MAXI/GSC observation of the X-ray outburst from the Be/X-ray binary pulsar A 0535+262

ATel #14732; M. Nakajima (Nihon U.), T. Mihara (RIKEN), H. Negoro, K. Kobayashi, K. Asakura, K. Seino (Nihon U.), T. Tamagawa, M. Matsuoka (RIKEN), T. Sakamoto, M. Serino, S. Sugita, K. Komachi, A. Yoshida (AGU), Y. Tsuboi, W. Iwakiri, H. Kawai, Y. Okamoto, S. Kitakoga (Chuo U.), M. Shidatsu (Ehime U.), N. Kawai, M. Niwano, R. Hosokawa (Tokyo Tech), S. Nakahira, Y. Sugawara, S. Ueno, H. Tomida, M. Ishikawa, M. Tominaga, T. Nagatsuka (JAXA), Y. Ueda, S. Yamada, S. Ogawa, K. Setoguchi, T. Yoshitake, Y. Goto, R. Uematsu (Kyoto U.), H. Tsunemi (Osaka U.), M. Yamauchi, Y. Nonaka, T. Sato, R. Hatsuda, R. Fukuoka (Miyazaki U.), T. Kawamuro (UDP/NAOJ), K. Yamaoka (Nagoya U.), Y. Kawakubo (LSU), M. Sugizaki (NAOC)
on 22 Jun 2021; 08:07 UT
Credential Certification: Motoki Nakajima (nakajima.motoki@nihon-u.ac.jp)

Tweet

The MAXI/GSC nova alert system triggered on an X-ray brightening from the Be/X-ray binary pulsar A 0535+262 on 2021-06-20 (MJD 59385). A preliminary analysis reveals that the latest 4-10 keV flux binned at 0.25 days centered on 2021-06-21.625 (MJD 59386.625) reached 0.475 ± 0.040 photons/s/cm² (380 ± 32 mCrab). The previous daily upper limit was <20 mCrab on 2021 June 9. There was no observation from 2021-06-09 to 2021-06-19, because the sun was close to A 0535+262. The onset of the current outburst is unknown. The 4-10 keV / 2-4 keV hardness ratio value of 3.2 ± 0.6 is comparable to that of the last giant outburst peak (ATel #14173).

This source has exhibited the periodic X-ray activity synchronized with its orbital period of 111.07 days (e.g. Camero-Arranz et al. 2012) since 2017 October. This is the longest consecutive X-ray activity observed ever in RXTE/ASM, Swift/BAT and MAXI/GSC data. Following the brightest giant outburst in 2020 November (ATel #14157,#14170,#14171,#14173,#14179,#14193,#14227), A 0535+262 showed the multi-peak outburst with the maximum flux of 50 mCrab (4-10 keV) in 2021 February (ATel #14392, #14401). After that, MAXI/GSC observed rebrightening in the current outburst. So such a series of outburst activity is similar to the ones observed in 2008-2011 (e.g. Moritani et al. 2011, Nakajima et al. 2014). We encourage the multi-wavelength follow-up observations to reveal the nature of this binary system.

The source light curves can be checked at the following pages;
MAXI(http://maxi.riken.jp/pubdata/v7lrkn/J0538+263/index.html),
Swift/BAT(https://swift.gsfc.nasa.gov/results/transients/1A0535p262/),
Fermi/GBM(https://gammaray.nsstc.nasa.gov/gbm/science/pulsars/lightcurves/a0535.html), and
the BeXRB monitor page(http://integral.esac.esa.int/bexrbmonitor/webpage_oneplot.php).