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New Outburst from A 0535+26 Beginning

ATEL # 2142; Mark H. Finger (USRA), Elif Beklen (METU), Ascension Camero-Arranz (NASA/FECYT)
on 31 Jul 2009; 21:52 UT
Distributed as an Instant Email Notice (Transients)
Password Certification: Dr. Mark H. Finger (

Subjects: X-ray, Gamma Ray, Binaries, Pulsars, Transients

103.51 s pulsations from the transient Be/X-ray binary pulsar A 0535+26 are currently being detected in the Fermi/GBM data. The current outburst was first detected on July 26 (MJD 55038).

Three previous outbursts have been observed with Fermi/GBM, the first detected from MJD 54720 - 54730, the second from MJD 54832 - 54842, and the third from MJD 54936 - 54954. These outbursts where also detected in the Swift/BAT, and the RXTE/ASM. In the Swift/BAT the peak daily rates for these outbursts were 125, 80, and 380 mCrab respectively.

We find that the higher flux outbursts begin at an earlier orbital phase, with the first outburst detected with Fermi/GBM beginning 4 days before periastron passage, the second 3 days, and the third 10 days. The current outburst was first detected 19 days before periastron, suggesting it will be brighter than any of the previous three. Observations with other observatories are encouraged.

GBM Pulsar Project

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R. E. Rutledge , Editor
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