Investigating neutrino production in Swift J1644+57

Abstract

The recent detection of astrophysical very-high-energy neutrinos by IceCube has spurred an intensive search for their sources. As possible sources of VHE neutrinos, tidal disruption events (TDEs) have been suggested. Here we investigate a jetted TDE - Swift J1644+57 which is the best measured TDE in multiple wavebands - as a candidate astrophysical neutrino source. TDEs occur when a star approaches a mas-sive black hole located at the centre of a galaxy. If the tidal radius is larger than the Swarzschild radius of the super massive black hole (SMBH) this leads to tidal forces violently disrupting the star. Matter accretes on the SMBH and produces luminous and long-lasting flares. We investigate the neutrino production in the TDE emission region using a hadronic code. This is done through a parameter study based on fits to the spectral energy distribution (SED) of the source, evaluating the expected neu-trino detection rate by IceCube. We explore how the expected neutrino detection rate depends on various parameters. The radiation transfer code produced the required fits for B = 60, 70, 80, 90 and 100 G with blob radius varying from Rblob = 10¹⁵, 10¹⁶ to 10¹⁷ cm. All the model fits in this study require bulk kinetic jet powers in the relativistic protons in the range Lp ∼ 10⁴⁷ − 10⁵²erg.s⁻¹. In the parameter study we noticed that when we set constant Rblob = 10¹⁵cm the neutrino detection probability is tν = 1 × 10⁻⁷ and tν = 2 × 10⁻⁸ for B = 60G and B = 100G, respectively. The parameter study shows that there is an anti-correlation between the magnetic field and the neutrino detection probability. Our study suggests that X-ray bright jetted TDEs are weak neutrino producing sites.