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ABSTRACT Recent radio observations and coincident neutrino detections suggest that some tidal disruption events (TDEs) exhibit late-time activities, relative to the optical emission peak, and these may be due to delayed outflows launched from the central supermassive black hole. We investigate the possibility that jets launched with a time delay of days to months, interact with a debris that may expand outwards. We discuss the effects of the time delay and expansion velocity on the outcomes of jet breakout and collimation. We find that a jet with an isotropic-equivalent luminosity of $$\lesssim 5 \times 10^{45}\, {\rm erg\, s}^{-1}$$ is likely to be choked for a delay time of $$\sim 3$$ months. We also study the observational signatures of such delayed choked jets. The jet–debris interaction preceding the breakout would lead to particle acceleration and the resulting synchrotron emission can be detected by current and near-future radio, optical and X-ray telescopes, and the expanding jet-driven debris could explain late-time radio emission. We discuss high-energy neutrino production in delayed choked jets, and the time delay can significantly alleviate the difficulty of the hidden jet scenario in explaining neutrino coincidences. 

Abstract Using general relativistic neutrino-radiation hydrodynamics simulations with the multi-group M1 scheme in one dimension, we investigate the collapse of massive, fully convective, and non-rotating white dwarfs (WDs), which are formed by accretion-induced collapse or merger-induced collapse, and the subsequent explosion. We produce initial WDs in hydrostatic equilibrium, which have super-Chandrasekhar mass and are about to collapse. The WDs have masses of $$1.6\, M_{\odot }$$ with different initial central densities specifically at $$1.0\times 10^{10}$$, $$4.0\times 10^{9}$$, $$2.0\times 10^{9}$$, and $$1.0\times 10^{9}\:\mbox{g}\:\mbox{cm}^{-3}$$. First, we examine the stability of initial WD in case weak interactions are turned off. Secondly, we calculate the collapse of WDs with weak interactions. We employ hydrodynamics simulations with Newtonian gravity in the first and second steps. Thirdly, we calculate the formation of neutron stars and accompanying explosions with general relativistic simulations. As a result, WDs with the highest density of $$10^{10}\:\mbox{g}\:\mbox{cm}^{-3}$$ collapse not by weak interactions but by the photodissociation of the iron, and three WDs with low central densities collapse by the electron capture as expected at the second step and succeed in the explosion with a small explosion energy of $$\sim\! 10^{48}\:$$erg at the third step. By changing the surrounding environment of WDs, we find that there is a minimum value of ejecta masses, which is $$\sim\! 10^{-5}\, M_{\odot }$$. With the most elaborate simulations of this kind so far, this value is one to two orders of magnitude smaller than previously reported values and is compatible with the estimated ejecta mass from FRB 121102. 

ABSTRACT Very-high-energy (VHE) photons around TeV energies from a gamma-ray burst (GRB) jet will play an essential role in the multimessenger era, with a fair fraction of the events being observed off-axis to the jet. We show that different energy photons (MeV and TeV photons in particular) arrive from different emission zones for off-axis observers even if the emission radius is the same. The location of the emission region depends on the jet structure of the surface brightness, and the structures are generally different at different energies, mainly due to the attenuation of VHE photons by electron–positron pair creation. This off-axis zone-shift effect does not justify the usual assumption of the one emission zone at a certain radius and also produces a time delay of VHE photons comparable to the GRB duration, which is crucial for future VHE observations, such as by the Cherenkov Telescope Array. 

Abstract Growing evidence from multiwavelength observations of extragalactic supernovae (SNe) has established the presence of dense circumstellar material in Type II SNe. Interaction between the SN ejecta and the circumstellar material should lead to diffusive shock acceleration of cosmic rays and associated high-energy emission. Observation of high-energy neutrinos along with the MeV neutrinos from SNe will provide unprecedented opportunities to understand unanswered questions in cosmic-ray and neutrino physics. We show that current and future neutrino detectors can identify high-energy neutrinos from an extragalactic SN in the neighborhood of the Milky Way. We present the prospects for detecting high-energy neutrino minibursts from SNe in known local galaxies, and demonstrate how the network of multiple high-energy neutrino detectors will extend the horizon for the identification of high-energy SN neutrinos. We also discuss high-energy neutrino emission from SN 2023ixf. 

Abstract High-energy neutrino andγ-ray emission has been observed from the Galactic plane, which may come from individual sources and/or diffuse cosmic rays. We evaluate the contribution of these two components through the multimessenger connection between neutrinos andγ-rays in hadronic interactions. We derive maximum fluxes of neutrino emission from the Galactic plane usingγ-ray catalogs, including 4FGL, HGPS, 3HWC, and 1LHAASO, and measurements of the Galactic diffuse emission by Tibet ASγand LHAASO. We find that the IceCube Galactic neutrino flux is larger than the contribution from all resolved sources when excluding promising leptonic sources such as pulsars, pulsar wind nebulae, and TeV halos. Our result indicates that the Galactic neutrino emission is likely dominated by the diffuse emission by the cosmic-ray sea and unresolved hadronicγ-ray sources. In addition, the IceCube flux is comparable to the sum of the flux of nonpulsar sources and the LHAASO diffuse emission especially above ∼30 TeV. This implies that the LHAASO diffuse emission may dominantly originate from hadronic interactions, either as the truly diffuse emission or unresolved hadronic emitters. Future observations of neutrino telescopes and air-showerγ-ray experiments in the Southern hemisphere are needed to accurately disentangle the source and diffuse emission of the Milky Way. 

Abstract The recent detection of high-energy neutrinos by IceCube in the direction of the nearby Seyfert/starburst galaxy NGC 1068 implies that radio-quiet active galactic nuclei can accelerate cosmic-ray ions. Dedicated multimessenger analyses suggest that the interaction of these high-energy ions with ambient gas or photons happens in a region of the galaxy that is highly opaque for GeV–TeV gamma rays. Otherwise, the GeV–TeV emission would violate existing constraints provided by the Fermi Large Area Telescope (LAT) and the Major Atmospheric Gamma Imaging Cherenkov. The conditions of high optical depth are realized near the central supermassive black hole (SMBH). At the same time, the GeV emission detected by the Fermi LAT is likely related to the galaxy’s sustained star formation activity. In this work, we derive a 20 MeV–1 TeV spectrum of NGC 1068 using 14 yr of Fermi LAT observations. We find that the starburst hadronic component is responsible for NGC 1068's emission above ∼500 MeV. However, below this energy, an additional component is required. In the 20–500 MeV range, the Fermi LAT data are consistent with hadronic emission initiated by non-thermal ions interacting with gas or photons in the vicinity of the central SMBH. This highlights the importance of the MeV band to discover hidden cosmic-ray accelerators. 

Multiwavelength observations have revealed that dense, confined circumstellar material (CCSM) commonly exists in the vicinity of supernova (SN) progenitors, suggesting enhanced mass losses years to centuries before their core collapse. Interacting SNe, which are powered or aided by interaction with the CCSM, are considered to be promising high-energy multimessenger transient sources. We present detailed results of broadband electromagnetic emission, following the time-dependent model proposed in the previous work on high-energy SN neutrinos [K. Murase, New prospects for detecting high-energy neutrinos from nearby supernovae, ]. We investigate electromagnetic cascades in the presence of Coulomb losses, including inverse-Compton and synchrotron components that significantly contribute to MeV and high-frequency radio bands, respectively. We also discuss the application to SN 2023ixf. Published by the American Physical Society2024 

Recent observations of high-energy neutrinos from active galactic nuclei (AGN), NGC 1068 and TXS $0506+056$ , suggest that cosmic rays (CRs) are accelerated in the vicinity of the central supermassive black hole and high-energy protons and electrons can cool efficiently via interactions with ambient photons and gas. The dark matter density may be significantly enhanced near the black hole, and CRs could lose energies predominantly due to scatterings with the ambient dark matter particles. We propose CR cooling in AGN as a new probe of dark matter-proton and dark matter-electron scatterings. Under plausible astrophysical assumptions, our constraints on sub-GeV dark matter can be the strongest derived to date. Some of the parameter space favored by thermal light dark matter models might already be probed with current multimessenger observations of AGN. Published by the American Physical Society2024 

Abstract Gamma-ray flares of blazars may be accompanied by high-energy neutrinos due to interactions of high-energy cosmic rays in the jet with photons, as suggested by the detection of the high-energy neutrino IceCube-170922A during a major gamma-ray flare from blazar TXS 0506+056 at the ∼3σsignificance level. In this work, we present a statistical study of gamma-ray emission from blazars to constrain the contribution of gamma-ray flares to their neutrino output. We construct weekly binned light curves for 145 gamma-ray bright blazars in the Fermi Large Area Telescope Monitored Source List adding TXS 0506+056. We derive the fraction of time spent in the flaring state (flare duty cycle) and the fraction of energy released during each flare from the light curves with a Bayesian blocks algorithm. We find that blazars with lower flare duty cycles and energy fractions are more numerous among our sample. We identify a significant difference in flare duty cycles between blazar subclasses at a significance level of 5%. Then using a general scaling relation for the neutrino and gamma-ray luminosities, $L_{\nu }\propto {\left(L_{\gamma }\right)}^{\gamma }$ with a weighting exponent ofγ= 1.0–2.0, normalized to the quiescent gamma-ray or X-ray flux of each blazar, we evaluate the neutrino energy flux of each gamma-ray flare. The gamma-ray flare distribution indicates that blazar neutrino emission may be dominated by flares forγ≳ 1.5. The neutrino energy fluxes for 1 week and 10 yr bins are compared with the decl.-dependent IceCube sensitivity to constrain the standard neutrino emission models for gamma-ray flares. Finally, we present the upper-limit contribution of blazar gamma-ray flares to the isotropic diffuse neutrino flux.