The Transient Universe Waiting in the Sky 2021
Scientific Program
Friday 26 November 2021
Chair: Rosa Becerra and Stéphane Basa
GRBs 2:
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9:00/16:00 Astro-COLIBRI: a new platform for multi-messenger astrophysics in real-time (20+5) Fabian Schussler
Astro-COLIBRI is a novel tool that evaluates alerts of transient observations in real time, filters them by user-specified criteria, and puts them into their multiwavelength and multimessenger context. Through fast generation of an overview of persistent sources as well as transient events in the relevant phase space, Astro-COLIBRI contributes to an enhanced discovery potential of both serendipitous and follow-up observations of the transient sky. In this contribution, the key features of Astro-COLIBRI are presented. I'll outline the architecture, summarize the used data resources and provide examples for applications and use cases like the search for high-energy gamma-ray counterparts to high-energy neutrinos, gamma-ray bursts and gravitational waves.
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The merger of a binary neutron star system results in the emission of a gravitational wave, a highly dense and magnetized environment, and the launch of a collimated relativistic jet which eventually produces a short gamma-ray burst (SGRB). Although the evolution of a jet-SGRB has been studied through different media, the evolution through a magnetized medium is not fully understood. Therefore, to understand the importance of the magnetic field of the medium, we studied the evolution of several SGRB-jets through media with different varying the magnetic field B using two-dimensional magneto-hydrodynamic relativistic numerical simulations. Specifically, we follow the evolution of jets-SGRB with luminosity L_{J}=2\times 10^{50} ergs s^{-1} and an opening angle \theta_{J}=10° through a medium with different distributions and magnitudes of B.
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9:45/16:45 3D Numerical Simulations of Structured Long GRB Jets (15+5) Gerardo Urrutia
Observations of GRB 170817A, the first unambiguous off-axis GRB, have been followed by numerous studies trying to understand the structure of GRB jets. It has been shown that, in short GRBs, the interaction with the environment resulting from the neutron star merger is responsible for shaping the jet structure. Nevertheless, the role of the initial jet structure at the launching point has not been studied in detail. In a previous study, we found that the initial structure of the jet plays indeed an important role in the jet dynamics and in determining the final structure of the jet when it propagates in a low-density environment characteristic of short GRBs. In this work, we explore the role played by the initial structure in jets propagating in a dense medium, characteristic of long GRBs produced during the collapse of massive stars. We perform 3D special relativistic, hydrodynamics simulations of top-hat and structured jets within a massive progenitor star. We consider jets dominated by kinetic and thermal energy. Additionally, we consider also jets propagating after a supernova (SN) explosion. We found that the initial structure of the jets is lost in pressure-dominated jets, while it is partially conserved in a kinetic-dominated jet. In addition, we found that the dynamics of the jet inside the progenitor star strongly depend on the presence of an associated SN, leading to faster acceleration and velocity in the jets.
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10:05/17:05 BALROG and RoboBA algorithms: Finding the best location for Fermi/GRBs (10+5) Kin López
We compare two different algorithms to determine the position of Fermi/GBM GRBS: the DoL algorithm of the RoboBA system created by the Fermi/GBM team, and the other one developed by the BALROG collaboration. Using 48 GRBs with known locations of instruments such as BAT on board of Swift, we directly compare the accuracy of both algorithms and estimate the systematic uncertainty of both algorithms. Based on the errors calculated for both algorithms, we make an estimate of the specific situations (taking into account the diversity of properties of GRBs) where each one works better.
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COFFEE BREAK
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On october 16th, 2019 the BAT instrument on board of the Swift satellite detected the prompt emission of the GRB191016A. After the Swift/BAT alert, we triggered optical photometric observations with the COATLI, DDOTI and RATIR ground-based telescopes from T+378.7s to T+30,492s (0.10 to 8.47hrs after BAT detection), in order to characterize the afterglow emission properties. These observations allowed us to describe the temporal evolution of the optical afterglow of GRB191016A with 4 different stages that were not completely identified in previous works. After the end of the overall prompt gamma emission, we observed the afterglow rise in the optical and Near- nfrared(NIR) wavelengths. We obtained a temporal rising index of 1.53±0.06 for the afterglow, peaking around T+1400s, which is followed by an early decay phase with a decay index of -1.41±0.02. We also identify a clear plateau in the optical light curve, from T+5000s to T+11000s and temporal index -0.65±0.07, after which the GRB afterglow recovers its regular decay at later times. Although many of the features observed in the optical light curves of GRBs are usually well explained in the framework of a reverse shock (RS) or forward shock (FS) scenario, the shallow temporal index obtained for the optical rise of the GRB191016A is not well fitted if only FS or RS are solely considered in our modeling. We proposed a theoretical model which combines these two emission components by considering a forward shock evolution with an embedded reverse shock at later times, and a ubsequent late energy injection from the central engine activity. We used this model to explain the temporal evolution of GRB191016A light curves, discuss its implications on the fireball properties and the circumburst density profile.
Neutrinos:
10:40/17:40 Monitoring the neutrino sky for the next Galactic supernova (15+5) Godefroy Vannoye
The observation of the neutrino burst coming from the next Galactic Core-Collapse SuperNova (CCSN) and its gravitational wave and electromagnetic counterparts will provide us invaluable information on this extreme phenomenon. KM3NeT is a neutrino telescope currently under construction in the Mediterranean Sea. It is able to detect low energy neutrinos coming from CCSNe by searching for an excess of coincidences above the optical background, making it sensitive to Galactic and near-Galactic events. With its integration in the SNEWS global alert network, and ongoing work to compute, transmit and combine the neutrino light-curves of different detectors, KM3NeT will play a key part in notifying other telescopes before the arrival of the other messengers. In this talk, I will present the real-time detection capabilities of KM3NeT, the additional information that can be brought by light-curve computations and the follow-up of external alerts.
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11:00/18:00 Neutrino emission in core-collapsed massive stars in different models (10+5) Alejandro González
A simultaneous detection of gravitational waves and a high-energy neutrino emission is highly desirable, and would help to understand the connection between the dynamics of the progenitor, the outflows and the environmental conditions. In this short talk, I will assess the efficiency of neutrino emission in different models beyond the standard model which could be useful to stablish a threshold in the time delay of the two events.
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11:15/18:15 Real-time Multi-Messenger Activities of KM3NeT (15+5) Feifei Huang
KM3NeT is a multi-purpose cubic-kilometer neutrino observatory in construction in the Mediterranean Sea. It consists of ORCA and ARCA (for Oscillation and Astroparticle Research with Cosmics in the Abyss, respectively), currently both with a few detection lines in operation. Although having different primary goals, both detectors can be used for neutrino astronomy over a wide energy range, from a few tens of MeVs to a few tens of PeV. In view of the growing field of time-domain astronomy, it is crucial to be able to identify neutrino candidates in real-time. Real-time searches can significantly increase the discovery potential of transient cosmic accelerators and refine the pointing directions in the case of poorly localized triggers, such as gravitational waves. KM3NeT has a fast online reconstruction and classification system, neutrino alerts will be sent nearly real-time to the astronomy community. The neutrino alerts consist of both self-triggered events of interest, such as multiplets and VHE events, and the results of online search for time/space coincidence given external electromagnetic and multi-messenger triggers. This talk presents the status of KM3NeT's real-time multi-messenger activities, the alert format, alert definitions, and the expected timeline of issuing public alerts.
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Closure