8,835 research outputs found
The variability of optical \feii emission in PG QSO 1700+518
It is found that \feii emission contributes significantly to the optical and
ultraviolet spectra of most active galactic nuclei. The origin of the
optical/UV \feii emission is still a question open to debate. The variability
of \feii would give clues to this origin. Using 7.5 yr spectroscopic monitoring
data of one Palomer-Green (PG) quasi-stellar object (QSO), PG 1700+518, with
strong optical \feii emission, we obtain the light curves of the continuum \lv,
\feii, the broad component of \hb, and the narrow component of \hb by the
spectral decomposition. Through the interpolation cross-correlation method, we
calculate the time lags for light curves of \feii, the total \hb, the broad
component of \hb, and the narrow component of \hb with respect to the continuum
light curve. We find that the \feii time lag in PG1700+518 is
days, and the \hb time lag cannot be determined. Assuming
that \feii and \hb emission regions follow the virial relation between the time
lag and the FWHM for the \hb and \feii emission lines, we can derive that the
\hb time lag is days. The \hb time lag calculated from the
empirical luminosity--size relation is 222 days, which is consistent with our
measured \feii time lag. Considering the optical \feii contribution, PG
1700+518 shares the same characteristic on the spectral slope variability as
other 15 PG QSOs in our previous work, i.e., harder spectrum during brighter
phase.Comment: 6 apges, ApJ, in pres
A note on black hole masses estimated by the second moment in Narrow Line Seyfert 1 Galaxies
The second moment of the H emission line is calculated for 329 narrow
line Seyfert 1 galaxies (NLS1s) selected from the Sloan Digital Sky Survey
(SDSS), which is used to calculate the central supermassive black hole (SMBHs)
mass of each. We find that the second moment depends strongly on the broader
component of the H line profile. We find that for the NLS1s requiring
two Gaussians to fit the H line the mean value of the SMBH mass from the
H second moment is larger by about 0.50 dex than that from the full
width at half maximum (FWHM). Using the gas velocity dispersion of the
core/narrow component of \oiii 5007 to estimate the stellar velocity
dispersion, , the new mass makes NLS1s fall very close to the \mbh
- \sigma_{*} relation for normal AGNs. By using measured directly
from SDSS spectra with a simple stellar population synthesis method, we find
that for NLS1s with mass lower than 10^7 \msun, they fall only marginally
below the \mbh - \sigma_{*} relation considering the large scatter in the
mass calculation.Comment: 8 paper, 5 figures, 1 tables, accepted for publication in MNRA
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