3C 138: Millimeter/submillimeter polarized flare
ATel #17193; Seiji Kameno, Elizabeth Artur, Yoshiharu Asaki, Luciano Cerrigone, Paulo Cortes, Andres Guzman, Kevin Harrington, Ruediger Kneissl, Evgenia Koumpia, Cristian Lopez, Gabriel Marinello, Sergio Martin, Hugo Messias, Jorge Morgado, Priscilla Nowajewski, Andres Perez, Kurt Plarre, Matias Radiszcz, Tsuyoshi Sawada, Yiqing Song, Ignacio Toledo, Celia Verdugo, Baltasar Vila Vilaro (Joint ALMA Observatory), Gianni Cataldi, Hiroshi Nagai, Kouichiro Nakanishi (NAOJ), Edward Fomalont (NRAO), Rosita Paradino (INAF)
on 19 May 2025; 15:05 UT
Credential Certification: Seiji Kameno (seiji.kameno@alma.cl)
Subjects: Radio, Millimeter, Sub-Millimeter, AGN, Quasar
The Atacama Large Millimeter/submillimeter Array (ALMA) is monitoring full-Stokes parameters of extragalactic radio sources at 40.0, 97.5, 154.9, 233.0, and 343.4 GHz. The telescope identified highly polarized flare in the CSS quasar 3C 138 (J0521+1638) at the coordinate of RA=05:21:09.886 DEC=+16.38.22.052 in J2000.0, following reports on gamma-ray (ATel #16845, #17107, #17180), X-ray (ATel #17142, and radio (ATel #17077, #17104) activities.
The flux densities (Stokes I) at the beginning of flare around 2023-06-03 were 1.210 +- 0.024 Jy (40.0 GHz), 0.682 +- 0.008 Jy (97.5 GHz), 0.470 +- 0.005 Jy (154.9 GHz), 0.349 +- 0.007 Jy (233.0 GHz), and 0.280 +- 0.004 Jy (343.4 GHz). They have increased to 2.578 +- 0.023 Jy (40.0 GHz), 2.041 +- 0.006 Jy (97.5 GHz), 1.522 +- 0.003 Jy (154.9 GHz), 1.446 +- 0.007 Jy (233.0 GHz), and 1.190 +- 0.023 Jy (343.4 GHz) on 2025-05-15. The polarization degree before the flare was 5% - 6% and sporadically flared to 11.0% +- 0.37% around 2024-01-13, and settled down to the normal level of 5% - 6%. The EVPA ~ -32 deg before the flare gradually changed to -57 deg on 2025-05-15. See also the plots.
Plots of total and polarized flux densities of 3C 138
