An outburst from a new Galactic bulge intermediate polar candidate in the XMM-Newton Galactic center lobe survey

For the past decades a rare subclass of cataclysmic variables, with magnetized white dwarfs (WD) as accretors has been studied and called intermediate polars (IP). IPs are very numerous but mostly faint X-ray sources in the Galactic center and bulge (GC/GB) region and there is evidence that they are responsible for a large fraction of the diffuse X-ray emission due to unresolved sources in the GB. In an ongoing deep X-ray survey (0.5-10 keV energy band) of ∼3x3 deg around the GC with the XMM-Newton observatory we conducted a systematic search for transient X-ray sources. Promising systems were analyzed for spectral, timing, and multi-wavelength properties to constrain their nature. We discovered a new highly variable (factor >20) X-ray source about 1.25 deg south of the GC. We found evidence making the newly discovered system a candidate IP. The X-ray light curve shows a period of 511±10 s which can be interpreted as the spin period of the WD. The X-ray spectrum is well fit by a bremsstrahlung model with a temperature of 13.9±2.5 keV, suggesting a WD of 0.4-0.5 solar masses. High X-ray absorption and absence of an optical counterpart are evidence that the source is most likely located in the GB. This system will help to understand the population of rarely observed IPs in the GB.In extension of this work a full study of the diffuse X-ray emission and point source population in the ongoing (to be completed this year) XMM-Newton GC survey is currently under way.