GRB060218 as a tidal disruption of a white dwarf by an intermediate-mass black hole

Roman V. Shcherbakov, Asaf Pe'Er, Christopher S. Reynolds, Roland Haas, Tanja Bode, Pablo Laguna

Research output: Contribution to journalArticlepeer-review

Abstract

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'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 in a tidal disruption provides a good fit to the soft X-ray light curve. The IMBH mass is found to be about 104 M in three independent estimates: (1) fitting the tidal disruption 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'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.

Original languageEnglish (US)
Article number85
JournalAstrophysical Journal
Volume769
Issue number2
DOIs
StatePublished - Jun 1 2013
Externally publishedYes

Keywords

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

ASJC Scopus subject areas

  • Astronomy and Astrophysics
  • Space and Planetary Science

Fingerprint

Dive into the research topics of 'GRB060218 as a tidal disruption of a white dwarf by an intermediate-mass black hole'. Together they form a unique fingerprint.

Cite this