Further MAXI/GSC observations show that GRS 1716-249/GRO J1719-24 is in outburst and currently in the hard state

ATel #9895; T. Masumitsu, K. Tanaka, T. Kawase, H. Negoro, (Nihon U.), M. Serino, W. Iwakiri (RIKEN), S. Ueno, H. Tomida, S. Nakahira, M. Ishikawa, Y. Sugawara (JAXA), T. Mihara, M. Sugizaki, 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 (Nihon U.), Y. Ueda, T. Kawamuro, T. Hori, S. Oda, A. Tanimoto (Kyoto U.), Y. Tsuboi, Y. Nakamura, R. Sasaki (Chuo U.), M. Yamauchi, K. Furuya (Miyazaki U.), K. Yamaoka (Nagoya U.) report on behalf of the MAXI team
on 23 Dec 2016; 02:07 UT
Credential Certification: Hitoshi Negoro (negoro@phys.cst.nihon-u.ac.jp)

Tweet

We report further observational results of the X-ray nova MAXI J1719-254 currently in outburst (Negoro et al. ATel #9876). The source has been slightly far (>= 8 deg) from the sun, which enables us to determine the source position statistically. The source position obtained from 10 scan transits from 11:16 UT on December 20 to 01:11 on December 21 is at
(R.A., Dec) = (259.907 deg, -25.065 deg) = (17 19 37, -25 03 54) (J2000)
with a statistical 90% C.L. elliptical error region with long and short radii of 0.06 deg and 0.04 deg, respectively. The roll angle of long axis from the north direction is 165.0 deg counterclockwise. There is an additional systematic uncertainty of 0.1 deg (90% containment radius).

The position of the black hole candidate GRS 1716-249/GRO J1719-24 is well inside of the error region of MAXI J1719-254 if we take the additional systematic uncertainty into account, and apart from the above best position by 0.05 arc degree. Thus, the X-ray nova in outburst is very likely to be GRS 1716-249.

The energy spectrum is likely to harden (see #9876), which suggests the source has undergone a transition to the hard state. A preliminary spectral analysis shows that a GSC spectrum averaged over scan transits from 01:05 to 22:50 on December 21 can be well represented by a power-law with a photon index of 1.62 +/- 0.06 (nH is fixed at 4e21atoms/cm2 (Tanaka 1993, IAU Circ. 5877)), which indicates the source is indeed in the hard state. The 2-10 keV flux is (3.3 +/- 0.3)e-9 erg/cm2/s (~140 mCrab).

MAXI data products for GRS 1716-249/GRO J1719-2