The effect of variability on the estimation of quasar black hole masses

Brian C. Wilhite, Robert J. Brunner, Donald P. Schneider, Daniel E. Vanden Berk

Research output: Contribution to journalArticlepeer-review


We investigate the time-dependent variations of ultraviolet (UV) black hole mass estimates of quasars in the Sloan Digital Sky Survey (SDSS). From SDSS spectra of 615 high-redshift (1.69 < z < 4.75) quasars with spectra from two epochs, we estimate black hole masses using a single-epoch technique, which employs an additional, automated night-sky line removal and relies on UV continuum luminosity and C iv /11549 emission-line dispersion. Mass estimates show variations between epochs at about the 30% level for the sample as a whole. We determine that for our full sample, measurement error in the line dispersion likely plays a larger role than the inherent variability in terms of contributing to variations in mass estimates between epochs. However, we use the variations in quasars with r-band spectral signal-to-noise ratio greater than 15 to estimate that the contribution to these variations from inherent variability is roughly 20%. We conclude that these differences in black hole mass estimates between epochs indicate that variability does not make a large contribution to the current factor of 2 scatter between mass estimates derived from low- and high-ionization emission lines.

Original languageEnglish (US)
Pages (from-to)791-800
Number of pages10
JournalAstrophysical Journal
Issue number2
StatePublished - Nov 10 2007


  • Galaxies: active
  • Quasars: general
  • Techniques: spectroscopic

ASJC Scopus subject areas

  • Astronomy and Astrophysics
  • Space and Planetary Science


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