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Refined position of MAXI J1932+091, ruling out the BL Lac object 2FGL J1931.1+0938

ATel #6184; M. Morii (RIKEN), A. Kawagoe (Chuo U.), H. Negoro (Nihon U.), T. Mihara, M. Sugizaki, M. Serino, J. Sugimoto, T. Takagi, A. Yoshikawa, M. Matsuoka (RIKEN), S. Ueno, H. Tomida, S. Nakahira, M. Kimura, M. Ishikawa, Y. E. Nakagawa (JAXA), M. Nakajima, K. Fukushima, T. Onodera, K. Suzuki, M. Fujita, T. Namba, F. Honda (Nihon U.), N. Kawai, T. Yoshii, Y. Tachibana (Tokyo Tech), A. Yoshida, T. Sakamoto, Y. Kawakubo, H. Ohtsuki (AGU), H. Tsunemi, D. Uchida (Osaka U.), Y. Ueda, M. Shidatsu, T. Kawamuro, T. Hori (Kyoto U.), Y. Tsuboi (Chuo U.), M. Yamauchi, Y. Morooka (Miyazaki U.), K. Yamaoka (Nagoya U.), report on behalf of the MAXI team
on 30 May 2014; 07:27 UT
Credential Certification: Mikio Morii (morii@hp.phys.titech.ac.jp)

Subjects: X-ray, Transient

Referred to by ATel #: 6186

We refine the error region of the X-ray transient source MAXI J1932+091 reported in ATel #6174 (K. Yamaoka et al.). The revised source position is (R.A., Dec) = (293.232 deg, +9.344 deg) = (19 32 56, +09 20 38) (J2000) with a statistical 90% C.L. elliptical error region with long and short radii of 0.36 deg and 0.33 deg, respectively. The roll angle of the long axis from the north direction is 25.0 deg counter-clockwise. Here, the additional systematic uncertainty is refined to be 0.03 deg (90%C.L.). The position of 2FGL J1931.1+0938, which was suggested as the counterpart in Atel #6174, is located at 0.66 deg from the best position and outside the error region with the statistical 99%C.L. plus the systematic uncertainty. On the other hand, the new Swift source Swift J193310.4+091141 (Kennea et al. ATel #6177) found by the follow-up observation for MAXI J1932+091 is located at 0.16 deg from the best position and within this current refined position. We also performed spectral analysis for GSC data over the scan transits at 10:25, 11:57, and 15:03 UT on 26 March, 2014. The 2-20 keV spectrum has a peak count rate around 6-7 keV, indicating a very hard spectrum. An absorbed power law fit with a column density fixed at 2.3 x 10^22 cm-2 (ATel #6177) gives a photon index of 0.6 +/- 0.5. Thus, the hard energy spectrum also implies that the flaring X-ray source MAXI J1932+091 is the variable X-ray star Swift J193310.4+091141, rather than 2FGL J1931.1+0938.