New CCD photometric investigation of the early-type overcontact binary BH Cen in the young star-forming Galactic cluster IC 2944

BH Cen is a short-period early-type binary with a period of 0.792 din the extremely young star-forming cluster IC 2944. New multi-color CCD photometric light curves in U, B, V, R and I bands are presented and are analyzed by using the Wilson-Devinney code. It is detected that BH Cen is a high-mass-ratio overcontact binary with a fill-out factor of 46.4% and a mass ratio of 0.89. The derived orbital inclination i is 88.9 degrees, indicating that it is a totally eclipsing binary and the photometric parameters can be determined reliably. By adding new eclipse times, the orbital period changes in the binary are analyzed. It is confirmed that the period of BH Cen shows a long-term increase while it undergoes a cyclic oscillation with an amplitude of A_3 = 0.024 d and a period of P_3 = 50.3 yr. The high mass ratio, overcontact configuration and long-term continuous increase in the orbital period all suggest that BH Cen is in the evolutionary state after the shortest-period stage of Case A mass transfer.The continuous increase in period can be explained by mass transfer from the secondary component to the primary one at a rate of˙M_2 = 2.8×10^(-6) M_⊙per year. The cyclic change can be plausibly explained by the presence of a third body because both components in the BH Cen system are early-type stars. Its mass is determined to be no less than 2.2 M_⊙at an orbital separation of about 32.5 AU. Since no third light was found during the photometric solution, it is possible that the third body may be a candidate for a compact object.

Chromospheric activity in several single late-type stars

New high-resolution echelle spectra of six single late-type Pleiades-like stars(V368 Cep, EP Eri, DX Leo, GJ 211, PW And and V383 Lac) were obtained with the 2.16 meter telescope at Xinglong Station in 2008–2010. Using the spectral subtraction technique, we analyzed our spectroscopic data and calculated the equivalent widths of excess emission from several indicators of chromospheric activity(Na I D1, D2, Hα and Ca II infrared triplet lines). All our results using chromospheric activity indicators confirmed the previous findings. In addition, the maximum amplitudes of chromospheric rotational modulation and the ratio of EW8542/EW8498 were found to rise with increasing v sin i velocity.

PREDICTION OF THE RHEOLOGICAL PROPERTIES OF STAR—TYPE BRANCHED POLYMER SOLUTIONS BY MEANS OF THE FIXED SPECTRUM MODEL

The Rouse-Zimm model with slippage was improved and the basic parameters of modelwere modified to explain the rheological properties of star-type branched polymersolutions. The theoretical results show good agreement with experimental data.

A catalog of early-type emission-line stars and Hα line profiles from LAMOST DR2

We present a catalog including 11 204 spectra of 10 436 early-type emission-line stars from LAMOST DR2, among which 9752 early-type emission-line spectra are newly discovered. For these earlytype emission-line stars, we discuss the morphological and physical properties of their low-resolution spectra. In this spectral sample, the Hα emission profiles display a wide variety of shapes. Based on the Hα line profiles, these spectra are categorized into five distinct classes: single-peak emission, single-peak emission in absorption, double-peak emission, double-peak emission in absorption, and P-Cygni profiles. To better understand what causes the Hα line profiles, we divide these objects into four types from the perspective of physical classification, which include classical Be stars, Herbig Ae/Be stars, close binaries and spectra contaminated by H II regions. The majority of Herbig Ae/Be stars and classical Be stars are identified and separated using a(H-K, K-W1) color-color diagram. We also discuss 31 binary systems that are listed in the SIMBAD on-line catalog and identify 3600 spectra contaminated by H II regions after cross-matching with positions in the Dubout-Crillon catalog. A statistical analysis of line profiles versus classifications is then conducted in order to understand the distribution of Hα profiles for each type in our sample. Finally, we also provide a table of 172 spectra with Fe II emission lines and roughly calculate stellar wind velocities for seven spectra with P-Cygni profiles.

Rotation Periods of Nine ROSAT Selected Solar-Type Stars

We monitored 16 X-ray selected young solar-type stars for light variation and found appreciable periodic light variability with amplitudes of a few hundredths of a magni-tude in nine of the objects. Using the method of Phase Dispersion Minimization (PDM) and Fourier analysis (software PERIOD04), the rotation periods of these stars were determined from the photometric data. The rotation periods of all nine stars are shorter than about 3days. It is suggested that, as with the Pleiades cluster, small amplitude light variations are quite common among young solar-type stars with rotation periods around 3 days or less. This gives further evidence for the spin up of solar-type stars predicted by models of angular momentum evolution of pre-main sequence stars.

High resolution spectroscopy of two young active late type stars within 20 parsecs of the Sun

We present high-resolution optical echell spectroscopy of HIP 544 and HIP 46843, two nearby solar like stars. The discovery of these young stars at such a close distance to the Sun is really a surprising phenomenon. It will help us to have a better understanding of the structure and evolutionary history of the Milky Way. The radial ve- locities (RV) of HIP 544 and HIP 46843 are measured to be –6.88±0.13km s -1 and 8.30±0.16km s-1, respectively, which are more accurate than before. The equivalent widths (EW) of the Li I 6707.8 absorption line of HIP 544 and HIP 46843 are mea- sured to be 110±5m A and 195±5m A respectively. Based on these properties, HIP 544 is estimated to be 100–800Myr old and HIP 46843 30–100Myr old using three relatively creditable methods.

Model Atmosphere Analysis of Some B-Type Stars

We present model atmosphere analysis for a sample of B-type stars in optical region to obtain their fundamental parameters e.g. effective temperature, surface gravities, and rotational velocities. Approximate masses for the sample of stars under study are obtained by comparing the resulted effective temperatures and surface gravities with the evolutionary tracks. Comparison between these masses and the empirical effective temperatures-mass relation revealed good agreement.

稳流器结构对导流式消防水炮流动特性的影响

为了探究一种新的最佳星形稳流器结构形式,选取六肋式星形稳流器,设计了5种不同长度且交叉排列的星形稳流器.基于CFD对安装有5种不同结构形式的星形稳流器的导流式消防水炮内流体的流动特性展开了数值模拟研究,分析了不同稳流器布置形式对导流式消防水炮内流体速度分布均匀性、轴线速度以及湍动能的影响,并对不同布置形式下的压力降进行了分析.数值研究结果表明,稳流器可有效改善消防水炮内轴线速度分布并降低消防水炮的进出口湍动能差,分段叉排布置的稳流器可显著提升稳流效果.其中,数量为2、长度为40 mm且交叉布置的稳流器组合最有利于提升消防水炮的综合性能.同体积条件下,通过缩短单个稳流器长度,增加稳流器叉排数量的分段错位布置提升消防水炮的性能作用有限.过多数量的叉排布置会造成逆流以及较大的压力损失.研究结果对星形稳流器在消防水炮内的优化设计具有一定借鉴作用.

Inhibitory actions of mibefradil on steroidogenesis in mouse Leydig cells： involvement of Ca^2＋ entry via the T-type Ca^2＋ channel

细胞内部的营地和 Ca2+ 在 Leydig 房间涉及 steroidogenic 活动的规定，它协调回答到 luteinizing 荷尔蒙(LH ) 和人的 chorionic gonadotropin (hCG ) 。然而， Ca2+ 入口的鉴定在 Leydig 房间 steroidogenesis 含有不是明确的。这研究的目的是识别影响 Leydig 房间 steroidogenesis 的 Ca2+ 隧道的类型。在在刚分裂的 Leydig 的 vitro steroidogenesis，老鼠的房间被 hCG 孵化导致。steroidogenesis 上的 mibefradil (通常认为的 T 类型 Ca2+ 隧道 blocker ) 的效果用反向的抄写(RT ) 被估计为 steroidogenic 的聚合酶链反应分析用放射性免疫测定的尖锐规章的蛋白质(星) mRNA 表示和睾丸激素生产。面对 1.0 mmol L ? 1 细胞外的 Ca2+ ，在 1 ～ 100 IU 的 hCG 显著地提高了两星 mRNA 水平和睾丸激素分泌物(P < 0.05 ) ，并且 hCG 的 stimulatory 效果被 mibefradil 显著地以一种剂量依赖者方式减少(P < 0.05 ) 。而且，当外部 Ca2+ 被省略时，睾丸激素生产的导致 hCG 的增加完全被移开，暗示那个 Ca2+ 条目为导致 hCG 的 steroidogenesis 被需要。而且，补丁夹钳研究揭示了在一个集中范围看见的 mibefradil 敏感的 Ca2+ 水流的存在将近 paralleled 那些禁止的 steroidogenesis。一起，我们的数据提供刺激 hCG 的 steroidogenesis 被在鼠标的 Leydig 房间由 T 类型 Ca2+ 隧道执行的 Ca2+ 入口部分地至少调停的证据。

Analysis of the X-ray emission of OB stars:O stars

We investigate the global properties of X-ray emission from O stars, analyzing the X-ray spectra of 32 O stars from archival data of the XMM-Newton space observatory. We examine two hypotheses about of the origin of X-ray emission from O stars. The first is a paradigm proposed by Pollock, that was revealed from an analysis of the ζ Ori X-ray observation. The second is the magnetically confined wind-shock(MCWS) model. For checking Pollock's hypothesis, we determine the distribution of the ratio of half width at half maximum(HWHM) to the wind terminal velocity for lines in spectra of all examined stars. In addition, we check three probable consequences from the MCWS model. We analyze if a correlation exists between the spectral hardness and such stellar parameters as the wind terminal velocity, stellar magnetic field and mass loss rate. The result showed that Pollock's hypothesis is not correct. We also established that not all consequences of the MCWS model considered by us are confirmed. In addition, our spectral analysis method indicated that O stars probably have clumped stellar winds with spherical clumps.

Solar-like and Mira-like oscillations of stars–A uniform excitation mechanism

Using a non-local and time-dependent theory of convection,we have calculated the linear non-adiabatic oscillations of the radial and low-degree F-p39 modes for evolutionary models from the main sequence to the asymptotic giant branch for stars with solar abundance(X=0.70,Z=0.02)in the mass range of 0.6–3.0 M⊙.The results show that low luminosity cool stars tend to be solar-like oscillators,whose low-order modes are stable,but intermediate and high order p-modes are pulsationally unstable;their unstable modes have a wide range in frequency and small values for amplitude growth rates.For stars with increasing luminosity and therefore lower temperature,the unstable modes shift towards lower orders,the corresponding range of frequency decreases,and the amplitude growth rate increases.High luminosity red giant stars behave like typical Mira-like oscillators.The effects of the coupling between convection and oscillations on pulsational instability have been carefully analyzed in this work.Our research shows that convection does not simply act as a damping mechanism for oscillations,and the complex nature of the coupling between convection and oscillations makes turbulent convection sometimes behave as damping,and sometimes as excitation.Such a picture can not only naturally account for the red edge of the instability strip,but also the solar-like oscillations in low luminosity red stars and Mira-like ones in high luminosity red giants.

Population I Cepheids and understanding star formation history of the Small Magellanic Cloud

In this paper, we study the age and spatial distributions of Cepheids in the Small Magellanic Cloud(SMC) as a function of their ages using data from the OGLE III photometric catalogue. A period- age relation derived for Classical Cepheids in the Large Magellanic Cloud(LMC) has been used to find the ages of Cepheids. The age distribution of the SMC Classical Cepheids is found to have a peak at log(Age) = 8.40 ± 0.10 which suggests that a major star formation event might have occurred in the SMC about 250 ± 50 Myr ago. It is believed that this star forming burst had been triggered by close interactions of the SMC with the LMC and/or the Milky Way. A comparison of the observed spatial distributions of the Cepheids and open star clusters has also been carried out to study the star formation scenario in the SMC.

The search for roAp stars: null results and new candidates from Strmgren-Crawford photometry

The rapidly oscillating Ap(roAp) stars exhibit pulsational photometric and/or radial velocity variations on time scales of several minutes, which are essential to test current pulsation models as well as our assumptions of atmospheric structure characteristics. In addition, their chemical peculiarity makes them very interesting for probing stellar formation and evolution in the presence of a global magnetic field. To date, a limited number of only 61 roAp stars is known to show photometric variability. On the other hand, a literature survey yields 619 unique stars that have unsuccessfully been searched for variability of this kind. Str o¨mgren-Crawford uvbyβ photometry of stars from both subgroups was used to investigate whether there is a selection bias for the investigated stars. We also present new photometric measurements(202 hours on 59 different nights) of 55 roAp candidates. We did not detect any new roAp star. Although our detection limits are comparable to other surveys, we also did not find pulsations in the known roAp star HD 12098, which may be a consequence of temporal amplitude changes. On the other hand, we do find some evidence for photometric variability of beta CrB at its spectroscopically derived pulsation period. From the uvbyβ photometry we conclude that the blue border of the roAp instability strip appears observationally well defined, whereas the red border is rather poorly known and studied.Within these boundaries, a total of 4646 candidates were identified which appear worth investigating for short-term pulsational variability.

Absolute parameters and physical nature of two W-UMa type binaries:V1123 Tau and V1128 Tau

We present high-precision,multi-band CCD photometry of two less-studied close binaries V1123 Tau and V1128 Tau.Complete covered light curves and a number of new times of light minima of the two eclipsing systems were obtained,based on which,revised orbital elements and new ephemerides were given.By adopting the Wilson-Devinney method,the light curves were analyzed.The photometric solutions confirm the W UMa-type nature of the binary systems.With the less-massive secondary slightly cooler than the primary,V1123 Tau could be classified as an Atype contact system.While V1128 Tau is typically considered a W-type W UMa star,the surface temperature of its secondary component is determined to be absolutely higher than the primary by about 270K.Combining with the results of radial-velocity solutions,we determined absolute parameters of the two systems.The mass,radius and luminosity for each component of V1123 Tau were derived as:1.36 ± 0.05M,1.37 ± 0.02R,and 2.01 ± 0.07L and 0.40 ± 0.02M,0.80 ± 0.01R,and 0.67 ± 0.04L,respectively.For V1128 Tau,the absolute parameters were computed to be 1.09 ± 0.03M,1.01 ± 0.01R,and 1.34 ± 0.06L and 0.58 ± 0.01M,0.76 ± 0.01R,and 0.91 ± 0.05L,respectively.Based on these results,the evolutionary status and the physical nature of the two binary systems are discussed,while also connecting with the theoretical models.

Photometric Monitoring of ROSAT-Selected Weak Line T Tauri Stars

We monitored the light curves of 22 weak-line T Tauri stars (WTTSs) discovered among the X-ray sources in the field of the Taurus-Auriga cloud. For 12 of the 22 WTTSs photometric periodic variability is confirmed and their rational periods are determined using Phase Dispersion Minimization (PDM) and Fourier analysis. Most of them are found to have periods shorter than one day. This gives further evidence for the spin up of solar-type stars predicted by the models of angular momentum evolution of pre-main sequence stars.

M-giant star candidates identified in LAMOST DR 1

We perform a discrimination procedure with the spectral index diagram of TiO 5 and Ca H2+Ca H3 to separate M giants from M dwarfs. Using the M giant spectra identified from LAMOST DR1 with high signal-to-noise ratio, we have successfully assembled a set of M giant templates, which show more reliable spectral features. Combining with the M dwarf/subdwarf templates in Zhong et al., we present an extended library of M-type templates which includes not only M dwarfs with a well-defined temperature and metallicity grid but also M giants with subtypes from M0 to M6. Then, the template-fitting algorithm is used to automatically identify and classify M giant stars from LAMOST DR1. The resulting catalog of M giant stars is cross-matched with 2MASS J H Ks and WISE W1/W2 infrared photometry. In addition, we calculated the heliocentric radial velocity of all M giant stars by using the cross-correlation method with the template spectrum in a zero-velocity rest frame.Using the relationship between the absolute infrared magnitude MJ and our classified spectroscopic subtype, we derived the spectroscopic distance of M giants with uncertainties of about 40%. A catalog of 8639 M giants is provided. As an additional result of this analysis, we also present a catalog of 101 690 M dwarfs/subdwarfs which are processed by our classification pipeline.

Distribution of SiO and OH Maser Stars in the Galactic Plane

The observational results of the Nobeyama 45-m SiO maser survey and the Arecibo 305-m OH maser survey are assembled for an analysis of the distribution and kinematics of late-type stars in the Galactic plane. It is found that neither SiO maser stars nor OH maser stars show any concentration to the spiral arms, which imply that they do not belong to the arm population and quite possibly they are low-mass stars in late stage of evolution. A rotational curve is also derived for these objects and a few features which may be real are discussed and compared with those derived from planetary nebulae and AGB stars.

Searching for classical Be stars in LAMOST DR1

We report on searching for Classical B-type emission-line(CBe) stars in the first data release of the Large Sky Area Multi-Object fiber Spectroscopic Telescope(LAMOST; also called the Guo Shou Jing Telescope). A total of 192 objects(including 12 previously known CBes) were identified as CBe candidates with prominent He I λ4387, He I λ4471 and Mg II λ4481 absorption lines, as well as Hβλ4861and Hαλ6563 emission lines. These candidates significantly increase the currently known sample of CBes by about 8%. Most of the CBe candidates are distributed near the Galactic Anti-Center due to the observing strategy used for LAMOST. Only two CBes are in star clusters. These two CBes have ages of 15.8 and 398 Myr, respectively.

High-α-Metal-Rich stars in the LAMOST-MRS survey and its connection with the galactic bulge

We report the detection of a large sample of high-α-metal-rich stars on the low giant branch with 2.6<log g<3.3 dex in the LAMOST-MRS survey.This special group corresponds to an intermediate-age population of 5-9 Gyr based on the[Fe/H]-[C/N]diagram and age-[C/N]calibration.A comparison group is selected to have a solarαratio at super metallicity,which is young and has a narrow age range around 3 Gyr.Both groups have thin-disk like kinematics but the former shows slightly large velocity dispersions.The special group shows a larger extension in a vertical distance toward 1.2 kpc,a second peak at smaller Galactic radius and a larger fraction of super metal rich stars with[Fe/H]>0.2 than the comparison group.These properties strongly indicate its connection with the outer bar/bulge region at R=3-5 kpc.A tentative interpretation of this special group is that its stars were formed in the X-shaped bar/bulge region,close to its corotation radius,where radial migration is the most intense,and brings them to present locations at 9 kpc and beyond.Low eccentricities and slightly outward radial excursions of its stars are consistent with this scenario.Its kinematics(cold)and chemistry([α/Fe]~0.1)further support the formation of the instability-driven X-shaped bar/bulge from the thin disk.

Equivalent Widths of 15 Extrasolar-Planet Host Stars

We present the equivalent widths of 15 extrasolar-planet hos stars.These data were based on the high-resoluton,high signal-to-noise ratio spectra obtained with the 2.16m telescope at Xinglong station.Te error in the Xinglong equivalent width is estimated by a comparison of these data with those given in previous studies of common stars.