MAXI/GSC detection of an X-ray brightening from the Be/X-ray binary pulsar LS V +44 17

ATel #15835; M. Nakajima, H. Negoro (Nihon U.), T. Mihara (RIKEN), K. Kobayashi, M. Tanaka, Y. Soejima (Nihon U.), T. Kawamuro, S. Yamada, T. Tamagawa, M. Matsuoka (RIKEN), T. Sakamoto, M. Serino, S. Sugita, H. Hiramatsu, H. Nishikawa, A. Yoshida (AGU), Y. Tsuboi, W. Iwakiri, J. Kohara, S. Urabe, S. Nawa, N. Nemoto (Chuo U.), M. Shidatsu, M. Iwasaki (Ehime U.), N. Kawai, M. Niwano, R. Hosokawa, Y. Imai, N. Ito, Y. Takamatsu (Tokyo Tech), S. Nakahira, S. Ueno, H. Tomida, M. Ishikawa, T. Kurihara (JAXA), Y. Ueda, S. Ogawa, K. Setoguchi, T. Yoshitake, K. Inaba, Y. Nakatani (Kyoto U.), M. Yamauchi, T. Sato, R. Hatsuda, R. Fukuoka, Y. Hagiwara, Y. Umeki (Miyazaki U.), K. Yamaoka (Nagoya U.), Y. Kawakubo (LSU), M. Sugizaki (NAOC)
on 30 Dec 2022; 09:18 UT
Credential Certification: Motoki Nakajima (nakajima.motoki@nihon-u.ac.jp)

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The MAXI/GSC nova alert system triggered a bright X-ray transient source on 2022 December 29 (MJD 59942). Assuming that the source flux was constant over the transits, we obtain the source position at (R.A., Dec) = (70.253 deg, 44.378 deg) = (04 41 00, +44 22 40) (J2000) with a 90% C.L. statistical error of 0.13 deg and an additional systematic uncertainty of 0.1 deg (90% containment radius). This position is consistent with the Be/X-ray binary pulsar LS V +44 17 (Yan et al. 2016, Usui et al. 2012). This is the third detection of this source by MAXI/GSC after 2010 March (ATel #2527) and 2011 April. The X-ray flux averaged over the scans from December 29 13:12 UT to December 30 01:35 UT was 160 ± 14 mCrab (4.0-10.0keV, 1 sigma error). Since the source locates in the region of the degraded camera, the onset date of the current outburst is unclear. The current X-ray outburst is also observed by Swift/BAT. According to the data in the 15-50 keV band, this outburst began on December 24, and the latest flux reached 261 ± 16 mCrab on December 29. This flux level is comparable to the previous peak observed in 2010. We encourage multi-wavelength observations to reveal the nature of this source.

The latest X-ray light-curve can be checked at the following pages;
MAXI ( http://maxi.riken.jp/pubdata/v7.7l/J0440+445/index.html ),
Swift/BAT ( https://swift.gsfc.nasa.gov/results/transients/weak/LSVp4417/ ),
Fermi/GBM ( https://gammaray.nsstc.nasa.gov/gbm/science/pulsars/lightcurves/rxj0440.html ), and
the BeXRB monitor page ( http://integral.esac.esa.int/bexrbmonitor/Plots/sim_plot_LSV+4417.html ).