Swift/XRT follow-up observations of unidentified INTEGRAL sources (2)
ATel #1323; R. Landi, N. Masetti, V. Sguera (INAF/IASF Bologna), M. Del Santo, A. Tarana (INAF/IASF Rome), A. B. Hill, A. J. Dean (Univ. Southampton), P. Caraveo, F. Senziani (INAF/IASF Milano)
on 8 Dec 2007; 16:10 UT
Credential Certification: Raffaella Landi (firstname.lastname@example.org)
Subjects: X-ray, Gamma Ray, Request for Observations
We report on X-ray follow-up observations performed with Swift/XRT of three
unidentified INTEGRAL sources in the third IBIS Survey Catalogue
(Bird et al. 2007, ApJS, 170, 175).
No X-ray source is detected at a confidence level > 3 sigma within the IBIS error box,
but just at its border XRT detects a source (at 3.4 sigma confidence level) located at
RA(J2000) = 05h 26m 14.58s and Dec(J2000) = -66d 30m 41.6s (5.5 arcsec uncertainty).
There are three USNO-B1.0 objects within the XRT error box, one of which is also listed in the
2MASS catalogue. This source is associated with the ROSAT PSPC X-ray source RX J0526.2-6630,
classified as a star of B0Ib spectral type in Simbad. The source 2-10 keV flux is ~ 2 x 10-14
erg cm-2 s-1.
In the XRT field of view we find a bright source (at 9.4 sigma confidence level)
located in the vicinity of the IBIS error box and possibly associated to diffuse emission.
Its coordinates are
RA(J2000) = 17h 44m 37.46s and Dec(J2000) = -32d 32m 20.2s (4 arcsec uncertainty), which suggest
an association with the ROSAT Faint Survey source 1RXS J174440.8-323303.
Within the XRT uncertainty there is a USNO-B1.0 object having magnitude R = 15.28-15.66,
which is also listed in the 2MASS survey. The source X-ray spectrum is either flat (Gamma ~0.8)
or steeper (Gamma = 1.8) but absorbed (NH ~2 x 1022 cm-2) with an
observed 2-10 keV flux of 2.4 x 10-12 erg cm-2 s-1.
No X-ray source is detected by XRT within the IBIS error box, but just outside there is a
bright source (at 20 sigma confidence level) located
at RA(J2000) = 19h 26m 27.03s and Dec(J2000) = +13d 22m 03.2s (3.7 arcsec uncertainty), which is most
likely associated with the ROSAT Bright Survey source (1RXS J192626.8+132153).
Within the XRT uncertainty, there are two IR counterparts in the 2MASS survey and three optical ones in the USNO-B1.0 survey.
The X-ray spectrum is described by an unabsorbed power law (Gamma ~1.5) plus a black body
component (kT ~0.15 keV). The 2-10 keV flux is 8.3 x 10-12 erg cm-2 s-1.