NOAO >   Observing Info >   Approved Programs >   2013A-0410

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Proposal Information for 2013A-0410


PI: Margaret L. Trippe, University of Maryland College Park, trippe@astro.umd.edu
Address: Department of Astronomy, University of Maryland, College Park, MD 20740, USA

CoI: Dheeraj R. Pasham, University of Maryland

Title: \center Optical spectroscopy of a mysterious periodic X-ray source

Abstract: We propose optical spectroscopy of the possible optical counterparts of a mysterious, highly-variable X-ray source discovered through an \it XMM-Newton observing campaign. The field containing this source has also been monitored by the \it Swift observatory for roughly 1600 days (4.5 years; ~ once every 4 days). Our analysis of the \it Swift/X-Ray Telescope (XRT) data (0.3-8.0 keV) reveals two interesting phenomena: (1) the source went into an outburst that lasted roughly 1250 days and (2) the source shows evidence for a 134 day period during this outburst. The X-ray (0.3-12.0 keV) spectra derived from the high- quality (100 ks exposures) \it XMM-Newton observations show evidence for a ``soft excess'' (excess soft X-rays above the canonical powerlaw fit to the energy spectrum), similar to those often seen in many active galactic nuclei (AGN). Furthermore, the X-ray to optical flux ratios, estimated through various \it Swift/UV telescope monitoring observations, are also consistent with the source being an AGN. If the source is indeed an AGN, this is interesting as a 134 day periodicity represents a phenomenon occurring close to the super-massive black hole. There is, however, no conclusive evidence to show that the mysterious source is an AGN. A preliminary quick-look image from the SOAR telescope shows that there are 9 optical point source within the \it XMM-Newton point spread function (PSF). Therefore, we request observing time to obtain optical spectra of these sources in order to conclusively identify the source producing the X-rays.


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