Broad-band radio behaviour of flaring blazar 4C+38.41

ATel #3360; E. Angelakis, L. Fuhrmann, I. Nestoras, R. Schmidt, J. A. Zensus, T. P. Krichbaum (F-GAMMA team, MPIfR, Bonn, Germany), H. Ungerechts, A. Sievers, D. Riquelme (IRAM, Granada, Spain)
on 18 May 2011; 15:11 UT
Credential Certification: Emmanouil Angelakis (angelaki@mpifr-bonn.mpg.de)

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Broad-band radio behaviour of flaring blazar 4C+38.41

Following the recent flaring activity of 4C38.41 (J1635+3808, RA= 16:35:15.5, DEC:+38:08:04.5, J2000) reported at NIR band with ATel #3238 and #3335 and gamma-rays with ATel #3333, we here report on the recent activity of the source at radio bands. The reported activity in the high energy bands seems to be taking place during a long-term increasing trend at cm/mm wavelengths.

The source has been observed with the Effelsberg 100-m and the IRAM 30-m telescope, since January and late March 2007, respectively. Since then, it has been showing a persistent, long-term increasing trend until May 2011, dominant at all wavelengths. Indicatively, at 4.85 GHz (60 mm) the flux density increased from 2.8 Jy on Jan. 29, 2007 to 3.5 Jy on May 1, 2011 and at 32 GHz (9 mm) from roughly 2 Jy on Feb. 24, 2007 to 3.6 Jy on May 5, 2011.The 4-year long light curves of the source can be found here. Interestingly, the frequencies below 23 GHz show a flattening / mild decrease over the last months.

The long term trend can also be seen in the temporal evolution of the spectrum, which appears rather flat as it can be seen here with some short-term fluctuations propagating from the mm bands towards longer cm wavelengths. No sign of a quiescent, optically thin spectrum is visible in F-GAMMA single dish data.

The F-GAMMA program will continue monitoring the source as part of its regular sample. Future events will be reported accordingly.

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 simultaneously within 40 minutes for Effelsberg and 10 minutes for the IRAM telescope while the cross-station coherency is of order of 10 days. All related details can be found at:
www.mpifr.de/div/vlbi/fgamma

F-GAMMA web site