Quasi-periodic variations in X-ray emission and long-term radio observations: Evidence for a two-component jet in Sw J1644+57

Abstract

The continued observations of Sw J1644+57 in X-ray and radio bands accumulated a rich data set to study the relativistic jet launched in this tidal disruption event. The X-ray light curve of Sw J1644+57 from 5-30 days presents two kinds of quasi-periodic variations: a 200 s quasi-periodic oscillation (QPO) and a 2.7 day quasi-periodic variation. The latter has been interpreted by a precessing jet launched near the Bardeen-Petterson radius of a warped disk. Here we suggest that the ∼200 s QPO could be associated with a second, narrower jet sweeping the observer line-of-sight periodically, which is launched from a spinning black hole in the misaligned direction with respect to the black hole's angular momentum. In addition, we show that this two-component jet model can interpret the radio light curve of the event, especially the re-brightening feature starting ∼100 days after the trigger. From the data we infer that inner jet may have a Lorentz factor of Γj ∼ 5.5 and a kinetic energy of E k, iso ∼ 3.0 × 10⁵² erg, while the outer jet may have a Lorentz factor of Γj ∼ 2.5 and a kinetic energy of E k, iso ∼ 3.0 × 10⁵³ erg. © 2014. The American Astronomical Society. All rights reserved..