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15-GHz monitoring of FSRQ S4 0954+658

ATel #7007; Guy Pooley (Cavendish Astrophysics, University of Cambridge)
on 29 Jan 2015; 14:25 UT
Credential Certification: Guy Pooley (ggp1@cam.ac.uk)

Subjects: Radio, Infra-Red, Optical, AGN, Blazar

Referred to by ATel #: 7046, 7750, 8445, 10327, 16010

Atel #6996 and #7001 report NIR brightening and an optical flare of about 2 mag in the FSRQ S4 B0954+658 (J0958+6533). The AMI Large Array at the MRAO, Cambridge has been observing this object as a phase calibrator for monitoring the nearby radio nucleus of M81; this incidentally provides measurements of the flux density of the FSRQ. At 15 GHz, the flux density varies between 1 and 2 Jy on timescales of the order of months. There are occasional apparent shorter-term variations, e.g. an a single-observation 'flare' of about 20% on 2014 Nov 02, which is not obviously the result of a technical problem. Since that date, the flux density of the source has remained nearly constant, between 1.4 and 1.6 Jy. Monitoring is continuing, usually on a daily basis. Plots of the data for 2014 and 2015 may be found at http://www.mrao.cam.ac.uk/~guy/J0958+6533/2014.ps and http://www.mrao.cam.ac.uk/~guy/J0958+6533/2015.ps