Y. H. Zhao

On X-ray variability in narrow-line and broad-line active galactic nuclei

We assembled a sample of broad-line and narrow-line active galactic nuclei (AGNs) observed by ASCA, the excess variances of which have been determined. The central black hole masses in this sample can be obtained from the reverberation mapping method and the width of the Hβ emission line. Using the black hole masses and the bolometric luminosity, the Eddington ratio (the ratio of the ionizing luminosity to the Eddington luminosity) can also be obtained. We confirmed the strong anticorrelation between X-ray variability and the central black hole mass found by Lu & Yu. In addition, we found that narrow-line Seyfert 1 galaxies (NLS1s) also follow this relation, with a larger scatter, and that there is only a weak correlation between the X-ray variability and the Eddington ratio, which suggests that rapid variability and narrow lines in NLS1s are mainly due to small central black holes in NLS1s, not the difference of circumnuclear gas around NLS1s. A strong correlation was found between the hard X-ray photon index and the Eddington ratio. If the suggestion of two distinct accretion classes [namely advection-dominated accretion flow (ADAF) and thin disc accretion] in AGNs is correct, the strong correlation between the photon index and the Eddington ratio shows that there exists a kind of two-zone accretion disc, in which the outer zone is a thin disc and the inner zone is an ADAF disc. Otherwise, the accretion process is thin disc accretion and ADAF accretion is not required.

The correlations between the twin kHz quasi-periodic oscillation frequencies of low-mass X-ray binaries

We analyzed the recently published kHz QPO data in the neutron star low-mass X-ray binaries (LMXBs), in order to investigate the different correlations of the twin peak kilohertz quasi-eriodic oscillations (kHz QPOs) in bright Z sources and in the less luminous Atoll sources. We find that a power-law relation

Black hole masses in narrow-line Seyfert 1 galaxies

\no\sim\nt^{b}

The black hole—bulge relation in active galactic nuclei

between the upper and the lower kHz QPOs with different indices:

The LAMOST stellar parameter pipeline at Peking University – lsp3

b\simeq

Masses, accretion rates and inclinations of AGNs

1.5 for the Atoll source 4U 1728-34 and

Galaxies around the giant double radio source DA 240. Redshifts and the discovery of an unusual association

b\simeq

Orientation and rotational parameters of asteroid 4179 Toutatis: new insights from Chang'e-2's close flyby

1.9 for the Z source Sco X-1. The implications of our results for the theoretical models for kHz QPOs are discussed.

A model for the upper kHz QPO coherence of an accreting neutron star

The masses of central supermassive black holes in a soft X-ray-selected sample of the narrow-line Seyfert 1 galaxies (NLS I s) are estimated by various methods to test the theoretical models. Apart from the methods using the Hβ linewidth and the [O III] linewidth, soft X-ray excess as a prominent character of NLS 1 s is used to estimate the black hole masses. The virial mass derived from the Hβ linewidth assuming random orbits of broad-line regions (BLRs) is consistent with that from the soft X-ray bump luminosity for NLS 1s, but with a larger scatter. The virial black hole masses showed that most of NLS1s are in the super-Eddington accretion state, while most of broad-line Seyfert 1 galaxies are not. We found that the black hole mass estimated from the [O III] linewidth is not in agreement with above two methods. Using the Eddington limit relation for the super-Eddington accretion suggested by Wang, we found that there are 16 NLSIs satisfied by this Eddington limit relation. The masses of these 16 NLS1s derived from X-ray luminosity are systematically larger than that from Hβ linewidth assuming random BLRs orbits. If the mass derived from X-ray luminosity is true, the mean disc inclination to the line of sight in these 16 NLS s is approximately 17°, which provided new support for the pole-on orientation effect in NLS 1 s.

Does Submillisecond Pulsar XTE J1739−285 Contain a Weak Magnetic Neutron Star or Quark Star?

We used the widths of H