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using an empirical relation between the broad-line region size and optical continuum luminosity, we estimated the black hole mass and accretion rate for 135 active galactic nuclei (agns) with double-peaked broad emission lines in two samples, one from the sloan digital sky survey (sdss) and the other from a survey of radio-loud broad emission line agns. with black hole masses ranging from 3; 107m to 5; 109m, these agns have dimensionless accretion rates (eddington ratios) between 0.001 and 0.1 and bolometric luminosity between 1043 and 1046 ergs s[1]1, both values being significantly larger than those of several previously known low-luminosity (lbol<1043 ergs s[1]1) double-peaked agns. the optical-x-ray spectra indices, ox, of these high-luminosity double-peaked agns are between 1 and 1.9, systematically larger than those of low-luminosity objects, which are around 1. modest correlations (with a spearman rank correlation coefficient of 0.60) of the ox value with the eddington ratio and bolometric luminosity have been found, indicating that double-peaked agns with higher eddington ratios or higher luminosity tend to have larger ox values. based on these results, we suggested that the accretion process in the central region of some high-luminosity double-peaked emission line agns (especially those with eddington ratios larger than 0.01) is probably different from that of low-luminosity objects, in which a well-known adaf-like accretion flow was thought to exist. it is likely that the accretion physics in some high-luminosity doublepeaked agns is similar to that in normal type 1 agns, which is also supported by the presence of possible big blue bumps in the spectra of some double-peaked agns with higher eddington ratios. we note that the prototype double-peaked emission line agn, arp 102b, which has a black hole mass of 108m and a dimensionless accretion rate of 0.001, may be an "intermediate" object between the high-and lowluminosity double-peaked agns. in addition, we found an apparent strong anticorrelation (with a spearman rank correlation coefficient of [1] 0.79) between the peak separation of double-peaked profiles and eddington ratios. however, such an anticorrelation is probably induced by a strong correlation between the peak separation and emission-line widths and needs to be confirmed by future work. if it is real, it may provide us another clue to understanding why double-peaked broad emission lines were hardly found in luminous agns with eddington ratios larger than 0.1.

an empirical relation between the broad line region (blr) size and optical continuum luminosity is often adopted to estimate the blr size and then the black hole mass of agns. however, optical luminosity may not be a good indicator of photoionizing luminosity for extremely radio-loud agns because the jets usually contribute significantly to the optical continuum. therefore, the black hole masses derived for blazar-type agns with this method are probably overestimated. here we first derived a tight empirical relation between the blr size and the hβ emission line luminosity, r(light -days)=24.05(lhβ/1042 ergs s−1)0.68, from a sample of 34 agns with the blr size estimated with the reverberation mapping technique. then we applied this relation to estimate the black hole masses of some agns and found that for many extremely radioloud agns the black hole masses obtained with the r -lhβ relation are systematically lower than those derived previously with the r-l5100 å relation, while for radio-quiet and slightly radio-loud agns the results obtained with these two methods are almost the same. the difference of black hole masses estimated with these two relations increases with the radio-loudness for extremely radio-loud agns, which is consistent with the fact that their equivalent widths of the hβ emission line become smaller at greater radio-loudness. if the small hβ equivalent widths of extremely radio-loud agns are indeed caused by the beaming effect, we argue that the optical emission line luminosity may be a better tracer of ionizing luminosity for blazartype agns and the black hole masses derived with the r-lhβ relation are probably more accurate.

the recently discovered tight correlation between supermassive black hole mass and central velocity dispersion for both inactive and active galaxies suggests a possibility to estimate the black hole mass from the measured central velocity dispersion. however, for most agns it is dicult to measure the central velocity dispersions of their host galaxies directly with spectroscopic studies. in this paper we adopt the fundamental plane for ellipticals to estimate the central velocity dispersion and black hole mass for a number of agns with morphology parameters of their elliptical host galaxies obtained by the hubble space telescope imaging observations. the estimated black hole masses of 63 bl lac objects, 10 radio galaxies, 10 radio-loud quasars and 9 radio-quiet quasars are mostly in the range of 107:5m to 109m. no signicant di erence in black hole mass is found for high-frequency peaked bl lacs and low-frequency peaked bl lacs, as well as for radio galaxies and radio-loud quasars. the eddington ratios of radio galaxies are substantially smaller than those of quasars. this suggests that the di erent observational features of these radio-loud agns may be mainly dominated by di erent accretion rate rather than by the black hole mass, which is in agreement with some evolutionary scenarios recently proposed for radio-loud agns. di erent to some previous claims, we found that the derived mean black hole mass for radio-loud quasars is only slightly larger than that of radio-quiet quasars. though the black hole mass distributions between radio-loud and radio-quiet quasars are statistically di erent, their eddington ratio distributions are probably from the same population. in addition, we noted that the relation between black hole mass and host galaxy luminosity we obtained using the fundamental plane provides further arguments for a nonlinear scaling law between supermassive black hole mass and galactic bulge mass.

a tight correlation between black hole mass (mbh) and central velocity dispersion (б) has been found recently for both active and quiescent galaxies. by applying this correlation, we develop a simple method to derive the inclination angles for a sample of 11 seyfert 1 galaxies that have both measured central velocity dispersions and black hole masses estimated by reverberation mapping. these angles, with a mean value of 36 [1] that agrees well with the result obtained by fitting the iron ka lines of seyfert 1 galaxies observed with asca, provide further support to the orientation-dependent unification scheme of active galactic nuclei (agns). a positive correlation of the inclinations with observed fwhms of the hb line and a possible anticorrelation with the nuclear radio loudness have been found. we conclude that more accurate knowledge of inclinations and broad-line region dynamics is needed to improve the black hole mass determination of agns with the reverberation mapping technique.

we estimated black hole masses for 9 seyfert 1 and 13 seyfert 2 galaxies in the palomar and cfa bright seyfert samples using the tight correlation between black hole mass and bulge velocity dispersion. combining other 13 seyfert 1s and 2 seyfert 2s in these samples but with black hole masses measured recently by reverberation mapping and stellar/gas dynamics, we studied the correlations of black hole masses with radio-loudness and bulge luminosities for a sample of 37 seyfert galaxies. we found that if radio-loudness is measured using the optical and radio luminosities of the nuclear components, the black hole masses of radio-loud seyfert 1s tend to increase with the radio-loudness. the black hole masses of all seyfert galaxies increase with the radio power, but seyfert galaxies have larger radio powers than nearby galaxies with the same black hole masses. in addition, the correlation between black hole masses and bulge v-band luminosities for seyfert galaxies is consistent with that found for quasars and normal galaxies. the combined sample of 37 seyfert galaxies, 15 quasars and 30 normal galaxies suggests a possible universal nonlinear relation between black hole and bulge masses, mbh/m1:74 0:14 bulge, which is slightly steeper than that found recently by laor (2001) for a smaller sample. this nonlinear relation is supported by a larger sample including 65 seyfert galaxies. the di rent mbh=mbulge ratio for galaxies with di erent bulge luminosities or di erent black hole masses may be explained by this relation. these results are consistent with some theoretical implications and are important for understanding the nature of radio emissions and the formation and evolution of supermassive black holes and galaxies.

we compare the theoretical predictions of the transition layer model with some observational features of quasi-periodic oscillations (qpos) in neutron star x-ray binaries. we found that the correlation between horizontal branch oscillation (hbo) frequencies and kilohertz (khz) qpo frequencies, the difference between the low-frequency qpos in atoll sources and hbos in z sources, and the correlation between the frequencies of low-frequency qpos and break frequencies can be well explained by the transition layer model, provided the neutron star mass is around 1.4 and the m angle between magneto-sphere equator and accretion disk plane is around 6. the observed decrease of peak separation between the two khz qpo frequencies with the increase of the khz qpo frequencies and the increase of qpo frequencies with the increase of inferred mass accretion rate are also consistent with the theoretical predictions of the transition layer model. in addition, we derive a simple equation that can be adopted to estimate the angle (d) between magnetosphere equator and accretion disk plane by use of the simultaneously observed qpo frequency data. we estimate this angle, in the range of 48, for

x-ray luminous radio-quiet high redshift qsos are rare and can be used for the investigation of several important astronomical questions. we have conducted a large area survey for radio-quiet high redshift qsos in the rosat all-sky survey, from which qso candidates are selected using the digitized objective prism spectra from the hamburg quasar survey. the 22 candidates with galactic latitudes larger than 35o were observed with the 2.16m telescope at xinglong station of beijing astronomical observatory. among the 19 new qsos in our sample, six are radio-quiet qsos with redshifts larger than 1.3 and three of them have redshifts larger than 2. thus we have doubled the number of known x-ray luminous, radio-quiet high redshift qsos in the surveyed sky area. the distribution of f1:4ghz=f1kev of radio-loud and radio-quiet qsos in this area shows two well separated peaks. this can be taken as an evidence for different emission mechanisms of the observed x-rays in the two subgroups.

the low dispersion (400a/mm) spectrum of the optical counterpart of a flat-spectrum radio source 87gb 080315.5 512613, which is one of two possible radio counterparts of 2eg j0809 5117, was obtained recently. the optical counterpart, which is 2:0200 away from 87gb 080315.5 512613 and 19:30 away from 2eg j0809 5117, was identied as a quasar with redshift of 1.14.we noted that mattox et al. (1997) suggested the other radio counterpart 87gb 080459.4 495915 (oj 508), which is 87:10 away from 2eg j0809 5117, is the more potential identication, though it was previously suggested to be the identication (with low condence) of another nearby egret source 2eg j0807 4849. our observation suggests that it is quite possible that 87gb 080315.5 512613 is the identication of 2eg j0809 5117 rather than 87gb 080459.4 495915. but we still can not exclude the possibility of 87gb 080459.4 495915 at present. moreover, in order to determine whether or not 87gb 080315.5 512613 is a blazer type quasar, the optical polarization and variability measures of its optical counterpart are strongly encouraged.

the effects of radial advection and thermal diffusion were considered in investigating the linear stability of an optically thin, two-temperature accretion disc. if the disc has very little advection, we prove that the thermal instability exists when the disc is geometrically thin. however, it disappears in a geometrically slim disc if the thermal diffusion is considered. moreover, if the disc is advection-dominated, the thermal instability does not exist. we also found that the instabilities of inertialacoustic modes exist only in a geometrically thin disc or an advection-dominated disc with a low mach number, whereas the lightman & eardley viscous instability always disappears in a two-temperature disc. a simple comparison also showed that an optically thin, bremsstrahlung cooling-dominated disc is generally more thermally unstable than a two-temperature disc if it is not advection-dominated.

based on the discussion of the applicability of the local approximation, the local stability of accretion disks with adveetion is studied together with the considerations of radial viscous force and thermal diffusion. for a geometrically thin, radiative cooling dominated disk, the thermal diffusion has nearly no effects on the thermal and viscous modes, which are both stable if the disk is also optically thick, and gas pressure dominated and are both unstable if the disk is either optically thick, radiation pressure dominated, or optically thin. the including of thermal diffusion, however, tends to stabilize the acoustic modes, which, if without advection, are unstable if the disk is optically thick, radiation pressure dominated, or optically thin, and which are stable if the disk is optically thick and gas pressure dominated. the including of very little advection has significant effects on two acoustic modes, which are no longer complex conjugates of each other. independent of the optical depth, the instability of the outward propagating mode (o-mode) is enhanced, and that of the inward propagating mode (i-mode) is damped if the disk is gas pressure dominated, while the instability of the o-mode is damped and that of the i-mode is enhanced if the disk is radiation pressure dominated. for a geometrically slim, adveetion-dominated disk, both the thermal and viscous modes, as well as the i-mode, are always stable if the disk is optically thin. the including of thermal diffusion tends to make these modes more stable. however, the o-mode can become unstable when q/mis very large (q is the ratio of adveetive to viscous dissipated energy and mis the maeh number), even if the thermal diffusion is considered. on the other hand, if the adveetiondominated disk is optically thick, we found there are no self-consistent acoustic modes in our local analyses. the thermal diffusion has no effect on the stable viscous mode but has a significant contribution to enhance the thermal instability.