Multiwavelength activity of the gamma-ray blazar PKS 2233-148

ATel #4222; K. V. Sokolovsky (ASC Lebedev/SAI MSU), D. J. Thompson, D. Donato (NASA/GSFC), S. Ciprini (ASDC and INAF Obs. of Rome), on behalf of the Fermi/LAT collaboration; P. G. Edwards, J. Stevens (CSIRO); S. J. Wagner, G. Cologna (LSW Heidelberg) on behalf of the ATOM team; P. S. Smith (Steward Obs.)
on 28 Jun 2012; 13:20 UT
Credential Certification: Kirill Sokolovsky (kirx@scan.sai.msu.ru)

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On 2012 June 4, the BL Lac-type blazar PKS 2233-148 showed a gamma-ray flare detected by Fermi/LAT and AGILE (ATel #4152, #4154). Preliminary analysis of further Fermi/LAT observations indicates continued gamma-ray activity of the source reaching the peak daily flux of (3.2+/-0.4)x10^-6 ph/cm^2/sec (E>100 MeV) on June 20 (estimated error is statistical only).

Radio observations with the Australia Telescope Compact Array (ATCA) on June 25 21h UT show the elevated flux density levels compared to previous ATCA, VLA, and RATAN-600 observations: at 9.0 GHz, a flux density S = 1.0 Jy and spectral index (across the 2 GHz bandwidth) a = 0.4 (S ~ nu^+a), at 19 GHz S = 1.3 Jy and a = 0.2, at 40 GHz S = 1.5 Jy and a = -0.1. The overall 9-40 GHz spectral index is slightly inverted (a = 0.3) compared to the historical value of a = -0.2 (ATel #2589). The flux density measurement accuracy is limited by calibration uncertainties on a few percent level. The source was unresolved by ATCA on baselines up to 6km.

Optical spectropolarimetry and spectrophotometry of PKS 2233-148 were obtained on June 17-21 using the Steward Observatory 1.54m Kuiper Telescope. Preliminary analysis indicates that the object brightened by 0.4mag in both V and R bands between the first 2 nights and then faded back during the next 3 nights. The level of linear polarization measured in the 5000-7000A range varies between 6 and 17% during this period, though the polarization angle remains relatively stable around PA~120 deg.

PKS 2233-148 has been observed continuously in the R band with the ATOM telescope in Namibia. On May 26, the brightness exceeded R = 16 and varied around R ~ 15 between June 2 and June 22. Since June 23 the flux has declined.

We encourage further multiwavelength observations to trace the flare development across the electromagnetic spectrum.

The previous flare of PKS 2233-148 detected in gamma-rays by Fermi/LAT (peak flux 0.7x10^-6 ph/cm^2/sec) and X-rays/UV by Swift was in April 2010 (ATel #2589). PKS 2233-148 is one of the Fermi/LAT monitored sources.

Historical PKS 2233-148 flux density measurements are available at the ATCA Calibrator Database.