Progress Report of the Monitor of Sgr A* with Japanese VLBI Network at 22 GHz until 2014/76
ATel #6004; M. Tsuboi, Y. Asaki(ISAS/JAXA), Y. Yonekura, Y. Miyamoto, (Ibaraki Univ.), H. Kaneko, 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), and M. Sekido(NICT)
on 24 Mar 2014; 08:10 UT
Credential Certification: Masato TSUBOI (tsuboi@vsop.isas.jaxa.jp)
Subjects: Radio, AGN, Black Hole, Transient
Referred to by ATel #: 6083
We have been monitoring Sgr A* at 22 GHz since Feb. 2013 with a sub-array of Japanese VLBI Network (JVN) (ATEL#4923, #5013) in order to explore the flux density variability with the G2 cloud approaching (Gillessen et al. Nature 2012, 418, 51). The sub-array consists of Mizusawa 10-m RT, Takahagi /Hitachi 32-m RT, and Gifu 11-m RT. Tsukuba 32-m RT and Kashima 34-m RT have joined it sometimes. Because the sub-array has projected baselines of 90- 140 km, we can observe the flux density of Sgr A* itself avoiding the contamination from extended structure surrounding Sgr A* and the flux density decrease by partially resolved-out. The data before 2013/180 had been reported in ATEL #5184. Here, we present the (preliminary) result after 2013/250. The intermission between 2013/180 and 2013/250 corresponds to the Japanese summer rainy season. The average flux density in DOY= 2013/250â2014/76 (46) is S\nu= 1.13+/- 0.23 Jy. The number in the parenthesis is number of observation epochs in the observation period. The error shows the scattering range (r.m.s.) of the observed flux densities. The average and scattering range are consistent with the previously observed values. They are also consistent with those of the VLA monitor (ATEL#5545, #5649, #5727 and #5969). We have observed no strong flare of Sgr A* until 2014/76.
