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Swift follow-up of X-ray transients in M31

ATEL # 899; W. Pietsch (MPE), F. Haberl (MPE), J. Greiner (MPE), H. Stiele (MPE)
on 27 Sep 2006; 16:44 UT
Password Certification: Wolfgang Pietsch (

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

On 2006, September 11, a 4 ks SWIFT observation of the M31 center field was performed to further monitor the outbursts of the X-ray transients reported in ATel #881. The black hole transient candidate SWIFT J004217.3+411532 dropped in source intensity by 20% compared to the SWIFT observation 10 days earlier. Its X-ray spectrum did not change significantly compared to the one reported in ATel #881. The observed 0.5-5.0 keV flux was 2.8x10^-12 erg s^-1 cm^-2 and the intrinsic source luminosity 3.5x10^38 erg s^-1 at a distance of 780 kpc. From the region of the Be/X-ray transient candidate XMMU J004215.8+411924 just three photons were recorded indicating a further decay by a factor of more than 5 with respect to the SWIFT observation 10 days earlier. This corresponds to an upper limit for the 0.5-10.0 keV intrinsic source luminosity of 5x10^36 erg s^-1 assuming a similar spectrum as for the XMM-Newton detection. We thank the Swift team for accepting and scheduling these target of opportunity observations.

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R. E. Rutledge , Editor
ATEL Mirror v1.0 Updates