MAXI/GSC observation of the possible long-term periodicity from the high-mass X-ray binary 4U 1210-64 (1ES 1210-646)
ATel #15771; M. Nakajima (Nihon U.), T. Mihara (RIKEN), H. Negoro, 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 (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 22 Nov 2022; 04:27 UT
Credential Certification: Motoki Nakajima (nakajima.motoki@nihon-u.ac.jp)
Subjects: X-ray, Binary, Neutron Star, Transient
4U 1210-64 (1ES 1210-646) is the peculiar X-ray binary discovered by the UHURU satellite (Forman et al. 1978). Since its first detection, the nature of the source had not been clear for 30 years. After the discovery of the 6.7 days periodicity observed by the RXTE/ASM in 2008 (Corbet et al. 2008; ATel#1861), the properties of the binary system were revealed by several X-ray observations (Masetti et al. 2010, Coley et al. 2014 and references therein). One of the intriguing results of this source is that source has exhibited two flux states (Coley et al. 2014, figure 1). These distinct states were examined by all RXTE/ASM data, Swift/BAT(MJD 55152-56141), and MAXI/GSC data (MJD 55061-56394). Following the previous works, we have investigated further temporal behavior of the flux states with the combined data spanning the past 27 years observed by the RXTE/ASM and the MAXI/GSC.
The 5-12 keV long-term light curve can be found at the following address,
http://maxi.riken.jp/figure/4U1210/4u1210_asm_gsc_125dbin.png .
The flux transition between the two distinct states continues and it seems to have a periodicity. We fit the long-term (ASM+MAXI) 5-12 keV light curve with the sum of the 1st - 5th order sine functions. The derived period is 5083+30-74 days, which is comparable to the doubled duration of the quiescent phase reported by Coley et al. (2014). In addition, we also confirmed that the eclipse of 6.71 days periodicity is derived from the MAXI/GSC data observed from MJD 58400 to 59898. Same as the previous works, no eclipse events were observed at the quiescent phase from MJD 56200 to 58400.
Multi-wavelength observations are encouraged to reveal the nature of the binary system.
