Optical counterpart candidate to XTE J1818-245
ATel #585; D. Steeghs, M. A.P. Torres (CfA), W. Pych (CAMK, Warsaw), I. Thompson (Carnegie)
on 18 Aug 2005; 03:25 UT
Distributed as an Instant Email Notice Request For Observations
Credential Certification: Danny Steeghs (dsteeghs@cfa.harvard.edu)
Subjects: Optical, X-ray, Binary, Black Hole, Transient
Referred to by ATel #: 588, 589
We report on the likely optical counterpart to the X-ray transient XTE J1818-245
(ATEL #578,#579).
Photometry was acquired with the Swope 1.0m telescope (Las Campanas Observatory,
Chile) during August 17 2005 23:19 UT - August 18 2005 00:18 UT. Our observations
consist of several 60/180s exposures in the R and V bands acquired with an image
quality of 1.3 arcsec.
Comparison of our images with the Digitized Sky Survey and 2MASS reveals the
presence of a single new point-like object within the error circle for the RXTE PCA
X-ray position reported in ATEL #579. The coordinates for this optical source are
R.A(J2000): 18:18:24.4, Dec(J2000): -24:32:18.0 based on astrometry relative to the
2MASS frame (estimated uncertainty 0.3 arcsec). A comparison with nearby USNO stars
suggests a magnitude near R=17.5.
We tentatively identify this object as the optical counterpart to XTE J1818-245.
Follow-up photometric observations and the acquisition of a spectrum to confirm the
optical counterpart are encouraged.
A finding chart for the candidate may be found at:
http:/hea-www.cfa.harvard.edu/~dsteeghs/Images/XTEJ1818-245.jpg
R-band finding chart for XTE J1818-245
