Extending the Eigenvector 1 Space to the Optical Variability of Quasars

TL;DR

This paper extends the Eigenvector 1 space for quasars by incorporating optical variability amplitude, revealing strong correlations with spectral features and luminosity, suggesting the Eddington ratio influences quasar variability.

Contribution

It introduces optical variability amplitude into the Eigenvector 1 space and demonstrates its correlations with spectral and luminosity properties of quasars.

Findings

Optical variability amplitude correlates with Fe II/Hβ ratio.

Optical variability amplitude correlates with Hβ line width.

Optical variability amplitude correlates with peak luminosity at 5007 Å.

Abstract

We introduce a new physical parameter, the optical variability amplitude, to the well-established Eigenvector 1 space of quasars and test a sample of long-term B-band light curves of 42 PG quasars monitored by Giveon et al. (1999). We find that the optical variability amplitude strongly correlates with the intensity ratio of Fe II to H$\beta$, H$\beta$ width and peak luminosity at 5007$\rm{\AA}$. We briefly discuss the physical meaning of our findings and suggest that the Eddington ratio may be a key factor in determining a quasar's variability.