neutrinos, CRs, VHE gamma-rays)
Title: Neutrinos from TXS 0506+056
Authors: S. Britzen, C. Fendt, M. Böttcher, et al.
We used archival data to perform a detailed analysis
of the time evolution of the jet of TXS 0506+056.
In this talk we will discuss the specifics of the jet
kinematics and in particular its possible relation to
neutrino emission.
A paper describing the results will be submitted soon.
Dario Carbone Key theme: Electromagnetic transients in multi-messenger signals
Title: Identifying EM counterparts to NS-NS mergers: an Optimized Radio Follow-up Strategy
Authors: Dario Carbone
Motivated by the discovery of GW170817, we determine the optimal observational setup for detecting and characterizing radio counterparts of nearby binary neutron star mergers. We simulate GW170817-like radio transients, and radio afterglows generated by fast jets, expanding in a low-density interstellar medium, observed from different viewing angles. We determine the optimal timing of GHz observations, assuming a sensitivity comparable to that of the JVLA. The optimization is done so as to ensure that physical properties can be correctly reconstructed with the minimum number of observations. Finally, we discuss how future radio arrays would improve the detectability of radio counterparts of binary neutron star mergers, and explore the ability of the same technique to be implemented to search for other type of radio transient sources.
Josep Colome Key theme: Multi-messenger technology and interoperability
Title: Telescope and space mission scheduling towards a multi-observatory framework
Authors: Josep Colome, Á. García-Piquer, J. Colomé, E. de Ona Wilhelmi, D. F. Torres, A. Bridger, J. Lightfoot, E. Díez, J. C. Morales, I. Ribas, F. Vilardell
Efficient scheduling of astronomical surveys is a challenge with an increasing complexity as the observation strategies are becoming more sophisticated and operational costs are higher. Astronomical surveys require a huge number of observations, being necessary to use efficient schedulers to fulfill and optimize specific constraints. STARS (Scheduling Telescopes as Autonomous Robotic Systems) provides optimal schedulers for diverse infrastructures, and has been successfully applied in several ground and space-based observatories. Currently, STARS is being extended to cover multi-observatory coordinated scheduling, a challenging and complex optimization problem to promote multi-messenger science that will allow an optimal operation of large astrophysical infrastructures.
Marta Colomer Molla Key theme: Sources of high-energy particles (neutrinos, CRs, VHE gamma-rays)
Title: Multimessenger searches with the ANTARES and KM3NeT neutrino telescopes
Authors: Marta Colomer Molla
The ANTARES neutrino telescope has been operating for more than ten years in the Mediterranean sea with the purpose of searching for high energy cosmic neutrinos. During the last few years, the multimessenger astronomy has become one of the most exciting topics for Cherenkov neutrino detectors. Thus, the ANTARES Collaboration is actively participating to the follow up of alerts sent by different experiments covering the full electromagnetic spectrum and gravitational wave interferometers. This allowed to set upper limits that constrain the neutrino emission from various sources, including Fast Radio Bursts, Gamma Ray Bursts, binary mergers and blazars. ANTARES also sends alerts that yield to an EM follow-up of the neutrino data. The latest results will be discussed.

The KM3NeT detectors, being deployed in the Mediterranean sea, will represent a step forward in terms of technology, larger detector volume and expected performances. As a result, the expectations for multimessenger searches are promising, aiming at detecting neutrino sources and proving them as high-energy cosmic rays accelerators. The expected sensitivities for the most relevant astrophysical events will be presented.
Job de Kleuver Key theme: Multi-messenger technology and interoperability
Title: Multi-messenger science in the European Astroparticle Physics Strategy 2017-2026
Authors: Job de Kleuver, General Secretary APPEC
Astroparticle physics is the fascinating field of research at the intersection of astronomy, particle physics and cosmology. It simultaneously addresses challenging questions relating to the micro-cosmos (the world of elementary particles and their fundamental interactions) and the macro-cosmos (the world of celestial objects and their evolution) and, as a result, is well-placed to advance our understanding of the Universe beyond the Standard Model of particle physics and the Big Bang Model of cosmology.

APPEC is the Astroparticle Physics European Consortium, a consortium of 19 funding agencies, national government institutions, and institutes from 17 European countries, responsible for coordinating and funding national research efforts in Astroparticle physics. Apart from promoting cooperation and coordination, a crucial APPEC activity is to formulate, update and realise the European Astroparticle Physics strategy. The most recent Strategy 2017-2026 was launched by APPEC in January 2018 (see

Key ingredients in the strategy are the 21 recommendations addressing 10 scientific issues with a top priority for Multi messenger science: What can we learn about the cataclysmic events in our Universe by combining all of the messengers – high-energy gamma rays, neutrinos, cosmic rays and gravitational waves – that we have at our disposal?

In addition crucial organisational aspects such as computing and data policies and connections to the fields of astrophysics and particle physics as well as important societal issues such as gender balance, education, public outreach and relations with industry are addressed. By acting coherently on these recommendations, Europe will be able to exploit fully the tantalising potential for new discoveries in good international collaboration.
Damien Dornic Key theme: Alert mechanism systems and fast response of facilities
Title: Multi-messenger real-time analysis framework of the KM3NeT neutrino telescope
Authors: D. Dornic
The KM3NeT Collaboration is instrumenting two deep-sea neutrino detectors in the Mediterranean Sea, a low energy site ORCA in France (5 GeV-10 TeV) and a high energy site ARCA in Italy (1 TeV-10 PeV). By observing astrophysical neutrino sources, KM3NeT will play an important role in the rapidly evolving multi-messenger field thanks to its extended energy range, its excellent angular resolution and its full sky coverage compared to other facilities. The construction is in progress on both sites and by beginning of 2020, a larger sensitivity is already expected in the whole energy range compared to the ANTARES detector.

A real-time analysis framework is being implemented to reconstruct rapidly track and cascade neutrino events, to provide rapid public/private alerts to the external telescopes for the most interesting neutrino candidates, and also to perform real-time follow-ups of external transient signals, such as gravitational waves, neutrinos and electromagnetic events. This will yield a significant discovery potential already during the construction phase and be essential for future improvements of our understanding of highest-energy astrophysical sources such as gamma-ray bursts, fast radio bursts or blazar flares.
Raphaël Duque Key theme: Electromagnetic transients in multi-messenger signals
Title: Neutron Star Merger Afterglows: Population Prospects for the Gravitational Wave Era
Authors: Raphaël Duque, Robert Mochkovitch, Frédéric Daigne
Following the historical observation of GW170817 and its electromagnetic follow-up, new neutron star merger afterglows are expected to be observed as counterparts to gravitational wave signals during the next science runs of the gravitational interferometer network. The diversity of the observed population of afterglows of these future events is subject to various factors, which are (i) intrinsic, such as the energy of the ejecta, (ii) environmental, such as the ambient medium density or (iii) observational, such as the viewing angle and distance of the source. Through prescribing a population of mergers and modelling their afterglows, we study the diversity of those events to be observed jointly in gravitational waves and electromagnetic bands. In the future, observables of detected events such as viewing angle, distance, afterglow peak flux or proper motion will form distributions which together with predictions from our study will provide insight on neutron star mergers and their environments.
Matthias Fuessling Key theme: Multi-messenger technology and interoperability
Title: Operational Concepts of the CTA Observatory in the Time Domain Astronomy
Authors: Matthias Fuessling, Jim Hinton, Karl Kosack, Alison Mitchell, Igor Oya for the CTA Observatory
The Cherenkov Telescope Array Observatory (CTAO) will be the first ground-based gamma-ray observatory open to the global community to propose observations and grant full access to the scientific data obtained. The CTAO will comprise more than one hundred telescopes at the two CTA array sites in the Northern and Southern Hemispheres. With its unprecedented sensitivity, ten times the sensitivity of existing instruments, and its large field of view of more than twice that of existing instruments (and up to several tens of degrees in divergent survey mode), the CTAO will become one of the cornerstones for observing transient phenomena in the era of multi-messenger astrophysics. We will give an overview of the operational challenges for the CTAO in the study of the transient universe and the concepts to overcome them.
Tamas Gal Key theme: The principles of Open Science
Title: Data and Software Preservation through Containerisation in KM3NeT
Authors: Tamas Gal
One crucial aspect of scientific research is interoperability and reproducibility. Methods, procedures, software and even hardware can be documented easily but a big challenge is to preserve software and data in a way that it remains re-usable on current and next generation computing systems. The KM3NeT collaboration has defined and developed workflows based on state of the art containerisation tools and techniques to achieve these goals while minimising the compatibility requirements.
The web-based open source Git-repository manager "GitLab" provides all the ingredients for future-proof software development including essential features like version management, issue tracking, discussion platforms and continuous integration. The latter is based on Docker, which performs operating-system-level virtualisation – also known as containerisation – and is used to declare the environment needed to run a specific software. Each software project is developed, compiled and tested in an isolated and independent container and later also deployed to a target production system as a single bundled image including all requirements.
These so called Docker images serve as a starting point for Singularity images, which is another containerisation solution specifically designed to run on HPC clusters and thus is well suited for fully reproducible analysis chains running on large and sometimes heterogeneous computer clusters and grids. Singularity images are already successfully used in production pipelines of the ANTARES experiment and has proven to be a convenient solution with minimal setup, maintenance and compatibility requirements.
In order to coordinate and describe such pipelines, a scheme using the Common Workflow Language has also been defined.
The strategy behind these methods and their general applicability are described in this contribution.
Francoise Genova Key theme: Multi-messenger technology and interoperability
Title: Access, Discovery and Interoperability of multi-wavelength/multi-messenger data
Authors: Françoise Genova, Mark Allen, Catherine Boisson, Eric Chassande-Mottin, Paschal Coyle, Andrew Lawrence, Fabio Pasian, Enrique Solano, Joachim Wambsganss, Michael Wise, and ASTERICS WP4 Team
Astronomy has been at the forefront of Open Science, by developing a common format, FITS, and a global disciplinary data sharing framework, the astronomical Virtual Observatory (VO), which allows all astronomers to find, access, interoperate and reuse data, as summarized by the so-called FAIR concept. A series of projects funded by the European Commission supported the coordination of Virtual Observatory activities in Europe (Genova at al., 2015, DOI:10.1016/j.ascom.2015.03.001). At the start of ASTERICS in 2015, the Virtual Observatory had been operational for years, with more than 100 “authorities” providing resources and widely used tools such as Aladin/AladinLite, TOPCAT and VOSA taking advantage of it.

Space and ground-based observatories had been involved from the beginning in the Virtual Observatory endeavour as developers participating in the definition of the VO standards and/or users providing their requirements and/or giving access to their data in the VO. ASTERICS was the occasion to build a closer relationship with large ESFRI-like projects, and moreover to include the astroparticle physics community, which is evolving from the development of experiments such as HESS or MAGIC to the implementation of observatories such as CTA. ASTERICS Work Package 4, Data Access, Discovery and Interoperability (DADI), includes VO teams from France, Germany, Italy, Spain and UK, and teams working on CTA, EGO-VIRGO, Km3Net, SKA and their pathfinders. ESO (ELT) is associated to ASTERICS, and ESA continues to be an active participant in the VO development in close collaboration with the other European VO teams. A large palette of wavelengths and messengers was thus represented. The aim was to optimize the scientific usage of data from the future large projects, and to make them active participants in the VO development.

DADI activities covered the three pillars identified for a successful VO development: support to science usage, which includes gathering end-user requirements, in particular through Schools aimed at early career researchers; support to data providers, which also includes gathering their requirements – the target was mainly ESFRI-like projects but two events were aimed at the general European astronomical data provider community; technological work to update the Virtual Observatory standards and tools, this work being coordinated at the international level by the International Virtual Observatory Alliance (IVOA). Highlights include the development of IVOA standards and tools used for multi-wavelength and multi-messenger astronomy. One can cite a standard suite to deal with multi-wavelength data; significant advances of the VO time domain standards; the completion of the HiPS sky tessellation standard, and its widespread implementation. CTA DADI partner was instrumental in developing a standard for Provenance in collaboration with VO teams. The use of the VO framework also enabled the development of the GWSky tool for gravitational wave event follow-up.

ASTERICS has then met a full success in bridging the astronomical Virtual Observatory with the astroparticle physics community. The next step is to interface the Virtual Observatory framework with the European Science Cloud, which will be the aim of the Connecting ESFRI projects to EOSC through VO framework Work Package of the ESCAPE Cluster.
Giancarlo Ghirlanda Key theme: Electromagnetic transients in multi-messenger signals
Title: Short Gamma Ray Bursts: what we have learnt from GW170817
Authors: Giancarlo Ghirlanda
The detection of the electromagnetic emission following the gravitational wave event GW170817 provided direct evidence of the progenitor nature of short Gamma Ray Bursts. A comparison the properties of GRB170817 with the population of short GRBs reveals some intriguing aspects. The short gamma ray emission, its delay with respect to the gravitational wave signal and the long lasting multi wavelength non-thermal emission unveiled the structure of the outflows from this source. High resolution radio observations showed that a relativistic jet, with an angular energy structure, was launched and successfully emerged from the merger ejecta. Some implications of a universal jet structure on the population of short GRBs and future prospects are discussed.
Kelly Gourdji Key theme: Gravitational Wave Sources in multi-messenger signals
Title: LOFAR triggered observations of gravitational wave merger events and GRBs
Authors: Kelly Gourdji, Antonia Rowlinson, Jess Broderick
On 17 August 2017, gravitational waves (GWs) from a binary neutron star inspiral (GW170817) were detected for the first time, by the Advanced LIGO and Advanced VIRGO GW detectors. A short gamma-ray burst was independently detected 1.7 s later, definitively launching the multimessenger era of astronomy. This triggered an observing campaign of unprecedented scale that covered the full electromagnetic spectrum. Ongoing monitoring of the radio emission in particular, which traces the high-velocity ejecta from the merger, has proven to be instrumental in discriminating between models of the merger event. Here, I outline the LOFAR rapid response and follow-up strategy of compact merger events such as GW170817, in particular making use of the telescope’s very large instantaneous field of view. I will describe the various relevant emission mechanisms and what is required in order to detect them using LOFAR. I will present initial LOFAR results from gravitational wave events. I also show how our LOFAR strategy can be applied to rapidly respond to GRBs and place constraints on the possible existence of a neutron star central engine in some cases. Finally, I present our results for long GRB 180706A.
Giuseppe Greco Key theme: Multi-messenger technology and interoperability
Title: Working with Gravitational-Wave sky localizations: new methods and implementations
Authors: G. Greco +
+ M. Branchesi, E. Chassande-Mottin, G. Stratta, G. Dálya, M.W. Coughlin, E. Brocato, P. Capellacci, P. Fernique, T. Boch, S. Derriere, F. Genova, M. Allen

The era of the multi-messenger astrophysics with Gravitational Waves (GW) requires the exploration of new methods and tools for real-time analysis, as well as, post-processing activities. The irregular and complex shapes of the GW sky localizations represent a new challenge for observational astronomers, who need to work with fast tiling, catalog queries, transient localizations, visibility and sky map comparisons. Here we show how gravitational wave sky maps can be easily and efficiently visualized and processed using Multi-Order Coverage (MOC) maps based on HEALPix sky tessellation using both Python language and the recent implementation in Aladin Desktop/LITE. In addition to this, we developed a specific interactive script, named GWsky, to effectively tile the sky localization of a gravitational-wave event providing accurate telescope pointings. We also show applications of these methods for educational purposes in Virtual Reality apps, high resolution images, and basic sonorization of the GW skymap.
Jason Hessels Key theme: Electromagnetic transients in multi-messenger signals
Title: Fast radio bursts
Authors: Jason Hessels
Fast radio bursts (FRBs) are millisecond-duration radio flashes, apparently originating at cosmological distances. As such, FRBs promise to provide a new view of extreme astrophysics in action - with, e.g., potential insights into the deaths of massive stars,
particle acceleration, and the properties of the intergalactic medium. While some FRBs may be associated with cataclysmic astrophysical explosions, there are also repeating FRBs, like FRB 121102, whose origin requires a more long-lived progenitor. FRB 121102 has been localized to an intense star-forming region in a dwarf galaxy at redshift z = 0.19. It is also associated with a persistent radio source and inhabits an environment of extreme magnetic field. The short durations of the bursts themselves argue that a neutron star is the likely source, but understanding how such a source can be visible at about 3 billion light years distance remains a puzzle. Perhaps FRB 121102 has a very different origin; its relation to the apparently non-repeating FRB population is also still unclear. FRBs thus remain a fascinating astrophysical mystery.

I will present an overview ofthe FRB phenomenon, including the first results from wide-field FRB discovery machines like CHIME and ASKAP.

Clemens Hoischen Key theme: Alert mechanism systems and fast response of facilities
Title: The H.E.S.S. transients alert system
Authors: C. Hoischen for the H.E.S.S. Collaboration
n the past few years we have witnessed the birth of multi-messenger astronomy with large world-wide observation campaigns, triggered by the detection of neutrino candidates and gravitational waves. A flexible mechanism to receive and process alerts of such detections is needed in order to reliably react in time. The H.E.S.S. experiment was able to participate in these campaigns and provided important measurements in the VHE gamma-ray band. This was made possible with the transients alert system which is installed in Namibia since 2016. This contribution will discuss the design of the alert system and its integration into the H.E.S.S. data acquisition.
Piotr Homola Key theme: The principles of Open Science
Title: Public engagement as a scientific tool to implement multi messenger strategies with the CREDO
Authors: Piotr Homola
The Cosmic-Ray Extremely Distributed Observatory (CREDO) uses the hunt for particle cascades from deep space as a vehicle for a unique ‘bottom-up’ approach to scientific research. By engaging the non-specialist public of all ages as ‘citizen scientists’ we create opportunities for lifelong learning for individuals as well as for cooperation and the sharing of common educational tools amongst institutions. The discoveries of these citizen scientists will feed directly into a pioneering new area of scientific research oriented on Cosmic Ray Ensembles (CRE). The detection (or non-detection) of such particle groups promises to open up a new method for exploring our universe, and a new channel on the multi-messenger stage, oriented on both astro- and geo-investigations. The opportunities this would create for cross-disciplinary research are significant and beneficial for individuals, networks of institutions and the global communities of both professional scientists and science enthusiasts.
Eric Howell Key theme: Gravitational Wave Sources in multi-messenger signals
Title: Joint gravitational wave - gamma-ray burst detection rates in the aftermath of GW170817
Authors: Eric Howell, Kendall Ackley, Antonia Rowlinson, David Coward
The observational follow-up campaign of the gravitational wave (GW) multi-messenger event GW170817/GRB170817A has shown that the prompt $\gamma$-rays are consistent with a relativistic structured jet observed from a wide viewing angle $\gtrsim 20$\deg. We perform Bayesian inference using the data from early and late EM observations to determine the jet profile of GRB170817A assuming a structured jet model. We use the geometric dependence on the burst luminosity to produce a short duration gamma-ray burst (sGRB) efficiency function with redshift, which folded in with binary neutron star detection rate, allows us to estimate the future joint GW/sGRB detection rates for LIGO and Virgo detectors.
We show that, if the jet structured profile of GRB170817A is a relatively common feature of sGRBs, then there is a realistic probability of another off-axis coincident detection during the third aLIGO/Virgo observing run (O3). We also find that up to 4 yr$^{-1}$ joint events may be observed during the advanced LIGO run at design sensitivity and up to 10 yr$^{-1}$ by the upgraded advanced LIGO configuration A+. We show that the detection efficiencies for wide-angled sGRB emissions will be limited by GRB satellites as the GW detection range increases through proposed upgrades. Therefore, although the number of coincident detections will increase with GW detector sensitivity, the relative proportion of detected binary neutron stars with $\gamma$-ray counterparts will decrease; 11\% for O3 down to 2\% during A+.
Johanna Jarvis Key theme: Open Science
Title: The benefits of public engagement
Authors: Johanna Jarvis
Engaging the general public and non-specialists in science and technology is becoming increasingly important. This short talk will explore the benefits of engagement for both the public and researchers as well as summarizing the techniques and media used to this end by the Dissemination, Engagement and Citizen Science (DECS) work package within ASTERICS.
Léa Jouvin Key theme: Sources of high-energy particles (neutrinos, CRs, VHE gamma-rays)
Title: Open data and tools for gamma-ray astronomy
Authors: Jouvin Léa
The upcoming new generation of the Imaging Air Cherenkov Telescop (IACT) of the Cherenkov Telescop Array (CTA) will reveal a new sky to the very high energies. With its higher sensitivity and better angular resolution, we will observe more and more complex emissions. Therefore, one of the most challenging aspect of the CTA software analysis tools will be to be able to separate the multiple components of a same emission. Moreover, CTA will be the first ground-based gamma-ray telescope array operated as an open observatory with public observer access. Contrary to the current IACT, like H.E.S.S., MAGIC or VERITAS, for which the data and software are mostly private to the collaborations operating the telescopes, the data and software will be public at a certain level of the analysis. This implies strong requirements to define the format and to design the software tools that will allow to perform high level analysis of IACT data. This open format, named DL3, is based on the FITS format and will contain a list of reconstructed gamma-ray events for each observation as well as the associated instrument response function.
The discussion on this format is still open and I will report on the current status. In order to test this format and the new tools, it is necessary to convert the current IACT data in this DL3 format. I will describe the current conversion of the IACT data to this format emphasizing the work we are currently doing in MAGIC. I will also present the recent H.E.S.S. data DL3 release of some of their archival data as well as the first joint likelihood analysis of the Crab Nebula spectrum combining MAGIC, HESS, VERITAS, FACT and Fermi DL3 data with Gammapy, one of the open-source tools currently developed for CTA high level analysis: . Those works are major steps towards a common legacy of the data and vehicle the strength of open and reproducible multi-instrument analysis in gamma-ray astronomy.
Aard Keimpema Key theme: The principles of Open Science
Title: Efficient remote interactive pipelines using CASA and Jupyter
Authors: Aard Keimpema
The size of astronomical datasets has increased dramatically over the years; terabyte sized datasets
are no longer an exception. This trend will only accelerate; the SKA is expected to produce nearly 1 TB
of archived data per day. Because of the data volumes involved, data reduction will most likely
be performed remotely in a science data centre, where the data is also archived. Furthermore, the data
reduction will have to rely on (semi-)automated pipelines. However, these pipeline do not have to operate
as black boxes to the end user. By embedding CASA, the most commonly used data reduction package for
radio astronomy, inside Jupyter, remote interactive pipelines can be created.

Jupyter is a web-based application which allows users to create interactive notebooks which can include
annotated text and graphics as well as executable code. Currently Jupyter supports more than 40 different
programming languages, including Python, R, and Matlab. Jupyter is designed be extended and makes it easy
to add additional languages.

In this talk I will present the Jupyter kernel for CASA we have created. The kernel allows all CASA tasks
to be run from inside a Jupyter notebook. Tasks which normally spawn a GUI window are wrapped so that their
output is displayed inside the notebook instead. The Jupyter kernel requires a custom build of CASA which we
distribute both as Docker- and Singularity images.

The notebook format has the great advantage that all steps of the data reduction are preserved inside
the notebook. This means that the whole data reduction process is self-documenting and fully repeatable.
It also allows users to very easily make changes to their pipeline and then rerun the pipeline steps affected.

In my talk I will also present the minimal recomputation framework, which was developed in a collaboration
between JIVE an U. Cambridge. In many cases using a pipeline is an iterative process where the pipeline
is run multiple times using a different set of parameters each time. Usually only a subset of all steps
in the pipeline need to be executed again each iteration. The minimal recomputation framework keeps track
of all dependencies for each task so that only task whose decencies have changed are re-computed.
Matthew Kerr Key theme: Electromagnetic transients in multi-messenger signals
Title: Glowbug, a Gamma-Ray Telescope for Bursts and Other Transients
Authors: Matthew Kerr, J. Eric Grove, Colleen Wilson-Hodge
We present the design and status of Glowbug, a gamma-ray telescope for bursts and other transients in the 30 keV to 2 MeV band. It was recently selected for funding by the NASA Astrophysics Research and Analysis program, with an expected launch in the early 2020s. Similar in concept to the Fermi Gamma Burst Monitor (GBM) and with similar sensitivity, Glowbug will join and enhance future networks of burst telescopes to increase sky coverage to short Gamma-Ray Bursts (SGRBs) from neutron star (NS) binary mergers, including possible SGRBs from NS-black hole mergers. With the recent discovery of the SGRB coincident with the gravitational wave transient GW170817, we know such events occur with reasonable frequency. Expanded sky coverage in gamma rays is essential, as more detections of gravitational waves from such mergers by ground-based interferometers will come in the next few years, and detecting an electromagnetic counterpart is a powerful probe of merger dynamics.
Felicia Krauss Key theme: Sources of high-energy particles (neutrinos, CRs, VHE gamma-rays)
Title: Neutrinos on ice - Blazars as counterparts to neutrinos above 100 TeV
Authors: Felicia Krauss, Kunal Deoskar, Michael Kreter, Matthias Kadler, Karl Mannheim, Joern Wilms
Ever since the discovery of a flux of charged high-energy particles from space - called cosmic rays - their origins are unclear, particularly at the highest energies. Active Galactic Nuclei (AGN) and their relativistic outflows of plasma, called jets, are the favored counterpart for high-energy cosmic-rays. AGN are powered by supermassive black holes at the center of their host galaxies and fueled by accreting surrounding matter. AGN with their jet closely aligned with our line-of-sight are called blazars. They could accelerate protons to relativistic speeds, which are then detected at Earth.

From the interactions of cosmic rays with photons, we also expect to observe neutrinos, which are not deflected by magnetic fields and are therefore ideal tracers of cosmic ray sources. With the recent detection of a cosmic neutrino flux, the search for the sources has started. One promising tool is the study of variability. So far, we have discovered two coincidences between a blazar outburst and the arrival of a high-energy neutrino, and I will discuss both cases in detail.

I have further studied blazars consistent with IceCube neutrinos independent of outbursts. From the spectral energy distributions (SEDs) it is possible to calculate the estimated neutrino numbers of blazars. The resulting numbers are in good agreement with the observed neutrino events. Currently, supermassive black holes are the best candidates for the origin of the very and ultra-high energy cosmic-ray emission.

Erik Kuulkers Key theme: Multi-messenger technology and interoperability
Title: Coordinating observations among ground and space-based telescopes in the multi-messenger era
Authors: E.Kuulkers, J.-U.Ness, A.Ibarra, J.Salgado, E.Salazar, R.Saxton, C.Sanchez, C.Gabriel, P.Kretschmar, M.Ehle
The emergence of time-domain multi-messenger (astro)physics asks for new and more efficient ways of interchanging information, as well as collaboration. Many space- and ground-based observatories have web pages dedicated to showing information about the complete observations and planned observation schedule. The aim is to standardise the exchange of information about observational schedules and set-ups between facilities and in addition, to standardise the automation of visibility checking for multiple facilities. To reach this, we propose to use the VO protocols (ObsTAP-like) to write services to expose these data to potential client applications and to develop cross facilities visibility servers.
Andrew Levan Key theme: Electromagnetic transients in multi-messenger signals
Title: ENGRAVE: Gravitational Wave Follow-up at the European Southern Observatory
Authors: the ENGRAVE consortium (A.J. Levan submitting)
The facilities of the European Southern Observatory, in particular, four, 8-m class telescopes on a single site, provide a unique and highly capable tool for multimessenger astronomy. The ENGRAVE consortium has recently been awarded a large programme at ESO for follow-up of GW sources located during the next science run, O3. In this talk, I will showcase the remarkable contributions that ESO facilities made to the observations of GW170817 (the best spectroscopic sequence, a remarkably accurate distance, exceptional constraints on the environment), and the core scientific aims for O3. Depending on the availability of triggers there may also be the opportunity to describe observations of new sources.
John Lightfoot Key theme: Alert mechanism systems and fast response of facilities
Title: A Platform for Multi-Messenger Observing
Authors: A. Bridger, J. Colomé, J. Lightfoot
MM observations bring together projects, people and instruments from very different areas of astronomy. There is a need for a central web platform where such people can meet, plan and discuss observations. We collect the requirements for such a platform and present a prototype.
Massimiliano Lincetto Key theme: Multi-messenger technology and interoperability
Title: Supernova detection and real-time alerts with the KM3NeT neutrino telescopes
Authors: Massimiliano Lincetto, Marta Colomer-Molla
The detection of a neutrino burst from the next galactic core-collapse supernova (CCSN) will yield major breakthroughs in different fields of fundamental physics. The KM3NeT ORCA and ARCA neutrino telescopes in the Mediterranean Sea are expected to observe a significant number of neutrino interactions through the detection of Cherenkov light mostly induced by inverse beta decay processes in sea water. The selection of photons in coincidence on the 31 photomultipliers of KM3NeT digital optical modules (DOMs) allows to discriminate the CCSN signal against 40K, bioluminescence and atmospheric muon backgrounds.

The detection sensitivity and the potential to resolve the time profile of the neutrinos have been studied by means of accurate Monte Carlo simulations coupled to in-depth studies of the KM3NeT background features. Online triggering criteria have been determined to send real time alerts for low-energy CCSN neutrino bursts, and also to meet the requirements for the integration in the SNEWS global alert network. In view of future developments, a preliminary study has been conducted on the determination of the neutrino arrival time and the fast triangulation of the source by different detectors to constrain the SN localisation in the sky.
Soheb Mandhai Key theme: Electromagnetic transients in multi-messenger signals
Title: The Rate of Short Duration Gamma-Ray Bursts in the Local Universe
Authors: Soheb Mandhai; Nial Tanvir; Gavin Lamb; Andrew Levan; David Tsang
Following the faint gamma-ray burst, GRB 170817A, coincident with a gravitational wave-detected binary neutron star merger at d?40 Mpc, we consider the constraints on a local population of faint short duration GRBs (defined here broadly as T90<4 s). We review proposed low-redshift short-GRBs and consider statistical limits on a d?200 Mpc population using Swift/Burst Alert Telescope (BAT), Fermi/Gamma-ray Burst Monitor (GBM), and Compton Gamma-Ray Observatory (CGRO) Burst and Transient Source Experiment (BATSE) GRBs. Swift/BAT short-GRBs give an upper limit for the all-sky rate of <4 y?1 at d<200 Mpc, corresponding to <5% of SGRBs. Cross-correlation of selected CGRO/BATSE and Fermi/GBM GRBs with d<100 Mpc galaxy positions returns a weaker constraint of ?12 y?1. A separate search for correlations due to SGR giant flares in nearby (d<11 Mpc) galaxies finds an upper limit of <3 y?1. Our analysis suggests that GRB 170817A-like events are likely to be rare in existing SGRB catalogues. The best candidate for an analogue remains GRB 050906, where the Swift/BAT location was consistent with the galaxy IC0327 at d?132 Mpc. If binary neutron star merger rates are at the high end of current estimates, then our results imply that at most a few percent will be accompanied by detectable gamma-ray flashes in the forthcoming LIGO/Virgo science runs.
Benito Marcote Key theme: Electromagnetic transients in multi-messenger signals
Title: Observing a Fast Radio Burst from radio wavelengths to very high energy gamma-rays
Authors: B. Marcote, T Hassan, J. Hoang, S. Inoue, MAGIC Collaboration
Fast Radio Bursts (FRBs) are astrophysical transient sources emitting bright radio flashes with a duration of only a few milliseconds. Discovered only ten years ago, nowadays we have detected tens of these events. However, their physical origin remains unclear, and a number of scenarios larger than the number of known FRBs has been proposed during these years.
The detection of multiple bursts in FRB 121102 (making this source the first known repeating FRB) excluded all cataclysmic scenarios for this particular FRB. Furthermore, the existence of repeating bursts allowed us to perform a precise localization of the source with the Karl G. Jansky Very Large Array (VLA) and the European VLBI Network (EVN). Together with optical observations we associated the bursts with a compact (<0.7 pc) persistent radio source located inside a low-metallicity star-forming region of a dwarf galaxy at a redshift of 0.19. This environment resembles the ones where superluminous supernovae or long-duration gamma-ray bursts are produced. Although the nature of this persistent source and the origin of the bursts remain unknown, the scenarios considering a neutron star/magnetar energizing a young superluminous supernova, or a system with a pulsar/magnetar in the vicinity of a massive black hole are the most plausible ones to date.
Although bursts from FRBs have been limited to radio wavelengths, several scenarios predict the existence of bursts at other wavelengths. To test these scenarios, we have conducted simultaneous observations with the Arecibo Telescope, the European VLBI Network, and the MAGIC telescopes to search for optical and very high energy gamma-ray bursts. We present in this talk the results of this campaign, which places the most stringent constraints on the putative optical and/or very high energy burst emission to date.
Bryan Miller Key theme: Alert mechanism systems and fast response of facilities
Title: Gemini Operations for Multi-Messenger Astronomy
Authors: Bryan Miller, Andy Adamson, John Blakeslee, Andy Stephens, Arturo Nunez
Gemini Observatory will be an important facility for following up time-domain discoveries in the multi-messenger era. We will summarize the Gemini instrumentation suite and operations model and describe how these will complement time-domain surveys. We will give updates on instruments that are under development, in particular, the SCORPIO broad-wavelength instrument is being designed specifically for transient followup. All new instruments will be delivered with data reduction pipelines and the data is delivered via a cloud-based science archive. Gemini has a variety of modes and time allocation processes in order to accommodate a broad range of project needs and timescales. Observations are carried out in queue (service), classical (visitor), and priority visitor (visitors execute the queue) modes. Time is allocated by regular partner TACS, a common large program TAC, and by peer review for "fast-turnaround" proposals. Queue observing allows Gemini to easily execute target-of-opportunity (TOO) observations and this capability will be very important for transient follow-up. Finally, we will review planned changes to our operations software to handle the expected increased volume of TOO triggers and to incorporate Gemini into the developing time-domain follow-up infrastructure.
Robert Mochkovitch Key theme: Electromagnetic transients in multi-messenger signals
Title: Prospects for kilonova signals in the gravitational wave era
Authors: R. Mochkovitch, R. Duque & F. Daigne (IAP, Paris)
At a distance of 40 Mpc, all electromagnetic counterparts of GW 170817 could be observed: the gamma-ray burst, its afterglow and a kilonova. In future GW detections of binary neutron star mergers at larger distances, the burst and its afterglow could be difficult to detect and the kilonova may remain the only accessible counterpart. In this situation, we provide for O3 and beyond the expected distribution of kilonova magnitudes and their expected detection rate as a function of the depth of the search.
Marco Molinaro Key theme: The principles of Open Science
Title: ESFRIs & VO: networking and discussing
Authors: Marco Molinaro & Fabio Pasian
Open Science is the combination of Open Data and Open Access
leading to interoperability of resources for science production.
Fostering new science through interoperability is the goal of
the International Virtual Observatory Alliance (IVOA), whose
standards provide the framework to allow Open Science in
Astronomy and Astrophysics.
Data Access, Discovery and Interoperability (DADI) is the
ASTERICS work package dealing with the dissemination of the
Virtual Observatory (VO) standards and technologies, gathering
needs from the scientific community and ESFRIs requirements
related to interoperability, and stirring them into updates
or additions to the VO scenario.
Within DADI, networking and discussion forums and training events
for the ESFRI partners (as well as for the general data providers)
have been held, to put together the thinking heads of the research
infrastructure (RI) projects and the staff having VO knowledge.
These events initially brought the interoperability perspective
to the large scientific collaborations and later allowed to feel
the pulse of how much of the VO technology was welcomed, used
and investigated by the RIs.
During the events, requirements and perspective on the open science
scenario were brought in by the projects and collaborations and
discussed with VO knowledgeable people.
This contribution tries to summarise what was discussed in
such a context, in terms of how useful and practical resource
interoperability is when a large collaboration has to intertwine
it with project requests.
Eman Moneer Key theme: Sources of high-energy particles (neutrinos, CRs, VHE gamma-rays)
Title: Eman moneer
Authors: The detection of high energy spectral cutoff of bright GRBs detected via Fermi telescope.
In this article, a joint-fit (GBM+LLE) spectral analysis is provided with a larger sample of 36 GRBs. These samples are detected simultaneously via GBM and LLE for long/bright bursts. Attempts have been made to constrain the high-energy cutoff Ec achievable by observations using the BandCut model.It is suggested that the shape of the GRB spectrum in the high-energy spectral cutoff region is relevant to the cutoff region of the primary particles within the prompt emission (Romoli et al., 2017). Only three out of 36 GRBs that show such spectral high-energy cutoffs, others (4 GRBs) show otherwise energy break Eb instead, and that is due to the BandCut model are not constraining well in the very end of the LLE energy band and turns to give a parameter values equivalent to the simple Band model with an energy peak Epeak seemingly close to the high energy cutoff Ec.
Daniel Morcuende Key theme: Sources of high-energy particles (neutrinos, CRs, VHE gamma-rays)
Title: Simulation of fluorescence radiation for Cherenkov observatories
Authors: Daniel Morcuende, Jaime Rosado, Fernando Arqueros, José Luis Contreras
Several techniques inside Astroparticle Physics use Extensive Air Showers (EAS) as a proxy to study very energetic particles that reach Earth. EAS themselves are detected through different means, among them the measurement of Cherenkov or fluorescence radiation produced in them. A detailed simulation of EAS is mandatory to develop, test and use these techniques, in this respect the most popular simulation program is the CORSIKA code. We will describe our work introducing the detailed description of the fluorescence radiation in CORSIKA at the same level as the current description of Cherenkov radiation, the first results obtained with it and possible future applications. It can be useful for several currently operating Cherenkov observatories, either imaging or non-imaging, fluorescence telescopes and the design of future innovative Astroparticle Physics observatories.
Denis MOURARD Key theme: Multi-messenger technology and interoperability
Title: About policies for multi-wavelengths/multi-messengers astrophysics
Authors: D. Mourard, S. Matheussen
We will summarize the status, opportunities and some future policy initiatives relevant to future multi-wavelength/multi-messenger (MW/MM) astrophysics. This summary is considered timely given the ramp-up in facilities and widening exploration of physics across the electromagnetic spectrum and beyond. The ASTERICS Policy Forum set out to review the current MW/MM landscape, and to derive some recommendations on how to proceed. These recommendations consider how it might be possible to harmonize joint and efficient scheduling, operation and interoperability of the various telescopes, and also to produce actionable outcomes in key policy areas.
Antonios Nathanail Key theme: Electromagnetic transients in multi-messenger signals
Title: Magnetized jets and explosions from the merger of a Neutron star binary
Authors: Antonios Nathanail
The connection between binary neutron star mergers with short-duration gamma-ray bursts (GRBs) was confirmed with the first coincident detection of gravitational waves together with electromag-
netic radiation from GW170817. The basic paradigm for short-duration GRBs includes an ultra-relativistic jet, but the low-luminosity prompt emission together with follow-up radio and X-ray observations have hinted that this picture may be different in the case of GW170817. In particular, it has been proposed that large amounts of the magnetic energy that is amplified after the merger, can be released when the remnant collapses to a black hole, giving rise to an explosion impacting on the merger ejecta. Through numerical simulations we investigate this scenario for a range of viewing angles, injected energies and matter densities at the time of the collapse, finding that the energy injection leads robustly to a wide-angle outflow. We discuss that this type of explosions are not yet ruled out by current afterglow observations of GW170817. We further present a detailed comparison between magnetized jets and hydrodynamical jets.
Ada Nebot Key theme: Multi-messenger technology and interoperability
Title: Exploring Time Domain Multi-Messenger Astronomy through the Virtual Observatory
Authors: A. Nebot, M. Allen, F. Genova, and the CDS team.
What do Cepheid stars, Binary Neutron stars, Supernovae explosions and Active Galactic Nuclei have in common? They are all variable objects, although the physical processes and the associated time-scales that govern their variability can be very different (pulsations, collapse, accretion, bursts, … with characteristic time-scales from milliseconds to hundreds of years). Some events can trigger follow-up observations and a fast reaction to those events can be crucial to determining the nature of the object. To better understand the nature of these objects and the mechanism behind the source of variation a multi-wavelength and even multi-messenger approach is sometimes needed. Last year for the first time there was a direct detection of gravitational waves and electromagnetic emission from colliding neutron stars. The discovery involved more than 70 ground and space based telescopes and more than 3000 astronomers. GW170817 beyond being of great relevance by it’s own helped us to better understand the need from the Time Domain Astronomy community to transmit events, collect and share information and to coordinate observations. The Virtual Observatory (VO) should match the common needs of the different scientific use cases. In this talk, we will give some highlights of the ASTERICS DADI work on enabling Time Domain astronomy in the VO, and coordinating the international effort in IVOA. This includes standards for spatial and temporal coverage, and Time Domain data as will be needed for Time Domain Multi-Messenger Astronomy. Other highlights include prototype visualisation tools taking into account the temporal dimension, and tools for fast cross-matching.
Jakob Nordin Key theme: Alert mechanism systems and fast response of facilities
Title: AMPEL: a streaming data analysis framework
Authors: Jakob Nordin
Multi-messenger astronomy and new high throughput variability surveys require the development of flexible tools for transient selection and analysis. I here present the Alert Management, Photometry and Evaluation of Lightcurves (AMPEL) system, a streaming data analysis framework. AMPEL incorporates an alert broker, but couples this with the capability to host user contributed software both to analyze and react to events. These tools are embedded in a framework that encourages provenance and keeps track of the varying information states that a transient displays. The latter concept includes information accreted with time but also varying data access levels and e.g. improved calibration. Taken together, AMPEL provides a tool that can assist both in the real-time parsing of transients, running realistic alert reaction simulations, and the final scientific analysis of transient data. The AMPEL live instance, hosted in DESY Zeuthen, is currently ingesting the live ZTF alert stream. Active science channels range from parsing this stream for correlations with IceCube neutrinos, searches for TDEs and observing Type Ia supernovae for cosmological distance estimates.
Andrea Palladino Key theme: Sources of high-energy particles (neutrinos, CRs, VHE gamma-rays)
Title: On the sources of high energy neutrinos
Authors: Andrea Palladino
The discovery of a diffuse flux of high energy neutrinos, provided by IceCube in the last few years, has open a new era in the field of Astroparticle Physics. Up to now, only one high energy neutrino has an identified counterpart, i.e. the blazar TXS 0506+056. All other high neutrinos still remain without any counterpart.

Blazars may explain the flux of astrophysical neutrinos, but the non observation of correlation between neutrinos and known blazars is a tricky point for this scenario. Other sources, such as Gamma-Ray Burst, are expected to contribute less than 1% to the high energy neutrino flux. Also the contribution of sources in which the interactions between protons and gas dominate seem to be disfavored, due to multi-messenger constraint coming from the comparison between the expected gamma-ray flux and the observed one. Therefore one of the most interesting question is: what is the source of the detected high energy neutrinos ?

This question has no answer for the moment and we are still in a period in which many possibilities are open. I will show that, under certain assumptions, blazars and starburst galaxies can provide a dominant contribution to the astrophysical neutrino flux. Moreover also neutrinos produced on the Galactic plane of our Galaxy are still into the game and they can produce interesting effects at low energy. The multi-messenger physics, particularly the connection between the neutrino flux and the gamma-ray flux, is a powerful tool to investigate the origin of astrophysical neutrinos. On the other hand, it is still premature to put strong constraints on the sources based on the multi-messenger and only future neutrino telescopes will fully clarify the origin of astrophysical neutrinos.
Debdutta Paul Key theme: Electromagnetic transients in multi-messenger signals
Title: The binary neutron star merger rate via the luminosity function of gamma-ray bursts
Authors: Debdutta Paul
Astrophysical transients are a signature of cataclysmic events, often associated with death of a system and the formation of compact objects. Gamma-ray bursts (GRBs) are transients associated with the collapse of a massive star into a black hole, and the merger of neutron star binaries to form a more massive neutron star or a low-mass black hole along with the emission of gravitational waves. Although it is impossible to predict individual GRBs, it is nonetheless important to make statistical predictions of the number detectable by a GRB monitor in the sky, and the true GRB rate of the universe. In this talk, I will present predictions of the event rate of the AstroSat/CZTI via careful studies of the luminosity function of short GRBs. Reasonable physical assumptions are made in modelling the true event rate, and simplifications are made whenever possible by using data from the existing GRB catalogues. Using the maximum distance to which the gravitational networks are sensitive in the past, present and future runs, stringent lower limits on the rate of binary neutron star mergers (BNSMs) are calculated by assuming that each BNSM produces a short GRB. In light of the detection of GW/EM170817, it is shown that the number will go up significantly in the next observing runs of aLIGO/VIRGO. Comparison of the short GRB rate with the BNSM rate calculated independently from the single source statistics of GW170817 reveals the presence of a slight tension that can have significant implications on the physics of the merger ejecta; however the scenario that each BNSM indeed produces a short GRB, cannot be ruled out.
Jonas P. Pereira Key theme: Gravitational Wave Sources in multi-messenger signals
Title: Large tidal deformabilities of hybrid stars with solid quark phases
Authors: Jonas P. Pereira, Nils Andersson, and Rafael C.R. de Lima
We show that tidal deformabilities of hybrid stars with solid quark cores and hadronic crusts ($\Lambda^{sol}$) may differ significantly from their perfect-fluid counterparts ($\Lambda^{perf}$). This is done in the usual context of nonradial perturbations with zero frequencies and phases presenting elastic aspects just when they are perturbed (unstrained background configurations). In this first study, we assume that solid aspects of the quark phase follow the LOFF prescription and a MIT-bag like model for the background, while for the hadronic part we choose an effective polytropic equation of state and take usual elastic parameters. We focus on the influence the energy density jump at the core-crust interface, boundary conditions and elasticity of the quark phase have on $\Lambda^{sol}$. We find that when there is no energy density jump at the core-crust interface, the $\Lambda^{sol}$ of a $1.4$ M$_{\bigodot}$ hybrid star decreases around $5-10\%$ with respect to $\Lambda^{perf}$ when shear stresses are discontinuous at the quark-hadron interface, and around $10-20\%$ when they are not. $\Lambda^{perf}$ is very sensitive to energy jumps (as known), differently from $\Lambda^{sol}$, which is sensitive to changes in core-crust boundary conditions. When the energy density jump increases, the difference between $\Lambda^{sol}$ and $\Lambda^{perf}$ decreases, even leading to $\Lambda^{perf}>\Lambda^{sol}$. Therefore, tidal deformabilities extracted from gravitational wave observations are very sensitive to elastic aspects of a quark core as well as core-crust boundary conditions to perturbations and hence could put constraints on poorly known crystalline aspects to quark matter and core-crust boundary layers in stars.
Emily Petroff Key theme: Alert mechanism systems and fast response of facilities
Title: A VOEvent Standard for Fast Radio Bursts
Authors: Emily Petroff
Fast radio bursts are a new class of transient radio phenomena currently detected as millisecond radio pulses with very high dispersion measures. As new radio surveys begin searching for FRBs a large population is already being detected, and real-time discoveries are soon expected, triggering a range of multi-wavelength and multi-messenger telescopes to search for repeating bursts and/or associated emission. In this talk I will present the method developed by the FRB community for disseminationg new triggers using Virtual Observatory Events (VOEvents). An additional advantage to the use of VOEvents for FRBs is that the events can automatically be ingested into the FRB Catalogue (FRBCAT) enabling real-time updates for public use. I will discuss the current FRB event standard, how it was developed, how it will be used, and some lessons that may be applicable to other transient communities as they try to standardize event communications.
Heike Prokoph Key theme: Electromagnetic transients in multi-messenger signals
Title: Follow-up observations of multi-messenger alerts with H.E.S.S.
Authors: Heike Prokoph for the H.E.S.S. Collaboration
Thanks to its rapid response time, excellent sensitivity and large field-of-view, the H.E.S.S. experiment is ideally suited to observe short time scale transient events. All these advantages are best exploited in a fully automatized system reacting to alerts from various partner observatories covering a variety of wavelengths and astrophysical messengers. Such a system is implemented in H.E.S.S. and in this contribution, we will provide an overview of the H.E.S.S. science programs to follow-up on multi-wavelength and multi-messenger alerts in the very-high-energy gamma-ray regime. We will present recent results of real-time ToO observations of gamma-ray, neutrino and gravitational wave alerts as well as a complementary search for VHE gamma-ray emission at longer timescales and will put them into the multi-wavelength context.
Judith Racusin Key theme: Multi-messenger technology and interoperability
Title: Future NASA Missions for Multi-Messenger Astrophysics
Authors: Judith Racusin
In this new era of multi-messenger astrophysics with the first detections of counterparts to gravitational wave and neutrino sources, the next generation of space-based instruments needs to be optimized for detecting, rapidly localizing, and characterizing them. These searches become especially more important as gravitational wave and neutrino experiments upgrade and become more sensitive in the next decade. We are exploring mission concepts on scales from CubeSats to large explorer missions designed specifically to explore this science in the 2020s. In this talk I will describe potential future missions including BurstCube, ISS-TAO, Bia, Nimble, TAP, and AMEGO. Each mission explores different parts of the observational phase space from gamma-ray bursts, afterglows, kilonovae, and other transient and variable sources in different cost scales with instruments sensitive from infrared to gamma-rays.
Ludwig Rauch Key theme: Electromagnetic transients in multi-messenger signals
Title: Searching for Optical Counterparts to High-Energy Neutrino Sources with ZTF
Authors: Ludwig Rauch
The IceCube neutrino observatory has detected a flux of extragalactic neutrinos. However, the origin of these neutrinos is still unknown. Among the possible candidates are Gamma-Ray Bursts (GRBs), Core-Collapse Supernovae (SNe), Active Galactic Nuclei (AGN) and Tidal Disruption Events (TDEs) - all are accompanied by a characteristic optical counterpart. The goal of this study is thus to identify the neutrino sources by detecting their optical counterpart with the Zwicky Transient Facility (ZTF). ZTF features a high cadence northern-sky survey enabling realtime correlation of optical transients with high-energy neutrino candidates. In this talk I will highlight the multi-messenger potential of ZTF for an online neutrino correlation study with IceCube.
Marc Ribó Key theme: Alert mechanism systems and fast response of facilities
Title: MAGIC follow-up of gravitational wave events in the third LIGO/Virgo observation run
Authors: M. Ribó, A. Stamerra, B. Patricelli, A. Berti, E. Moretti, et al. for the MAGIC Collaboration
The search for gravitational wave (GW) signals has been very successful in the first two observations runs (O1 and O2) of the LIGO and Virgo experiments. In total, eleven GW events were detected: ten from the coalescence of
binary black hole systems and one from a binary neutron star system (GW170817). The latter in particular is the perfect example of the multi-messenger approach in astrophysics, thanks to the detection of an electromagnetic (EM) counterpart as a short gamma-ray burst, GRB170817A. The EM follow-up performed by instruments at different wavelengths is crucial to identify the astrophysical counterpart, the host galaxy, the nature of the remnant and the properties of its environment. Imaging Atmospheric Cherenkov Telescopes (IACTs) join the follow-up effort searching for very-high energy emission (E>100 GeV). The relatively narrow field of view, few square degrees, of IACTs poses a challenge in the detection of the counterpart in the large uncertainty region provided by the interferometers. A well designed and optimised observational strategy is therefore needed to maximize the probability to select the region hosting the counterpart. Among the IACT experiments, the MAGIC collaboration joined the EM follow-up community in 2014, performing the first follow-up of a GW candidate event (GW151226) by a Cherenkov Telescope. While the next observation run is approaching, MAGIC is optimising the GW follow-up strategy taking into account the information provided with the GW alert, the observational constraints, and taking advantage of its fast repositioning system adopted for GRBs. In this contribution we will present the MAGIC follow-up strategy of GW events, showing different observational approaches depending on the information available from interferometers and EM instruments.
Marc Ribó Key theme: Sources of high-energy particles (neutrinos, CRs, VHE gamma-rays)
Title: MAGIC as a Neutrino Follow-Up Instrument
Authors: M. Ribó, A. Fattorini, K. Satalecka, E. Bernardini, et al. for the MAGIC Collaboration
Since 2012, the stereoscopic IACT system MAGIC, located on La Palma, Canary Islands, has been involved in neutrino follow-up campaigns. The MAGIC telescopes are sensitive to gamma events with energies between ~30 GeV and tens of TeV. In 2017 MAGIC detected for the first time very high energy gamma-ray emission from the blazar TXS 0506+056, spatially correlated with an extremely high-energy neutrino event observed by IceCube. Every time a potentially astrophysical neutrino is detected by IceCube, an alert with the reconstructed coordinates is published. MAGIC uses an automated alert response system and performs follow-up observations in search of a correlated gamma-ray flux. The reconstructed neutrino direction is given with an uncertainty, typically about 0.2-1 degree. Since the MAGIC angular resolution is much smaller, the analysis needs to be modified to detect sources in a certain sky region. In case of non-detection, information about the flux upper limits in the entire IceCube event error region should be provided for correct interpretation of the data. Here we present a method for creating sky maps to identify point sources or to derive flux upper limits for the desired sky region, based on a maximum likelihood approach included in the SkyPrism software. Results of Neutrino follow-up observations by MAGIC are shown.
Philip Ruehl Key theme: Sources of high-energy particles (neutrinos, CRs, VHE gamma-rays)
Title: Searches for ultra-high-energy photons at the Pierre Auger Observatory
Authors: Philip Ruehl for the Pierre Auger Collaboration
One of the key challenges in astroparticle physics is identifying the sources of cosmic rays at the highest energies (above 10^18 eV). In this context, the search for ultra-high energy photons is of high interest. Observing
photons of such energies would impact astrophysics and particle physics as well as fundamental physics and would be an important contribution to multimessenger astronomy. The Pierre Auger Observatory near Malargu?e, Argentina, is the largest air-shower experiment for the detection of ultra-high energy cosmic rays. It consists of an array of about 1660 water Cherenkov detectors arranged on a triangular grid which covers an area of more than 3000 km^2. 27 fluorescence telescopes at four sites overlooking the detector array provide an independent and complementary method for air-shower detection.
In the contribution, the various activities at the Pierre Auger Observatory concerning searches for ultra-high energy photons will be presented and the current results will be summarized. In addition, future prospects will be discussed.
Om Sharan Salafia Key theme: Electromagnetic transients in multi-messenger signals
Title: Multi-messenger characterization of BH-NS mergers
Authors: Om Sharan Salafia
Abstract: the third observing run of the network of advancedgravitational wave detectors is approaching, featuring an improvedsensitivity and thus a larger expected number of detections. Weare therefore in a position to expect the first detection of theinspiral and merger of a black hole - neutron star binary (BH-NS)to take place in the near future. These systems offer anunprecedented opportunity to answer fundamental questions aboutthe nature of their components - stellar black holes and neutronstars - and about the binary formation channels and evolution. Inthis context, we developed a series of semi-analytical models topredict the properties of all the jet- and kilonova-relatedelectromagnetic counterparts of BH-NS mergers, and we defined waysto relate their properties to those of the progenitor binary. As aresult, we show that the observation and modeling of theelectromagnetic counterparts of a BH-NS merger, when combined withinformation from the gravitational wave signal, can help to breakdegeneracies in the parameter space, leading to better constraintson the intrinsic parameters of the binary such as the black holespin.
Filip Samuelsson Key theme: Sources of high-energy particles (neutrinos, CRs, VHE gamma-rays)
Title: The limited contribution of gamma-ray bursts to ultra-high energy cosmic rays
Authors: Filip Samuelsson, Damien Bégué, Felix Ryde, and Asaf Pe'er
The acceleration site for ultra-high energy cosmic rays is still an open question despite extended research. In this talk, I will present the results we presented in a paper a couple of months ago, where we reconsider the prompt phase of gamma-ray bursts as a possible candidate for this acceleration. Using properties of the prompt photon spectra, we constrain the maximum proton energy in optically thin synchrotron and photospheric models. We find that neither of the models favour acceleration of protons to $10^{20}$ eV in high-luminosity bursts. We repeat the calculations for low-luminosity gamma-ray bursts considering both protons and completely stripped iron and find that the highest obtainable energies are < $10^{19}$ eV and < $10^{20}$ eV for protons and iron respectively, regardless of the model. We conclude therefore that, gamma-ray bursts, including low-luminosity bursts, contribute little to none to the ultra-high energy cosmic rays. Any association between ultra-high energy cosmic rays and gamma-ray bursts would require very efficient acceleration, favour photospheric origin of the prompt gamma-rays, and result in high prompt optical spectral fluxes.
Volodymyr SAVCHENKO Key theme: Electromagnetic transients in multi-messenger signals
Title: Hunting for elusive multimessenger transients with INTEGRAL
Authors: V. Savchenko on behalf of a larger collaboration
Recent years have been marked by the accelerated development of time domain astronomy, owing to the evolution of observational techniques in wide-field rapid optical and radio surveys, as well as the development of the computing resources and methods necessary to promptly interpret overwhelmingly rich observational data. In addition, new kinds of observatories dedicated to gravitational waves and neutrinos have reached a degree of maturity that has enabled breakthrough multi-messenger observations of previously undetected fundamental physical processes in space. Short and energetic events are generally easier to separate from the background than persistent sources, and this is why the first truly multi-messenger signals were also detected as transient events.

The properties or even the very nature of many of the new classes of transient sources remain obscure: they are typically associated with peculiar supernovae, mergers of compact objects, or tidal disruption events. In order to decipher the complex physical processes at play in these exceptional systems, it is vital to collect exhaustive and diverse observations of the source, and in particular, observations in different energy bands. Among the most interesting, and yet the most challenging is the observation of the hard X-ray and gamma-ray emission: it often reveals a distinct emission component that points to the most dense and energetic regions at the heart of the source.

The INTEGRAL spacecraft is especially well-equipped to observe unpredictable, short-lived, and energetic hard X-ray and gamma-ray transients. It carries a collection of detectors that monitor the entire sky with over 80% duty cycle and simultaneously perform deep and sensitive observations of a large sky region spanning 30x30 degrees. Interpreting the observations collected by these instruments is challenging, especially when the analysis has to be done with real-time efficiency, a critical element needed for the community follow-up of these often quickly fading transients.

I will highlight recent pioneering observations of short energetic transients made with INTEGRAL. I will begin by discussing the observations of gamma-ray bursts, in particular in association with the gravitational wave events and high-energy neutrinos. Then, I will review how INTEGRAL observations of fast hard X-ray transients helps to reveal mechanisms at the core of the some of short energetic transients likely associated with the deaths of the massive stars. Finally, I will discuss how the recent discoveries in the domain of multi-messenger transients were made possible by a global effort to achieve a new degree of automation and interoperability.
Volodymyr SAVCHENKO Key theme: Multi-messenger technology and interoperability
Title: Astrophysical Online Data Analysis powered by provenance data model
Authors: V. Savchenko on behalf of a larger collaboration
We present the Online Data Analysis (ODA) platform, developed at Common Data Center Infrasture of UniGE to facilitate reduction and analytics of astronomical data. The currently publicly available version allows to effortlessly explore and exploit observations of ESA's INternational Gamma-Ray Laboratory (INTEGRAL) as well as Polar GRB polarization detector. The platform can be accessed through a simple on-line interface, suitable for researchers not familiar with INTEGRAL data reduction but interested in astrophysical phenomena. More evolved configuration of the analysis can be achieved through detailed formulation of the requests to the service through an HTTP API. Our goal is to combine both quick-look in-browser analysis (providing robust but simple results) and fine-grained control through the API for the domain experts (allowing interoperability and integration in federated data analysis workflows).

The analysis results at different degrees of reduction are archived as static products, annotated and indexed with the respective provenance graphs. This structure allows to follow the lineage of the scientific products from the raw spacecraft data to the final scientific publication. These products can be referenced with unique identifiers, derived from their provenance, suitable for assigning citeable DOI (e.g., through Zenodo). These references address statically available archive products, while at the same time referring to the online analysis platform, allowing to trace every analysis step, and re-execute the pipeline, reproducing the result from scratch, optionally introducing changes testing robustness of the result. Wherever possible, we will provide an interface conforming to the VO standards for astronomical data products.

Simple, immediate, automated, and reliable interface to the diverse astronomical data has proven to be most important in the multi-messenger time domain astronomy. We discuss the services which have been developed for promptly sharing INTEGRAL data for transients which were exploited in the recent observations of different multi-messenger transients. Finally, we discuss the integration of these services with the ODA platform.
Stephen Sclafani Key theme: Sources of high-energy particles (neutrinos, CRs, VHE gamma-rays)
Title: Constraints on neutrino emission in the local universe using 2MASS redshift survey with IceCube
Authors: Steve Sclafani, IceCube Collaboration
The distribution of galaxies within the Local Universe (z < 0.03) is characterized by strong anisotropic features. Experiments looking for astrophysical neutrino sources can take advantage of these features to establish potential spatial correlations between a neutrino events and overdensities in the galaxy distributions in the sky. We present the results of a correlation searches using the time-integrated, Seven-Year Point Source dataset of the Icecube Experiment. Analysis was performed using the 2MASS Redshift Survey (2MRS) Catalog, looking for correlation of neutrino emission with the local galaxy density distributions. This assumes neutrinos are produced via diffuse Ultra-High Energy Cosmic Rays (UHECR) interacting with matter, the galaxy matter density serving as a target for cosmic ray interactions and thus preserving the profile. No correlations were observed and limits are placed on the flux of neutrinos from these interactions.
Monica Seglar-Arroyo Key theme: Electromagnetic transients in multi-messenger signals
Title: Searches for counterparts of Gravitational Waves with VHE gamma-ray observatorie
Authors: Monica Seglar-Arroyo
The recent milestones in multi-messenger astronomy have opened new ways to study the Universe. Unprecedented follow-up campaigns have established the value of combining different messengers providing complementary information about an astrophysical event. Covering very different timescales and all accessible energy ranges, these campaigns allow to identify and study the nature and evolution of a broad range of astrophysical phenomena.

In this contribution, we focus on the intersection between very-high energy (VHE) electromagnetic radiation and gravitational waves. In particular, observations with VHE gamma-ray instruments can constrain the non-thermal, high-energy radiation emitted during and after the merger of compact binary systems. We will provide a review of the status of the various programs and present an overview over recent results from searches for VHE counterparts to gravitational wave events. We will especially stress the complementarity between Imaging Atmospheric Cherenkov Telescope systems and large field-of-view water Cherenkov detectors. Finally, we will provide an outlook on the multi-messenger programs of various future VHE instruments.
Bernardino Spisso Key theme: Multi-messenger technology and interoperability
Title: ROAst (ROot extension for Astronomy)
Authors: Bernardino Spisso
The ROOT analysis framework is one of the most used software for the analysis and it is considered the “de facto” standard for high-energy physics. The goal of ROAst (ROot extension for Astronomy) is to extend the ROOT capabilities adding packages and tools for astrophysical research “bridging” the two worlds. The focus is on the astronomical catalogues integration and on the support for the astronomical coordinates transformations, manipulations as well as the graphical representation of the considered astronomical objects. In order to speed-up the future catalogues implementations, the general architecture relies on an intermediate abstraction layer, all the catalogues implementation share the same methods simplifying the
access. The support for two local test catalogues the UCAC4 and the URAT1 are available and most important ROAst supports the on-line Virtual Observatory (VO) catalogues and VizieR on-line catalogue repository. Beside, ROAst features a set of coordinate and time conversion methods, which are catalogue-independent. Supported coordinate systems are: equatorial, galactic, ecliptic, horizontal astronomical coordinates (using Lat-Long or UTM as geographical coordinates) with mutual transformations. Moreover, ROAst provides a graphic support library which relies on the ROOT graphic tools. All ROOT graphical options are automatically integrated. The idea is to supply a basic set of graphical tools that is fully consistent with the ROOT environment leaving the customization of the plot to the user.
Finally, ROAst features Moon and Sun position.
Robert Stein Key theme: Electromagnetic transients in multi-messenger signals
Title: Search for High-Energy Neutrinos from Populations of Optical Transients
Authors: Robert Stein, Alexander Stasik, Anna Frackowiak
Since the detection of high-energy cosmic neutrinos at the IceCube Neutrino Observatory in 2013, there has been an on-going search to find suitable transient or variable source candidates. Despite recent evidence identifying a flaring blazar as a possible neutrino source, the vast majority of the diffuse neutrino flux measured by IceCube remains unexplained. The latest IceCube results testing time-dependent correlation between neutrinos and both Core-Collapse Supernovae and Tidal Disruption Events will be presented. In view of new, upgraded and future time domain optical surveys (such as ZTF, ASAS-SN and LSST), a strategy for future multi-messenger analysis will also be presented. Efficient allocation of future follow-up resources will be required to better measure or constrain the neutrino flux contribution from optical transient populations.
Simona Maria Stellacci Key theme: Multi-messenger technology and interoperability
Title: CORELib: COsmic Ray Event Library
Authors: Simona Maria Stellacci
CORELib is a collection of simulated showers induced by primary cosmic rays and a common framework to produce and manage such large production. Indeed, CORELib provides high statics background simulation for various astroparticles and astronomy experiments. The simulations are obtained employing widely used CORSIKA simulation framework and the GRID infrastructure as computational resources; in the current productions the observation level is placed at sea level, while the Standard European Atmospheric Model is used. The parameters of simulations are available and easily accessible to the users.
Two different primary energy spectra are considered: one with -2 spectral index and one with flat spectrum. Four different high energy models are evaluated: QGSJET01 with CHARM option, QGSJET01 with TAULEP option, QGSJETII with TAULEP option and EPOS with TAULEP option.
The common low energy model chosen is GHEISHA.
Protons and Heavy Nuclei (He, C, N, O, Fe) induced showers are simulated. Proton induced showers two production are available: with and without Cherenkov radiation.
All the information about every single shower is stored in SQLite database queryable by the user.
In order to simplify the access at the library, a dedicate tool named CORANT is used to translate from binary to ASCII the CORSIKA output files. The information about showers is placed in separated files, one for each particles class (EM, Hadrons, Muons, Neutrinos ).
The whole production of CORELib will be downloaded through an open access at the CNAF, the Information Technology national center of INFN (Italian Institute for Nuclear Physics) .
Sander ter Veen Key theme: Alert mechanism systems and fast response of facilities
Title: LOFAR's fast response capabilities
Authors: S. ter Veen, A. Rowlinson, J. D. Mol, A. R. Renting, A. K. Klazema
Abstract: In the Era of Multi-messenger astrophysics it is important that instruments can follow up on other instruments in a fast and automatic fashion. The Low Frequency Array (LOFAR), a large distributed telescope in the Netherlands, we have two fast response mode. Firstly, buffers are installed of 5 seconds for each individual antenna. These can be read out and then pointed in any direction. In this way we can look in the past. Secondly, a rapid response mode is installed in which a new observation can override the current observating program and repoint the telescope within 5 minutes. In this contribution I will present these two modes and give a hint of the science that can be done with it.
Aaron Tohuvavohu Key theme: Electromagnetic transients in multi-messenger signals
Title: Swift in the multi-messenger era: GW + neutrino follow-up results and opportunities for the future
Authors: Aaron Tohuvavohu
Swift's rapid slewing, flexible planning, and multi-wavelength instruments make it the most capable space-based follow-up engine for finding poorly localized sources, and a critical component of multi-messenger campaigns. Swift's transient response has played critical roles in follow up of GW and neutrino triggers, and Swift GRBs serve as a trigger for targeted GW and neutrino searches. Swift made important contributions to the discovery and characterization of the kilonova AT 2017gfo, discovering the UV emission and providing the deepest X-ray upper limits in the first 24 hours after the trigger, strongly constraining the dynamics and geometry of the counterpart. Swift also tiled 92% of the galaxy convolved error region down to average X-ray flux sensitivities of 10?12 erg cm?2 s?1 and UV magntiudes of ~19, significantly increasing our confidence that AT 2017gfo is indeed the counterpart to GW 170817 and sGRB 170817. The earliest pointed observations in response to IC-170922 were performed by Swift, and TXS 0506+056 was identified as a possible source. Further monitoring in the UV and X-ray with Swift were critical to building the SED of TXS 0506+056, and constraining the hadronic component of the jet. Swift will continue to play a critical role in the new era of multi-messenger astronomy, but there remains significant room for improvement of Swift's operational capabilities and observing strategy to maximize the scientific yield of this powerful observatory. Swift is currently performing the Swift Gravitational Wave Galaxy Survey, pre-imaging 5000 of the brightest galaxies within 100 Mpc, to provide X-ray and UV templates for transient searches in response to GW detected BNS mergers. We outline areas of improvement to the observing strategy itself for optimal tiling of the LVC localization regions. We also discuss ongoing work on operational upgrades that will decrease latency in our response time to transient events, and minimize impact on pre-planned observations, while maintaining spacecraft health and safety. These upgrades further allow complex positional and temporal biasing of the Swift Burst Alert Telescope, increasing the likelihood of detecting a short GRB associated with a GW detected binary neutron star merger. I will address how the community can further utilize these capabilities and challenges ahead in the high alert-rate multi-messenger era.
Agata Trovato Key theme: The principles of Open Science
Title: GWOSC: Gravitational Wave Open Science Center
Authors: Agata Trovato for the LIGO/Virgo collaboration
The LIGO and Virgo collaborations actively pursue an open science programme. Gravitational-wave strain data are publicly released through the website along with the information and tools necessary to understand and use the data. This contribution will give an overview of the past and current activities related to this topic, including the recent release of the Catalog of Compact Binary Mergers (GWTC-1) and will give a sense of its impact on science, teaching and other applications.
Rob van der Meer Key theme: Multi-messenger technology and interoperability
Title: RISCAPE: European Research Infrastructures in the International Landscape
Authors: C. Baldovin, M. Timmer, R. van der Meer, R. Vermeulen
European Research Infrastructures in the International Landscape – RISCAPE - is a H2020 funded project to map the international landscape of research infrastructures, in particular in respect to the major European research infrastructures. The project focuses on finding what kind of major research facilities exist worldwide and how the European facilities position themselves in comparison.

RISCAPE includes eight disciplines: Environmental Sciences, Biomedical Sciences, Physics and Engineering, Energy, Astronomy and Astroparticles, Social Sciences, Cultural Heritage, Digital Humanities and Language, and e-Infrastructures. The University of Helsinki is the coordinator of this initiative and ASTRON, the Netherlands Institute for Radio astronomy, leads the Astronomy and Astroparticles work package.

To achieve its goal RISCAPE engages in different initiatives:

• Establish a close interaction with a stakeholder panel representing main user groups of the report, including representatives from ESFRI, OECD and Member state funding agencies to ensure usability and focus of the Report.

• Use close cooperation with other projects and initiatives in the European research infrastructures development to ensure consistency with the existing landscape work. Particularly, RISCAPE builds on the European Research Infrastructures (RIs) in the ESFRI landscape report (2016) and on the landscape analysis done in the H2020 cluster projects.

• Leverage the experts on the European RIs with extensive knowledge on the disciplines involved and RI development in Europe. RISCAPE benefits on the contacts and tools developed in the cluster and international RI collaboration projects to maximize the discipline-specific usability of the results.

The resulting Report and the used methods will be independently peer reviewed to maximize the usability and objectivity of the information provided for the EU strategic RI development and policy.

RISCAPE started in January 2017 and will run until December 2019.
Chantal van Tour Key theme: Multi-messenger technology and interoperability
Title: White rabbit time and frequency transfer in SURFnet8 network for VLBI purposes
Authors: C. van Tour, P. Boven, R. Smets, P. Hinrich, P. Maat, J.C.J. Koelemeij, A. Szomoru
As part of the Cleopatra work package from the ASTERICS project we studied the stability and accuracy of an optical time and frequency transfer (TFT) link for multi-messenger astronomy, primarily for VLBI observations. The TFT link is established with switches that use the White Rabbit (WR) protocol to distribute time and frequency through optical fiber. Improvements by OPNT were made to the open-hardware WR switches to achieve a higher frequency stability and lower phase noise. Furthermore, OPNT developed dedicated bi-directional optical amplifiers to extend the reach of the TFT link.

To demonstrate the TFT link, the WR switches were incorporated in the new SURFnet8 network, by making use of alien wavelengths. While standard optical fiber networks for telecommunication or data communication use uni-directional connections, the WR protocol requires bi-directional connections. In order to accommodate a TFT service in addition to operational data communication services, significant modifications were made to the SURFnet8 network. Special filters where used to separate the alien wavelength for the TFT service from the wavelengths used for the production data communication services. We have shown that these changes did not impact the performance of the SURFnet8 network. This provides a good perspective to develop future TFT services over the SURFnet8 photonic infrastructure, beyond the scope of the ASTERICS project.

The demonstrated TFT link distributes the hydrogen maser’s time and frequency signals through a master WR switch at the WSRT facility in Westerbork to a slave WR switch at the radio telescope in Dwingeloo. In order to test the WR service over a long distance, an additional loop from Westerbork to Groningen and back to Westerbork was made before traveling to Dwingeloo, extending the path from 34 km to 134 km. The time and frequency stability over the full path has been measured and analyzed by temporarily moving the slave WR switch to Westerbork. The results show that the frequency stability is already within two times the stability of a brand-new hydrogen maser after an averaging time of 1000 s, and within one order of magnitude for all averaging times. Furthermore, all significant fiber delay asymmetries in this optical link were measured and agree with the predicted values within experimental uncertainties. All these results together indicate that the TFT link can support VLBI observations.

A further step is to distribute the time and frequency from the WSRT facility to the LOFAR facility in Buinen, where it will be used to distribute accurate and stable time and frequency signals in their array of antennas.
Harro Verkouter Key theme: Multi-messenger technology and interoperability
Title: Are you up for faster dissemination of your data?
Authors: Harro Verkouter
The ease with which it is possible to transfer (very) large file(s) over a network connection has not scaled with the explosion of available bandwidth witnessed over the last decade. This is obvious when attempting to use standard tools like ftp or scp over long, fat, links.

In Very Long Baseline Interferometry (VLBI) we have been building experience transferring (very) large amounts of data over global network links since 2006. The VLBI specific application makes use of the high-speed UDP-based Data Transfer (UDT) protocol.

This knowledge has been used to develop a faster, generic, open source file transfer utility from scratch. Tests on a 10Gbps link from The Netherlands to New Zealand have shown it to outperform the standard protocols.
Jacco Vink Key theme: Electromagnetic transients in multi-messenger signals
Title: The Athena X-ray mission and its synergy with the next generation of multi-messenger facilities
Authors: Jacco Vink on behalf of the Athena Community
ESA’s L-class Athena mission, to be launched around 2030, will provide the high energy astrophysics community with
an X-ray telescope of unprecedented sensitivity, combing high throughput ( 1.4 m^2 effective area), with a spatial
resolution of 5” and a spectral resolution of 2.5 eV. When Athena will be launched many other observational
facilities will have moved into a new era, not only limited to the optical and the radio, but also in the domain of multi-messenger astrophysics.

In the electromagnetic domain CTA, a very-high energy gamma-ray telescope, covering photon energies from 10 GeV up to 200 TeV,
will be a natural counterpart to Athena, with CTA covering inverse Compton radiation from the same electron populations producing X-ray synchrotron emission,
but in addition CTA is sensitive to radiation produced through pion production by very-high energy protons and other massive particles. This latter process also produces
energetic neutrinos. By 2030 very-high energy neutrino astronomy should be in full swing, with the completion of KM3NeT and potential upgrades of IceCube.
Together with cosmic-ray experiments like the Pierre Auger Observatory and Telescope Array, the prime target of these facilities is to understand the origin of cosmic rays, and its
acceleration mechanism in various sources. High energy particles are also a by product of the mergers of neutron stars, and perhaps black holes. Athena will target the thermal and non-thermal
X-ray emission detected by upgraded version of the gravitational wave detectors LIGO and Virgo, and with perhaps a next generation detector like the Einstein Telescope,
which will be online or in full development. In addition, in the 2030s, probably not long after the launch of Athena, the space-based gravitational wave detector LISA will be able to
detect all supermassive black hole mergers in the Universe. Provided the localisation can be secured, Athena will provide the best X-ray instrument to detect sources on a cosmological

The sources targeted by these multimessenger facilities will in most cases be high energy sources, which in many cases will be X-ray sources.
As a result, Athena will provide important information on these sources, as X-ray emission is often not limited by statistics as much as
other multimessenger fields. The typical targets for which we expect that a combination of Athena and other facilities will prove important
are various types of AGN (in particular blazars), which are suspected to be sources of cosmic rays, and should therefore produce both high energy neutrinos
and gamma-ray emission. For gravitational wave sources Athena will help to understand the aftermath of neutron star-neutron star mergers (or NS-black hole mergers),
and constrain or potentially detect electromagnetic radiation from black hole-black hole mergers. Other sources of interest are supernova remnants, pulsar wind nebulae,
gamma-ray bursts, and high density regions where we expect cosmic-ray interactions. Athena will add to these studies its ability to obtain detailed physical parameters
by high resolution spectroscopy, and/or reveal faint emission from distant sources.

This synergy between Athena and especially the multimessegner facilities will be discussed.
Thomas Vuillaume Key theme: Alert mechanism systems and fast response of facilities
Title: High Performance Computing applied to the Cherenkov Telescope Array data analysis
Authors: Thomas Vuillaume, Pierre Aubert, Jean Jacquemier, Florian Gaté, Gilles Maurin, Giovanni Lamanna
The Cherenkov Telescope Array (CTA) is the next generation of ground-based gamma-ray telescopes for gamma-ray astronomy. Two arrays will be deployed composed of 19 telescopes in the Northern hemisphere and 99 telescopes in the Southern hemisphere. Due to its very high sensitivity, CTA will record a tremendous amount of data that represent a computing challenge to the reconstruction software, in particular for real-time analysis that is required for the emission of alerts to other observatories.

We develop High-Performance Computing (HPC) solutions able to tackle these challenges and to perform the reconstruction of CTA raw data maximizing the usage of computing resources and thus minimizing their cost. The developed algorithms are organized in a reduction pipeline following the same organization as the one used for offline analysis, thus ensuring results consistency and minimizing maintenance resources.
The HPC approach will be presented along with the obtained physics and computing performances compared to the state of the art.
Roy Williams Key theme: Multi-messenger technology and interoperability
Title: Finding Diamonds in the Muck with Space-Time Crossmatch
Authors: Roy Williams
Spatial crossmatch has been a mainstay of data astronomy for years: first, because combining wavelengths provides better astrophysical information, but also because objects uninteresting on one wavelength may be much more interesting in multiple wavelengths. Space-time crossmatch introduces an additional dimension, correlating sub-threshold events in multi-messenger transient catalogues. For example, the LIGO and IceCube projects have searched catalogs of GRB's for associated gravitational-wave or neutrino triggers, and searched pulsar catalogs for associated periodic signals.

This talk explores tools for discovery using optical transient databases. Given any catalogue of non-optical transients -- GW, neutrino, cosmic ray, gamma ray -- there may be undiscovered optical counterparts that match the sky position and time window. Confirming such a counterpart would be a major discovery, not obvious in either of the original catalogues. In the Edinburgh-Belfast "Lasair" project, we are building a platform where astronomers can bring their ideas and run explorations and searches: we will present prototypes of tools for space-time crossmatch in the (current) ZTF and (future) LSST transient surveys.
Michitoshi Yoshida Key theme: Multi-messenger technology and interoperability
Title: J-GEM collaboration: an optical-infrared follow-up observation network
Authors: Michitoshi Yoshida, Yousuke Utsumi, Masaomi Tanaka, Nozomu Tominaga and J-GEM collaboration
J-GEM is a world-wide network of follow-up observations for gravitational wave transients in optical-infrared bands utilizing Japanese observation facilities. J-GEM consists of 11 telescopes across wide longitude range of the globe. We succeeded to observe the optical-infrared counterpart of GW170817 with Subaru Telescope which is a facility joining the J-GEM collaboration after 17 hours of the GW event. We present the current status of the low latency follow-up observation system of J-GEM and early results during LIGO/Virgo O3.
Sylvia Zhu Key theme: Gravitational Wave Sources in multi-messenger signals
Title: Continuous gravitational waves from axion clouds
Authors: S. J. Zhu, D. Tsuna, R. Brito, M. A. Papa, N. Kawanaka, H.-B. Eggenstein
Axions and axion-like particles of mass 1e-14 to 1e-12 eV can quickly form clouds with large occupation numbers around stellar-mass black holes via the superradiance instability. This axion cloud - black hole system acts like a gravitational-wave 'atom,' and would emit long-lived, monochromatic, continuous gravitational waves (CWs) from axion annihilations and level transitions. The CWs from annihilations could be detectable by the current generation of ground-based gravitational-wave interferometers, given reasonable assumptions about the Galactic isolated black hole population, and would produce a signature that is distinct from the more standard CW signals from isolated neutron stars. I will present the expected CW signal from axion annihilations, based on simulations of the Galactic isolated black hole population informed by X-ray studies.

Abstracts without link to participant.

Name Key theme / Title / Authors / Abstract
NEMMA3155464 Key theme: The principles of Open Science
Title: The ASTERICS VO schools. Getting closer to the astronomical community
Authors: Enrique Solano, Ada Nebot Gómez-Morán
The main goal of ASTERICS WP4 (“Data Access, Discovery and Interoperability”) was to ensure that the ESFRI products are openly accessible via the Virtual Observatory framework to the whole European and also international communities. Training and educating the next generation of users on how to efficiently use these new resources was identified as one of the most important objectives within this workpackage.

In this context, four Virtual Observatory (VO) schools were organised with a twofold objective: on the one hand, to expose European astronomers (in particular early-career people) to the variety of VO tools and services available today so that they can use them efficiently for their own research and, on the other hand, to gather feedback and requirements from this intense and diverse usage. During the school, VO experts guided the participants on the usage of such tools through a series of real life science cases. Participants also had the opportunity to develop their own science cases.

More than 130 participants from 15 different European countries attended the schools. Feedback gathered from participants demonstrated that the goals of the schools were fulfilled. The schools were efficient steps forward in the process of building an astronomical VO community both within ASTERICS and beyond the project’s borders across Europe.
NEMMA3155464 Key theme: Alert mechanism systems and fast response of facilities
Title: The SVO Discovery Tool
Authors: Enrique Solano, Almudena Velasco
The SVO Discovery Tool is a tool developed and maintained by the Spanish Virtual Observatory whose goal is to give an answer to the most basic VO question: “Given an object / list of objects, I want to know all the information that is available in archives about it / them”.

This information can be presently gathered in different ways using existing VO tools but there was a lack of a tool that efficiently executes this search and returns the specific information demanded by the user.

In its current version, the SVO Discovery Tool accepts a list of objects and/or coordinates and offers the possibility of gathering a list of physical parameters from Vizier, the photometry in a format ready to be
used by VOSA as well as the list of spectra and images.

In this poster we describe the main functionalities of the tool, in particular its application to projects with an alert system like Gaia.




ASTERICS is a project supported by the European Commission Framework Programme Horizon 2020 Research and Innovation action under grant agreement n.653477