MAXI/GSC detection of renewed activity from the gamma-ray source IGR J17379-3747

ATel #11447; H. Negoro (Nihon U.), S. Nakahira (RIKEN), S. Ueno, H. Tomida, M. Ishikawa, Y. Sugawara, N. Isobe, R. Shimomukai (JAXA), T. Mihara, M. Sugizaki, W. Iwakiri, 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, T. Kawase, A. Sakamaki, W. Maruyama (Nihon U.), Y. Ueda, T. Hori, A. Tanimoto, S. Oda, T. Morita, S. Yamada (Kyoto U.), Y. Tsuboi, Y. Nakamura, R. Sasaki, H. Kawai, T. Sato (Chuo U.), M. Yamauchi, C. Hanyu, K. Hidaka (Miyazaki U.), T. Kawamuro (NAOJ), K. Yamaoka (Nagoya U.), and M. Shidatsu (Ehime U.)
on 20 Mar 2018; 07:51 UT
Credential Certification: Hitoshi Negoro (negoro@phys.cst.nihon-u.ac.jp)

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The MAXI/GSC nova alert system (Negoro et al. 2016, PASJ, 68, S1) triggered on a faint X-ray transient source at 19:01 UT on March 19 2018 in 1d and 4d time bins. Assuming that the source flux was constant over each transit at 14:23 and 17:28 on the same day, we obtain the source position at
(R.A., Dec) = (264.733 deg, -37.948 deg) = (17 38 55, -37 56 52) (J2000)
with a statistical 90% C.L. elliptical error region with long and short radii of 0.41 deg and 0.34 deg, respectively. The roll angle of the long axis from the north direction is 180.0 deg counterclockwise. There is an additional systematic uncertainty of 0.1 deg (90% containment radius). The X-ray flux averaged over the two scans was 37 +- 11 mCrab (4.0-10.0keV, 1 sigma error). Preliminary GSC data analysis showed that the source flux in the 4-10 keV band has been increasing since March 14, whereas the 2-4 keV flux rapidly increased to about 20 mCrab on March 14 and declined.

The gamma-ray source IGR J17379-3747 (Bird et al. 2007, ApJS, 170, 175, also see Curran et al. 2013, arXiv 1107.2045v1) lies 0.26 deg from the center of the above error region. Interestingly, Swift/BAT 15-50 keV data (Krimm et al. 2013, ApJSS 209, 14; https://swift.gsfc.nasa.gov/results/transients/weak/IGRJ17379-3747/) also showed slight increase in the X-ray flux on March 14-18, but which was not significant on March 19 ((-0.2+/-3.0)e-3 c/cm2/s). On the other hand, the INTEGRAL Galactic Bulge Monitoring Program (Kuulkers et al. 2003, A&A, 466, 595; http://integral.esac.esa.int/BULGE/SOURCES/IGR_J17379-3747/IGR_J17379-3747.html ) data demonstrate a long-term upward trend in hard X-rays for about 100 days.

IGR J17379-3747 exhibited outbursts on February 2004 and September 2008 (e.g., ATel #1709, #1711, #1714; also see by C. Markwardt https://asd.gsfc.nasa.gov/Craig.Markwardt//galscan/html/XTE_J1737-376.html). MAXI/GSC data also showed weak 2-10 keV X-ray enhancement (~10 mCrab) probably from this source in the middle of February 2014. These suggest that IGR J17379-3747 undergoes outbursts every 4-5 years.

Trigger information of IGR J17379-3747