A Second Recent Outburst of XTE J1748-361 (or A1744-36)

ATel #265; C. B. Markwardt (NASA/GSFC and U. Maryland) and J. H. Swank (NASA/GSFC)
on 9 Apr 2004; 15:21 UT
Distributed as an Instant Email Notice Request For Observations
Credential Certification: Craig B. Markwardt (craigm@lheamail.gsfc.nasa.gov)

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In November, 2003, Remillard et al. detected a transient with the RXTE ASM, designated XTE J1748-361, which they speculated may be the 1976 Ariel source A1744-36 (ATEL #204).

The RXTE PCA scans of the galactic center confirmed the November outburst (Nov 2.1 UT; 2-10 keV flux 13 mCrab). Since then the source was unobservable until Feb 7, 2004, and undetectable after that (< 0.5 mCrab).

A PCA scan on Apr 7.3 has again detected the source, with flux 12 mCrab. In a follow-up pointed observation on Apr 8.8, the flux was 16 mCrab, indicating the flux may still be increasing. Weak QPOs are detectable at approximately 1.8 and 3.9 Hz with total fractional r.m.s. amplitudes of about 12%. The X-ray spectrum is consistent with a power law with index 1.9.

The source intensities from PCA scans have been fitted with the fixed position, R.A. = 17 48 19.22, DEC = -36 07 16.6 (J2000), of the source reported by McClintock et al. (ATEL #205), which was reported by Rupen (ATEL #210) to have a marginal radio detection. However the fit could be indistinguishably consistent with the ASM position for XTE J1748-361, and in particular the position of the Chandra source (ATEL #238), which has been the brighter radio source (ATEL #210).

Observations now at other wavelengths and with imaging capability will establish at least one transient in the region.