Non-detection of flare at 22 GHz of Sgr A* induced by the approaching G2 cloud in February and March 2013
ATel #4923; M. Tsuboi, Y. Asaki(ISAS/JAXA), Y. Yonekura(Ibaraki Univ.), H. Kaneko, Y. Miyamoto, M. Seta, N. Nakai (Univ. of Tsukuba), O. Kameya, M. Miyoshi(NAOJ), H. Takaba, K. Wakamatsu(Gifu Univ.), Y. Fukuzaki(GSI), T. Morimitsu(Univ. of Tokyo), M. Sekido(NICT), T. Omodaka, T. Handa(Kagoshima Univ.), and A. Takumi(OUJ)
on 28 Mar 2013; 10:23 UT
Credential Certification: Masato TSUBOI (tsuboi@vsop.isas.jaxa.jp)
Subjects: Radio, Black Hole, Transient
We have started monitor observations of Sgr A* with a short-baseline VLBI(Mizusawa10-m RT, Takahagi32-m RT, Tsukuba32-m RT, and Gifu11-m RT) which is a subset of the Japanese VLBI Network in order to search the increase of 22-GHz emission from Sgr A* induced by the interaction of the G2 cloud with the accretion disk (Gillessen et al. 2012, Nature, 481, 51). Even for the ordinary Sgr A*, small flare(Delta S/S ~ 10-20 %) has been detected repeatedly at 22 GHz (e.g. Yusef-Zadeh et al. 2006, ApJ, 650, 189) although no such flare has been detected at lower frequency (see the archival data of GBI). And high angular resolution better than 1â is necessary to measure the flux density of Sgr A* suppressing unnecessary contribution from the surrounding HII region. The average flux density at 22 GHz of Sgr A* was 1.03+-0.04 Jy (preliminary) in the observing period from 11 February to 24 March 2013. This flux density is consistent with the previously observed values. We have detected no large flare by the approaching G2 cloud in the period.
