Fading of the broad H-beta emission in OQ 208 from Copernico spectroscopic observations

ATel #15354; Bo-Wei Jiang (Key Laboratory for Particle Astrophysics, Institute of High Energy Physics, CAS, China), Paola Marziani (INAF, Astronomical Observatory of Padua, Italy), Jian-Min Wang, Pu Du (Key Laboratory for Particle Astrophysics, Institute of High Energy Physics, CAS, China), Mauro D'Onofrio, Maria Bazzicalupo, Luca Cortese, Alberto Floris, Benedetta Mestichelli (Dipartimento di Fisica & Astronomia, University of Padua, Italy)
on 29 Apr 2022; 13:35 UT
Credential Certification: Paola Marziani (Paola.marziani@inaf.it)

Tweet

We report the strong fading of the Hβ emission in the broad line radio galaxy OQ 208 (z=0.07666+-0.00004) from observations obtained at the Copernico 1.82m telescope of INAF on Mount Ekar in Italy.

The Hβ broad component flux dropped by a factor of 4 with respect to the previous SDSS spectroscopic observations, obtained on 2006-02-27 (MJD=53793.35611).

The peak of Hβ broad component redshifted by 2800 km/s with respect to the quasar rest frame set by the H-beta NC that made this object peculiar among AGN has apparently disappeared in the Copernico spectroscopic observations on 2022-03-28 (MJD=59666.03495), after it had remained visible since its identification more than 40 years ago (Osterbrock, D. E. & Cohen, R. 1979, MNRAS, 187, 61). A multicomponent model of the Hβ profile suggests that a fainter emission feature may now be present at a shift of ~6000 km/s with respect to the rest frame.

The fading is also associated with a minimum in the photometric light curve. g and V magnitudes were estimated from the unfiltered AFOSC acquisition images, using two nearby red stars with SDSS photometry (RA=211.72104d Dec=28.45457d, g≈ 14.75, g-r ≈0.75; RA=211.75555d Dec=28.47607d, g ≈ 15.57, g-r ≈ 0.44):

The  Zwicky Transient Facility (ZTF)  data consistently show  an increase  by 0.35 magnitudes from MJD 58202.85867 to 59449.70255.