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J0854+2006 (OJ 287) : mm/sub-mm flare with polarization angle change

ATel #14952; Seiji Kameno, Paulo Cortes, Edward Fomalont, Ruediger Kneissl, Antonio Hales, Celia Verdugo, Matias Radiszcz, Kurt Plarre, Cristian Lopez, Satoko Takahashi, Jose Fernandez, Jorge Garcia, Charles Hull, Pei-Ying Hsieh, Hugo Messias, David Rebolledo, Gabriel Marinello, Enrique Macias, Juan Cortes, Sergio Martin, Stuartt Corder (Joint ALMA Observatory), Claudia Agliozzo, Marie-Lou Gendron-Marsolais, Alvaro Ribas, Alejandro Santamaria, Chentao Yang, Eric Villard (European Southern Observatory), Brenda Matthews, Gerald Schieven (National Research Council Canada)
on 4 Oct 2021; 13:51 UT
Credential Certification: Seiji Kameno (seiji.kameno@alma.cl)

Subjects: Radio, Millimeter, Sub-Millimeter, AGN, Blazar

The Atacama Large Millimeter/submillimeter Array (ALMA) has been monitoring the blazar J0854+2006 (OJ 287) at 97.5, 233, and 343.5 GHz. The total flux densities at 97.5, 233, and 343.5 GHz achieved at 6.22 +- 0.19 Jy, 4.38 +- 0.14 Jy, and 3.87 +- 0.14 Jy, respectively, on 2021-09-29 (Gaussian convolution with a 5-day width). They have been doubled since the last trough values of 3.14 +- 0.10 Jy, 2.31 +- 0.11 Jy, and 1.94 +- 0.06 Jy on 2021-05-01. Linearly polarized flux densities are also high with the polarization degree of (6.0 +- 3.3)%, (6.6 +- 1.5)%, and (9.5 +- 0.5)%, respectively. The electric-vector position angles (EVPAs) of linear polarization have changed from -44.6 +- 2.4 deg, -45.5 +- 1.5 deg, and -44.0 +- 4.1 deg in April 2021 to -15.9 +- 8.3 deg, -19.6 +- 7.6 deg, and -12.2 +- 0.6 deg in September 2021 by ~30 deg. In addition to the latest flare event, there are identified but unreported flares coupled with polarization variations in June 2014, July 2015, December 2015, April 2016, August 2016, January 2018, and February 2020. See the detail of mm/sub-mm measurements: http://www.alma.cl/~skameno/AMAPOLA/J0854+2006.flux.html

Stokes parameter measurements of J0854+2006