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Detection of a large increase of the size of the Be disk from the X-ray binary A 0535+262

ATel #6043; A. Camero-Arranz (IEEC/ICE), M. Ozbey-Arabaci (METU), J. Fabregat (University of Valencia), J. Gutierrez-Soto (Valencian International University, IAA/CSIC), Mark H. Finger (USRA), V. Peris, and O. Brevia (University of Valencia) on behalf of a larger collaboration
on 5 Apr 2014; 10:14 UT
Distributed as an Instant Email Notice Transients
Credential Certification: Ascension Camero-Arranz (camero@ice.cat)

Subjects: Optical, X-ray, Request for Observations, Binary, Transient, Pulsar

Referred to by ATel #: 7029, 14157, 14392

We report on the evolution of the Hα equivalent width (EW) of the Be/X-ray binary system A 0535+262/HD 245770, using observations performed with the spectrograph Albireo, at the 1.5 m telescope of the Observatorio de Sierra Nevada (Granada, Spain) on 2012-03-26 22:27:59.000 UTC (MJD 56012.936), and recently with the spectrograph located at the 51 cm telescope of the Observatorio de Aras de los Olmos of the University of Valencia on 2014-Mar-07 at 21:07:00.000 UTC (MJD 56723.879), and also with the TFOSC spectrometer at the 1.5 m telescope RTT150 of the TÜBİTAK National Observatory (Antalya, Turkey) on 2014-03-18 19:57:14.688 UTC (MJD 56734.831) and 2014-03-19 19:58:30.746 UTC (MJD 56735.832).

Our monitoring allowed us to observe the Hα line always in emission and with its EW changing from -7.0±0.4 Å (MJD 56012.936), during X-ray quiescent state, to -14.60±0.18 Å (MJD 56723.879), -14.96±0.14 Å (MJD 56734.831), and -14.52±0.13 Å (MJD 56735.832), coinciding with the reawakening of this source (ATels#5931,#5941, and #5942). The most recent Hα emission line profiles were single-peaked. In addition, the Hβ line was found to be in emission (single-peaked) with an EW of 2.05±0.05 Å. The HeI 5875, 6678 and 7065 emission line profiles were double-peaked, with EWs of 1.38±0.01, 0.85±0.01 and 1.85±0.04 Å, respectively. A preliminary comparative study shows that the HeI lines exhibited V/R variations and R dominated emission profiles.

In addition, Fermi/GBM has detected pulsation from A 0535+26 in 5 intervals of 6 days each, between February 22 and March 30. A frequency of 9.6755(2) mHz was measured in the interval of  February 22.0-28.0.  Since the end of the 2001 March outburst the pulsar has spun down at an average rate of -1.136(5)x10-13 Hz/s.

Despite the weakness of this new X-ray normal outburst, our results imply that the disk has already reached the maximum size shown during the X-ray giant outbursts of e.g.1994 and 2005 (Camero-Arranz et al. 2012, ApJ, 754, 20, and references therein). Our data do not allow us to confirm the presence of a warped component in the Be disk as in the 2009 and 2011 large events (Moritani et al. 2011, PASJ, 63, 25; Moritani et al. 2013, PASJ, 65, 83). However, we note that the current behavior of this system resembles its previous re-brightening of 2008 (ATels#2142,#2146,#2161, and #2277), in which the Hα emission line EW during the first normal outburst before the large event of 2009 was similar to our measurements from 2014. More observations are then encouraged in order to cover possible upcoming events.

GBM Pulsar Project