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MAXI/GSC detection of an X-ray flare in the direction of 4U 2206+54

ATEL # 2271; H.Negoro (Nihon u.), S.Nakahira (Aoyama u.), S.Miyoshi (Nihon u.), R.Ishiwata (Nihon u.), T.Mihara (Riken), N.Kawai (TokyoTech.), M.Sugizaki (Riken), M.Nakajima (Nihon u.), K.Yamaoka (Aoyama u.), M.Matsuoka (JAXA) and the MAXI team.
on 29 Oct 2009; 16:14 UT
Password Certification: Tatehiro Mihara (

Subjects: X-ray, Request for Observations, Binaries, Neutron Stars, Transients
Referred to by ATEL #: 2273

On 2009-10-29 at 23:36 (UT), MAXI/GSC detected a bright X-ray source at R.A.=332.8, Dec.=54.2 (J2000) with an estimated systematic uncertainty of about 1 degree. The 2-20 keV flux of the source was 120 +/- 15 mCrab. The position is consistent with a high-mass X-ray binary pulsar 4U 2206+54. The source was present at least for 40 seconds during the transit of the MAXI/GSC field of view over the source. The source was not detected at previous or following scans that occurred at 2009-10-29 20:55, 22:27, 23:58 and 2009-10-30 1:07 (UT) with a typical 3-sigma upper limit of 30 mCrab. We tentatively identify this detection as an X-ray flare from 4U 2206+54, based on the position, spectral hardness, and the highly variable nature, although this peak flare flux is considerably higher than those in previous observations (e.g. Reig et al. A&A 494, 1073, (2009)). MAXI (Matsuoka et al. PASJ 61, 999, (2009)) is currently in the commissioning phase. The systematic uncertainty in localization will be improved with the progress of the alignment calibration.

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