MAXI/GSC detection of a new X-ray outburst of 4U 1630-472

ATel #9427; T. Masumitsu, H. Negoro (Nihon U.), S. Ueno, H. Tomida, S. Nakahira, M. Ishikawa, Y. Sugawara (JAXA), T. Mihara, M. Sugizaki, M. Serino, W. Iwakiri, M. Shidatsu, J. Sugimoto, T. Takagi, M. Matsuoka (RIKEN), N. Kawai, N. Isobe, S. Sugita, T. Yoshii, Y. Tachibana, Y. Ono, T. Fujiwara, S. Harita, Y. Muraki (Tokyo Tech), A. Yoshida, T. Sakamoto, Y. Kawakubo, Y. Kitaoka (AGU), H. Tsunemi, R. Shomura (Osaka U.), M. Nakajima, K. Tanaka, T. Kawase (Nihon U.), Y. Ueda, T. Kawamuro, T. Hori, A. Tanimoto (Kyoto U.), Y. Tsuboi, Y. Nakamura, R. Sasaki (Chuo U.), M. Yamauchi, K. Furuya (Miyazaki U.), K. Yamaoka (Nagoya U.), Y. E. Nakagawa (JAMSTEC)
on 30 Aug 2016; 05:26 UT
Credential Certification: Hitoshi Negoro (negoro@phys.cst.nihon-u.ac.jp)

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We report a new X-ray outburst of the black hole candidate 4U 1630-472 from MAXI/GSC observations. A preliminary analysis of GSC data shows X-ray flux increase from 2016 August 27 (MJD 57627). 1-day averaged 4-10 keV fluxes after the correction of photon leaks from the nearby bright source GX 340-0 are 0.027 +/- 0.006 photons/cm^2/s (~ 23 mCrab) on August 27, 0.060 +/- 0.007 ph/cm^2/s on August 28, and 0.125 +/- 0.009 ph/cm^2/s on August 29.

The Swift/BAT light curve of 4U 1630-472 (http://http://swift.gsfc.nasa.gov/results/transients/weak/4U1630-472/) also shows increase of hard X-rays from August 27, which indicates that the flux increase detected by MAXI is from this source.

This is the 4th detection of outbursts from 4U 1630-472 since the MAXI launch in 2009, and the previous outbursts started from 2009 December 26 (MJD 55191, ATel #2363), 2011 December 17 (MJD 55912, ATel #3830), and 2015 Jan. 25 (MJD 57047, ATel #6991). In the previous outbursts, the source has exhibited peculiar properties in time profiles of the outbursts and state transitions.
Follow-up observations are encouraged.

MAXI Public Data Products of 4U 1630-472