NOAO >   Observing Info >   Approved Programs >   2011B-0242

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Proposal Information for 2011B-0242


PI: Elisa Nichelli, INAF - Astronomical Observatory of Rome, elisa.nichelli@oa-roma.inaf.it
Address: via Frascati, 33, Monteporzio Catone (Rome) 00040, Italy

CoI: GianLuca Israel, INAF - Astronomical Observatory of Rome
CoI: Alberto Moretti, INAF - Astronomical Observatory of Brera
CoI: Vincenzo Testa, INAF - Astronomical Observatory of Rome
CoI: Andrea Kunder, CTIO NOAO
CoI: Elena Mason, ESA STScI
CoI: Luigi Stella, INAF - Astronomical Observatory of Rome

Title: Optical study of a peculiar X--ray pulsator

Abstract: During the systematic timing analysis of ~ 3000 \textitSwift- XRT serendipitous sources we identified several new X-ray pulsators, among which is SWIFT J1819.2-1706. The modulation observed in the X- ray flux (~ 400 s; detection significance >9\sigma), together with the spectral information retrieved (an absorbed black body at kT=2.2(1) keV), suggests that we are looking at a compact object (a white dwarf or a neutron star) hosted by a binary system. However, no photometric or spectroscopic information have been found in optical archival data within the error circle given by \textitSwift-XRT position of the source (~3^\rm \prime\prime radius), while the DSS image of the region indicates that SWIFT J1819.2-1706 has a very faint counterpart (V~20). This rules out any scenario invoking the presence of an high mass companion, but even considering Cataclysmic Variable or Low Mass X-ray Binary scenarios the faintness of this object is extremely peculiar. The deep multiband photometric study we propose will allow us to perform a color-magnitude study and to search for variabilities in the counterpart candidates' light curves, which will translate in unveiling the nature of SWIFT J1819.2-1706 through the unambiguous detection of its optical counterpart.


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