Rapid 15 GHz radio flare in the flat spectrum radio quasar CGRaBS J1738+3224
ATel #4861; Talvikki Hovatta, Mislav Balokovic, Walter Max-Moerbeck, Timothy Pearson, Anthony Readhead (Caltech)
on 5 Mar 2013; 21:03 UT
Credential Certification: Talvikki Hovatta (thovatta@caltech.edu)
Subjects: Radio, Optical, Blazar
We have observed a rapid flux density increase in the flat spectrum radio quasar CGRaBS J1738+3224 (z=0.126). Since 2008, the source has been observed approximately twice per week at
15 GHz with the Owens Valley Radio Observatory (OVRO) 40m Telescope as part of our gamma-ray blazar monitoring program (Richards et al. 2011, ApJS, 194, 29). On February 25, J1738+3224 reached a flux density of (321.6 +/- 8.2) mJy, nearly 4 times its median flux density and over 5 times its pre-flare flux density, last measured on December 21, 2012. Since January 21, the flux density has steadily increased from (143.6 +/- 10.9) mJy to its current flaring levels thereby doubling its flux density in just one month. The OVRO light curve is available on the
program website (log in with username 'guest' and no password).
This kind of rapid flaring has not been observed in this source since the OVRO monitoring began. Preliminary analysis of data from March 2 indicates that the source is still at the high flux density level. Optical observation on March 4 with the Palomar 60-inch telescope indicates that the source is not exceptionally bright in the optical with r = 16.18 +/- 0.02. This is ~0.5 magnitude fainter than the published value from SDSS DR8 and generally fainter than other published optical fluxes.
OVRO will continue to observe the source within the regular monitoring program. We encourage multiwavelength observations of this source during this extreme radio event.
The OVRO 40m monitoring program is supported in part by NASA grants NNX08AW31G and NNX11A043G, and NSF grants AST-0808050
and AST-1109911.
