2017/05/08 by Nibedita Kalita, Alok C. Gupta, Paul J. Wiita +4 · 13 citations
Physics and Astronomy · #Astronomy #Astrophysical Phenomena and Observations #Astrophysics #Astrophysics and Cosmic Phenomena #Blazar #Compton scattering #Electron #Emission spectrum #Galaxies: Formation, Evolution, Phenomena #Galaxy #Gamma ray #Optics #Photon #Physics #Quasar #Scattering #Spectral line #Spectral shape analysis #Ultraviolet #astro-ph.HE
paper · pdf · doi:10.1093/mnras/stx1108
published in Monthly Notices of the Royal Astronomical Society 469(4), 3824-3839 (Oxford University Press) · 17 pages, 8 figures, 3 tables; Accepted for publication in MNRAS
arxiv created 2017/05/08 · openalex publication_date 2017/05/08 · openalex created_date 2017/05/19 · arxiv updated 2017/12/08 · openalex updated_date 2026/08/05
We analyse the 2.5–10 keV X-ray spectra of the luminous quasar 3C 273 and simultaneous observations in UV wavelengths from XMM–Newton between 2000 and 2015. The lowest flux level ever was observed in 2015. The continuum emission from 3C 273 is generally best described by an absorbed power-law but during extremely low states the addition of fluorescence from the K-shell iron line improves the fit. We study the spectral evolution of the source during its extended quiescent state and also examine connections between the X-ray and ultraviolet emissions, which have been seen in some, but not all, previous work. We detect a possible anticorrelation between these two bands during the low state that characterized 3C 273 for most of this period; however, this was not present during a flaring state. A harder-when-brighter trend for the X-ray spectrum was observed in these long-term observations of 3C 273 for the first time. We suggest that the X-ray emission in 3C 273 is the result of inverse Compton scattering of soft UV seed photons (emitted from the local environment of the AGN), most likely in a thermal corona. We can explain the significant temporal variation of the spectral continuum as an outcome of changing optical depth of the Comptonizing medium, along the lines of the wind-shock model proposed by Courvoisier and Camenzind.