2014/08/22 by W. P. Maksym, W. Peter Maksym, M. P. Ulmer +10 · 4 citations
Physics and Astronomy · #Astrophysical Phenomena and Observations #Galaxies: Formation, Evolution, Phenomena #Gamma-ray bursts and supernovae
paper · doi:10.1093/mnras/stu1485
A likely tidal disruption of a star by the intermediate-mass black hole (IMBH) of a dwarf galaxy was recently identified in association with Abell 1795. Without deep spectroscopy for this very faint object, however, the possibility of a more massive background galaxy or even a disk-instability flare from a weak AGN could not be dismissed. We have now obtained 8 hours of Gemini spectroscopy which unambiguously demonstrate that the host galaxy is indeed an extremely low-mass (M_∗∼ 3× 108 \rm M\odot) galaxy in Abell 1795, comparable to the least-massive galaxies determined to host IMBHs via other studies. We find that the spectrum is consistent with the X-ray flare being due to a tidal disruption event rather than an AGN flare. We also set improved limits on the black hole mass (\rm log[M\bullet/\rm M\odot] ∼ 5.3 - 5.7) and infer a 15-year X-ray variability of a factor of > 104. The confirmation of this galaxy-black hole system provides a glimpse into a population of galaxies that is otherwise difficult to study, due to the galaxies' low masses and intrinsic faintness, but which may be important contributors to the tidal disruption rate.