NRAO VLA service monitoring observations of Sgr A*

ATel #5545; Claire J. Chandler(NRAO) and Lorant O. Sjouwerman(NRAO)
on 5 Nov 2013; 01:11 UT
Credential Certification: Lorant Sjouwerman (lsjouwer@nrao.edu)

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As part of an ongoing community service observing program to follow the expected encounter of the G2 cloud with the black hole Sgr A* in 2013 (https://science.nrao.edu/enews/5.10/index.shtml#g2_encounter), the NRAO Very Large Array observed the Sgr A region starting 2013 October 26 00:52 UT for two hours, cycling through the standard observing bands at their default 8-bit (i.e., up to 2 GHz bandwidth) continuum frequencies. The data from the monitoring program are publicly available through the NRAO data archive immediately after observing has completed, and the flux densities are published by NRAO staff as soon as the data are reduced. The October 26 data were reduced with a modified VLA CASA pipeline, and the flux density of Sgr A* was measured as listed below. Due to the configuration of the VLA (i.e., B-configuration), and Sgr A* being embedded in the extended emission of the circumnuclear disk and the supernova shell, the lower frequency measurements are upper limits. The cumulative results of the monitoring effort are posted on the service observing web page https://science.nrao.edu/science/service-observing and so far do not indicate a significant brightening of the emission from the direction of Sgr A* over the period 2012 October to 2013 October, within the calibration uncertainties. Measurements of 2013 October 26: 1.5 GHz (1.6 Jy upper limit) 3.0 GHz (0.9 Jy upper limit) 5.5 GHz 0.81 10.0 GHz 0.91 +/-10% Jy 14.0 GHz 1.05 +/-10% Jy 21.2 GHz 1.20 +/-10% Jy 32.0 GHz 1.38 +/-10% Jy 41.0 GHz 1.47 +/-10% Jy