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How fast do quasar emission lines vary? First results from a program to monitor the Balmer lines of the Palomar-Green Quasars

Authors :
Maoz, Dan
Smith, Paul S
Jannuzi, Buell T
Kaspi, Shai
Netzer, Hagai
Source :
Astrophysical Journal, Part 1. 421(1)
Publication Year :
1994
Publisher :
United States: NASA Center for Aerospace Information (CASI), 1994.

Abstract

We have monitored spectrophotometrically a subsample (28) of the Palomar-Green Bright Quasar Sample for 2 years in order to test for correlations between continuum and emission-line variations and to determine the timescales relevant to mapping the broad-line regions of high-luminosity active galactic nuclei (AGNs). Half of the quasars showed optical continuum variations with amplitudes in the range 20-75%. The rise and fall time for the continuum variations is typically 0.5-2 years. In most of the objects with continuum variations, we detect correlated variations in the broad H-alpha and H-beta emission lines. The amplitude of the line variations is usually 2-4 times smaller than the optical continuum fluctuations. We present light curves and analyze spectra for six of the variable quasars with 1000-10,000 A luminosity in the range 0.3-4 x 10(exp 45) ergs/s. In four of these objects the lines respond to the continuum variations with a lag that is smaller than or comparable to our typical sampling interval (a few months). Although continued monitoring is required to confirm these results and increase their accuracy, the present evidence indicates that quasars with the above luminosities have broad-line regions smaller than about 1 1t-yr. Two of the quasars monitored show no detectable line variations despite relatively large-amplitude continuum changes. This could be a stronger manifestation of the low-amplitude line-response phenomenon we observe in the other quasars.

Subjects

Subjects :
Astrophysics

Details

Language :
English
ISSN :
0004637X
Volume :
421
Issue :
1
Database :
NASA Technical Reports
Journal :
Astrophysical Journal, Part 1
Notes :
NAG5-1630, , NAS5-29293
Publication Type :
Report
Accession number :
edsnas.19950035664
Document Type :
Report
Full Text :
https://doi.org/10.1086/173624