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ATEL # 1699; C. B. Markwardt (CRESST/U.Md./NASA/GSFC), D. Pereira (WYLE/NASA/GSFC), J. H. Swank (NASA/GSFC)
on 5 Sep 2008; 20:42 UT
Password Certification: Craig B. Markwardt (firstname.lastname@example.org)
Subjects: X-ray, Request for Observations, Binaries, Black Holes, Neutron Stars, Transients
Referred to by ATEL #: 1700, 1704
During regular scans of the galactic bulge and ridge regions on 2008-08-29, RXTE PCA discovered a new source. A dedicated follow-up scan on 2008-08-30 produced a best-fit position of RA, Dec = 249.35, -49.80 (J2000), with a 95% error radius of 6 arcmin. Note that because of galactic ridge emission, and significant source variability, the true uncertainties may have a non-statistical component. We designate this source XTE J1637-498.
In retrospect, the source was detected in PCA bulge scans on Aug 25.5, 29.3, Sep 1.4 and 5.1 with 2-10 keV fluxes of 2.5, 3.9, 2.6 and 1.8 mCrab, respectively, with typical uncertainties of about 0.6 mCrab. Thus, the source may have peaked already. Before the detection, the typical 95% upper limit is about 1 mCrab.
Examining the small amounts of timing data available during scans, no obvious timing signatures were present, such as pulsations, bursts or high frequency QPOs, although there may be a ~0.2 Hz QPO. Little pointed data is available for spectral analysis. Thus, at this time, the nature of the source is still uncertain.