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To study the quality of stellar spectra of the Large Sky Area Multi-Object Fiber Spectroscopic Telescope (LAMOST) and the correctness of the corresponding stellar parameters derived by the LASP (LAMOST Stellar Parameter Pipeline), the outlier analysis method is applied to the archived AFGK stars in the fifth data release (DR5) of LAMOST. The outlier factor is defined in order to sort more than 3 million stellar spectra selected from the DR5 Stellar Parameter catalog. We propose an improved Local Outlier Factor (LOF) method based on Principal Component Analysis and Monte Carlo to enable the computation of the LOF rankings for randomly picked sub-samples that are computed in parallel by multiple computers, and finally to obtain the outlier ranking of each spectrum in the entire dataset. Totally 3,627 most outlier ranked spectra, around one-thousandth of all spectra, are selected and clustered into 10 groups, and the parameter density distribution of them conforms to the parameter distribution of LAMOST DR5, which suggests that in the whole parameter space the probability of bad spectra is uniformly distributed. By cross-matching the 3,627 spectra with APOGEE, we obtain 122 common ones. The published parameters calculated from LASP agree with APOGEE for the 122 spectra although there are bad pixels or bad flux calibrations in them. On the other hand, some outlier spectra show strong nebular contamination warning the corresponding parameters should be carefully used. A catalog and a spectral atlas of all the 3,627 outliers can be found at the link http://paperdata.china-vo.org/LY_paper/dr5Outlier/dr5Outlier_resource.zip., 29 pages, 14 figures, accepted by Astronomy and Computing

Long gamma-ray bursts (GRBs) are considered to be originated from core collapse of massive stars. It is believed that the afterglow property is determined by the density of the material in the surrounding interstellar medium. Therefore, the circumburst density can be used to distinguish between an interstellar wind $n(R) \propto R^{\rm -k}$, and a constant density medium (ISM), $n(R) = const$. Previous studies with different afterglow samples, show that the circumburst medium of GRBs is neither simply supported by an interstellar wind, nor completely favored by an ISM. In this work, our new sample is consisted of 39 GRBs with smoothly onset bump-like features in early X-ray afterglows, in which 20 GRBs have the redshift measurements. By using a smooth broken power law function to fit the bumps of X-ray light curves, we derive the full width at half-maximum (FWHM) as the feature width ($\omega$), as well as the rise and decay time scales of the bumps ($T_{\rm r}$ and $T_{\rm d}$). The correlations between the timescales of X-ray bumps are similar to those found previously in the optical afterglows. Based on the fireball forward shock (FS) model of the thin shell case, we obtain the distribution of the electron spectral index $p$, and further constrain the medium density distribution index $k$. The new inferred $k$ is found to be concentrated at 1.0, with a range from 0.2 to 1.8. This finding is consistent with previous studies. The conclusion of our detailed investigation for X-ray afterglows suggests that the ambient medium of the selected GRBs is not homogeneous, i.e., neither ISM nor the typical interstellar wind., Comment: 11 pages, 3 figures and 2 tables; accepted for publication in ApJ

We firstly derive the stellar population properties: age and metallicity for $\sim$ 43,000 low redshift galaxies in the seventh data release (DR7) of the Large Sky Area Multi-Object Fiber Spectroscopic Telescope (LAMOST) survey, which have no spectroscopic observations in the Sloan Digital Sky Survey(SDSS). We employ a fitting procedure based on the small-scale features of galaxy spectra so as to avoid possible biases from the uncertain flux calibration of the LAMOST spectroscopy. We show that our algorithm can successfully recover the average age and metallicity of the stellar populations of galaxies down to signal-to-noise$\geq$5 through testing on both mock galaxies and real galaxies comprising LAMOST and their SDSS counterparts. We provide a catalogue of the age and metallicity for $\sim$ 43,000 LAMOST galaxies online. As a demonstration of the scientific application of this catalogue, we present the Holmberg effect on both age and metallicity of a sample of galaxies in galaxy pairs., Comment: 15 pages, 9 Postscript figures, accepted for publication in The Astrophysical Journal Supplement Series

This work is to retrieve emission-line spectra from the “Unknown” data set in LAMOST DR7 V1.2, most of which are low signal-to-noise ratios spectra. In the work, we perform emission line search and redshift calculations on the Unknown data set to get possible emission line galaxy spectra. Taking the galaxy spectra released by LAMOST as templates, the Product Quantization (PQ) based approximate nearest neighbor (ANN) search is used to retrieve the nearest neighbors of each spectrum. We keep the spectra for which the calculated redshift and the published redshift of the template meet the threshold, and 16,188 spectra with emission lines are obtained from the LAMOST DR7 Unknown data set. After visual inspection of spectra 10,266 spectra are left, in which 5828 spectra are identified as emission-line galaxies, 1782 spectra show ionization nebula features, and other 2656 are not clearly classified. Among 5828 spectra, 5720 can be found in Strasbourg astronomical Data Center catalog, Sloan Digital Sky Survey catalog, or NASA/IPAC Extragalactic Database catalog. The 108 spectra (corresponding to 106 unique coordinates of R.A. and decl.) which have no record in these three databases are new discoveries; for the 1782 spectra showing ionization nebula features, most of them have radial velocities less than 150 kilometers per second. We check them with the latest version of WISE H ii catalog V2.0 (short for HIICat V2) and 985 out of the 1782 spectra belong to 72 H ii regions. Of these H ii regions, 43 were previously identified while the other 29 are newly identified in this work including 797 newly observed spectra. Besides, there are still 2656 spectra that cannot be clearly classified although they have obvious emission lines and with small redshift. Finally, 106 new emission-line galaxies and 29 new Galactic H ii regions are identified, and we conclude that the ANN method sped up by the PQ algorithm is efficient in solving the problem of pairing spectra with massive data set to figure out their classes. We present our result at the link http://paperdata.china-vo.org/LY_paper/Work2/pressWork2_last.zip.

Photometric analysis of the contact binaries TIC 393943031 and TIC 89428764 was carried out using Transiting Exoplanet Survey Satellite and SuperWASP data for the first time. Using the Wilson–Devinney code, we have found that TIC 393943031 is a low-mass-ratio deep contact binary with a fillout factor of 50.9(±1)% and a mass ratio of q = 0.163 ± 0.001. TIC 89428764 is a medium and low-mass-ratio contact binary with a fillout factor of 34.5(±1)% and a mass ratio of q = 0.147 ± 0.001. Furthermore, the period study reveals both the stars exhibit continuously increasing periods, the increasing rate is 4.21 × 10−7 day yr−1 for TIC 393943031 while 6.36 × 10−7 day yr−1 for TIC 89428764. The possible reason is mass transfer from the secondary component to the primary component for both stars. Meanwhile, we discussed their evolutionary phases and orbital angular momenta.

The Jurkevich method is a useful method to explore periodicity in the unevenly sampled observational data. In this work, we adopted the method to the light curve of Cyg X-1 from 1996 to 2012, and found that there is an interesting period of 370 days, which appears in both low/hard and high/soft states. That period may be correlated with black hole physics and accretion disk geometry.

We test the possible evolutionary tracks of stars with various masses (1.8 M� , 1.9 M� , 2.0 M� , 2.1 M� , 2.2 M� ) and metallicities Z (0.008, 0.010, 0.012), including both models with and without convective core overshooting. At a given mass and metallicity, the models with a larger overshoot predict a larger radius and age of the star. Based on the observedfrequencyof oscillations and the position of � Oph on the H-R diagram, we obtain two distinct better-fitting models: the solutions with mass M =1 .9 Mfavor a radius in the range 10.55 ± 0.03 Rwith an age of 1.01 ± 0.08Gyr; the solutions with mass M =2 .0 Mfavor a radius in the range 10.74 ± 0.03 Rwith an age of 0.95 ± 0.11Gyr. Furthermore, we investigate the in- fluence of overshooting on the internal structure and the pulsation properties, and find that increasing the convective core overshoot significantly decreases non-radial mode inertia, while also increasing the mode amplitude. Therefore, the estimation of stellar mass and age might be modified by convective core penetration.

Solar-like oscillations have recently been observed in the red giant ɛ Ophiuchi (G9.5III). The large frequency separation is found to be 4.8 μHz, non-radial oscillation mode has been shown to exist. Based on the observed frequency of oscillations and the position of ɛ Ophiuchi on the Hertzsprung-Russell diagram and by adopting a method of combined calculation of stellar evolution and oscillations, some preliminary constraints on the mass, metal abundance, age and radius of this star have been obtained.

Taking into account the helium and metal diffusion, we explore the possible evolutionary status and perform seismic analysis of MOST target: the star $\epsilon$ Eridani. We adopt the different input parameters to construct the models by fitting the available observational constraints: e.g., $T_{eff}$, $L$, $R$, $[Fe/H]$. From computation, we obtain the average large spacings of $\epsilon$ Eridani about $194\pm 1 \mu$Hz. The age of the diffused models has been found to be about 1 Gyr, which is younger than one determined previously by models without diffusion. We found that the effect of pure helium diffusion on the internal structure of the young low-mass star is slight, but the metal diffusion influence is obvious. The metal diffusion leads the models to have much higher temperature in the radiation interior, correspondingly the higher sound speed in the interior of the model, thereby the larger frequency and spacings.

Taking into consideration the effects of rotation and interior magnetic field during the lifetime of the star, we reconstruct the model of a Cen B to satisfy the latest non-asteroseismic and asteroseismic observational constraints. We find that the effects can induce a change of about 0.3 mu Hz in the large frequency spacings and can speed up the star's evolution. The model of a Cen B has thereby been improved.

Reconstructing the evolution history of the dark energy equation of state parameter $w(z)$ directly from observational data is highly valuable in cosmology, since it contains substantial clues in understanding the nature of the accelerated expansion of the Universe. Many works have focused on reconstructing $w(z)$ using Type Ia supernova data, however, only a few studies pay attention to Hubble parameter data. In the present work, we explore the merit of Hubble parameter data and make an attempt to reconstruct $w(z)$ from them through the principle component analysis approach. We find that current Hubble parameter data perform well in reconstructing $w(z)$; though, when compared to supernova data, the data are scant and their quality is worse. Both $\Lambda$CDM and evolving $w(z)$ models can be constrained within $10\%$ at redshifts $z \lesssim 1.5$ and even $5\%$ at redshifts 0.1 $\lesssim$ z $\lesssim$ 1 by using simulated $H(z)$ data of observational quality., Comment: 25 pages, 11 figures

The Large Sky-Area Multi-Object Fiber Spectroscopic Telescope (LAMOST) Data Release 3 provided 341 691 K giant stars with stellar parameters. Based on the models of Law & Majewski, we identified 252 K giant stars in the leading stream associated with the Sagittarius (Sgr) dwarf galaxy. We obtained 132 K giant stars belonging to the trailing arm of Sgr using the model of Belokurov et al. We studied the metallicity distribution of member stars along the streams and found a flat gradient in the first wrap of the leading stream, –(0.88±0.3) × 10 −3 dex/( ° ) in the second wrap of the leading stream and –(1.2±0.3) × 10 −3 dex/( ° ) in the first wrap of the trailing stream. Moreover, we obtained a combined metallicity gradient with our sample and data from the literature. We also analyzed the properties of an overdensity, which is located in the leading stream of the Sgr.

With the post-genome era coming, it is interesting to establish a new bioinformatics database, further integrate related information of the sequences and develop new methods to reveal the mechanism of life based on databases of sequence. We have built a professional bioinformatics database of non-coding miRNA named G-microRNA by means of PHP, MYSQL and so on. The database integrates more than 2,000 miRNA sequences including several model organisms-human, arabidopsis thaliana and virus. The pre-calculated Z curves and characteristics of each sequence are displayed in the database. Simultaneously, we have improved analytic softwares, selected famous predicting tools and hundreds of outstanding references, and shared our database in the internet. The construction of the database will provide much useful information and operation platform for bioinformatics further research.

The basic intent of this paper is to model 70 Ophiuchi A using the latest asteroseismic observations as complementary constraints and to determine the fundamental parameters of the star. Additionally, we propose a new quantity to lift the degeneracy between the initial chemical composition and stellar age. Using the Yale stellar evolution code (YREC7), we construct a series of stellar evolutionary tracks for the mass range $M$ = 0.85 -- 0.93 $M_{\odot}$ with different composition $Y_{i}$ (0.26 -- 0.30) and $Z_{i}$ (0.017 -- 0.023). Along these tracks, we select a grid of stellar model candidates that fall within the error box in the HR diagram to calculate the theoretical frequencies, the large- and small- frequency separations using the Guenther's stellar pulsation code. Following the asymptotic formula of stellar $p$-modes, we define a quantity $r_{01}$ which is correlated with stellar age. Also, we test it by theoretical adiabatic frequencies of many models. Many detailed models of 70 Ophiuchi A have been listed in Table 3. By combining all non-asteroseismic observations available for 70 Ophiuchi A with these seismological data, we think that Model 60, Model 125 and Model 126, listed in Table 3, are the optimum models presently. Meanwhile, we predict that the radius of this star is about 0.860 -- 0.865 $R_{\odot}$ and the age is about 6.8 -- 7.0 Gyr with mass 0.89 -- 0.90 $M_{\odot}$. Additionally, we prove that the new quantity $r_{01}$ can be a useful indicator of stellar age., 23 pages, 5 figures, accepted by New Astronomy