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SWIFT J004159.3+410539 - A new X-ray transient in M31

ATEL # 2262; F. Haberl, M. Henze, W. Pietsch (Max-Planck-Institut fuer extraterrestrische Physik), M. Orio (INAF Padova and UW Madison)
on 26 Oct 2009; 8:10 UT
Password Certification: Frank Haberl (

Subjects: X-ray, Transients

A 7 ks observation with SWIFT from 2009 Oct. 22, 14:29 to Oct. 23, 02:30 UT revealed a new bright transient in M31 at R.A.(J2000) = 00:41:59.3, Dec.(J2000) = +41:05:39 (uncertainty 3.7 arcseconds) near the edge of the field of view of the XRT. The X-ray spectrum of this source, designated SWIFT J004159.3+410539, can be modelled by an absorbed powerlaw with an absorption column density of 1.4x1021 cm-2 and a photon index of 1.9. The observed 0.2-10.0 keV flux was 4.5x10-12 erg cm-2 s-1 with a corresponding intrinsic source luminosity of 4.6x1037 ergs s-1 (assuming a distance of 780 kpc). The X-ray light curve shows variations by a factor of ~3 on time scales of ~20 min, but no significant period was found. We thank the SWIFT team for accepting and scheduling the observations.

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