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A Chandra Observation of the Recurrent Supersoft X-ray Transient in NGC 300

ATEL # 1626; A.K.H. Kong (NTHU, Taiwan), R. Di Stefano (CfA)
on 22 Jul 2008; 15:12 UT
Password Certification: Albert Kong (

Subjects: X-ray, Binaries, Black Holes, Transients

We report a Chandra observation of the supersoft X-ray transient (XMMU J005510.7-373855) recently in outburst in NGC 300 (Kong & Di Stefano 200; ATel #1560). A 10ks DDT observation was taken on 2008 July 8 UT with ACIS-S in Very Faint mode. The supersoft X-ray transient was clearly detected with all photons from below 0.7 keV. The energy spectrum is well fitted with an absorbed blackbody model with N_H=(4.3+/-1)e20 cm^-2 and kT=61+/-6 eV (90% confidence). The spectrum is entirely consistent with previous XMM-Newton observations (Kong & Di Stefano 2003). The 0.2-2 keV unabsorbed luminosity is 7.8e37 erg/s while the bolometric luminosity is 1.6e38 erg/s. Comparing to the Swift observations taken in 2008 May and June, the source was slightly fainter during the Chandra observation.

We thank Belinda Wilkes and the Chandra DDT team for approving and executing this DDT observation.

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R. E. Rutledge , Editor
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