092303

We will study a candidate intermediate-mass black hole (IMBH) we have recentlydiscovered in the halo of the nearby (dvirgul135 Mpc) elliptical galaxy NGC 6099. Thesource had a soft (thermal) X-ray spectrum with a luminosity Lx virgul 5e42 erg/s ina 2012 XMM-Newton observation up from Lx virgul 7e40 erg/s seen in a (short) 2009Chandra observation. With a new XMM-Newton observation we will explore itsspectral evolution or transient behaviour and constrain the origin of thethermal emission and the mass range of the accreting object. If confirmed as anoff-nuclear IMBH its X-ray properties will help us focus our search for thiselusive class of object relics of dwarf satellite accretion during major galaxyassembly. [truncated! Please see actual data for full text]