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ATEL # 2424; P.A. Curran (MSSL-UCL), P.A. Evans (U. Leicester), M. Still (NASA ARC), C. Brocksopp (MSSL-UCL), C. Done (U. Durham)
on 5 Feb 2010; 21:57 UT
Password Certification: Martin Still (firstname.lastname@example.org)
Subjects: Optical, X-ray, Binaries, Transients, Variables, Stars
Swift obtained ~1.4ks of pointed observations of the recently discovered X-ray transient, XTE J1752-223 (ATEL #2258) on 2010-02-04 from 14:11 UT. The source had just emerged from approximately 90 days of being sun constrained to pointed observations.
The Swift-XRT flux, in line with those from MAXI (ATEL #2387), has increased from an average of ~3.2-9 erg/cm2/s, in the period from 2009-10-25 to 2009-11-03, to ~1.6-8 erg/cm2/s. The spectrum has also evolved from having an average power law of photon index =1.45 before the sun constrained period to having a steeper power law (photon index ~3.9) with a thermal blackbody component at kT~0.50keV. The steepening of the photon index and emergence of a significant thermal component was also observed in spectra from RXTE (ATEL #2269, #2391).
We have produced preliminary photometry of the two Swift-UVOT v band objects consistent with the Swift-XRT position (ATEL #2261), including the suggested optical counterpart (ATEL #2263) at v=17.0. Neither exhibit any significant variability either before, or since, the pre-constrained observations.
Swift observations of the source are ongoing but are moon-constrained from 2010-02-07 to 2010-02-11. We thank the Swift team for scheduling the observations.