Rapid millimeter and centimeter band flux density increase in the gamma-ray blazar BL Lacertae
ATel #4565; Talvikki Hovatta (Caltech), Joseph L. Richards (Purdue), Walter Max-Moerbeck (Caltech), Timothy J. Pearson (Caltech), Anthony C. S. Readhead (Caltech)
on 10 Nov 2012; 22:06 UT
Credential Certification: Talvikki Hovatta (thovatta@caltech.edu)
Subjects: Radio, Millimeter, Blazar
We have observed a rapid flux density increase of BL Lacertae (2200+420) at 15 GHz (2 cm) and 95 GHz (3 mm) following the report on highest millimeter flux density ever observed at the SMA (ATel #4557). Since 2009, BL Lacertae 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 7 November 2012, BL Lacertae reached a flux density of (9.6 +/- 0.2) Jy after a rapid increase of 1.5 Jy in just 5 days from (8.1 +/- 0.2) Jy on 2 November. These are similar to flux density levels reported in August 2012 by the F-GAMMA program (ATel #4349) but the rapid rise time indicates a possibility for further increase.
Since August 2012 BL Lacertae has been observed as part of a gamma-ray blazar monitoring program with the Combined Array for Research in Millimeter-wave Astronomy (CARMA) at 95 GHz. On 6 November 2012, BL Lacertae reached a flux density of (19.8 +/- 3) Jy increasing by over 7 Jy since 24 October when its flux density at our 3mm observations was (12.7 +/- 1.9) Jy. Preliminary analysis of an observation on 10 November 2012 indicates that the flux has remained high at (18.4 +/- 2.8) Jy.
These rapid flux density changes along with the activity at other wavebands earlier this year (ATels #4028, #4031, #4155, #4271) and more recently within the F-GAMMA program (ATel #4349) and SMA, Herschel and Swift (ATel #4557) indicate that the source is undergoing an extreme flaring event. We will continue monitoring BL Lacertae with the OVRO 40m Telescope within our regular monitoring program twice per week and on weekly time scales with CARMA. Further multiwavelength observations are encouraged.
The OVRO 40m monitoring program is supported in part by NASA grants NNX08AW31G and NNX11A043G, and NSF grants AST-0808050 and AST-1109911. Support for CARMA construction was derived from the states of California, Illinois, and Maryland, the James S. McDonnell Foundation, the Gordon and Betty Moore Foundation, the Kenneth T. and Eileen L. Norris Foundation, the University of Chicago, the Associates of the California Institute of Technology, and the National Science Foundation. Ongoing CARMA development and operations are supported by the National Science Foundation under a cooperative agreement, and by the CARMA partner universities.
