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Radio observations of PKS 1510-089 at 43 GHz during July 2011

ATel #3523; P. P. Beaklini (IAG/USP), T. P. Dominici (MCT/LNA), Z. Abraham (IAG/USP)
on 2 Aug 2011; 00:46 UT
Credential Certification: Tania Dominici (tdominici@lna.br)

Subjects: Radio, Blazar

Referred to by ATel #: 3698, 3799

PKS 1510-089 has been monitored at 43 GHz since the beginning of the year with its 13.7 m Itapetinga Radio telescope in Atibaia, SP, Brazil. We reported here the behavior of the source at this frequency during the epochs of the two gamma-ray flares observed during July 2011, by AGILE and Fermi instruments (ATel #3470, ATel #3473 and ATel #3509).

The first one occurred near July 4. Bachev et al. (ATel #3479) reported that no optical variability was found about two days after the gamma-ray flare and, probably, there was no optical counterpart. However, at radio frequencies, Fuhrmann et al. (ATel #3500) showed that, according with their observations around July 8, PKS 1510-089 was brighter at 2.6, 15 and 23 GHz in comparison with the flux densities measured during June 2011. We observed the source on July 12 and registered a flux density of F(43 GHz)= 3.42 +/- 0.39 Jy. On June 2, F(43 GHz) = 2.13 +/- 0.41 Jy. Therefore, we also found an increase of flux density at 43 GHz around the first flare of July.

An increase of the optical flux between July 24 and 26 was communicated by Hauser et al. (ATel #3509) and their preliminary analysis of Fermi/LAT public data indicated the possibility of a second gamma-ray flare. We observed PKS 1510-089 on 27 July and obtained F(43 GHz) = 2.76 +/- 0.36 Jy. Within the errors, the blazar was in the same level observed on July 12.

Comparing the behavior of the source since the beginning of the year, we can say that the variability at 43 GHz observed during the month of July, when the gamma-ray flares occurred, was not different from the variability observed at other epochs during 2011. The mean flux density at 43 GHz measured during the monitoring campaign of 2011 until now is 2.79 +/- 0.13 Jy.