Emission-line variability and the broad-line region of quasi-stellar objects. I - Time scales and photon densities

1987 ◽  
Vol 322 ◽  
pp. 164 ◽  
Author(s):  
Wei Zheng ◽  
E. Margaret Burbridge ◽  
Harding E. Smith ◽  
Ross D. Cohen ◽  
Steven E. Bradley
Keyword(s):  
Emission Line ◽  
Time Scales ◽  
Broad Line ◽  
Stellar Objects ◽  
Broad Line Region ◽  
Line Region ◽  
Quasi Stellar Objects

scholarly journals The Amplitude–Time Lag Relation for Emission-Line Flares of AGN

1994 ◽  
Vol 159 ◽  
pp. 173-176
Author(s):  
Ivan I. Shevchenko
Keyword(s):  
Emission Line ◽  
Time Lag ◽  
Light Curves ◽  
Broad Line ◽  
Broad Line Region ◽  
Line Region ◽  
Relative Increment ◽  
Models Comparison ◽  
Emission Line Spectrum ◽  
Phase Functions

The amplitude–time lag (“ΔA-Δt”) relation is considered in order to describe behaviour of the emission-line spectrum of an active galactic nucleus during a separate active event. Here ΔA, called the amplitude, is the maximum relative increment of the flux in a line, and Δt is the time lag between the maximum of the ionizing continuum flare and the maximum of the flare in a line. As suggested by Shevchenko (1988), the construction and analysis of such relations can be used to discriminate between broad-line region models. Comparison of theoretical “ΔA-Δt” relations with the observed one composed by data for flares in various lines during a separate active event, is proved to be a useful tool for investigating the geometry of a broad-line region, for studies of the form of phase functions of a typical line-emitting cloud in various lines, as well as for clearing up the duration and amplitude of the initial flare in the ionizing continuum. The advantage of this method is that it utilizes the most general observed characteristics of the emission-line flares and nevertheless provides basic information on the allowed BLR models before the detailed modelling of emission-line light curves is performed.

scholarly journals On BLR Size Estimates in Reverberation Models

2009 ◽  
Vol 5 (S267) ◽  
pp. 209-209
Author(s):  
Alexander V. Melnikov ◽  
Ivan I. Shevchenko
Keyword(s):  
Emission Line ◽  
Cross Correlation ◽  
Light Curves ◽  
Time Lags ◽  
Broad Line ◽  
Broad Line Region ◽  
Correlation Methods ◽  
Line Region ◽  
Size Estimates

Following the approach of Melnikov & Shevchenko (2008), we explore how the nonlinearity in the emission-line luminosity Ll of a broad-line region cloud, in its dependence on the ionizing continuum flux Fi incident on the cloud, affects estimates of the size of the broad-line region by means of cross-correlation methods. We show that the estimates obtained by straightforward cross-correlation of emission-line and continuum light curves can significantly underestimate the BLR size. We demonstrate examples of direct reverberation modelling of AGN emission-line light curves taking into account the nonlinearity of the “Ll–Fi” relation. This nonlinearity allows one to explain the differences in the time lags for different lines. Cross-correlation estimates of the BLR size turn out to be small in comparison to the estimates obtained by the direct reverberation modelling.

scholarly journals Peculiar emission line spectra of core extremely red BOSS quasars at z∼2–3: orientation and/or evolution?

2020 ◽  
Vol 634 ◽  
pp. A116 ◽  
Author(s):  
M. Villar Martín ◽  
M. Perna ◽  
A. Humphrey ◽  
N. Castro Rodríguez ◽  
L. Binette ◽  
...  
Keyword(s):  
Emission Line ◽  
Near Infrared ◽  
Outer Part ◽  
Line Emission ◽  
Optical Emission ◽  
Broad Line ◽  
Broad Line Region ◽  
Line Region ◽  
Evolutionary Phase

Context. Core extremely red quasars (core ERQ) have been proposed to represent an intermediate evolutionary phase in which a heavily obscured quasar blows out the circumnuclear interstellar medium with very energetic outflows before it becomes an optical quasar. Aims. We investigate whether the properties of core ERQ fit the AGN orientation-based unification scenario. Methods. We revised the general UV and optical emission line properties of core ERQ in the context of the orientation-based scenario. We used diagnostic diagrams based on UV emission line ratios and UV-to-optical line kinematic information to compare the physical and kinematic gas properties of core ERQ with those of other luminous narrow- and broad-line AGN. In particular, we provide a revised comparison of the [OIII] kinematics in 21 core ERQ (20 from Perrotta et al. 2019, MNRAS, 488, 4126 and SDSS J171420.38+414815.7, based on GTC EMIR near-infrared spectroscopy) with other samples of quasars with matching luminosity with the aim of evaluating whether core ERQ host the most extreme [OIII] outflows. Results. The UV line ratios suggest that the physical properties (e.g., density and metallicity) of the ionised gas in core ERQ are similar to those observed in the broad-line region of blue nitrogen-loud quasars. The [OIII] outflow velocities of core ERQ are on average consistent with those of very luminous blue type 1 quasars, although extreme outflows are much more frequent in core ERQ. These similarities can be explained in the context of the AGN unification model under the assumption that core ERQ are viewed with an intermediate orientation between type 2 (edge-on) and type 1 (face-on) quasars. Conclusions. We propose that core ERQ are very luminous but otherwise normal quasars viewed at an intermediate orientation. This orientation allows a direct view of the outer part of the large broad-line region from which core ERQ UV line emission originates; the extreme [OIII] outflow velocities are instead a consequence of the very high luminosity of core ERQ.

scholarly journals Complex broad emission line profiles of AGN – Geometry of the broad line region

2009 ◽  
Vol 53 (7-10) ◽  
pp. 121-127 ◽  
Author(s):  
E. Bon ◽  
N. Gavrilović ◽  
G. La Mura ◽  
L.Č. Popović
Keyword(s):  
Emission Line ◽  
Broad Line ◽  
Line Profiles ◽  
Broad Line Region ◽  
Broad Emission ◽  
Line Region ◽  
Broad Emission Line

scholarly journals Is the Broad-Line Region Expanding?

1997 ◽  
Vol 159 ◽  
pp. 222-223
Author(s):  
Kan Liang ◽  
Xiang-Tao He ◽  
Zhong-min Wang ◽  
Jun-Han You
Keyword(s):  
High Resolution ◽  
Emission Line ◽  
High Redshift ◽  
Optical Observations ◽  
Broad Line ◽  
Broad Absorption ◽  
Broad Line Region ◽  
Line Region ◽  
Radial Outflow ◽  
Almost All

We suggest that the broad-line regions (BLRs) of QSOs with broad emissionlines (BALs) are expanding, i.e., the clouds are undergoing radial outflow, as illustrated simply in Fig. 1. At least the following observational facts can be explained: 1.Optical observations show that some moderate and high-redshift QSOs have BALs. The number of these QSOs is about 3–10% of all QSOs (Foltz et al. 1990). One can see in Fig. 2 that very low-redshift QSOs have no BALs.2.Almost all BAL QSOs exhibit zabs < zem.3.High-resolution observations reveal that the widths of the broad absorption lines are narrower than that of the corresponding emission line for all BAL QSOs, i.e. Δλ ab < Δλ em.

scholarly journals Emission-Line Variability and the Nature of the Broad-Line Region

1989 ◽  
Vol 134 ◽  
pp. 97-99
Author(s):  
B. M. Peterson
Keyword(s):  
Emission Line ◽  
Strong Correlation ◽  
Emission Lines ◽  
Broad Line ◽  
Rapid Variability ◽  
Broad Line Region ◽  
Line Region

Variability of the emission-line spectra of broad-line AGNs is now a well-established phenomenon (see Peterson 1988 for a review). The rapid variability of the emission lines and the strong correlation between continuum and line fluxes suggests broad-line region (BLR) dimensions too small to be consistent with theoretical estimates based on photoionization equilibrium considerations.

scholarly journals Reverberation Mapping Analysis of the Broad-Line Region in Seyfert Galaxy NGC 4151

1998 ◽  
Vol 188 ◽  
pp. 424-425
Author(s):  
S.J. Xue ◽  
F.Z. Cheng
Keyword(s):  
Emission Line ◽  
Time Lag ◽  
Seyfert Galaxy ◽  
Broad Line ◽  
Reverberation Mapping ◽  
Ngc 4151 ◽  
Broad Line Region ◽  
Spectroscopic Monitoring ◽  
Line Region ◽  
The Continuum

One of the primary goals of AGN variability studies has been to determine the size of broad-line region (BLR) through the reverberation mapping technique. In a recent international multiwavelength spectroscopic monitoring campaign, NGC 4151 has been observed intensively by ground-based telescopes for a period of over 2 months, with a typical temporal resolution of 1 day. The main result from this optical campaign is that finding the variation in the emission line flux (Hβ or Hα) lagging the continuum by 0-3 days (1993 campaign: Kaspi et al. 1996). This is in contrast to the past results in which a time lag of 9±2 days was found for the same emission line (1988 campaign: Maoz et al. 1991). Such a BLR “size problem” may be caused by a different variability timescale of the ionizing continuum or a real change in BLR gas distribution in the 5.5 yr interval between the two watch campaigns. In order to clarify which of the two possibilities is most likely the real case, we performed further reverberation analysis on both optical datasets.

Sign in / Sign up

Export Citation Format

Share Document