Shrinking of the Be disk whilst the X-ray activity increases in the binary system A0535+262
ATel #7029; A. Camero-Arranz (IEEC/ICE), M. D. Caballero-Garcia (CTU-Prague), J. Fabregat (University of Valencia), M. Jelinek (IAA-CSIC), A. Castro-Tirado (IAA) and V. Peris (University of Valencia) on behalf of a larger collaboration
on 5 Feb 2015; 16:09 UT
Distributed as an Instant Email Notice Transients
Credential Certification: Ascension Camero-Arranz (camero@ice.cat)
Subjects: Optical, X-ray, Binary, Transient, Pulsar
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 COLORES at the 0.6 m telescope BOOTES-2 (Málaga, Spain) on 2015-01-27 at 22:05:31.736 UTC (MJD 57049.920), and with the spectrograph located at the 51 cm telescope of the Observatorio de Aras de los Olmos of the University of Valencia on 2015-01-29 at 01:00:00 UTC (MJD 57051.042).
Our results found the Hα line (in emission) with an EW of the order of -6.6±0.9 Å (MJD 57049.920) and -7.9±0.2 Å (MJD 57051.042). This means that the size of the Be disk has decreased to half of the value measured on 2014 March 19 (see ATel #6043), being similar to our estimate during quiescence on 2012 March. Recently, this system showed a weak enhancement in the optical luminosity (ATel #6969), and a weak reawakening of X-ray pulsar's activity was thus expected. MAXI detected this source on 2015 January 29 (ATel #7015), and the Swift/BAT monitoring web site is currently detecting its rise with a flux of 570±20 mCrab (MJD 57057).
We note that the current behavior of this system may resemble the giant outburst of 2011 in which the EW of the Hα line was initially of the order of -9.5 Å (see e.g. Camero-Arranz et al. 2102). Since our data do not allow us to confirm the presence of a warped component in the Be disk (see Moritani et al. 2013), high-resolution spectroscopic observations from other ground-based telescopes are encouraged.