Relativistic jet activity from the tidal disruption of a star by a massive black hole

Abstract

Supermassive black holes have powerful gravitational fields with strong gradients that can destroy stars that get too close, producing a bright flare in ultraviolet and X-ray spectral regions from stellar debris that forms an accretion disk around the black hole. The aftermath of this process may have been seen several times over the past two decades in the form of sparsely sampled, slowly fading emission from distant galaxies, but the onset of the stellar disruption event has not hitherto been observed. Here we report observations of a bright X-ray flare from the extragalactic transient Swift J164449.3+573451. This source increased in brightness in the X-ray band by a factor of at least 10,000 since 1990 and by a factor of at least 100 since early 2010. We conclude that we have captured the onset of relativistic jet activity from a supermassive black hole. A companion paper comes to similar conclusions on the basis of radio observations. This event is probably due to the tidal disruption of a star falling into a supermassive black hole, but the detailed behaviour differs from current theoretical models of such events.

DISCOVERY OF AN OUTFLOW FROM RADIO OBSERVATIONS OF THE TIDAL DISRUPTION EVENT ASASSN-14li

“…We conclude with several important implications of our results. First, the velocity and kinetic energy of the outflow in ASASSN14li are significantly lower than inferred for the two relativistic γ-ray TDEs previously detected in the radio (Figure 6), which represent  a few percent of the TDE population (Bloom et al 2011;Burrows et al 2011;Zauderer et al 2011;Mimica et al 2015). Although the TDE sample with detected radio emission is small, this is reminiscent of the same relation observed in Type Ib/c core-collapse supernovae (Type Ib/c SNe) and long-duration gamma-ray bursts (LGRBs), in which a small fraction of events (LGRBs: ∼1% by volumetric rate) produce energetic relativistic outflows while the bulk of the population (Type Ib/c SNe) produces lower energy non-relativistic outflows ( Figure 6; Margutti et al 2014).…”

“…Theoretical calculations indicate that most tidal disruption events (TDEs) lead to superEddington fallback, which in turn drives outflows (Rees 1988;Evans & Kochanek 1989;Strubbe & Quataert 2009;Guillochon & Ramirez-Ruiz 2013). The discovery of luminous radio emission from the γ-ray TDE Sw J1644+57 revealed the formation of a relativistic jetted outflow (Zauderer et al 2011;Berger et al 2012), but such events represent at most a few percent of the TDE population (Bloom et al 2011;Burrows et al 2011;Zauderer et al 2011;Mimica et al 2015). While the sample of well-studied TDE candidates has expanded greatly in recent years, direct evidence for outflows in the bulk of the TDE population, discovered through optical, ultraviolet (UV), and X-ray observations, has been lacking.…”

Radio Counterparts of Compact Binary Mergers Detectable in Gravitational Waves: A Simulation for an Optimized Survey

“…The areal densities of type Ibc supernovae(SNe Ibc; Berger et al 2003;Soderberg et al 2006b), low-luminosity GRBs(LLGRB; Soderberg et al 2006a;Barniol Duran et al 2015), and tidal disruption events(TDEs) without strong jets Holoien et al 2015;van Velzen et al 2016) are so small that it will be quite rare to detect them as false positive transients. Although off-axis long GRBs(LGRBs; van Eerten et al 2010; Ghirlanda et al 2014) and tidal disruption events with strong jets (TDE(jet); Burrows et al 2011;Zauderer et al 2011;Berger et al 2012) can be false positive transients, they will be identified earlier through their optical counterparts or can be filtered by identifying their host galaxies since the typical distance of these events is far beyond the detectable distance of the GW networks.…”

Discovery of a tidal disruption event candidate from the 2XMM catalog

“…This is not seen in BH X-ray binaries in the thermal state and may be intrinsic to TDEs. Although the TDE candidate Swift J164449.3+573451 also showed large fast variability, its origin is not so clear and can be produced in the jet [15] or due to fast variations in the mass accretion rate as above [25]. The fast variability is seldom studied for other TDE candidates, due to their lack of X-ray data of high quality.…”

“…Most TDE candidates more or less show the above properties. Swift J164449.3+573451 and Swift J2058.4+0516 are two exceptions, which are hard X-ray transients and are probably due to observation of a relativistic jet pointed toward us [15][16][17].…”