Swift J1753.6-2545: GROND discovery of a candidate counterpart
ATel #4904; Arne Rau, Fabian Knust (both MPE), Sebastian Schmidl (TLS Tautenburg), Jochen Greiner (MPE)
on 21 Mar 2013; 14:00 UT
Credential Certification: Arne Rau (arau@mpe.mpg.de)
Subjects: Optical, X-ray, Binary, Black Hole, Transient
We report on optical-near-Infrared follow-up observations of the transient Swift J1753.6-2545 (ATels #4769, #4789, #4802, #4804, #4818, #4899) with GROND (Greiner et al. 2008, PASP 120, 405) at the 2.2m MPG/ESO telescope at La Silla Observatory (Chile). Simultaneous imaging in g'r'i'z'JHK was obtained on 2013-01-28, 2013-02-07, and 2013-02-17. Image subtraction between the first and third epoch of observations reveals a decaying K-band source consistent with the Chandra X-ray location (ATel #4899) at the following position:
RA(J2000) = 17:53:39.85 (268.41604 deg)
Dec(J2000) = -25:45:14.2 (-25.7539 deg)
with an uncertainty of 0".3 in both coordinates.
Due to the high source density in the field, coupled with the large Galactic foreground reddening of E(B-V)~19mag (Schlafly et al. 2011, ApJ 737, 103), the candidate counterpart is only detected in the K-band. In the first epoch (2013-01-28) the source had a brightness of ~16.5mag (AB system, calibrated vs 2MASS field stars) and faded by >1mag by the time of observations taken on 2013-02-17.
