Deep spectroscopy of the M-V similar to-14.8 host galaxy of a tidal disruption flare in A1795


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 disc-instability flare from a weak active galactic nucleus (AGN) could not be dismissed. We have now obtained 8 h of Gemini spectroscopy which unambiguously demonstrates that the host galaxy is indeed an extremely low mass (M-star similar to 3 x 10(8) M-circle dot) 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 (log[M-lozenge/M-circle dot] similar to 5.3-5.7) and infer a 15 yr X-ray variability of a factor of greater than or similar to 10(4). 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.

galaxies: clusters: individual: Abell 1795, galaxies: distances and redshifts, galaxies: dwarf, galaxies: kinematics and dynamics, galaxies: nuclei, X-rays: bursts, MASSIVE BLACK-HOLES, STELLAR POPULATION SYNTHESIS, SCALING RELATIONS, GLOBULAR-CLUSTER, EMISSION-LINES, WHITE-DWARFS, ABELL 1795, X-RAY, SPECTRA, STARS, Astronomy & Astrophysics
Maksym, W. et al. (2014): Deep spectroscopy of the MV ∼ −14.8 host galaxy of a tidal disruption flare in A1795. Monthly Notices of the Royal Astronomical Society, 444(1). DOI: