Optical/IR Candidate for IGR J18483-0311
J. P. Halpern
A highly redenned star should be considered a possible binary companion of the transient X-ray source IGR J18483-0311 ( Chernyakova et al., ATEL #157; Molkov et al. 2003; Bird et al. 2006). The ROSAT HRI source 1RXH J184817.3-031017 noted by Chernyakova et al. as a falling within 0.7' of the INTEGRAL position is coincident with a star at coordinates R.A. = 18h 48m 17.20s, Decl. = -03° 10' 16.8" (J2000) whose magnitudes in the USNO-B1.0 and 2MASS catalogs are R=19.26, I=15.32, J=10.74, H=9.29, and K=8.46. This star was suggested as a possible counterpart by Stephen et al. (2006). Optical or IR spectroscopy to classify it should be obtained.
I note that there is also a weak, uncataloged ASCA source at R.A. = 18h 48m 18.20s, Decl. = -03° 10' 16" (J2000), which is consistent with both the ROSAT and the INTEGRAL position. In the Figures below, the 0.7' radius circle represents the INTEGRAL position, R.A. = 18h 48m 15.36s, Decl. = -03° 10' 08.4" (J2000), and its 1&sigma uncertainty according to Bird et al. 2006.
[There is a brighter ASCA source at R.A. = 18h 48m 18.5s, Decl. = -03d 18' 51" (J2000) that also appears to be uncataloged.]
UPDATE: Swift observed this source brightly
on 2006 February 16 and again on 2006 March 5. It confirms
the ROSAT and optical counterpart discussed above and indicated
with the cross on the MDM images. Now, an optical spectrum of this
star is needed.
In addition, Swift detects a weak source at the position of the
other ASCA source to the south, with a refined position
of R.A. = 18h 48m 17.3s, Decl. = -03d 19' 10" (J2000).
A finding chart from the DSS for the latter source is appended
below. There are 2-3 potential optical candidates near this
position. Spectroscopy may be able to identify this source as well.
In addition, Swift detects a weak source at the position of the other ASCA source to the south, with a refined position of R.A. = 18h 48m 17.3s, Decl. = -03d 19' 10" (J2000). A finding chart from the DSS for the latter source is appended below. There are 2-3 potential optical candidates near this position. Spectroscopy may be able to identify this source as well.
IGR J18483-0311, M. Chernyakova, A. Lutovinov, F. Capitanio, N. Lund, & N. Gehrels, ATEL #157 (2004)
First results from TOO Observations of the Aql X-1 Field with INTEGRAL, S. Molkov, A. Lutovinov, & S. Grebenev, A&A, 411, L357-L361 (2003)
Using the ROSAT Catalogues to find Counterparts for the Second IBIS/ISGRI Survey Sources, J.B. Stephen, et al., A&A, 445, 869-873 (2006)
The Second IBIS/ISGRI Soft Gamma-ray Source Catalog, A.J. Bird, et al., Ap.J., 636, 765-776 (2006)
IGR J18483-0311: An Accreting X-ray Pulsar Observed by INTEGRAL, V. Sguera, et al., A&A, in press (astro-ph/0702477)
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