Broad band radio outburst of gamma-ray flaring blazar 4C+28.07

ATel #3674; I. Nestoras, L. Fuhrmann, E. Angelakis, R. Schmidt, T. P. Krichbaum, J. A. Zensus (MPIfR, Bonn, Germany), H. Ungerechts, A. Sievers, D. Riquelme (IRAM, Granada, Spain)
on 8 Oct 2011; 15:48 UT
Credential Certification: Lars Fuhrmann (lfuhrmann@mpifr-bonn.mpg.de)

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Responding to ATel #3670 reporting the recent Fermi LAT flaring activity of 4C+28.07 (J0237+2848) at gamma-rays on October 3, 2011, and the optical follow-up reported in ATel #3672, we here report its past and recent behavior at radio bands as observed by the F GAMMA program.

Long-term activity:
The source has been observed with the Effelsberg 100-m and the IRAM 30-m telescopes since January and June 2007, respectively. After reaching a high state in mid-2008, the source switched to a long-term decreasing trend reaching its minimum in 2010 (mm-bands: early 2010; cm-bands: up to end 2010).

Recent activity:
After this low-state in 2010, the source started to increase its flux again (mm-band: early 2010) at all observed frequencies with a clear time delay towards lower frequencies. This rising behavior is still continuing till present. For instance, at 10.45 GHz the flux increased from 2.43+/-0.05 Jy to 3.16+/-0.07 Jy, at 14.6 GHz from 2.39+/-0.07 Jy to 2.82+/-0.11 Jy and for 23 GHz from 2.20+/-0.12 Jy to 2.75+/-0.15 Jy for the period of January to September 2011. At 86 GHz the source increased from 1.94+/-0.06 Jy to 2.95+/-0.13 Jy for the period February 23, 2011 to September 30, 2011. This continued high radio activity is very likely related to the flaring event reported at gamma-rays. The radio light curves can be accessed separately at low, intermediate and high frequencies. Alternatively, also 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:
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 of order of 10 days. Data products are publicly accessible here.