| Autor: |
Sirola, Christopher J., Turnshek, David A., Weymann, Ray J., Monier, Eric M., Morris, Simon L., Roth, Miguel R., Krzeminski, Wojtek, Kunkel, William E., Duhalde, Oscar, Sheaffer, Steven |
| Zdroj: |
The Astrophysical Journal; March 1998, Vol. 495 Issue: 2 p659-671, 13p |
| Abstrakt: |
We have examined optical brightness changes in 151 luminous, moderate-redshift QSOs with unknown variability properties. Short exposures were obtained using CCD detectors on the 40 inch (102 cm) Swope Telescope at Las Campanas Observatory. Some of the observations were taken as early as 1987, with the bulk of them beginning in 1990 and continuing through the beginning of 1994. Observations of individual QSOs were typically taken several times per year in Vand/or Gunn rfilters. Brightness variations have been determined relative to stars contained in an ? 6 arcmin2field. We investigated the characteristics of the brightness variations using the ensemble structure function for three QSO object classes: radio quiet QSOs with broad absorption lines (BALs) in their spectra, radio quiet QSOs without BALs, and radio-loud quasars that systematically lack BALs. We find that ? 2/3 of the entire sample show very quiescent variations, with changes typically less than 0.15 mag yr-1(proper time), corresponding to individual structure function slopes less than 0.0225 mag2yr-1. We have designated these objects optically weak variables (OWVs), while the remainder of the sample with larger variations are designated optically strong variables (OSVs). |
| Databáze: |
Supplemental Index |
| Externí odkaz: |
|
