Fermi-LAT realtime follow-ups of high-energy neutrino alerts (original) (raw)
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Neutrino emission from the direction of the blazar TXS 0506+056 prior to the IceCube-170922A alert
Science (New York, N.Y.), 2018
A high-energy neutrino event detected by IceCube on 22 September 2017 was coincident in direction and time with a gamma-ray flare from the blazar TXS 0506+056. Prompted by this association, we investigated 9.5 years of IceCube neutrino observations to search for excess emission at the position of the blazar. We found an excess of high-energy neutrino events, with respect to atmospheric backgrounds, at that position between September 2014 and March 2015. Allowing for time-variable flux, this constitutes 3.5σ evidence for neutrino emission from the direction of TXS 0506+056, independent of and prior to the 2017 flaring episode. This suggests that blazars are identifiable sources of the high-energy astrophysical neutrino flux.
Search for a cumulative neutrino signal from blazar flares using IceCube data
Proceedings of 35th International Cosmic Ray Conference — PoS(ICRC2017)
Blazars are active galactic nuclei which have their relativistic particle jet pointing towards Earth and have been observed to emit gamma rays to very high energies. They are also candidates for the yet-unknown accelerators of ultra-high-energy cosmic rays. In such a scenario, their gamma-ray emission might be associated with neutrinos produced by hadronic interactions in the jet. Correlating the astrophysical neutrinos detected by IceCube, a cubic-kilometre neutrino telescope at the South Pole, with the gamma-ray emission from blazars could therefore reveal the origin of cosmic rays. In our method we focus on periods where blazars show an enhanced gamma-ray flux, as measured by Fermi, thereby reducing the background of the search. At the same time we test for the combined emission of a whole blazar population in a stacked search. A detection of such a neutrino flux could lead to the discovery of a source class responsible for cosmic-ray acceleration. We present sensitivities and discovery potentials for a selection of Fermi monitored sources and one year of IceCube data.
Multimessenger observations of a flaring blazar coincident with high-energy neutrino IceCube-170922A
Science (New York, N.Y.), 2018
Previous detections of individual astrophysical sources of neutrinos are limited to the Sun and the supernova 1987A, whereas the origins of the diffuse flux of high-energy cosmic neutrinos remain unidentified. On 22 September 2017, we detected a high-energy neutrino, IceCube-170922A, with an energy of ~290 tera-electron volts. Its arrival direction was consistent with the location of a known γ-ray blazar, TXS 0506+056, observed to be in a flaring state. An extensive multiwavelength campaign followed, ranging from radio frequencies to γ-rays. These observations characterize the variability and energetics of the blazar and include the detection of TXS 0506+056 in very-high-energy γ-rays. This observation of a neutrino in spatial coincidence with a γ-ray-emitting blazar during an active phase suggests that blazars may be a source of high-energy neutrinos.
Search for neutrino emission from gamma-ray flaring blazars with the ANTARES telescope
Astroparticle Physics, 2012
The ANTARES telescope is well-suited to detect neutrinos produced in astrophysical transient sources as it can observe a full hemisphere of the sky at all times with a high duty cycle. Radio-loud active galactic nuclei with jets pointing almost directly towards the observer, the so-called blazars, are particularly attractive potential neutrino point sources. The all-sky monitor LAT on board the Fermi satellite probes the variability of any given gamma-ray bright blazar in the sky on time scales of hours to months. Assuming hadronic models, a strong correlation between the gamma-ray and the neutrino fluxes is expected. Selecting a narrow time window on the assumed neutrino production period can significantly reduce the background.
Fermi blazars as candidate neutrino emitters: a study of temporal coincidence with IceCube events
2021
Multimessenger astronomy provides a unique tool for exploring the universe at the highest energies: the association between neutrinos and their astrophysical sources would constitute a powerful probe of the high-energy sky. In 2017, the neutrino event IceCube-170922A was found to be coincident in arrival time and direction with an enhanced γ-ray activity from the blazar TXS 0506+056 at redshift z ∼ 0.34, and it was associated to this source at the 3σ confidence level. This discovery motivates further research in the field of the blazar-neutrino connection. In this work, the temporal coincidence between the arrival times of IceCube neutrinos and the γ-ray (0.1 − 300 GeV) emission from a sample of Fermi-detected blazars is investigated. The spatial coincidence for the same sample had been investigated in a previous reference work. Different criteria for the definition of the flaring state of a source were adopted depending on the blazar class (HBL/IBL or LBL) and a subsample of 4 flar...
Multimessenger Gamma-Ray and Neutrino Coincidence Alerts Using HAWC and
Astrophysical Journal, 2021
The High Altitude Water Cerenkov (HAWC) and IceCube observatories, through the Astrophysical Multimessenger Observatory Network (AMON) framework, have developed a multimessenger joint search for extragalactic astrophysical sources. This analysis looks for sources that emit both cosmic neutrinos and gamma rays that are produced in photohadronic or hadronic interactions. The AMON system is running continuously, receiving subthreshold data (i.e., data that are not suited on their own to do astrophysical searches) from HAWC and IceCube, and combining them in real time. Here we present the analysis algorithm, as well as results from archival data collected between 2015 June and 2018 August, with a total live time of 3.0 yr. During this period we found two coincident events that have a false-alarm rate (FAR) of <1 coincidence yr–1, consistent with the background expectations. The real-time implementation of the analysis in the AMON system began on 2019 November 20 and issues alerts to the community through the Gamma-ray Coordinates Network with an FAR threshold of <4 coincidences yr–1.
Proceedings of 37th International Cosmic Ray Conference — PoS(ICRC2021)
Gamma-ray bursts (GRBs) are among the most powerful events observed in our universe and have long been considered as possible sources of ultra-high-energy cosmic rays, which makes them promising neutrino source candidates. Previous IceCube searches for neutrino correlations with GRBs focused on the prompt (main emission) phase of the GRB and found no significant correlation between neutrino events and the observed GRBs. This motivates us to extend our search beyond the prompt phase. We perform analyses looking for evidence of neutrino emission up to 14 days before and after the prompt phase of GRBs. These analyses rely on a sample of candidate muon-neutrino events observed by IceCube from May 2011 to October 2018. The analyses are model-independent. Two of them scan different time-windows for possible neutrino emission, while a third analysis targets precursor emission based on GRB precursor observations by Fermi-GBM. We discuss the results and implications of these searches including limits on the contribution of GRBs to the diffuse neutrino flux.
First search for neutrinos in correlation with gamma-ray bursts with the ANTARES neutrino telescope
Journal of Cosmology and Astroparticle Physics, 2013
A search for neutrino-induced muons in correlation with a selection of 40 gammaray bursts that occurred in 2007 has been performed with the ANTARES neutrino telescope. During that period, the detector consisted of 5 detection lines. The ANTARES neutrino telescope is sensitive to TeV-PeV neutrinos that are predicted from gamma-ray bursts. No events were found in correlation with the prompt photon emission of the gamma-ray bursts and upper limits have been placed on the flux and fluence of neutrinos for different models.