Search for: All records

Abstract When a star undergoes core collapse, a vast amount of energy is released in a ∼10 s long burst of neutrinos of all species. Inverse beta decay in the star’s hydrogen envelope causes an electromagnetic cascade that ultimately results in a flare of gamma rays—an “echo” of the neutrino burst—at the characteristic energy of 0.511 MeV. We study the phenomenology and detectability of this flare. Its luminosity curve is characterized by a fast, seconds-long rise and an equally fast decline, with a minute- or hour-long plateau in between. For a near-Earth star (distanceD≲ 1 kpc) the echo will be observable at near future gamma-ray telescopes with an effective area of 10³cm²or larger. Its observation will inform us on the envelope size and composition. In conjunction with the direct detection of the neutrino burst, it will also give information on the neutrino emission away from the line of sight and will enable tests of neutrino propagation effects between the stellar surface and Earth. 

Abstract We discuss the possible association of an astrophysical neutrino (IC220405B) with the recently reported, extremely energetic tidal disruption event (TDE) candidate AT2021lwx (ZTF20abrbeie, aka “Scary Barbie”) at redshiftz= 0.995. Although the TDE is about 2.°6 off the direction of the reconstructed neutrino event (outside the 90% confidence level localization region), the TDE candidate shares some important characteristics with so-far-reported neutrino–TDE associations: a strong infrared dust echo, high bolometric luminosity, a neutrino time delay with respect to the peak mass accretion rate of the order of a hundred days, and a high observed X-ray luminosity. We interpret this new association using an isotropic emission model, where neutrinos are produced by the collision of accelerated protons with infrared photons. After accounting for the high redshift of AT2021lwx (by interpreting the data in the supermassive black hole (SMBH) frame), we find that the expected neutrino fluences and neutrino time delays are qualitatively comparable to the other TDEs. Since data are only available up to 300 days postpeak in the SMBH frame, significant uncertainties exist in the dust echo interpretation, and therefore in the predicted number of neutrinos detected, ${\mathcal{N}}_{\nu }\simeq 3.0\times {10}^{-3}-0.012$. We recommend further follow-up of this object for an extended period and suggest refining the reconstruction of the neutrino arrival direction in this particular case. 

Heavy sterile neutrinos can be produced in core-collapse supernovae (CCSNe), which are superb particle generators because of their high densities and temperatures. If the sterile neutrinos are long-lived, these may be produced inside the supernova core and escape the stellar envelope, later decaying into SM particles like photons and neutrinos. In this work, we first improve the original analytical calculation of the γ-ray fluxes from decays. We then revisit the bounds on the sterile neutrino parameter space from the non-observation of γ -rays from SN1987A by the Solar Maximum Mission (SMM) and constraints from the diffuse γ -ray background arising from sterile neutrino decays. We find that the constraints arising from both the SMM data and the diffuse γ -ray background are weaker than those that have previously appeared in the recent literature. Finally, we study the sensitivity of several present and near-future γ -ray telescopes such as e-ASTROGAM and Fermi-LAT, assuming a nearby future galactic CCSN. We show that future observations can probe mixing angles as low as |U_τ/μ4|²∼ 5 × 10^-17. 

Whitepaper for the 2023 NSAC Long Range Plan