Neutrino Emissions from Tidal Disruption Remnants

Abstract

We study high-energy neutrino emissions from tidal disruption remnants around supermassive black holes (SMBHs). The neutrinos are produced by the decay of charged pions originated in ultra-relativistic protons which are accelerated there. In the standard theory of tidal disruption events (TDEs), there are four distinct phases from circularization of stellar debris to superand sub-Eddington accretion flows to radiatively inefficient accretion flows (RI-AFs). In addition, we consider the magnetically arrested disk (MAD) state in both the super-Eddington accretion and RIAF phases. We find that there are three promising cases to produce neutrino emissions: the super-Eddington accretion phase with the MAD state and the RIAF phase with both non-MAD and MAD states. In the super-Eddington MAD state, the enhanced magnetic field makes it possible to accelerate the protons up to an energy of E p,max ∼ 0.35 PeV (M bh /10 7.7 M ⊙ ) 41/48 with the other given appropriate parameters. The neutrino energy estimated at the peak of the energy spectrum is then E ν,pk ∼ 67 TeV (M bh /10 7.7 M ⊙ ) 41/48 . For M bh 10 7.7 M ⊙ , the neutrino light curve is proportional to t −65/24 , while it follows the standard t −5/3 decay rate for M bh < 10 7.7 M ⊙ . In both cases, the neutrino luminosity is nearly Eddington. Such a high luminosity and characteristic light curve diagnose the MAD state in TDEs. In the RIAF phase, we find E p,max ∼ 0.45 PeV (M bh /10 7 M ⊙ ) 5/3 and E ν,pk ∼ 0.35 PeV (M bh /10 7 M ⊙ ) 5/3 , and its light curve is proportional to t −10/3 . This indicates one can identify if the existed RIAFs are the TDE origin or not.Although E p,max ∼ 25 PeV (M bh /10 7 M ⊙ ) −1/12 in the RIAF with the MAD state, the resultant neutrino luminosity is too weak to be detected with IceCube. The tidal disruption remnants are potentially a population of hidden neutrino sources invisible in gamma rays.

Tidal Disruption Events and High-energy Neutrinos

“…ii The accretion disk [43] iii The disk corona [46] iv The wind/outflow [46] In general, models agree that the conditions appear consistent with requirements for both PeV neutrino production, and the subsequent detection of a neutrino alert from such a TDE with IceCube. The observations thus suggest that the TDE population contributes to the astrophysical neutrino flux, though the ZTF observations would be compatible with a contribution as small as 2% of the astrophysical neutrino alerts [28].…”

“…These are checked to see whether they belong to populations that have been proposed as possible cosmic-ray and neutrino sources. Such populations include Gamma-Ray Bursts (GRBs) [32], supernovae with evidence of circumstellar medium interaction [33] or choked jets [34], Active Galactic Nuclei (AGN) [35] and in particular blazars [36], and TDEs [37][38][39][40][41][42][43][44][45][46][47]. Right: Properties of the neutrinos observed in that period, from [28].…”

“…TDEs have been long-predicted to be sources of cosmic rays and neutrinos [37][38][39][40][41][42][43][44][45][46][47], and were thus always a prime target of our ZTF neutrino follow-up program [10]. However, in light of the identification of AT2019dsg as a probable neutrino source, numerous models have been updated to reflect our increased knowledge of TDEs and their observational properties.…”

A concordance scenario for the observed neutrino from a tidal disruption event

“…We conclude that TDEs might be a promising class of neutrino emitters. While we have presented only one model here, other possibilities are conceivable, such as the interaction of an isotropic outflow with UV photons 17 , non-relativistic shocks forming in the environment 29 or a neutrino production from the accretion disk itself, especially radiatively inefficient accretion flows or magnetically arrested disk states 14 ; the neutrino production may also happen in a hot corona similar to that of an active galactic nucleus (AGN) 30 . Our model is unique in that we have emphasized the connection to the X-ray observations, we have described the late, post-peak neutrino observation, and we have obtained a sufficiently high neutrino fluence to describe the observations in spite of a relatively small assumed SMBH mass.…”

Theoretical interpretation of the observed neutrino emission from Tidal Disruption Events

“…In addition, radio emission -nearly constant over 90 days -was found, and was interpreted as due to a mildly relativistic outflow. Theoretical interpretations speculate that the abundant UV photons could be a target for the neutrino production [2], whereas other possible production sites include a disk corona or hidden winds, possibly induced by collisions among tidal streams [3], or the disk itself [4]. Our recent work, Ref.…”