We derive the optical afterglow luminosity distributions at different epoches for gamma-ray bursts (GRBs) from a sample of 146 GRBs that have a well-sampled optical afterglow lightcurve, then explore the luminosity function of GRB optical afterglows using the Monte Carlo simulation. We show that an intrinsic broken power-law luminosity function can well reproduced the observed magnitude distributions.

Using RXTE observations, we investigate the evolution of inner disk radius (Rin) of Cir X-1 during two cycles and find obvious orbital modulation. We argue that the modulation is attributed to its high orbital eccentricity. The disk luminosity is inversely with the inner disk temperature (kTin), which is ascribed to the slow increase of kTin and, however, the rapid decrease of Rin during the passage for the neutron star to depart from the companion star.

We summarise the results of observing faint cataclysmic variables from the Catalina Real-Time Transient Survey, resulting in confirming the theoretically predicted maximum in the orbital period histogram near a period of 80 minutes.

We explore the origin of the radio emission from the low-luminosity active galactic nuclei (LLAGNs), by investigating the ADAF model with a hybrid of thermal and nonthermal electrons. We find that the radio emission of LLAGNs is severely underpredicted by pure ADAF model, and can be naturally explained by the ADAF model with a hybrid electron population. Our model can roughly reproduce the anti-correlation between the mass-corrected radio loudness and the Eddington ratio for the LLAGNs. We further model the SEDs of each source, and find that roughly all sources can be well fitted if a small fraction of the steady state electron energy is ejected into the nonthermal electrons.

Collecting a sample of 50 narrow-line Seyfert 1 galaxies (NLS1s) and 44 broad-line Seyfert 1 galaxies (BLS1s), we show that the theoretical maximum starburst line derived by Kewley et al. can separate well BLS1s from NSL1s on the BPT diagrams, and the [N II]λ 6584/Hα ratio increases along the list from NLS1s to BLS1s. We suggest that: (1) they have a sequence from low metallicities to high metallicities between NLS1s and BLS1s; (2) with regard to the “star-froming sequence” of Kewley et al. who noted that it forms a tight sequence from low metallicities to high metallicities, the sequence may be connected to the NLS1-BLS1 sequence of “active galactic nucleus (AGN)” sequences.

By using our one-epoch EVN+Merlin data and some archived VLBA data, we present the radio properties of 9 ultra-high-energy synchrotron peak BL Lacs (UHBLs) selected as all BL Lacs with log (νpeak/Hz)>20 from Nieppola et al. . Our results support that UHBLs might be the less Doppler beamed versions of HBLs with similar jet power.

We propose that a magnetar could be formed during the core collapse of massive stars or coalescence of two normal neutron stars, through collecting and inheriting the magnetic fields magnified by hyperaccreting disk. After the magnetar is born, its dipole magnetic fields in turn have a major influence on the following accretion. The decay of its toroidal field can fuel the persistent X-ray luminosity of either an SGR or AXP; however the decay of only the poloidal field is insufficient to do so.

Narrow-line Seyfert 1 (NLS1) galaxies, as active galactic nuclei with low-mass black holes and high accretion rates, are important targets when addressing questions related to black hole growth and accretion physics. We have studied the correlations among the optical emission-line and continuum properties of a sample of NLS1 galaxies, in comparison with a sample of broad-line Seyfert 1 galaxies. We have shown that the density of the narrow-line region is a key component of Eigenvector 1 space. Density turned out to be as important as the Eddington ratio L/LEdd. This result therefore establishes a close link between central engine and host properties, and places new constraints on host - black hole co-evolution.

An anti-correlation between the optical brightness and the strength of the Hα emission was observed from two Be/X-ray binaries, A0535+26 and MXB 0656-072: when the optical brightness showed a decrease, the intensity of the Hα emission displayed an obvious increase. This anti-correlation is interpreted as the result of the mass ejection from the Be star. After the mass ejection event, a cavity or low-density region will be developing in the inner parter of the circumstellar disk. The X-ray outbursts of the Be/X-ray binaries might be connected with the mass ejections from the Be star.

We present some results obtained by high resolution spectroscopic observations for symbiotic stars EG And, AG Dra, and BX Mon in recent years which were performed with 1.8-m reflector and echelle spectrograph BOES at Bohyunsan Optical Astronomy Observatory, Youngcheon, South Korea. The variations of Hα emission line during a night and the variations of H Balmer lines and He I emission lines among several analyzed lines over months and years are shown and discussed.

We study the multiwavelength properties of an optically selected sample of Low Ionization Nuclear Emission-line Regions (LINERs), in an attempt to determine the accretion mechanism powering their central engine. We show how their X-ray spectral characteristics, and their spectral energy distribution compare to luminous AGN, and briefly discuss their connection to their less massive counter-parts galactic black-hole X-ray binaries.

The bottom magnetic fields of neutron stars (NSs) in LMXBs are found to be proportionally related to their accretion rate, i.e. Z (Atoll) source with Eddington (less Eddington) rate is associated with a stronger value of about B ~109 G (B ~108 G). We discuss the relation between the jet formation of NS and its bottom magnetic field strength, and pointed out that the accretion powered millisecond pulsar will not exclude the jet production, furthermore the appearance of kHz QPOs may be also coexistence with the jets. The observer's viewing angle to the NS rotating axis may be a significant factor for observing the jet, pulsar or kHz QPO.

The broadband SEDs of four gamma-ray NLS1s are compiled and explained with the leptonic model. It is found that their characteristics and fitting parameters of the observed SEDs are more like FSRQs than BL Lacs.

By collecting 17 short gamma-ray bursts with necessary data, we find a correlation of Lp ∝ Ep,i1.7, which is very consistent with that derived from a greatly expanded sample of 148 Swift long gamma-ray bursts. It is argued that the radiation mechanism of both long and short gamma-ray bursts should be similar, i.e., of quasi-thermal origin caused by the photosphere and the dissipation occurring very near the central engine. In addition, we suggest that the Ep,i-Lp relation can be used to identified a burst among normal short bursts, short bursts with extended emission and long bursts with short-hard properties. We also find the ratio of peak energy to fluence in the prompt γ-ray band is a prospective discriminator, similar to the traditional duration time.

X-ray source IGR J17091-3624 was discovered by INTEGRAL observatory on 2003 April (Kuulkers 2003). A outburst was detected with Swift/Burst Alert Telescope (BAT) in late January 2011 (Krimm 2011). IGR J17091-3624 has a similar timing phenomena to microquasar GRS 1915+105(Belloni 2000; Altamirano 2011). We have analyzed the evolution of temporal and spectral characteristic of IGR J17091-3624 during the 2011 outburst. We find that (1) all the QPOs can be divided into two types, QPO-AB and QPO-C, (2) a small outburst tracks clockwise in the HID, (3) the relationship between hardness and disk color temperature forms a V-shape. Those results will give a strong constraint on the disk radiative process.

We report 4-epoch VLBA observations of 3C 66A at 22GHz. The resulting images show a typical core-jet structure. We combine our results with some previous results to investigate the proper motions of the jet components. The kinematics of 3C 66A is quite complicated; mildly superluminal motions as well as apparent inward motions have been detected for some components. The inward motions may imply position change of the observed core.

We investigate the radius of the recycled pulsar in double pulsar PSR J0737-3039. In the standard accretion spin-up model, the recycled pulsar spin up continues until arriving at a minimum spin period, or so-called “equilibrium period”, which is related to stellar magnetic field, accretion rate, mass and radius. If present spin period is much longer than that at birth, the spin-down age can give the realistic true age estimation for normal pulsar J0737-3039B. Base on the above conditions, we estimate the radius of millisecond pulsar (MSP) J0737-3039A by assuming its true age is same as the spin-down age of its companion J0737-3039B. We obtained that the radius of J0737-3039A ranges approximately from 5 to 27 km.

We discuss two methods to estimate black hole (BH) masses using X-ray data only: from the X-ray variability amplitude and from the photon index Γ. The first method is based on the anti-correlation between BH mass and X-ray variability amplitude. Using a sample of AGN with BH masses from reverberation mapping, we show that this method shows small intrinsic scatter. The second method is based on the correlation between Γ and both the Eddington ratio Lbol/LEdd and the bolometric correction Lbol/L2−10keV.

We investigate the optical variability of 7658 quasars from SDSS Stripe 82. Taking advantage of a larger sample and relatively more data points for each quasar, we estimate variability amplitudes and divide the sample into small bins of redshift, rest-frame wavelength, black hole mass, Eddington ratio, and bolometric luminosity, respectively, to investigate the relationships between variability and these parameters. An anti-correlation between variability and rest-frame wavelength is found. The variability amplitude of radio-quiet quasars shows almost no cosmological evolution, but that of radio-loud ones may weakly anti-correlate with redshift. In addition, variability increases as either luminosity or Eddington ratio decreases. However, the relationship between variability and black hole mass is uncertain; it is negative when the influence of Eddington ratio is excluded, but positive when the influence of luminosity is excluded. The intrinsic distribution of variability amplitudes for radio-loud and radio-quiet quasars are different. Both radio-loud and radio-quiet quasars exhibit a bluer-when-brighter chromatism. Assuming that quasar variability is caused by variations of accretion rate, the Shakura–Sunyaev disk model can reproduce the tendencies of observed correlations between variability and rest-frame wavelength, luminosity as well as Eddington ratio, supporting that changes of accretion rate play an important role in producing the observed optical variability. However, the predicted positive correlation between variability and black hole mass seems to be inconsistent with the observed negative correlation between them in small bins of Eddington ratio, which suggests that other physical mechanisms may still need to be considered in modifying the simple accretion disk model.

Using an evolutionary population synthesis code, we modeled the global emission of X-ray binaries in late-type galaxies, its relations with other physical properties (i.e., optical luminosity, stellar mass, etc.) of the galaxies, and their evolution with redshift over the cosmic history, which may be investigated further by future high-resolution X-ray and optical observations.