Tidally disrupted stars as a possible origin of both cosmic rays and neutrinos at the highest energies

Daniel Biehl,Cecilia Lunardini,Denise Boncioli,Walter Winter

doi:10.1038/s41598-018-29022-4

Daniel Biehl, Cecilia Lunardini + Show 2 more

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https://doi.org/10.1038/s41598-018-29022-4

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Abstract

Tidal Disruption Events (TDEs) are processes where stars are torn apart by the strong gravitational force near to a massive or supermassive black hole. If a jet is launched in such a process, particle acceleration may take place in internal shocks. We demonstrate that jetted TDEs can simultaneously describe the observed neutrino and cosmic ray fluxes at the highest energies if stars with heavier compositions, such as carbon-oxygen white dwarfs, are tidally disrupted and these events are sufficiently abundant. We simulate the photo-hadronic interactions both in the TDE jet and in the propagation through the extragalactic space and we show that the simultaneous description of Ultra-High Energy Cosmic Ray (UHECR) and PeV neutrino data implies that a nuclear cascade in the jet is developed by photo-hadronic interactions.

Highlights

The discovery of high-energy (~0.1–1 PeV) astrophysical neutrinos[1] has triggered substantial research on their possible origin
This pure injection composition has been found to approximate the results obtained with a mixed carbon-oxygen (C-O) injection, which might be expected in the disruption of a C-O white dwarfs (WD)
Note that for the Ultra-High Energy Cosmic Ray (UHECR) data the statistical errors are smaller than the systematics ones; we find that the 99.99% CL region in Fig. 2 is wide enough to be representative of the fit results that can be obtained if systematics are included

Summary

Introduction

The discovery of high-energy (~0.1–1 PeV) astrophysical neutrinos[1] has triggered substantial research on their possible origin These neutrinos come probably from outside our galaxy, and can naturally arise from a flux of parent protons or nuclei. Three jet-hosting (“jetted”) TDEs have been robustly identified in X-rays observations[22,23,24] (see also25,26), with the best observed one being Swift J1644 + 5722 Overall, they are consistent with a supermassive black hole (SMBH, M > 105M ) disrupting a main sequence star[22,27]. Refs[28,34] focused on the recent observation of a mixed nuclear composition of UHECRs by the Pierre Auger Observatory[36] They discussed how TDEs offer an attractive and natural explanation of the composition if the disrupted stars have mid-to-heavy compositions. The nuclear cascade in the source is modeled explicitly, using techniques that have been successfully applied before to GRBs37,38

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