MAXI/GSC detection of renewed X-ray activities of SAX J1324.5-6313/MAXI J1327-627 and H 1658-298/MAXI J1702-301

ATel #7943; H. Negoro (Nihon U.), K. Furuya (Miyazaki U.), S. Ueno, H. Tomida, S. Nakahira, M. Kimura, M. Ishikawa, Y. E. Nakagawa (JAXA), T. Mihara, M. Sugizaki, M. Serino, M. Shidatsu, J. Sugimoto, T. Takagi, M. Matsuoka (RIKEN), N. Kawai, Y. Tachibana, T. Yoshii (Tokyo Tech), A. Yoshida, T. Sakamoto, Y. Kawakubo, H. Ohtsuki (AGU), H. Tsunemi, R. Imatani (Osaka U.), M. Nakajima, T. Masumitsu, K. Tanaka (Nihon U.), Y. Ueda, T. Kawamuro, T. Hori (Kyoto U.), Y. Tsuboi, S. Kanetou (Chuo U.), M. Yamauchi, D. Itoh (Miyazaki U.), K. Yamaoka (Nagoya U.), M. Morii (ISM) report on behalf of the MAXI team
on 23 Aug 2015; 00:10 UT
Distributed as an Instant Email Notice Transients
Credential Certification: Hitoshi Negoro (negoro@phys.cst.nihon-u.ac.jp)

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At 07:53 UT on 2015 August 21 (MJD 57255), the MAXI/GSC nova alert system triggered a faint X-ray enhancement at the position
(R.A., Dec) = (201.875 deg, -62.794 deg) = (13 27 29, -62 47 39) (J2000)
with a 90% C.L. statistical error of 0.33 deg and an additional systematic uncertainty of 0.1 deg (90% containment radius). The position is apart from that of a transient low-mass X-ray binary SAX J1324.5-6313 by 0.55 deg. The 4-10 X-ray photon flux averaged over 18 scan transits from 16:29 on August 20 to 23:17 on August 21 was 0.0087 +/- 0.0034 counts/cm2/s (~ 8 mCrab).

During the scan transit at 09:25 on August 21, a flare-like activity, of which the 4-10 keV photon flux was 0.071 +/- 0.023 c/cm2/s (~65 mCrab), was also observed from the region at
(R.A., Dec) = (202.670 deg, -62.490 deg) (J2000)
with a statistical 90% C.L. elliptical error region with long and short radii of 0.60 deg and 0.43 deg, respectively. The roll angle of long axis from the north direction is 106.0 deg counterclockwise. If the flare data is excluded, the position is consistent with that of SAX J1324.5-6313;
(R.A., Dec) = (201.629 deg, -63.061 deg) = (13 26 30, -63 03 40) (J2000)
with a statistical error of 0.44 deg. The 4-10 X-ray photon flux averaged over 17 scan transits becomes, however, less significant, 0.0061 +/- 0.0034 counts/cm2/s.

At 17:05 UT on August 21, the nova alert system also triggered an X-ray transient source at the position,
(R.A., Dec) = (255.542 deg, -30.130 deg) = (17 02 10, -30 07 47) (J2000)
with an elliptical error region with long and short radii of 0.30 deg and 0.24 deg, respectively. The roll angle is 150.0 deg counterclockwise. The position is consist with that of a transient low-mass X-ray binary H 1658-298 (4U 1704-30), 0.185 deg apart from the best position. The 4-10 keV flux has gradually increased since the beginning of August 21. The X-ray flux averaged over 7 scan transits from 02:20 to 11:36 on August 22 was 0.030 +/- 0.007 c/s/cm2 (~25 mCrab).

SAX J1324.5-6313 is a very low persistent emission source with less than 1e-12 erg/cm2/s (Cornelisse et al. 2002, A&A, 392, 931), and no recent activity was reported. H 1658-298 often exhibited X-ray bursts in 1970s, but it also has been in a prolonged off state since 1980s (White, Nagase, and Parmar, 1995, in "X-ray Binaries", eds Lewin, van Paradijs, and van den Heuvel). From both the sources, no significant burst activity has not been observed, yet. So, we tentatively name the sources, MAXI J1327-627 and MAXI J1702-301, respectively.

We encourage followup observations to confirm activities of these new or long-off-state sources.