A second HLX-1-like object in CXO J122518.6+144545

Intermediate mass black holes are crucial as building blocks for supermassive BHs, but observational evidence for their existence is still scarce. The brightest ULXs may be good IMBH candidates: the strongest case is ESO 243-49 HLX-1 (Farrell et al. 2009), an X-ray source that reaches a luminosity of more than 10E42 erg/s. It is thought to host a BH of 20,000 solar masses. Up until now, HLX-1 is the only known object of its kind. Most candidate ULXs with comparable luminosities have turned out to be background AGN. Finding more HLX-1 like objects would be an important step forward in the search for IMBHs. We have investigated the X-ray source CXOJ122518.6+144545 (J1225; Jonker et al. 2010) with Chandra. It was found in an observation from 2008, at a luminosity of 2E41 erg/s, making it the second most luminous ULX after HLX-1. We did not detect the source in November 2012 and in April and July 2014, but in our last observation on November 20 it was again visible at 5E40 erg/s.