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The Optical Counterpart to XTE J1752-223

ATEL # 2263; M. A. P. Torres (CfA), P. G. Jonker (SRON/CfA), D. Steeghs (Warwick/CfA), H. Yan (CCAPP, The Ohio State U.), J. Huang, A. M. Soderberg (CfA)
on 26 Oct 2009; 12:36 UT
Distributed as an Instant Email Notice (Transients)
Password Certification: Manuel Torres (

Subjects: Optical, Request for Observations, Binaries, Black Holes, Transients
Referred to by ATEL #: 2268, 2269

We report the discovery of the optical counterpart to the new X-ray transient and suggested black hole candidate XTE J1752-223 (ATELs #2258, #2259, #2261).

Our observations consist of three 180s i'-band images obtained with the 6.5m Magellan Baade telescope during 2009 Oct 26 00:02-00:18 UT using IMACS. The frames were acquired with an image quality of ~1.0" and conditions were not photometric. An astrometric calibration of the data was obtained using USNO-B1.0 objects in the field of view. This delivered a positional rms of 0.15".

Comparison of our images with the Digitized Sky Survey, 2MASS and UKIDSS shows a new bright point-like source at R.A (J2000)=17:52:15.09, Dec (J2000)=-22:20:32.4 inside the 5.0" Swift/XRT position reported by Markwardt et al. (2009, ATel #2261). The optical counterpart is saturated in our images due to the high sky background and the brightness of the source. A visual inspection of the field using the USNO-B1.0 catalogue suggests that the source may be as bright as 15-16 mag in the red band.

Given the brightness of the counterpart, follow-up observations at all wavelengths, in particular optical spectroscopy, are encouraged while the source is still accessible from the ground.

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