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MAXI/GSC detection of a soft X-ray transient MAXI J1630-276

ATel #10984; H. Negoro, T. Kawase, A. Sakamaki (Nihon U.), S. Ueno, H. Tomida, M. Ishikawa, Y. Sugawara, N. Isobe, R. Shimomukai (JAXA), T. Mihara, M. Sugizaki, S. Nakahira, W. Iwakiri, M. Shidatsu, F. Yatabe, Y. Takao, M. Matsuoka (RIKEN), N. Kawai, S. Sugita, T. Yoshii, Y. Tachibana, S. Harita, K. Morita (Tokyo Tech), A. Yoshida, T. Sakamoto, M. Serino, Y. Kawakubo, Y. Kitaoka, T. Hashimoto (AGU), H. Tsunemi, T. Yoneyama (Osaka U.), M. Nakajima (Nihon U.), Y. Ueda, T. Hori, A. Tanimoto, S. Oda (Kyoto U.), Y. Tsuboi, Y. Nakamura, R. Sasaki, H. Kawai (Chuo U.), M. Yamauchi, C. Hanyu, K, Hidaka (Miyazaki U.), T. Kawamuro (NAOJ), and K. Yamaoka (Nagoya U.)
on 18 Nov 2017; 04:36 UT
Distributed as an Instant Email Notice Transients
Credential Certification: Hitoshi Negoro (negoro@phys.cst.nihon-u.ac.jp)

Subjects: X-ray, Black Hole, Blazar, Neutron Star, Quasar, Transient

Referred to by ATel #: 11173, 11198

The MAXI/GSC nova-alert system triggered on a faint uncatalogued X-ray transient source at 11:42 UT on 2017 November 17. Assuming that the source flux was constant over the transit, we obtain the source position at
(R.A., Dec) = (247.682 deg, -27.607 deg) = (16 30 43, -27 36 25) (J2000)
with a statistical 90% C.L. elliptical error region with long and short radii of 0.27 deg and 0.23 deg, respectively. The roll angle of the long axis from the north direction is 36.0 deg counterclockwise. There is an additional systematic uncertainty of 0.1 deg (90% containment radius). The X-ray flux averaged over the scan was 45 +- 7 mCrab (4.0-10.0keV, 1 sigma error).

Preliminary analysis shows that weak enhancement in soft X-rays has been recognized since the scan transit 15:38 on 2017 November 16. There is no significant variability in the MAXI/GSC data.

Two ROSAT X-ray Survey sources are present just out of the elliptical error region, 1RXS J163200.2-273335 (0.28 deg apart) and 1RXS J163035.5-275500 (0.31 deg). The nature of the two sources and this transient are all unknown, then we tentatively name the source J1630-276.

Multi-wavelength followup observations are encouraged even though the source is close to the Sun (15.8 deg).

Detection information for MAXI J1630-276