IGR J17597-2201 = XTE J1759-220
ATel #156; C. B. Markwardt (U. Maryland & NASA/GSFC) and J. H. Swank (NASA/GSFC)
on 1 May 2003; 14:09 UT
Credential Certification: Craig B. Markwardt (firstname.lastname@example.org)
Subjects: X-ray, A Comment, Binary, Neutron Star, Transient
Referred to by ATel #: 1054
We report that the transient detected by Lutovinov et al. (ATEL #155),
IGR 17597-220, is at a position consistent with a transient which has
been active since at least 07 Feb 2001, when it was first detected in
RXTE PCA galactic bulge scans.
Dedicated PCA scans on 19 May 2001 determined a best fit PCA position
to be R.A. = 18h00.0m, Decl. = -22o03m (equinox 2000.0; estimated
uncertainty 4'). The XTE designation of XTE J1759-220 was generated
based on a preliminary position from the PCA bulge scans.
The X-ray flux has varied erratically between 2 and 17 mCrab (2-10
keV) since detection, with alternating calm and flaring periods. For
the past year, the flux has been more stable (3-6 mCrab). Over the
time period of the reported INTEGRAL detection (16-26 Apr 2003), the
2-10 keV flux in the PCA scans has been 4.5-7.2 mCrab, with no obvious
trend. Before Feb 2001, the X-ray flux was less than approximately 1
In RXTE PCA pointed observations on 01 and 03 June 2001; and 09 and 11
Oct 2001, there was evidence of dipping behavior (~30% dips; ~5 min
duration). A period of 1-3 hours is suggested, but highly
unconstrained because of the time sampling. No QPOs or pulsations
The PCA X-ray spectrum was consistent with power law plus soft
emission, with photon indices ranging between 1.8 and 2.9. An
emission line associated with Fe K, (centroid 6.5-6.7 keV) is present
with equivalent widths in the 130-250 eV range.
On 22.843 Apr 2003, during a PCA bulge scan this year, an apparent
X-ray burst was detected from a position consistent with the source.
Unfortunately, the scan contained only the tail of the burst, and so a
reliable peak flux is not yet available.
The combination of these observations suggests that IGR J17597-2201 (=
XTE J1759-220) is a neutron star in a short-period binary.