Table of contents

By using Data Analysis Pipeline (DAP) products of Mapping Nearby Galaxies at Apache Point Observatory (MaNGA), which are publicly available from the SDSS Data Release 15, we analyze the local properties at the SN explosion sites and global properties of different types of SN host galaxies to explore the explosion environments of different types of SNe. In our sample, there are 67 SN host galaxies in the field of view of MaNGA, including 32 Type Ia, 29 core collapse SNe (CCSNe), 1 superluminous SN (SLSN), 1 Type I and 4 unclassified type of SNe, with which we can apply the K-S test for analysis and derive statistically robust results. Due to the limited sample size, we could not remove the mass dependence in this work, which is likely the true driver of the trends for the properties presented in this work. The global star formation rate (SFR) and EW(Hα) for SN Ia hosts are slightly lower than those for CCSN hosts on average. SN Ia host galaxies are ∼0.3 dex more massive than CCSN hosts, which implies that the number ratio of CCSNe to Type Ia SNe will decrease with increasing stellar mass of host galaxies. The stellar population age of SN Ia host galaxies is older than that of CCSN hosts on average. There is no significant difference between different types of SN hosts for some properties, including local SFR density (ΣSFR), and local and global gas-phase oxygen abundance. For most galaxies in our sample, the global gas-phase oxygen abundance estimated from the integrated spectra of SN hosts can represent the local gas-phase oxygen abundance at the SN explosion sites with small bias.

With aperture synthesis (AS) technique, a number of small antennas can be assembled to form a large telescope whose spatial resolution is determined by the distance of two farthest antennas instead of the diameter of a single-dish antenna. In contrast from a direct imaging system, an AS telescope captures the Fourier coefficients of a spatial object, and then implement inverse Fourier transform to reconstruct the spatial image. Due to the limited number of antennas, the Fourier coefficients are extremely sparse in practice, resulting in a very blurry image. To remove/reduce blur, "CLEAN" deconvolution has been widely used in the literature. However, it was initially designed for a point source. For an extended source, like the Sun, its efficiency is unsatisfactory. In this study, a deep neural network, referring to Generative Adversarial Network (GAN), is proposed for solar image deconvolution. The experimental results demonstrate that the proposed model is markedly better than traditional CLEAN on solar images. The main purpose of this work is visual inspection instead of quantitative scientific computation. We believe that this will also help scientists to better understand solar phenomena with high quality images.

A pure two-body problem has seven integrals including the Kepler energy, the Laplace vector and the angular momentum vector. However, only five of them are independent. When the five independent integrals are preserved, the two other dependent integrals are naturally preserved from a theoretical viewpoint; but they may not necessarily be from a numerical computational viewpoint. Because of this, we use seven scale factors to adjust the integrated positions and velocities so that the adjusted solutions strictly satisfy the seven constraints. Noticing the existence of the two dependent integrals, we adopt the Newton iterative method combined with singular value decomposition to calculate these factors. This correction scheme can be applied to perturbed two-body and N-body problems in the solar system. In this case, the seven quantities associated with each planet slowly vary with time. More accurate values can be given to the seven slowly-varying quantities by integrating the integral invariant relations of these quantities and the equations of motion. They should be satisfied with the adjusted solutions. Numerical tests show that the new method can significantly reduce the rapid growth of numerical errors for all orbital elements.

Statistical relations are useful tools to comprehend the intrinsic physics processes of gamma-ray bursts (GRBs). In this work we collect spectral lag (τ), variability (V) and optical peak time (t_p,o). We find that there is a correlation between variabilities and spectral lags, reading as V = −0.0075 (±0.0007) × log₁₀τ + 0.0351 (±0.0024). There may also exist a relatively weak positive tendency between GRBs optical band peak times and their spectral time lags. Its Pearson coefficient is 0.398, which indicates a weak linear correlation. If we contain some "negative spectral lag" samples, then the latter relation would be worse due to two outlying points. The τ-V relation is consistent with previous studies, and the positive trend between τ and t_p,o indicates the spectral lag of GRB might be caused by the curvature effect, but this conclusion is not significant.

We perform a set of non-radiative hydro-dynamical (NHD) simulations of a rich cluster sized dark matter halo from the Phoenix Project with three different numerical resolutions, to investigate the effect of hydrodynamics alone on the subhalo population in the halo. Compared to dark matter only (DMO) simulations of the same halo, subhaloes are less abundant for relatively massive subhaloes (M_sub > 2.5 × 10⁹h⁻¹M_⊙, or V_max > 70 km s⁻¹) but more abundant for less massive subhaloes in the NHD simulations. This results in different shapes in the subhalo mass/V_max function in two different sets of simulations. At given subhalo mass, the subhaloes less massive than 10¹⁰h⁻¹M_⊙ have larger V_max in the NHD than DMO simulations, while V_max is similar for the subhaloes more massive than the mass value. This is mainly because the progenitors of present day low mass subhaloes have larger concentration parameters in the NHD than DMO simulations. The survival number fraction of the accreted low mass progenitors of the main halo at redshift 2 is about 50 percent higher in the NHD than DMO simulations.

We study spectral and temporal properties of Galactic short orbital period transient black hole XTE J1118+480 during its 2005 outburst using archival data of RXTE PCA and HEXTE instruments in the combined energy range of 3 – 100 keV. Spectral analysis with the physical two component advective flow (TCAF) model allows us to understand the accretion flow properties of the source. We found that this outburst of XTE J1118+480 is an unconventional outburst as the source was only in the hard state (HS). Our spectral analysis suggests that during the entire outburst, the source was highly dominated by the low angular momentum sub-Keplerian halo rate. Since the source was active in radio throughout the outburst, we make an effort to estimate X-ray contribution of jets to total observed X-ray emissions from the spectral analysis with the TCAF model. The total X-ray intensity shows a similar nature of evolution as that of radio and jet X-ray fluxes. This allowed us to define this 'outburst' also as a jet dominated 'outburst'. Total X-ray flux is also found to subside when jet activity disappears. Our detailed spectral analysis also indicated that although the source was only in the HS during the outburst, in the late declining phase the spectrum became slightly softer due to the slow rise in the Keplerian disk rate.

Observations by the method of lunar occultations at the 6-m telescope of the SAO RAS reach a resolution limit better than 1 mas. We have devised a new method of observation, which allows obtaining the curves of lunar occultations simultaneously in different ranges of the visible part of the spectrum, and conducted the first observations using a modified optical system. In January 2019, applying the new method, the magnitude differences of the components of the binary star HD 36524 in the R and I bands were measured, which were 1.5 and 1.3 mag, respectively, in good agreement with values calculated from the Gaia mission. According to the obtained data, it was determined that with this method it is possible to reach a signal-to-noise ratio of about 5–10 for stars of 10th magnitude. We discuss the applicability of the proposed optical scheme for the study of binary stars.

This study reports that the carbon star CGCS 673 is a semi-regular (SR) variable star with a period of 135 d and an amplitude of 0.18 mag in the V-band. The light curve obtained by this study correlates well with the SR classification as the photometric data obtained show noticeable periodicity in the light changes of CGCS 673 that is occasionally interrupted by a period of irregular variability. The derived period and colour index obtained from our data and those from professional databases indicate that the attributes of this star fall within the parameters of the SR class of variable stars. Following our notification of the discovery that this star is a variable source, CGCS 673 has received the AAVSO Unique Identifier of (AAVSO UID) 000-BMZ-492.

Short timescale flux variations are closely related to the energy release process of magnetic reconnection during solar flares. Radio light curves at 1, 2, 3.75, 9.4, and 17 GHz of 209 flares observed by the Nobeyama Radio Polarimeter from 2000 to 2010 are analyzed with a running smooth technique. We find that the impulsive component (with a variation timescale shorter than 1 s) of 1 GHz emission of most flares peaks at a few tens of solar flux unit and lasts for about 1 minute and the impulsive component of 2 GHz emission lasts a shorter period and peaks at a lower flux level, while at the three high frequency channels the occurrence frequency of flares increases with the decrease of the flux density up to the noise level of the corresponding background. However, the gradual components of these emissions have similar duration and peak flux density distributions. We also derive the power spectrum on different timescales and a normalized wavelet analysis is used to confirm features on short timescales. At a time resolution of 0.1 s, more than ∼60% of these radio light curves show significant flux variation on 1 s or shorter time scales. This fraction increases with the decrease of frequency and reaches ∼100% at 1 GHz, implying that short timescale processes are universal in solar flares. We also study the correlation between the impulsive radio flux densities and soft X-ray fluxes obtained with the GOES satellites and find that more than 65% of the flares with an impulsive component have their impulsive radio emission reach a peak value ahead of the soft X-ray fluxes and this fraction increases with the radio frequency.

The first charge-coupled device photometric light curves in B, V, R_c, and I_c bands of the short-period contact binary star OQ Cam are presented. Through analyzing the light curves with the Wilson-Devinney code, it is found that OQ Cam is a W-type shallow contact binary star with a contact degree of f = 20.2%. Based on the O – C analyzing, the orbit period displays a long term increasing with a rate of dP/dt = 4.40 × 10⁻⁷ d yr⁻¹. The increasing in orbit period can be interpreted by mass transfer from the less massive component to the more massive one. As the orbit period increases, OQ Cam would evolve from the present shallow contact configuration to a non-contact stage. So it may be a potential candidate to confirm the thermal relaxation oscillation theory.

Vertical profile of turbulence strength (${C}_{n}^{2}$) is one of the most important attributes for evaluating a site's astronomical performances. Although seeing is commonly used for describing turbulence strength, it can only represent the integral of all layers of the turbulence above the observer. Other techniques which can be applied to produce ${C}_{n}^{2}$, such as DIMM-MASS, SCIDAR, etc., all rely on rather complex systems to do the measurements. In this paper, we present an idea to evaluate the relative strength of turbulence with entropies of short exposure images taken at different conjugated heights of the turbulence. Initial experimental results are also presented in the paper.

With telescope apertures becoming larger and larger, the deployment of large-field telescopes is becoming increasingly popular. However, optical path calibration is necessary to ensure the image quality of large-field and large-diameter telescopes. In particular, focal plane attitude calibration is an essential optical path calibration technique that has a direct impact on image quality. In this paper, a focal plane attitude detection method using eight acquisition cameras is proposed based on the calibration requirements of the wide-field telescope, LAMOST (Large Sky Area Multi-Object Fiber Spectroscopic Telescope). Comparison of simulation and experimental results shows that the detection accuracy of the proposed method can reach 30 arcsec. With additional testing and verification, this method could be used to facilitate regular focal plane attitude calibration for LAMOST as well as other large-field telescopes.

QiTai Telescope (QTT), the world's biggest full-steerable telescope, will be constructed in Xinjiang, China. Its extra high operating frequency (115 GHz) imposes strict requirements on the accuracy of the reflector, while its large aperture (110 m) increases the impact of antenna weight and environment on surface accuracy. However, the panels of reflector will deform under the influence of gravity and the environment. Therefore, to compensate for the performance degradation caused by this deformation, a technique called active surface adjustment has been proposed. The existing adjustment methods cannot detect the deformation caused by environment of the reflector surface in real time, which can result in a delay in the compensation. Consequently, it is difficult to achieve an optimal compensating result. To solve this problem, a real-time method to estimate the large-aperture reflector antenna surface by calculating the antenna panel position based on edge sensors is proposed in this paper. In the proposed method, a panel coordinate transfer matrix has been formulated and the data measured from these edge sensors can then be treated as input for the proposed transfer matrix to calculate the actual position of the antenna panel in real time. A numerical simulation has been carried out in the QTT model and the results obtained show that the proposed real-time method is a promising tool to estimate the large reflector surface position in real time. It is believed that this active surface adjustment method has laid the foundation for new methods that will be developed to compensate for the reflector electrical performance.

In the first Gravitational-Wave Transient Catalogue of LIGO and Virgo, all events are announced having zero eccentricity. In the present paper, we investigate the performance of SEOBNRE, which is a spin-aligned eccentric waveform model in time-domain. By comparing with all the eccentric waveforms in SXS library, we find that the SEOBNRE coincides perfectly with numerical relativity data. Employing the SEOBNRE, we re-estimate the eccentricities of all black hole merger events. We find that most of these events allow a possibility for existence of initial eccentricities at 10 Hz band, but are totally circularized at the observed frequency (≳ 20 Hz). The upcoming update of LIGO and the next generation detector like Einstein Telescope will observe the gravitational waves starting at 10 Hz or even lower. If the eccentricity exists at the lower frequency, then it may significantly support the dynamical formation mechanism taking place in globular clusters.

The detection of gravitational waves (GWs) by pulsar timing arrays (PTAs) is not only a very important supplementation of the verification of general relativity but also a new window to study the evolution of supermassive binary black holes and the early universe. However, so far the detection sensitivity of PTAs is not good enough to catch signals of GWs due to the disturbance of various noises. In this paper we explore the influences of the correlated noises caused by the reference clock errors and solar system ephemeris errors in pulsar timing on the detection of stochastic gravitational waves background (GWB). We demonstrate the power-law integrated sensitivity curves of GWB detection under the impacts from these correlated noises. From the simulated data, we find that the influence of different reference time-scale is non-negligible, and the influence is even quite huge if one uses a very old version of solar system ephemeris. However, the impact from these correlated noises on the sensitivity curve is very limited for the real observational data released by international pulsar timing arrays (IPTA). We also calculate the signal-to-noise ratios based on the theoretical GW amplitude permitted by observations. Moreover, we study how the detection sensitivity increases with more pulsar number and longer observation.

The frequent detection of binary mergers of ∼30 M_⊙ black holes (BHs) by the Laser Interferometer Gravitational-Wave Observatory (LIGO) rekindled researchers' interest in primordial BHs (PBHs) being dark matter (DM). In this work, we investigated PBHs distributed as DM with a monochromatic mass of 30 M_⊙ and examined the encounter-capture scenario of binary formation, where the densest central region of DM halo dominates. Thus, we paid special attention to the tidal effect by the supermassive black hole (SMBH) present. In doing so, we discovered a necessary tool called loss zone that complements the usage of loss cone. We found that the tidal effect is not prominent in affecting binary formation, which also turned out to be insufficient in explaining the totality of LIGO's event rate estimation, especially due to a microlensing event constraining the DM fraction in PBH at the mass of interest from near unity to an order smaller. Meanwhile, an early-universe binary formation scenario proves so prevailing that the LIGO signal in turn constrains the PBH fraction below one percent. Thus, people should put more faith in alternative PBH windows and other DM candidates.

We present a radio polarization study of the supernova remnant CTB 80 based on images at 1420 MHz from the Canadian Galactic Plane Survey, at 2695 MHz from the Effelsberg survey of the Galactic plane and at 4800 MHz from the Sino-German λ6 cm polarization survey of the Galactic plane. We obtained a rotation measure (RM) map using polarization angles at 2695 MHz and 4800 MHz as the polarization percentages are similar at these two frequencies. RM exhibits a transition from positive values to negative values along one of the shells hosting the pulsar PSR B1951+32 and its pulsar wind nebula. The reason for the change in sign remains unclear. We identified a partial shell structure, which is bright in polarized intensity but weak in total intensity. This structure could be part of CTB 80 or part of a new supernova remnant unrelated to CTB 80.

HIP 53731 is a binary consisting of stars of the spectral types K0 and K9. The orbit of this object was constructed previously by Cvetković et al. and improved by Tokovinin. It should be noted that there is a 180° ambiguity in the position angles of some published measurements. Speckle interferometric observations were obtained in 2007–2020 (21 measurements) at the 6-m telescope of the SAO RAS (BTA) by the authors of this article. The analysis of new data together with previously published ones made it possible to construct an accurate orbit of HIP 53731 and to halve the already known values of the orbital period of the system. As a result of the study, the mass sum, the masses of each component and their spectral types were determined by two independent methods. According to the qualitative classification of orbits, the orbital solution has grade 2 – "good" (observations cover more than half of the orbital period and correspond to different phases).

We investigated the pulsar radio luminosity (L), emission efficiency (ratio of radio luminosity to its spin-down power $\dot{E}$), and death line in the magnetic field (B) versus spin period (P) diagram. We found that the dependence of pulsar radio luminosity on its spin-down power ($L-\dot{E}$) is very weak, shown as $L\sim {\dot{E}}^{0.06}$, which deduces an equivalent inverse correlation between emission efficiency and spin-down power as $\xi \sim {\dot{E}}^{-0.94}$. Furthermore, we examined the distributions of radio luminosity of millisecond and normal pulsars and found that for the similar spin-down powers, the radio luminosity of millisecond pulsars is about one order of magnitude lower than that of the normal pulsars. The analysis of pulsar radio flux suggests that these correlations are not due to a selective effect but are intrinsic to the pulsar radio emission physics. Their radio radiations may be dominated by the different radiation mechanisms. The cut-off phenomenon of currently observed radio pulsars in B – P diagram is usually referred as the "pulsar death line", which corresponds to $\dot{E}\approx {10}^{30}$ erg s⁻¹ and is obtained by the cut-off voltage of electron acceleration gap in the polar cap model of pulsar proposed by Ruderman and Sutherland. Observationally, this death line can be inferred by the actual observed pulsar flux S ≥ 1mJy and 1 kpc distance, together with the maximum radio emission efficiency of 1%. However, the observation data show that the 37 pulsars pass over the death line, including the recently observed two pulsars with long periods of 23.5 s and 12.1 s, which violate the prediction of the polar cap model. At present, the actual observed pulsar flux can reach 0.01mJy by FAST telescope. This will arise the observational limit of spin-down power of pulsars as low as $\dot{E}\approx {10}^{28}$ erg s⁻¹. This means that the new death line is downward shifted two orders of magnitude, which might be favorably referred as the "observational limit–line". Accordingly, the pulsar theoretical model for the cut-off voltage of gap should be heavily modified.

We implement a numerical model reported in the literature to simulate the evolution of a galaxy composed of four matter components, such as: a dark-matter halo; a rotating disk of stars; a spherical bulge of stars and a ring of molecular gas. We show that the evolution of this galaxy model is stable at least for 10 Gyr (Gyr = 10⁹ years). We characterize the resulting configuration of this galaxy model by figures of the circular velocity and angular momentum distribution; the tangential and radial components of the velocity; the peak density evolution and the radial density profile. Additionally, we calculate several models of equal-mass galaxy binary collisions, such as: (i) frontal and (ii) oblique (with an impact parameter), (iii) two models with initial conditions taken from a 2-body orbit and (iv) a very close passage. To allow comparison with the galaxy model, we characterize the dynamics of the collision models in an analogous way. Finally, we determine the de Vaucouleurs fitting curves of the radial density profile, on a radial scale of 0–100 kpc, for all the collision models irrespective of the pre-collision trajectory. To study the radial mass density and radial surface density profiles at a smaller radial scale, 0–20 kpc, we use a four-parameter fitting curve.

Quasi-biennial Oscillations (QBOs) of the Sun have a significant meaning as a benchmark of solar cycle, not only for understanding the dynamo action but also in terms of space weather prediction. In this paper, the hand-drawn sunspot images recorded from the Purple Mountain Observatory are used to investigate the solar QBOs and the Gnevyshev gap of the sunspot relative numbers (Rs) and group sunspot numbers (Rg) during the period 1954–2011. The main results are as follows: (1) both the Rs and Rg exhibit similar periods including the 22-year magnetic cycle, the 11-year Schwabe cycle, and the QBOs modes; (2) the reconstructed QBOs of both data sets exhibit coherent behavior and tend to have a high amplitude during the maximum phase of each solar cycle; (3) the Gnevyshev gap is produced by the superposition of the QBOs and the 11-year Schwabe cycle, and the Rs is better to study the variation of the Gnevyshev gap rather than the Rg.