Broad line region and black hole mass of PKS 1510-089 from spectroscopic reverberation mapping

Abstract

Reverberation results of a flat spectrum radio quasar PKS 1510-089 are presented from 8.5-years long spectroscopic monitoring carried out in 9 observing seasons between December 2008 to June 2017 at Steward Observatory. Optical spectra show strong H$\beta$, H$\gamma$, and Fe II emission lines overlaying on a blue continuum. All the continuum and emission line light curves show significant variability with a fractional root-mean-square variation of $37.30\pm0.06$% ($f_{5100}$), $11.88\pm0.29$% (H$\beta$) and $9.61\pm0.71$% (H$\gamma$), however, along with thermal radiation from accretion disk non-thermal emission from jet also contribute to $f_{5100}$. Several methods of time series analysis (ICCF, DCF, von Neumann, Bartels, JAVELIN, $\chi^2$) are used to measure lag between continuum and line light curves. The observed frame BLR size is found to be $61.1^{+4.0}_{-3.2}$ ($64.7^{+27.1}_{-10.6}$) light-days for H$\beta$ (H$\gamma$). Using $\sigma_{\mathrm{line}}$ of $1262\pm247$ km s$^{-1}$ measured from the rms spectrum, the black hole mass of PKS 1510-089 is estimated to be $5.71^{+0.62}_{-0.58} \times 10^{7} M_{\odot}$.