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Renewed activity of the transient binary system HDE 245770/ A 0535+26

ATel #3166; Ascension Camero-Arranz (USRA), Mark H. Finger (USRA), Colleen Wilson-Hodge(NASA/MSFC), Peter A. Jenke (NASA/ORAU), Iain Steele (Liverpool J. Moore's University), J. Gutierrez-Soto (Valencian International University and Instituto de Astrofisica de Andalucia) and Malcolm J. Coe (University Southampton)
on 14 Feb 2011; 20:56 UT
Credential Certification: Ascension Camero-Arranz (Ascension.Camero@uv.es)

Subjects: Optical, X-ray, Binary, Neutron Star, Transient, Pulsar

Referred to by ATel #: 3173, 3176, 3198, 3204

Pulsations from the transient Be/X-ray binary pulsar A 0535+26 have been detected in the Fermi/GBM data since Feb 10, 2011 (MJD 55602). The previous reported outburst (ATel #2970) of this source occurred in October 2010. The renewed X-ray activity began approximately 11 days before the next periastron passage (Feb 20th). The flux of this source for Feb 13, 2011 using the Earth Occultation technique is 0.053+/-0.011 photons/cm^2/s (~157+/-34 mCrab) in the 12-25 keV band. The pulse frequency measured over 12-13 February was 9.6755(3) mHz.

Preliminary analysis of spectra of the optical counterpart HDE 245770 from the Observatory of Liverpool (La Palma, Spain) and from the Observatory of Sierra Nevada (Granada, Spain), show ongoing optical line emission from the star. The H-alpha equivalent width (an indicator of the size of the Be star's circumstellar disk) was -10.0 Angstrom on Jan 19th (MJD 55580). Further observations are underway.

GBM Pulsar and Earth Occultation Projects