Table of contents

The spatial clustering of QSOs is an important measurable quantity which can be used to infer the properties of dark matter halos that host them. We construct a simple QSO model to explain the linear bias of QSOs measured by recent observations and explore the properties of dark matter halos that host a QSO. We assume that major mergers of dark matter halos can lead to the triggering of QSO phenomena, and the evolution of luminosity for a QSO generally shows two accretion phases, i.e., initially having a constant Eddington ratio due to the self-regulation of the accretion process when supply is sufficient, and then declining in rate with time as a power law due to either diminished supply or long term disk evolution. Using a Markov Chain Monte Carlo method, the model parameters are constrained by fitting the observationally determined QSO luminosity functions (LFs) in the hard X-ray and in the optical band simultaneously. Adopting the model parameters that best fit the QSO LFs, the linear bias of QSOs can be predicted and then compared with the observational measurements by accounting for various selection effects in different QSO surveys. We find that the latest measurements of the linear bias of QSOs from both the SDSS and BOSS QSO surveys can be well reproduced. The typical mass of SDSS QSOs at redshift 1.5 < z < 4.5 is ∼ (3 – 6) × 10¹²h⁻¹M_⊙ and the typical mass of BOSS QSOs at z ∼ 2.4 is ∼ 2 × 10¹²h⁻¹M_⊙. For relatively faint QSOs, the mass distribution of their host dark matter halos is wider than that of bright QSOs because faint QSOs can be hosted in both big halos and smaller halos, but bright QSOs are only hosted in big halos, which is part of the reason for the predicted weak dependence of the linear biases on the QSO luminosity.

We present a study of a fossil cluster, SDSS J0150–1005 (z ≃ 0.364), with high spatial resolution based on the imaging spectroscopic analysis of Chandra observations. The Chandra X-ray image shows a relaxed and symmetric morphology, which indicates that SDSS J0150–1005 is a well-developed galaxy cluster with no sign of a recent merger. According to the isothermal model, its global gas temperature is 5.73 ± 0.80 keV, and the virial mass is 6.23 ± 1.34 × 10¹⁴M⊙. Compared with the polytropic temperature model, the mass calculated based on the isothermal model is overestimated by 49% ± 11. The central gas entropy, S_{0.1 r200} = 143.9 ± 18.3 keV cm², is significantly lower than the average value of normal galaxy clusters with similar temperatures. Our results indicate that SDSS J0150–1005 formed during an early epoch.

A disk-corona model for fitting the low/hard (LH) state of the associated steady jet in black hole X-ray binaries (BHXBs) is proposed based on the large-scale magnetic field configuration that arises from the coexistence of the Blandford-Znajek (BZ) and Blandford-Payne (BP) processes, where the magnetic field configuration for the BP process is determined by the requirement of energy conversion from Poynting energy flux into kinetic energy flux in the jet. It is found that corona current is crucial to guarantee the consistency of the jet launching from the accretion disk. The relative importance of the BZ and BP processes in powering jets from black hole accretion disks is discussed, and the LH state of several BHXBs is fitted based on our model. In addition, we suggest that magnetic field configuration can be regarded as the second parameter for governing the state transition of BHXBs.

Time-series photometric observations were made for the high amplitude δ Scuti star CW Ser between 2011 and 2012 at the Xinglong Station of National Astronomical Observatories, Chinese Academy of Sciences. After performing the frequency analysis of the light curves, we confirmed the fundamental frequency of f = 5.28677 c d⁻¹, together with seven harmonics of the fundamental frequency, which are newly detected. No additional frequencies were detected. The O — C diagram, produced with the 21 newly determined times of maximum light combined with those provided in the literature, helps to obtain a new ephemeris formula of the times of maximum light with the pulsation period of 0.189150355 ± 0.000000003 d.

Equivalent widths and line widths of Ca II infrared triplet emission lines were measured in the high-resolution optical spectra of 39 young stellar objects. We found that the equivalent widths of the emission lines decrease with stellar evolution. It has often been claimed that strong chromospheric activity is generated by a dynamo process caused by fast rotation of the photosphere. However, we found no clear correlation between the strength of the Ca II lines and the stellar rotation velocity. Instead, we found that the objects with high mass accretion rates had stronger Ca II emission lines. This correlation supports the turbulent chromosphere model or the magnetic accretion theory for classical T Tauri stars. We also noticed that the equivalent widths of Ca II lines in transitional disk objects are one-tenth of those in classical T Tauri stars, even if the masses of the circumstellar disks are comparable.

SN 2006oz is a super-luminous supernova with a mysterious bright precursor that has resisted explanation in standard models. However, such a precursor has been predicted in the dual-shock quark nova model of super-luminous supernovae — the precursor is the supernova event while the main light curve of the super-luminous supernova is powered by the Quark-Nova (explosive transition of the neutron star to a quark star). As the supernova is fading, the Quark-Nova re-energizes the supernova ejecta, producing a "double-humped" light curve. We show that the quark nova model successfully reproduces the observed light curve of SN 2006oz.

The different timing results of the magnetar Swift J1822.3–1606 are analyzed and understood theoretically. It is noted that different timing solutions are caused not only by timing noise, but also because the period derivative is decreasing after the outburst. Both the decreasing period derivative and the large timing noise may originate from wind braking associated with the magnetar. Future timing of Swift J1822.3–1606 will help clarify whether or not its period derivative is decreasing with time.

Cataclysmic variables are special celestial bodies because they have particular light curves and spectra. The mechanisms for generating emission lines radiated from dwarf novae in their quiescent phases are studied. We assume that the incident radiation field which is emitted by a hot source (white dwarf and boundary layer) irradiates the gaseous layer evaporated from the accretion disk, and the emission lines are radiated from the gas. We model the fluxes of emission lines by using the photoionization code CLOUDY. Using this method, we input some reasonable parameters and get a series of simulated spectra. In order to find a simulated spectrum which is the best fit to an observed spectrum, we use a cross-correlation method to match them. After the calculation, we use the approximation that the parameters of the simulated spectrum can simulate the observed spectrum. Finally, we learn more about the physical conditions of the system.

This is a study designed to analyze the relationship between ground level enhancements (GLEs) and their associated solar active regions during solar cycles 22 and 23. Results show that 90.3% of the GLE events that are investigated are accompanied by X-class flares, and that 77.4% of the GLE events originate from super active regions. It is found that the intensity of a GLE event is strongly associated with the specific position of an active region where the GLE event occurs. As a consequence, the GLE events having a peak increase rate exceeding 50% occur in a longitudinal range from W20° to W100°. Moreover, the largest GLE events occur in a heliographic longitude at roughly W60°. Additionally, an analysis is made to understand the distributional pattern of the Carrington longitude of the active regions that have generated the GLE events.

As an extension of the "teleparallel" equivalent of general relativity, f(T) gravity is proposed to explain some puzzling cosmological behaviors, such as accelerating expansion of the Universe. Given the fact that modified gravity also has impacts on the Solar System, we might test it during future interplanetary missions with ultrastable clocks. In this work, we investigate the effects of f(T) gravity on the dynamics of the clock and its time transfer link. Under these influences, the Λ-term and the α-term of f(T) gravity play important roles. Here, Λ is the cosmological constant and α represents a model parameter in f(T) gravity that determines the divergence from teleparallel gravity at the first order approximation. We find that the signal of f(T) gravity in the time transfer is much more difficult to detect with the current state of development for clocks than those effects on dynamics of an interplanetary spacecraft with a bounded orbit with parameters 0.5 au ≤ a ≤ 5.5 au and 0 ≤ e ≤ 0.1.

Ground-based and space-borne observatories used for studying exoplanet transits now and in the future will considerably increase the number of exoplanets known from transit data and the precision of the measured times of transit minima. Variations in the transit times can not only be used to infer the presence of additional planets, but might also provide opportunities to test the general theory of relativity in these systems. To build a framework for these possible tests, we extend previous studies on the observability of the general relativistic precessions of periastron in transiting exoplanets to variations in secular transit timing under parametrized post-Newtonian formalism. We find that if one can measure the difference between observed and predicted variations of general relativistic secular transit timing to 1 s yr⁻¹ in a transiting exoplanet system with a Sun-like mass, a period of ∼ 1 day and a relatively small eccentricity of ∼ 0.1, general relativity will be tested to the level of ∼ 6%.

The Multi-wavelength Spectrometer is a medium-dispersion (R ∼ 130000) grating spectrometer installed on the New Vacuum Solar Telescope at the Fuxian Solar Observatory, Yunnan Astronomical Observatory, Chinese Academy of Sciences. It is designed to accurately observe the velocity and magnetic fields of the Sun. The present configuration of this spectrometer allows us to simultaneously observe three different solar spectral lines. This work is dedicated to showing the first observations carried out in both the Hα and Ca II 8542 Å lines. We give a detailed description of the data reduction process, focusing on the retrieval of a flat field from the high-resolution spectral data. Two different methods are also performed and compared to eliminate the residual fringe in the reduced data. The real spectral resolution and instrumental profile are analyzed based on the final results, which indicate that this spectrometer presently satisfies the expected performance and it is ready for further scientific observations.

Using a sky brightness monitor at the Xinglong station of National Astronomical Observatories, Chinese Academy of Sciences, we collected data from 22 dark clear nights and 90 moon nights. We first measured the sky brightness variation with time for dark nights and found a clear correlation between sky brightness and human activity. Then with a modified sky brightness model of moon nights and data from these nights, we derived the typical value for several important parameters in the model. With these results, we calculated the sky brightness distribution under a given moon condition for the Xinglong station. Furthermore, we simulated the sky brightness distribution of a moon night for a telescope with a 5° field of view (such as LAMOST). These simulations will be helpful for determining the limiting magnitude and exposure time, as well as planning the survey for LAMOST during moon nights.