1,500 research outputs found
The sizes of BLRs and BH masses of double-peaked broad low-ionization emission line objects
In this paper, the sizes of the BLRs and BH masses of DouBle-Peaked broad
low-ionization emission line emitters (dbp emitters) are compared using
different methods: virial BH masses vs BH masses from stellar velocity
dispersions, the size of BLRs from the continuum luminosity vs the size of BLRs
from the accretion disk model. First, the virial BH masses of dbp emitters
estimated by the continumm luminosity and line width of broad H are
about six times (a much larger value, if including another dbp emitters, of
which the stellar velocity dispersions are traced by the line widths of narrow
emission lines) larger than the BH masses estimated from the relation which is a more accurate relation to estimate BH masses. Second, the
sizes of the BLRs of dbp emitters estimated by the empirical relation of
are about three times (a much larger value, if
including another dbp emitters, of which the stellar velocity dispersions are
traced by the line widths of narrow emission lines) larger than the mean
flux-weighted sizes of BLRs of dbp emitters estimated by the accretion disk
model. The higher electron density of BLRs of dbp emitters would be the main
reason which leads to smaller size of BLRs than the predicted value from the
continuum luminosity.Comment: 7 pages, two figures and one table. Accepted by MNRA
The Correlation Between Spectral Index And Accretion Rate For AGN
In this paper, we present a correlation between the spectral index
distribution (SED) and the dimensionless accretion rate defined as
for AGN. This quantity is used as a substitute of
the physical accretion rate. We select 193 AGN with both broad H and
broad H, and with absorption lines near MgI from SDSS
DR4. We determine the spectral index and dimensionless accretion rate after
correcting for both host galaxy contribution and internal reddening effects. A
correlation is found between the optical spectral index and the dimensionless
accretion rate for AGN, including low luminosity AGN ( sometimes called "dwarf AGN" (Ho et al. 1997)). The existence
of this correlation provides an independent method to estimate the central BH
masses for all types of AGN. We also find that there is a different correlation
between the spectral index and the BH masses for normal AGN and low luminosity
AGN, which is perhaps due to the different accretion modes in these two types
of nuclei. This in turn may lead to the different correlations between BH
masses and optical continuum luminosity reported previously (Zhang et al.
2007a), which invalidates the application of the empirical relationship found
by Kaspi et al. (2000, 2005) to low luminosity AGN in order to determine their
BLR sizes.Comment: 10 pages, 7 figures, accepted for publication in MNRA
3C 390.3: more stable evidence that the double-peaked broad Balmer lines originate from an accretion disc near a central black hole
In this manuscript, the structure of broad emission line regions (BLRs) of
well-mapping double-peaked emitter (AGN with broad double-peaked low-ionization
emission lines) 3C390.3 is studied. Besides the best fitted results for
double-peaked broad optical balmer lines of 3C390.3 by theoretical disk model,
we try to find another way to further confirm the origination of double-peaked
line from accretion disk. Based on the long-period observed spectra in optical
band around 1995 collected from AGN WATCH project, the theoretical disk
parameters of disk-like BLRs supposed by elliptical accretion disk model
(Eracleous et al. 1995) have been well determined. Through the theoretical
disk-like BLRs, characters of observed light-curves of broad double-peaked
H of 3C390.3 can be well reproduced based on the reverberation mapping
technique. Thus the accretion disk model is preferred as one better model for
BLRs of 3C390.3. Furthermore, we can find that different disk parameters should
lead to some different results about size of BLRs of 3C390.3 from the one
measured through observational data, which indicates the measured disk
parameters are significantly valid for 3C390.3. After that, the precession of
theoretical elliptical disk-like BLRs being considered, we can find that the
expected line profile in 2000 by theoretical model is consistent with the
observed line profile by HST around 2000. Based on the results, we can further
believe that the origination of broad double-peaked balmer emission lines of
3C390.3 are from accretion disk around central black hole.Comment: 17 pages, 11 figures, MNRAS accepte
A Hazard Analysis Based Approach to Improve the Landing Safety of a Blended-wing-body Remotely Piloted Vehicle
AbstractThe BUAA-BWB remotely piloted vehicle (RPV) designed by our research team encountered an unexpected landing safety problem in flight experiments. It has obviously affected further research project for Blended-wing-body (BWB) aircraft configuration characteristics. Searching for a safety improvement is an urgent requirement in the development work of the RPV. Combining with vehicle characteristics, a new systemic method called System-Theoretic Process Analysis (STPA) has been imported to apply on the RPV flight experiment hazard analysis. An uncontrolled system behavior âpath sagging phenomenonâ is identified by implementing a 3 degree of freedom simulation based on wind tunnel experiment data and establishing landing safety system dynamics archetype, then a derived safety improvement requirement emerges. To obtain higher safety design effectiveness and considering safety design precedence, a new longitudinal control surface âbelly-flapâ is used to eliminate hazards in landing. Finally, Flight experiments show that the hazardous factor has been correctly identified and the landing safety has been efficiently improved
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