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ATEL # 2847; Mark H. Finger (USRA) for the Fermi/GBM Pulsar Team
on 18 Sep 2010; 0:26 UT
Password Certification: Dr. Mark H. Finger (Mark.Finger@msfc.nasa.gov)
Subjects: X-ray, Gamma Ray, Request for Observations, Binaries, Pulsars, Transients
Referred to by ATEL #: 3048, 3077
The transient Be/X-ray binary pulsar XTE J1946+274 is undergoing another outburst. Fermi/GBM began detecting a pulsation from the source on September 11. The flux in Swift/BAT has reached 45 mCrab. The previous outburst, which reached 300 mCrab in Swift/BAT, began in early June (ATel #2663), after a long interval of quiescence.
Wilson et al. (2003, ApJ, 584, 996) found from pulse timing that the source has an orbital period of 169 days. In the series of outbursts that began in September 1998 and continued until September 2001, the source initially showed two outbursts per orbit. As the series of outbursts evolved, the outburst peaks shifted in orbital phase. This behavior remains unexplained.
Observations in other wavelengths are encouraged, particularly those which are sensitive to the state of the Be star decretion disk.
GBM Pulsar Project