Emission-line Variability during a Nonthermal Outburst in the Gamma-Ray Bright Quasar 1156+295

• Published in: The Astrophysical journal Vol. 926; no. 2; pp. 180 - 198
• Main Authors: Hallum, Melissa K., Jorstad, Svetlana G., Larionov, Valeri M., Marscher, Alan P., Joshi, Manasvita, Weaver, Zachary R., Williamson, Karen E., Agudo, Iván, Borman, George A., Casadio, Carolina, Fuentes, Antonio, Grishina, Tatiana S., Kopatskaya, Evgenia N., Larionova, Elena G., Larionova, Liyudmila V., Morozova, Daria A., Nikiforova, Anna A., Savchenko, Sergey S., Troitsky, Ivan S., Troitskaya, Yulia V., Vasilyev, Andrey A.
• Format: Journal Article
• Language: English
• Published: Philadelphia The American Astronomical Society 01.02.2022; IOP Publishing
• Subjects: Accretion; Accretion disks; Astrophysics; Blazars; Clouds; Emission; Emission lines; Fluctuations; Gamma rays; High energy astrophysics; High-luminosity active galactic nuclei; Quasars; Radiation; Radiation-cloud interactions; Relativistic effects; Synchrotron radiation; Synchrotrons; Wavelengths
• ISSN: 0004-637X; 1538-4357
• DOI: 10.3847/1538-4357/ac4710

Abstract We present multi-epoch optical spectra of the γ -ray bright blazar 1156+295 (4C +29.45, Ton 599) obtained with the 4.3 m Lowell Discovery Telescope. During a multiwavelength outburst in late 2017, when the γ -ray flux increased to 2.5 × 10 −6 phot cm −2 s −1 and the quasar was first detected at energies ≥100 GeV, the flux of the Mg ii λ 2798 emission line changed, as did that of the Fe emission complex at shorter wavelengths. These emission-line fluxes increased along with the highly polarized optical continuum flux, which is presumably synchrotron radiation from the relativistic jet, with a relative time delay of ≲2 weeks. This implies that the line-emitting clouds lie near the jet, which points almost directly toward the line of sight. The emission-line radiation from such clouds, which are located outside the canonical accretion-disk related broad-line region, may be a primary source of seed photons that are up-scattered to γ -ray energies by relativistic electrons in the jet.