GRB060218 AS A TIDAL DISRUPTION OF A WHITE DWARF BY AN INTERMEDIATE-MASS BLACK HOLE

作者：Shcherbakov Roman V^*; Pe' er Asaf; Reynolds Christopher S; Haas Roland; Bode Tanja; Laguna Pablo

来源：Astrophysical Journal, 2013, 769(2): UNSP 85.

DOI：10.1088/0004-637X/769/2/85

• accretion, accretion disks
• black hole physics
• radiation mechanisms: general
• supernovae: general
• X-rays: bursts
• X-rays: individual (GRB060218)

The highly unusual pair of a gamma-ray burst (GRB) GRB060218 and an associated supernova, SN2006aj, has puzzled theorists for years. A supernova shock breakout and a jet from a newborn stellar mass compact object have been proposed to explain this pair%26apos;s multiwavelength signature. Alternatively, we propose that the source is naturally explained by another channel: the tidal disruption of a white dwarf (WD) by an intermediate-mass black hole (IMBH). This tidal disruption is accompanied by a tidal pinching, which leads to the ignition of a WD and a supernova. Some debris falls back onto the IMBH, forms a disk, which quickly amplifies the magnetic field, and launches a jet. We successfully fit soft X-ray spectra with the Comptonized blackbody emission from a jet photosphere. The optical/UV emission is consistent with self-absorbed synchrotron emission from the expanding jet front. The temporal dependence of the accretion rate (M) over dot(t) in a tidal disruption provides a good fit to the soft X-ray light curve. The IMBH mass is found to be about 10(4) M-circle dot in three independent estimates: (1) fitting the tidal disruption (M) over dot(t) to the soft X-ray light curve, (2) computing the jet base radius in a jet photospheric emission model, and (3) inferring the mass of the central black hole based on the host dwarf galaxy%26apos;s stellar mass. The position of the supernova is consistent with the center of the host galaxy, while the low supernova ejecta mass is consistent with that of a WD. The high expected rate of tidal disruptions in dwarf galaxies is consistent with one source observed by the Swift satellite over several years at a distance of 150 Mpc measured for GRB060218. Encounters with WDs provide much fuel for the growth of IMBHs.

• 出版日期2013-6-1