Conveners
GWMS
- Steven Schramm (Universite de Geneve (CH))
GWMS
- Steven Schramm (Universite de Geneve (CH))
GWMS: numerical analysis
- Steven Schramm (Universite de Geneve (CH))
GWMS
- Nicolas Produit (Universite de Geneve (CH))
GWMS: intensity interferometry
- Nicolas Produit (Universite de Geneve (CH))
The identification of gamma rays in coincidence with high-energy neutrinos has a fundamental importance in the multimessenger astronomy. This type of observations is essential for constraining the source localization, determining the source type and understanding the emission mechanisms. We investigate the Cherenkov Telescope Array Observatory (CTAO) prospects for detecting the...
Accretion shocks in the large-scale structure of the universe are promising sources of ultra-high-energy cosmic rays (UHECRs). In addition to accelerating UHECRs, these shocks should produce distinct multimessenger signatures, including synchrotron radio emission, gamma rays, and neutrinos. We investigate how a hierarchical shock acceleration frameworkโprogressing from supernova remnant...
Neutron star (NS) mergers are amongst the most promising multimessenger sources in the Universe, as demonstrated by the coincident detection of gravitational waves (GWs) with multi-wavelength electromagnetic (EM) radiation for GW170817. NS merger remnants are thought to launch relativistic jets which produce short gamma-ray bursts (sGRBs). However, the exact nature of the NS post-merger...
The recent announcement of the detection of the ultra-high-energy (UHE) neutrino event KM3-230213A by the KM3NeT telescope represents a critical opportunity to explore the origins of cosmic neutrinos and their potential gamma-ray counterparts. With an inferred neutrino energy exceeding 100 PeV, this event stands as the most energetic neutrino observed to date. The large offset from the...
The Pierre Auger Observatory is the largest air-shower detector in the world, offering unparalleled exposure to photons with energies above $5 \times 10^{16}$ eV.
Since the start of data collection almost two decades ago, numerous searches for photons have been conducted using the detection systems of the Observatory.
These searches have led to the most stringent upper limits on the diffuse...
The discovery of joint sources of high-energy neutrinos and gravitational waves has been a primary target for the LIGO, Virgo, KAGRA, and IceCube observatories. The joint detection of high-energy neutrinos and gravitational waves would provide insight into cosmic processes, such as progenitor dynamics and outflows. The joint detection of multiple cosmic messengers can also elevate the...
The blazar J1048+7143 (a.k.a. J1044+71) is a promising candidate for harboring a supermassive binary black hole (SMBBH) inspiral on the verge of merging. Its gamma-ray, optical, infrared and radio light curves show consistent quasi-periodic oscillations (QPOs) with a period of years. The flares in gamma rays, optical and infrared consist each of two subflares, while in radio, the emission...
Crystal Eye is a new concept of space-based all sky monitor for the observation of 10 keV - 30 MeV photons exploiting a novel detection technique, which foresees enhanced localization capability and functionality in an unprecedented energy range with respect to the current instruments. This is now possible, thanks to the use of new materials (scintillator crystals) and sensors (like Silicon...
Binary black holes (BBHs) in the vicinity of Active Galactic Nuclei (AGNs) are particularly interesting systems from both a cosmological and astrophysical point of view. Matter and radiation fields within the dense AGN environment could produce electromagnetic and neutrino emission in addition to gravitational waves (GWs). Moreover, interactions between BBHs and AGN accretion disks are...
We present recent results of the TELAMON program, which is using the Effelsberg 100-m telescope to monitor the radio spectra of active galactic nuclei (AGN) under scrutiny in astroparticle physics, namely TeV blazars and neutrino-associated AGN since 2020. The radio variability of these sources and its correlation with high-energy activity are studied based on the first five years of...
Multimessenger observations, combining electromagnetic radiation and neutrinos, offer critical insights into the high-energy processes occurring in astrophysical sources. Recent coincident detections of high-energy neutrinos from the direction of blazars highlight them as ideal candidates for multimessenger modeling, and at the same time underscore the necessity of accurate modeling frameworks...
Active Galactic Nuclei (AGN) and starburst galaxies are multimes-
senger sources in the Universe, emitting from radio/infrared energies
to gamma-ray and neutrino energies. NGC 1068 is a Seyfert II galaxy
with a starburst ring that has been proven to emit the neutrinos de-
tected by Icecube through hadronic processes most likely happening
in the AGN corona. Two high-energy neutrinos with...
The collapse of the core of a massive star at the end of its life can give rise to one of the most powerful phenomena in the Universe. Because of violent mass motions that take place during the explosion, Core Collapse Supernovae have been considered a potential source of detectable gravitational waveforms for decades. However, their intrinsic stochasticity makes almost impossible modeling and...
The IceCube Neutrino Observatory searches for the origins of astrophysical neutrinos using various techniques to overcome the significant backgrounds produced by cosmic-ray air showers. One such technique involves combining the neutrino data with other cosmic messengers to identify spatial and temporal correlations. IceCube contributes to multi-messenger astrophysics by providing alerts for...
The IceCube Neutrino Observatory actively participates in multi-messenger follow-ups of gravitational-wave (GW) events. With the release of the Gravitational-Wave Transient Catalog (GWTC)-2.1 and -3, the sub-threshold GW event information from the third observation run of the LIGO-Virgo-KAGRA (LVK) detectors is publicly available. These sub-threshold GWs are identified via template-based and...
The Einstein Telescope (ET), the third generation of gravitational wave detector is aimed at advancing multi-messenger astrophysics with strong synergy between current and future generation electromagnetic follow-up facilities, focusing mainly on the transients. Typically, the prompt emission from Gamma-ray bursts (GRBs) is observed within the 10 keV-10 MeV spectrum. However, detection at...
The detection of transient phenomena such as Gamma-Ray Bursts (GRBs), Fast Radio Bursts (FRBs), stellar flares, novae, and supernovaeโalongside novel cosmic messengers like high-energy neutrinos and gravitational wavesโhas transformed astrophysics in recent years. Maximizing the discovery potential of multi-messenger and multi-wavelength follow-up observations, as well as serendipitous...
The diffuse astrophysical neutrino flux measured in the very high energy range introduced unresolved issues about the origin of these events and underlined as a viable solution the multi-component scenario. Recent studies show that galaxies with high star formation rate (above teens Mo/year) can be responsible of a seizable fraction of the observed astrophysical flux. Despite their low...
We have shown in [1] that at ultra-high-energy (UHE) the Galactic diffuse gamma-ray emission is very patchy, due to the short residence time of cosmic rays in the Galaxy and the scarcity of Galactic PeVatrons. However, such a patchiness remains hard to firmly attribute to the diffuse component of the Galactic emission due to the presence of a population of unresolved pulsars whose contribution...
The IceCube Neutrino Observatory, located at the South Pole, covers a cubic kilometer of Antarctic ice, designed to detect astrophysical neutrinos in the TeV-PeV energy range. While IceCube has recently identified a diffuse flux of neutrinos originating from the Galactic Plane, specific sources of astrophysical neutrinos within the Milky Way remain elusive. Hadronic gamma-rays, produced...
Gamma-ray bright active galactic nuclei (AGN) have been one of the most promising source classes of high-energy astrophysical neutrinos detected by IceCube. The first evidence of an IceCube point source was a blazar detected by the Fermi Large Area Telescope (LAT), TXS 0506+056. Previous analyses have ruled out GeV-bright blazars as the predominant contributor to the high-energy astrophysical...
Binary neutron star (BNS) mergers are the source of most ultrahigh-energy cosmic rays, making them key astrophysical events for multi-messenger studies. The joint detection of gravitational waves (GW170817 by GW detectors) along with spatially coincident short gamma-ray burst (sGRB) GRB170817A has established a clear connection between BNS mergers and sGRBs. In our recent study, we investigate...
Abstract: The VERITAS Stellar Intensity Interferometer (VSII) uses an intensity interferometric technique to measure the angular extent of stellar envelopes of hot (OBA) stars and binary systems. VSII has previously demonstrated the ability to reconstruct the sub-milliarcsecond angular diameters of individual stellar photospheres (eps Ori, bet CMa, bet Uma) with a precision better than 5%....
Along with their gamma-ray observations at very high energies (VHE, 20 GeV - 100 TeV), the two 17-m MAGIC telescopes (at Roque de los Muchachos Observatory, La Palma, Spain) have also been utilized as an optical stellar intensity interferometer (SII) for the last six years. The calibration and validation of the setup, alongside the first measurement of the stellar angular diameter of 13...
The MAGIC telescopes are two imaging atmospheric Cherenkov telescopes (IACTs) located at the Roque de los Muchachos Observatory (La Palma, Spain). Many observations performed with a high night-sky background have been dedicated to stellar intensity interferometry (SII), since very-high-energy (VHE, 20 GeV - 100 TeV) gamma-ray observations have reduced sensitivity during these periods. The...
A resolved optical image of a gamma-ray emitter would be of enormous scientific interest. For gamma-ray sources associated with interacting stars (colliding winds or novae), stellar intensity interferometry (SII), envisioned as a second observing mode at the Cherenkov Telescope Array Observatory (CTAO), could yield images of the systems in visible light. Recent radius measurements of massive...
The quantum properties of a gas of bosons were predicted by Einstein 100 years ago. The first experimental measurements of its consequences were performed by Hanbury-Brown & Twiss in 1954, when measuring the size of bright stars by correlating the arrival times of photons detected by two optical telescopes. Extremely large telescopes, 10ps resolution single photon detectors bring the key...
Recent developments in single-photon avalanche diodes (SPADs) have lowered detector time resolution to under tens of picoseconds full width half maximum (FWHM). In 1956, the pioneer experiment of Hanbury Brown and Twiss (HBT) on measuring the sizes of bright stars was limited by the time resolution of their detectors and their telescope size. The QUASAR project aims at building SPAD-based...
