Swift J1644+57: an ideal test bed of radiation mechanisms in a relativistic super-Eddington jet

Abstract

Within the first 10 days after Swift discovered the jetted tidal disruption event (TDE) Sw J1644+57, simultaneous observations in the radio, near-infrared, optical, X-ray and gammaray bands were carried out. These multiwavelength data provide a unique opportunity to constrain the emission mechanism and make-up of a relativistic super-Eddington jet. We consider an exhaustive variety of radiation mechanisms for the generation of X-rays in this TDE, and rule out many processes such as SSC, photospheric and proton synchrotron. The infrared to gamma-ray data for Sw J1644+57 are consistent with synchrotron and external-inverse-Compton (EIC) processes provided that electrons in the jet are continuously accelerated on a time scale shorter than ∼ 1% of the dynamical time to maintain a power-law distribution. The requirement of continuous electron acceleration points to magnetic reconnection in a Poynting flux dominated jet. The EIC process may require fine tuning to explain the observed temporal decay of the X-ray lightcurve, whereas the synchrotron process in a magnetic jet needs no fine tuning for this TDE.

Radiative interaction between the relativistic jet and optically thick envelope in tidal disruption events

“…(1) Many different radiation mechanisms for the γ/Xray continuum in Swift J1644+57 have been discussed by Crumley et al (2016). The leading candidates are synchrotron emission from electrons accelerated by magnetic reconnection and the external radiation being inverse-Compton scattered by electrons in the jet (hereafter EIC model).…”

Jets from Tidal Disruption Events

“…In the following, we consider three popular radiation mechanisms for the X-ray emission: synchrotron, synchrotron self-Compton (SSC), and external inverse-Compton (EIC). The discussion in this section mainly follows Crumley et al (2016). All quantities in the jet comoving frame are denoted with a prime ( ), and quantities without a prime are measured in the rest-frame of the BH (or host galaxy).…”

“…We conclude that SSC emission is not a viable mechanism for generating the X-rays from TDE jets. A more comprehensive study of the full parameter space is presented by Crumley et al (2016), where the authors show that the SSC scenario cannot avoid an excess at a different wavelength or requiring too much energy.…”

External inverse-Compton emission from jetted tidal disruption events

“…magnetic dissipations, see and Crumley et al (2015)), the EIC emission proposed in this work has typical luminosity of 10 45 − 10 48 erg s −1 and could be detected by current generation of X-ray telescopes up to high redshift z ∼ 1. Future wide field-of-view X-ray surveys, such as eROSITA (Merloni et al 2012), Einstein Probe, LOFT (Feroci et al 2012) will be able to find a large number of jetted TDEs and the EIC model could be tested.…”

“…One of the biggest puzzles in the two jetted TDEs Sw J1644+57 and Sw J2058+05 is the radiation mechanism of X-rays (see Crumley et al 2015, for a thorough discussion of X-ray generation processes in TDE jets) Is it possible that the X-rays are from EIC emission? Thermal emission from Sw J2058+05 is detected in near-IR, optical and UV bands (Cenko et al 2012;Pasham et al 2015), thanks to the small dust extinction in the host galaxy (AV 0.5 mag).…”