No Arabic abstract
The uncertainty region of the highly energetic neutrino IceCube200107A includes 3HSP J095507.9+355101 ($z$~=~0.557), an extreme blazar, which was detected in a high, very hard, and variable X-ray state shortly after the neutrino arrival. Following a detailed multi-wavelength investigation, we confirm that the source is a genuine BL Lac, contrary to TXS 0506+056, the first source so far associated with IceCube neutrinos, which is a masquerading BL Lac. As in the case of TXS0506+056, 3HSP J095507.9+355101 is also way off the so-called blazar sequence. We consider 3HSP J095507.9+355101 a possible counterpart to the IceCube neutrino. Finally, we discuss some theoretical implications in terms of neutrino production.
3HSP J095507.9+355101 is an extreme blazar which has been possibly associated with a high-energy neutrino (IceCube-200107A) detected one day before the blazar was found to undergo a hard X-ray flare. We perform a comprehensive study of the predicted multimessenger emission from 3HSP J095507.9+355101 during its recent X-ray flare, but also in the long term. We focus on one-zone leptohadronic models, but we also explore alternative scenarios: (i) a blazar-core model, which considers neutrino production in the inner jet, close to the supermassive black hole; (ii) a hidden external-photon model, which considers neutrino production in the jet through interactions with photons from a weak broad line region; (iii) a proton synchrotron model, where high-energy protons in the jet produce $gamma$-rays via synchrotron; and (iv) an intergalactic cascade scenario, where neutrinos are produced in the intergalactic medium by interactions of a high-energy cosmic-ray beam escaping the jet. The Poisson probability to detect one muon neutrino in ten years from 3HSP J095507.9+355101 with the real-time IceCube alert analysis is $sim 1%$ ($3%$) for the most optimistic one-zone leptohadronic model (the multi-zone blazar-core model). Meanwhile, detection of one neutrino during the 44-day-long high X-ray flux-state period following the neutrino detection is $0.06%$, according to our most optimistic leptohadronic model. The most promising scenarios for neutrino production also predict strong intra-source $gamma$-ray attenuation above $sim100$ GeV. If the association is real, then IceCube-Gen2 and other future detectors should be able to provide additional evidence for neutrino production in 3HSP J095507.9+355101 and other extreme blazars.
Individual astrophysical sources previously detected in 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 approximately 290 TeV. Its arrival direction was consistent with the location of a known gamma-ray blazar TXS 0506+056, observed to be in a flaring state. An extensive multi-wavelength campaign followed, ranging from radio frequencies to gamma-rays. These observations characterize the variability and energetics of the blazar and include the first detection of TXS 0506+056 in very-high-energy gamma-rays. This observation of a neutrino in spatial coincidence with a gamma-ray emitting blazar during an active phase suggests that blazars may be a source of high-energy neutrinos.
Recently the IceCube collaboration and 15 other collaborations reported the spatial and temporal coincidence between the neutrino event IceCube-170922A and the radio-TeV activity of the blazar TXS 0506+056. Their further analysis on 9.5 years of IceCube data discovered neutrino flare between September 2014 and March 2015, when TXS 0506+056 is however in quiescent state. We analyze the Fermi-LAT data in that direction, and find another bright GeV source PKS 0502+049, which is at an angle of $1.2^{circ}$ from TXS 0506+056, with strong activties during the neutrino flare. No other bright GeV source was detected in the region of interest. Though PKS 0502+049 is $1.2^circ$ separated from TXS 0506+056, it locates within the directional reconstruction uncertainties of 7 neutrinos, out of the 13 neutrino events during the neutrino flare. Together with the observed high flux of the $gamma$-ray flare, it may be unreasonable to fully discard the (partial) contribution of PKS 0502+049 to the neutrino flare. The single source assumption used in the neutrino data analysis might need to be revisited.
Although many high-energy neutrinos detected by the IceCube telescope are believed to have anextraterrestrial origin, their astrophysical sources remain a mystery. Recently, an unprecedenteddiscovery of a high-energy muon neutrino event coincident with a multiwavelength flare from ablazar, TXS 0506+056, shed some light on the origin of the neutrinos. It is usually believed that ablazar is produced by a relativistic jet launched from an accreting supermassive black hole (SMBH).Here we show that the high-energy neutrino event can be interpreted by the inelastic hadronuclearinteractions between the accelerated cosmic-ray protons in the relativistic jet and the dense gasclouds in the vicinity of the SMBH. Such a scenario only requires a moderate proton power in thejet, which could be much smaller than that required in the conventional hadronic model whichinstead calls upon the photomeson process. Meanwhile, the flux of the multiwavelength flare fromthe optical to gamma-ray band can be well explained by invoking a second radiation zone in thejet at a larger distance to the SMBH. In our model, the neutrino emission lasts a shorter time thanthe multiwavelength flare so the neutrino event is not necessarily correlated with the flare but it is probably accompanied by a spectrum hardening above a few GeV.
We present an all-sky search for muon neutrinos produced during the prompt $gamma$-ray emission of 1172 gamma-ray bursts (GRBs) with the IceCube Neutrino Observatory. The detection of these neutrinos would constitute evidence for ultra-high energy cosmic ray (UHECR) production in GRBs, as interactions between accelerated protons and the prompt $gamma$-ray field would yield charged pions, which decay to neutrinos. A previously reported search for muon neutrino tracks from Northern Hemisphere GRBs has been extended to include three additional years of IceCube data. A search for such tracks from Southern Hemisphere GRBs in five years of IceCube data has been introduced to enhance our sensitivity to the highest energy neutrinos. No significant correlation between neutrino events and observed GRBs is seen in the new data. Combining this result with previous muon neutrino track searches and a search for cascade signature events from all neutrino flavors, we obtain new constraints for single-zone fireball models of GRB neutrino and UHECR production.