Quasi-simultaneous, full-Stokes millimeter radio observations of the blazar PKS 1741-03 with the IRAM 30m Telescope in the proximity of the neutrino event IceCube-220205B
ATel #15222; Ioannis Myserlis (IRAM, MPIfR), Ivan Agudo (IAA-CSIC), Carolina Casadio (IA-FORTH), Clemens Thum (IRAM), Thalia Traianou (IAA-CSIC), Juan Escudero (IAA-CSIC), Joana Kramer (MPIfR) on behalf of the POLAMI collaboration
on 11 Feb 2022; 13:50 UT
Credential Certification: Ioannis Myserlis (imyserlis@iram.es)
Subjects: Radio, Millimeter, Neutrinos, AGN, Blazar, Quasar
On February 5, 2022 the IceCube collaboration reported the GOLD event IC-220205B, in the proximity of the bright blazar PKS 1741-03 (GCN #31554). Three days later, we performed full-Stokes observations of this blazar at 3.5mm and 1.3mm with the IRAM 30m telescope, within the framework of the POLAMI monitoring program and we report here our findings. For more details about the POLAMI program visit http://polami.iaa.es/.
Our observations of PKS 1741-03 on February 8, 2022 (MJD 59618.3875) yield a total flux density (Stokes I) of 2.49 +/- 0.12 Jy at 3.5mm (86.24 GHz) and 1.27 +/- 0.06 Jy at 1.3mm (228.93 GHz), corresponding to a typical optically thin spectral index of -0.69. The source is significantly linearly polarized at 3.5mm with linear polarization degree of 3.2 +/- 0.5 % and polarization angle of 79.9° +/- 4.8°. At 1.3mm, its linear polarization was measured at a 2.5σ level to be 5.1 +/- 2 % with a similar polarization angle of 81.3° +/- 8.8°. Moreover, in both bands no significant circular polarization was detected.
Based on the recent and past observations by the POLAMI monitoring program, the source seems to be currently in a low total flux density state at millimeter wavelengths, in agreement with radio observations at longer wavelengths reported in ATel #15215. The latest high flux state recorded by POLAMI was around January - March 2021 with a total flux density of 6.27 +/- 0.31 Jy and 5.53 +/- 0.28 Jy at 3.5mm on 27 Jan 2021 (MJD 59241.5008) and 9 Mar 2021 (MJD 59282.2804), respectively, and 2.83 +/- 0.14 Jy at 1.3mm on 9 Mar 2021 (MJD 59282.2804), corresponding again to a spectral index of -0.69 in March 2021. However, it is interesting to note that the linear polarization degree of the source was lower during that high total flux density state (1.8 +/- 0.6 % at 3.5mm), suggesting that the linearly polarized flux remained stable at about 80-110 mJy, albeit with a polarization angle almost perpendicular to the current value (-11.7° +/- 7.3° at 3.5mm). We also note that the polarization angle has been rotating steadily since January 2021 with a mean rate of 0.24°/day. Finally, no circular polarization was detected also during its high total flux density state in early 2021.
We will continue monitoring the blazar PKS 1741-03 with the POLAMI program at high-cadence and report any changes of its activity in total flux density, linear or circular polarization.
POLAMI program website
