Extreme variability quasars. II. SDSS sp. fitting

In this work we present the spectral fitting to their SDSS spectra and study the spectral variation in 1259 EVQs with multiepoch SDSS spectra (after prudently excluding spectra with potentially unreliable spectroscopic photometry). We find a clear "bluer-when-brighter" trend in EVQs, consistent with previous findings of normal quasars and active galactic nuclei.

We detect significant intrinsic Baldwin effect (iBeff, i.e., smaller line equivalent width at higher continuum flux in individual active galactic nuclei) in the broad MgII and CIV lines of EVQs. Meanwhile, no systematical iBeff is found for the broad H{beta} line, which could be attributed to strong host contamination at longer wavelengths. Remarkably, by comparing the iBeff slope of EVQs with archived changing-look quasars, we show that the changing-look quasars identified in the literature are most likely a biased (due to its definition) subpopulation of EVQs, rather than a distinct population of quasars.