The near-infrared counterpart to SWIFT J1842.5-1124
ATel #1720; M. A.P. Torres (CfA), D. Steeghs (Warick/CfA), P. G. Jonker (SRON/CfA), J. E. Greene (Princeton), K. N. Hainline (UCLA)
on 17 Sep 2008; 15:21 UT
Credential Certification: Manuel Torres (mtorres@cfa.harvard.edu)
Subjects: Infra-Red, Binary, Black Hole, Neutron Star, Transient
We report on near-infrared follow-up observations of the field
containing the currently active X-ray transient SWIFT J1842.5-1124
(ATel #1706, ATel #1716).
Our observations consist of a series of 10s Ks-band images
totalling 270s on source and acquired on 2008 Sep 15 23:36 - 23:45 UT
with the PANIC camera mounted on the 6.5m Baade telescope at Las
Campanas Observatory. Sky conditions were good with a seeing of
0.4". Additional 3s exposures were obtained to derive an
astrometric and absolute flux calibration of the data using 2MASS
objects in the field of view. This delivered a positional RMS <0.15'
and a zero-point accuracy of < 0.15 mag.
Our mosaic image (see finder) shows a bright point-like source at
R.A (J2000)=18:42:17.44, Dec (J2000)=-11:25:03.95 consistent with the
0.6" Swift/UVOT position reported for the optical counterpart
(Markwardt et al. 2008, ATel #1716). Pre-outburst K-band imaging is
available from the UKIDSS survey obtained in September 2005
(http://www.ukidss.org). These show marginal evidence for a source at
the above position indicating it was much fainter at the time and thus
confirming it as the near-infared counterpart to SWIFT
J1842.5-1124. PSF-fitting photometry of the PANIC images yields
Ks=14.90 +/- 0.05 for the counterpart and from the UKIDSS imaging we
estimate Ks ~ 17.4 or less during quiescence.
Finding chart for J1842.5
