Gamma-ray blazar BL Lacertae: the highest recorded cm/mm radio flux over the past 30 years

ATel #4349; V. Karamanavis, I. Myserlis, L. Fuhrmann, E. Angelakis, I. Nestoras, T. P. Krichbaum, J. A. Zensus (F-GAMMA team, MPIfR, Bonn, Germany), H. Ungerechts, A. Sievers, D. Riquelme (IRAM, Granada, Spain)
on 31 Aug 2012; 15:26 UT
Credential Certification: Lars Fuhrmann (lfuhrmann@mpifr-bonn.mpg.de)

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We report on the recent flaring behavior of 2200+420 (BL Lacertae) at radio bands as observed by the F-GAMMA program.

Recent activity:
Radio observations performed with the Effelsberg 100-m and the IRAM 30-m telescopes reveal that BL Lacertae is currently in high state - the highest since the historical maximum of 1981 as observed by the University of Michigan Radio Astronomy Observatory (about 16 Jy at 14.5 GHz, e.g. Aller et al. 1999, see also UMRAO light curve). The highest flux densities have been measured at mm-wavelengths during observations on August 3, 2012. Specifically, BL Lacertae reached 8.91 +/- 0.78 Jy at 9mm (32.00 GHz) as observed with the Effelsberg 100-m telescope. The IRAM 30-m observations of July 30, 2012 yielded flux densities of 10.94 +/- 0.89 Jy at 3mm (86GHz) and 10.90 +/- 0.78 Jy at 2mm (142GHz), respectively. During our last Effelsberg observations on August 20 we obtained the highest flux densities also at cm-bands: a value of 9.42 +/- 0.27 Jy has been observed at 2cm (14.60 GHz), while at 1.3cm (23 GHz) the flux density reached 10.03 +/- 0.34 Jy. The flux density at 9mm (32.00 GHz) reached 8.54 +/- 0.30, while the latest IRAM 30-m observations (August 27) show values of 9.78 +/- 0.59 Jy and 9.42 +/- 0.66 Jy at 3 and 2mm wavelengths, respectively. These values may indicate the beginning of a decrease of flux densities at short wavelengths.

Long-term activity:
The aforementioned values are the highest recorded at their respective wavelengths since the start of the F-GAMMA program in 2007. In particular, the current maximum is part of a long-term increasing trend (starting around mid-2008) showing several more rapid sub-flares superimposed. We also note the recent optical and gamma-ray activity of BL Lacertae announced in ATel #4031 and ATel #4028 likely related to the radio activity of the source reported here.

The F-GAMMA radio light curves can be accessed separately at low, intermediate and high frequencies. A cummulative plot resides here. Alternatively, the evolution of its spectrum as a function of time can be accessed.

The source will be continuously monitored and possible future activity will be reported through the current platform.

F-GAMMA program:
The F-GAMMA (Fermi-GST AGN Multi-frequency Monitoring Alliance) program is the coordinated effort of several observatories and research teams to probe AGN physics through the multi-frequency monitoring approach. The core program relies on monthly observations with the Effelsberg 100-m radio telescope (operating at 8 frequencies between 2.6 and 43 GHz), the IRAM 30-m telescope (observing at 86 and 142 GHz) and additional measurements with the APEX 12-m telescope (operating at 345 GHz). The core sample consists of roughly 60 Fermi-GST/LAT monitored blazars. The data are taken quasi-simultaneously within 40 minutes for Effelsberg and truly simultaneous at the IRAM telescope while the cross-station coherency is better than 10 days. Data products are publicly accessible here.