Query : 2007A&A...470..491T

2007A&A...470..491T - Astronomy and Astrophysics, volume 470, 491-496 (2007/8-1)

Line and continuum variability of two intermediate-redshift, high-luminosity quasars.


Abstract (from CDS):

It has been shown that the luminosity of active galactic nuclei and the size of their broad line region obey a simple relation of the type RBLR=aLγ, from faint Seyfert nuclei to bright quasars, allowing single-epoch determination of the central black hole mass MBH=bLγΔ2Hβ from their luminosity L and width of Hβ emission line. Adopting this mass determination for cosmological studies requires the extrapolation to high redshift and luminosity of a relation whose calibration relies so far on reverberation mapping measurements performed for L≲1046erg/s and redshift z≲0.4. We initiated a campaign for the spectrophotometric monitoring of a few luminous, intermediate redshift quasars whose apparent magnitude, V<15.7, allows observations with a 1.8 m telescope, aimed at proving that emission lines vary and respond to continuum variations even for luminosities >1047erg/s, and determining eventually their MBH from reverberation mapping. We have repeatedly performed simultaneous spectrophotometric observations of quasars and reference stars to determine relative variability of continuum and emission lines. We describe the observations and methods of analysis. For the quasars PG 1634+706 and PG 1247+268 we obtain light-curves respectively for CIII](λλ1909Å), MgII(λλ2798Å) and for CIV(λλ1549Å), CIII](λλ1909Å) emission lines with the relevant continua. During 3.2 years of observation, in the former case no continuum variability was detected and the evidence for line variability is marginal, while in the latter case both continuum and line variability are detected with high significance and the line variations appear correlated with continuum variations. The detection of the emission line variability in a quasar with L∼1047erg/s encourages the continuation of the monitoring campaign which should provide a black hole mass estimate in another 5-6 years, constraining the mass-luminosity relation in a poorly explored range of luminosity.

Abstract Copyright:

Journal keyword(s): galaxies: active - quasars: emission lines - quasars: general - quasar: individual: PG 1634+706 - quasars: individual: PG 1247+268

CDS comments: Paragraph 2.2 PG 1647+706 is a probable misprint for PG 1634+706.

Simbad objects: 5

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Number of rows : 5
N Identifier Otype ICRS (J2000)
ICRS (J2000)
Mag U Mag B Mag V Mag R Mag I Sp type #ref
1850 - 2023
1 QSO J0831+5245 QSO 08 31 41.7108197808 +52 45 17.616994560   19.2   14.5 13.9 ~ 538 1
2 3C 273 BLL 12 29 06.6998257176 +02 03 08.597629980   13.05 14.830 14.11   ~ 5669 1
3 LB 19 QSO 12 50 05.7146863848 +26 31 07.598352000   16.12 15.92     ~ 200 0
4 QSO B1634+7037 QSO 16 34 28.9917184368 +70 31 32.393436960   14.90 14.66     ~ 267 0
5 QSO J2156+2242 QSO 21 56 47.4626727576 +22 42 49.875258132   15.2       ~ 16 0

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