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MAXI/GSC detects a new activity from Be pulsar A0535+262

ATEL # 2970; T. Mihara (RIKEN), M. Nakajima (Nihon U.), T. Yamamoto, M. Sugizaki, M. Suzuki, Y.E. Nakagawa, T. Sootome, M. Matsuoka (RIKEN), N. Kawai, M. Morii, K. Sugimori, R. Usui (Tokyo Tech), K. Kawasaki, S. Ueno, H. Tomida, M. Kohama, M. Ishikawa (JAXA), A. Yoshida, K. Yamaoka, S. Nakahira (AGU), H. Tsunemi, M. Kimura (Osaka U.), H. Negoro, H. Ozawa, F. Suwa (Nihon U.), Y. Ueda, N. Isobe, S. Eguchi, K. Hiroi (Kyoto U.), A. Daikyuji (Miyazaki U.), A. Uzawa, T. Matsumura, K. Yamazaki (Chuo U.) report on behalf of the MAXI team
on 25 Oct 2010; 21:33 UT
Distributed as an Instant Email Notice (Transients)
Password Certification: Motoki Nakajima (

Subjects: X-ray, Binaries, Neutron Stars, Pulsars, Transients
Referred to by ATEL #: 3020, 3075

An increase of X-ray flux of the Be/X-ray binary pulsar A0535+26 has been observed with MAXI/GSC since 2010 October 14. The current activity is clearly out of the outburst phase (only 0.7 x ~110-day orbital period since the last outburst peak), and probably is a precursor activity. Assuming that it is a precursor, this is the fifth detection of the consecutive activities following the ~110-day orbital cycle (Moritani+ 2010), although the average interval of the last four outbursts has been significantly longer at about 115 days. Assuming this 115-day outburst period, the series of outbursts and precursor events observed by MAXI took place at same phases, ~0.2 and ~0.95 respectively, where the phase zero is taken at MJD 55153.5, the periastron passage prior to the previous giant outburst (Atel #2324, #2336, #2337, #2343). This change in outburst period may indicate a secular change in the size, density, or orientation (possibly precession) of the circumstellar disk of the companion Be star. The latest light curve and folded light curve are available at the following URL: and also in the news page URL:

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R. E. Rutledge , Editor
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