RBS 1032: a dwarf-nucleated spheroidal galaxy with an intermediate-mass black hole hosted in a globular cluster

Abstract

We report here the multiwavelength observations of the bright supersoft X‐ray source, RBS 1032. Most likely, its optical counterpart is a non‐emission‐line dwarf galaxy with a prominent nucleus. Line and band indices of this nucleus, clearly suggest that its optical spectrum is dominated by the nuclear supermassive globular clusters. No radio and infrared (IRAS) emissions are detected from this dwarf galaxy. Weak near‐infrared (2MASS) emissions have been detected. The optical‐to‐near‐infrared colours are consistent with the globular clusters than those of active galactic nuclei. We have shown here that RBS 1032 is not a foreground object. However, with the available data the possibility of RBS 1032 being a classical nova cannot be completely ruled out. We have demonstrated that RBS 1032 is not a X‐ray‐bright optically normal galaxy. In contrast, we have illustrated that the super‐soft X‐ray emissions of RBS 1032 may be from a binary system, consisting of an intermediate‐mass (∼5 × 104 M⊙) black hole with a white dwarf companion. Most likely this system is hosted by one of the nuclear globular clusters of the dwarf galaxy.

RBS 1032: A Tidal Disruption Event in Another Dwarf Galaxy?

“…In order to evaluate the applicability of such decay models, we consider the plausible M • range. Ghosh et al (2006) When n for L X ∝ t −n is left free, we find n = 2.5 ± 1.3, which is closer to the Guillochon & Ramirez-Ruiz (2013) suggestion of t −2.2 for a surviving stellar core than to the Keplerian n = 5/3 value, but compatible with both.…”

“…If so, the Ghosh et al (2006) attribution of RBS 1032 to SDSS J114726.69+494257.8 is likely correct.…”

“…We used XSPEC 6 to fit the spectra to zbbody, zpowerlw, and diskbb models, in order to compare to the analysis of ROSAT data by Ghosh et al (2006). With only ∼17 net PN counts (32 total), meaningful constraint of N H is not possible.…”

“…The optical counterpart was initially suggested to be a star by Zickgraf et al (2003). Later work by Ghosh et al (2006) using the Sloan Digital Sky Survey (Ahn et al 2014), the Russian-Turkish 1.5 m telescope in Anatalya, Turkey, and the 6 m telescope of the Special Astrophysical Observatory in Russia, however, showed the most likely optical counterpart to be a dwarf galaxy at z ∼ 0.026 without emission lines, SDSS J114726.69+494257.8. They considered, and rejected as unlikely, numerous possible explanations for the Xray emission.…”

XMMSL1J063045.9-603110: a tidal disruption event fallen into the back burner

“…Up to now, a limited number (∼65) of tidal disruption candidates have been observationally identified 7 , mainly in the optical-UV and soft X-ray bands (e.g. Gezari 2012, and references therein; Komossa 2015, and references therein), both involving massive galaxies, that is, SMBHs (Kormendy & Richstone 1995;Kormendy & Gebhardt 2001), and dwarf galaxies, which possibly host intermediatemass black holes at their centres (Ghosh et al 2006;Maksym et al 2013Maksym et al , 2014aDonato et al 2014). The discovery of new tidal disruption candidates would certainly improve our understanding of the physics behind them, and if they were detected in dwarf galaxies, we might be able to determine plausible destroyer intermediate-mass black holes.…”