Spectroscopic Observations of Ten Galactic Wolf-Rayet Stars at Bosscha Observatory:Determination of Stellar Parameters and Mass-loss Rates

We present optical spectra of 10 Galactic Wolf-Rayet(WR)stars that consist of five WN and five WC stars.The optical observation was conducted using a low-resolution spectrograph NEO-R1000(λ/Δλ~1000)at GAO-ITB RTS(27.94 cm,F/10.0),Bosscha Observatory,Lembang.We implemented stellar atmosphere Postdam Wolf-Rayet(PoWR)grid modeling to derive stellar parameters.The normalized optical spectrum can be used to find the best model from the available PoWR grid,then we could derive stellar temperature and transformation radius.To derive luminosity,stellar radius and color excess,we conducted a Spectral Energy Distribution(SED)analysis with additional data on the near-ultraviolet spectrum from the International Ultraviolet Explorer(IUE)database,and UBV and 2MASS JHK broadband filter data.Additional analysis to derive asymptotic terminal wind velocity was conducted from the P-Cygni profile analysis of the high-resolution IUE ultraviolet spectrum.With previously derived parameters,we could determine the mass loss rate of the WR stars.Furthermore,we compared our results with previous work that used PoWR code and the differences are not more than 20%.We conclude that the PoWR spectral grid is sufficient to derive WR stellar parameters quickly and could provide more accurate initial parameter input to the PoWR program code.

Polarization variability arising from clumps in the winds of Wolf-Rayet stars

Polarimetric and photometric variability of Wolf-Rayet （WR） stars as caused by clumps in the winds is revisited. In our model, which is improved from Li et al., radial expansion of the thickness is accounted for, but we retain dependence on the β velocity law and stellar occultation effects. We again search for parameters that can yield results consistent with observations in regards to the mean polarization p, the ratio R = σp/σphot of polarimetric to photometric variability and the volume filling factor fV. Clump generation and spatial distribution are randomized by the Monte Carlo method so as to produce clumps which are, in the mean, distributed uniformly in space and have time intervals that obey a Gaussian distribution. The generated clumps move radially outward with a velocity law determined by a β index, and the angular size of clumps is assumed to be fixed. By fitting the observed σp/σphot and the volume filling factor fv, clump velocity taw index β （- 2） and clump ejection rate .N （- 1） are inferred, and are found to be well constrained. In addition, the subpeak features of broad emission lines seem to support the clump ejection rate. Meanwhile, the fraction of total mass loss rate that is contained in clumps is obtained by fitting observed polarization. We conclude that this picture of the clumps＇ properties produces a valuable diagnostic of WR wind structure.

Are Massive Main Sequence Stars and Wolf-Rayet Stars Detectable Sources of the Intersteller Medium ^(26)A1?

Taken the recent experiments of nuclear physics into account,the massive main sequence stars and Wolf-Rayet stars are hard to provide enough interstellar medium ^(26)A1 to be detected,which is discussed in the text.

Free Energy of Anisotropic Strangeon Stars

Can pulsar-like compact objects release further huge free energy besides the kinematic energy of rotation?This is actually relevant to the equation of state of cold supra-nuclear matter,which is still under hot debate.Enormous energy is surely needed to understand various observations,such asγ-ray bursts,fast radio bursts and softγ-ray repeaters.In this paper,the elastic/gravitational free energy of solid strangeon stars is revisited for strangeon stars,with two anisotropic models to calculate in general relativity.It is found that huge free energy(>10^(46)erg)could be released via starquakes,given an extremely small anisotropy((p_(t)-p_(r))/p_(r)~10^(-4),with pt/pr the tangential/radial pressure),implying that pulsar-like stars could have great potential of free energy release without extremely strong magnetic fields in the solid strangeon star model.

Rotating Massive Strangeon Stars and X-Ray Plateau of Short GRBs

Strangeon stars,which are proposed to describe the nature of pulsar-like compact stars,have passed various observational tests.The maximum mass of a non-rotating strangeon star could be high,which implies that the remnants of binary strangeon star mergers could even be long-lived massive strangeon stars.We study rigidly rotating strangeon stars in the slowly rotating approximation,using the Lennard-Jones model for the equation of state.Rotation can significantly increase the maximum mass of strangeon stars with unchanged baryon numbers,enlarging the mass-range of long-lived strangeon stars.During spin-down after merger,the decrease of radius of the remnant will lead to the release of gravitational energy.Taking into account the efficiency of converting the gravitational energy luminosity to the observed X-ray luminosity,we find that the gravitational energy could provide an alternative energy source for the plateau emission of X-ray afterglow.The fitting results of X-ray plateau emission of some short gamma-ray bursts suggest that the magnetic dipole field strength of the remnants can be much smaller than that of expected when the plateau emission is powered only by spin-down luminosity of magnetars.

An Asymmetric Galactic Stellar Disk Traced by OB-type Stars from LAMOST DR7

Using 9943 OB-type stars from LAMOST DR7 in the solar neighborhood,we fit the vertical stellar density profile with the model including a single exponential distribution at different positions(R,Φ).The distributions of the scale heights and scale length show that the young disk traced by the OB-type stars is not axisymmetric.The scale length decreases versus the azimuthal angleΦ,i.e.,from.■kpc withΦ=-3°to■kpc withΦ=9°.Meanwhile we find signal of non-symmetry in the distribution of the scale height of the north and south of the disk plane.The scale height in the north side shows signal of flaring of the disk,while that of the south disk stays almost constant around h_(s)=130 pc.The distribution of the displaceeent of the disk plane Z_(0)also shows variance versus the azimuthal angleΦ,which displays significant differences with the warp model constrained by the Cepheid stars.We also test different values for the position of the Sun,and the distance between the Sun and the Galactic center affects the scale heights and the displacement of the disk significantly,but that does not change our conclusion that the disk is not axisymmetric.

On the Identification of N-rich Metal-poor Field Stars with Future Chinese Space Station Telescope

During the long term evolution of globular clusters(GCs), some member stars are lost to the field. The recently found nitrogen-rich(N-rich) metal-poor field stars are promising candidates of these GC escapees, since N enhancement is the fingerprint of chemically enhanced populations in GCs. In this work, we discuss the possibility of identifying N-rich metal-poor field stars with the upcoming Chinese Space Station Telescope(CSST). We focus on the main survey camera with NUV, u, g, r, i, z, y filters and slitless spectrograph with a resolution about 200.The combination of UV sensitive equipment and prominent N-related molecular lines in the UV band bodes well for the identification: the color–color diagram of(u-g) versus(g-r) is capable of separating N-rich field stars from normal halo stars, if metallicity can be estimated without using the information on u-band photometry.Besides, the synthetic spectra show that a signal-to-noise ratio of 10 is sufficient to identify N-rich field stars. In the near future, a large sample of N-rich field stars found by CSST, combined with state-of-the-art N-body simulations will be crucial to deciphering GC-Galaxy co-evolution.

Probing the Galactic Halo with RR Lyrae Stars.VI.The Radial Velocity Curve Templates of RRc Stars

We present radial velocity(RV)curve templates of RR Lyrae first-overtone(RRc)stars constructed with the Mg I b triplet and Hαlines using time-domain Medium-Resolution Survey spectra of seven RRc stars from Large Sky Area Multi-Object Fiber Spectroscopic Telescope(LAMOST)Data Release 9.Additionally,we derive the relation between the stellar RV curve amplitudes and g-band light curve amplitudes from Zwicky Transient Facility(ZTF)public survey.For those RRc stars without ZTF g-band light curves,we provide the conversions from the light curve amplitudes in ZTF r-and i-bands,Gaia G-band,and V-band from the All-Sky Automated Survey for Supernovae to those in ZTF g-band.We validate our RV curve templates using the RRc star SV Scl and find the uncertainties of systemic RV are less than 2.11 km s~(-1)and 6.08 km s~(-1)based on the Mg I b triplet and Hαlines,respectively.We calculate the systemic RVs of 30 RRc stars using the RV curve templates constructed with the Mg I b triplet and Hαlines and find the systemic RVs are comparable with each other.This RV curve template will be particularly useful for obtaining the systemic RV of RRc using the LAMOST spectroscopy.

Period–Luminosity Relationship forδScuti Stars Revisited

The Gaia DR3 parallax approach was used to estimate the absolute parameters of 2375δScuti stars from the ASAS catalog.The selected stars have a variety of observational characteristics,with a higher than 80%probability of beingδScuti stars.We have displayed all the stars in the Hertzsprung-Russell diagram along with theδScuti instability strip,the Zero Age Main Sequence and the Terminal Age Main Sequence.Then,we determined which fundamental and overtone modes each star belongs to using pulsation constant(Q)calculations.In addition,we evaluated the parameters in the Q calculation equation using three machine learning methods,which showed that surface gravity and temperature have the greatest effect on its calculation.The Period-Luminosity(P-L)relationship of theδScuti stars was also revisited.Eventually,using least squares linear regression,we made four linear fits for fundamental and overtone modes and updated their relationships.

Detecting short-term gravitational waves from post-merger hyper-massive neutron stars with a kilohertz detector

Gravitational waves emanating from binary neutron star inspirals,alongside electromagnetic transients resulting from the aftermath of the GW170817 merger,have been successfully detected.However,the intricate post-merger dynamics that bridge these two sets of observables remain enigmatic.This includes if,and when,the post-merger remnant star collapses to a black hole,and what are the necessary conditions to power a short gamma-ray burst,and other observed electromagnetic counterparts.Our focus is on the detection of gravitational wave(GW)emissions from hyper-massive neutron stars(NSs)formed through binary neutron star(BNS)mergers.Utilizing several kilohertz GW detectors,we simulate BNS mergers within the detection limits of LIGO-Virgo-KARGA O4.Our objective is to ascertain the fraction of simulated sources that may emit detectable post-merger GW signals.For kilohertz detectors equipped with a new cavity design,we estimate that approximately 1.1%-32%of sources would emit a detectable post-merger GW signal.This fraction is contingent on the mass converted into gravitational wave energy,ranging from 0.01M_(sun)to 0.1M_(sun).Furthermore,by evaluating other well-regarded proposed kilohertz GW detectors,we anticipate that the fraction can increase to as much as 2.1%-61%under optimal performance conditions.

Variable Stars in the 50BiN Open Cluster Survey.Ⅲ.NGC 884

Open clusters are the basic building blocks that serve as a laboratory for the study of young stellar populations in the Milky Way.Variable stars in open clusters provide a unique way to accurately probe the internal structure,temporal and dynamical evolutionary stages of individual stars and the host cluster.The most powerful tool for such studies is time-domain photometric observations.This paper follows the route of our previous work,concentrating on a photometric search for variable stars in NGC 884.The target cluster is the companion of NGC869,forming the well-known double cluster system that is gravitationally bound.From the observation run in 2016 November,a total of 9247 B-band CCD images and 8218Ⅴ-band CCD images were obtained.We detected a total of 15 stars with variability in visual brightness,including five Be stars,three eclipsing binaries,and seven of unknown types.Two new variable stars were discovered in this work.We also compared the variable star content of NGC 884 with its companion NGC 869.

Life Origin in the Milky Way Galaxy: III. Spatial Distribution of Overheated Stars in the Solar Neighborhood

A concept of ensemble averaged stellar reactors is developed to study the dynamics of processes occurring in stars, allocated in the ~200 pc solar neighborhood. According to the effective temperature value, four stellar classes are identified, for which the correlation coefficients and standard deviation are counted. The theory of the buoyancy terrestial elements is generalized to stellar systems. It was suggested that stars are over-heated due to the shift parameters of the nuclear processes occurring inside the stars, which leads to the synthesis of transuranium elements until the achievement of a critical nuclear mass and star explosion. The heavy transuranium elements sink downward and are concentrated in the stellar depth layers. The physical explanation of the existence of the critical Chandrasekhar star limit has been offered. Based on the spatial analysis of overheated stars, it was suggested that the withdrawal of the stellar reactor from the equilibrium state is a consequence of extragalactic compression inside the galaxy arm due to the arm spirality (not to be confused with the spirality of the galaxy itself).

On the Surface Helium Abundance of B-type Hot Subdwarf Stars from the WD+MS Channel of Type Ia Supernovae

The origin of intermediate helium (He)-rich hot subdwarfs is still unclear.Previous studies have suggested that some surviving Type Ia supernovae (SNe Ia) companions from the white dwarf+main-sequence (WD+MS)channel may contribute to the intermediate He-rich hot subdwarfs.However,previous studies ignored the impact of atomic diffusion on the post-explosion evolution of surviving companion stars of SNe Ia,leading to the aspect that they could not explain the observed surface He abundance of intermediate He-rich hot subdwarfs.In this work,by taking the atomic diffusion and stellar wind into account,we trace the surviving companions of SNe Ia from the WD+MS channel using the one-dimensional stellar evolution code MESA until they evolve into hot subdwarfs.We find that the surface He-abundances of our surviving companion models during their core He-burning phases are in a range of-1■log(N_(He) N_(H))■0,which are consistent with those observed in intermediate He-rich hot subdwarfs.This seems to further support the notion that it is possible for surviving companions of SNe Ia in the WD+MS channel to form some intermediate He-rich hot subdwarfs.

Isolation in the Ruins: Post-Apocalyptic Loneliness in Peter Heller’s The Dog Stars

Peter Heller’s The Dog Stars is a fascinating meditation of post-apocalyptic loneliness.Set in a dismal world devastated by a devastating virus,the story centers on the protagonist Hig’s experience and response as he navigates a terrain devoid of human connection and meaning.This paper investigates the complexities of loneliness,focusing on Hig’s response to the loss of his wife and dog.Furthermore,it delves into the transformational power of companionship,including Hig’s link with his dog Jasper and his ultimate connection with Cima and her father.The fragmented narrative style of the novel mirrors Hig’s internal struggle,offering a raw and intimate portrayal of his journey towards reconnection and hope.Through the novel,Heller offers his profound thinking on the significance of connection in overcoming even post-apocalyptic loneliness.

数字近景摄影大尺寸三坐标测量系统V-STARS的测试与应用

介绍了数字近景摄影大尺寸柔性三坐标测量系统V-STARS的配置、测量原理和测量过程,对其三维坐标及平面度的测量重复性进行了实际测试,与激光跟踪仪进行了平面度的比对测试,并将V-STARS系统成功应用于某17 m网状天线的型面测量与调整工程实践中。

STARS开放体系结构的可复用资产库框架

一、前言近年来由于面向对象等新技术的支持,软件构件技术已经成为热点。人们认识到为了充分利用构件和完成大量构件的生产、分类、检索、集成和维护任务,构件库及其相关工具将变得十分重要。国内的相关研究工作已经展开,青鸟工程在“九五”期间的主要任务之一便是研究基于“构件—构架”模式的软件复用技术,为我国软件企业提供良好的技术装备。国外对此也有巨大的投入,在美国军方与政府部门发起的项目中,到93年底已经有了CARDS/AS-SET/DSRS(合称CAD)等大型可复用资产库系统,并且开始考虑资产库间的相互合作。

V-STARS工业摄影三坐标测量系统精度测试及应用

随着现代先进制造业的发展,工业摄影测量技术广泛应用于几何量的尺寸测量、精密零部件或产品的三维外形检测等领域,尤其在航天产品的质量控制中发挥着越来越重要的作用。作为当今最成熟的工业三坐标摄影测量系统,V-STARS的测量精度一直受到关注。因此,分别测试了V-STARS单相机和双相机系统的坐标测量、平面度测量精度和测量重复性。最后,利用V-STARS系统对Φ17.2 m网状天线的型面进行了检测,测量精度优于0.3 mm,使天线型面精度调整到3 mm以内,满足设计要求。

V-STARS摄影测量系统及其在抛物面天线测量中的应用

抛物面天线在通讯、遥感、气象观测、天文观测等领域得到广泛的应用,抛物面天线的表面精度对微波通信和观测的效率起着关键作用,本文基于V-STARTS摄影测量软件,在天线反射面上粘贴测量标志,通过摄影来测量天线表面曲线并建立起三维模型,这种方法简化并缩短了测量过程,降低了人为误差对测量精度的影响,有效的提高天线测量的精度和效率.

V—STARS数字摄影三坐标测量系统的精度测试及应用

以激光跟踪测量系统和经纬仪测量系统所测量值为参照，对V-STARS单相机系统的平面与坐标测量精度进行了比对测试，并测试了其重复性；此外还对双相机系统的平面度测量结果与单相机的进行了比较。测试结果表明V—STARS单相机系统在2．5m范围内测量精度优于0．03mm。利用V-STARS系统对某17．2m口径网状天线的型面进行了检测，测量精度优于0．3mm，并使天线型面精度调整到3mm以内，满足了设计要求。

骨科机器人联合Starr骨盆复位架治疗Tile C型骨盆环骨折

目的:探讨骨科机器人联合Starr骨盆复位架治疗Tile C型骨盆环骨折的临床疗效。方法:2019年10月至2021年5月采用机器人联合Starr骨盆复位架治疗14例Tile C型骨盆环骨折患者,男9例,女5例;年龄33~69岁。14例患者均为新鲜闭合骨折且不合并股骨、胫腓骨骨折等损伤。入院后4~7 d完成手术,术中在可透视碳素床,通过Starr骨盆复位架牵引复位骨盆环,联合骨科机器人治疗C型骨盆环骨折。观察手术时间、出血量、单枚螺钉置入透视次数、骨折复位质量、患肢功能及并发症等。采用Matta评分标准进行放射学复位评价,末次随访采用Majeed骨盆功能评分系统进行临床疗效评价。结果:14例患者均顺利完成手术,手术时间84~141 min,手术出血量20~50 ml,单枚螺钉置入透视次数4~9次。14例患者均获得随访,随访时间12~24个月。术后所有骨折获得骨性愈合,愈合时间3~7个月,未发现内固定断裂、螺钉松动、感染、神经损伤等并发症。依据Matta影像学复位评估标准:优9例,良4例,可1例。末次随访采用Majeed骨盆功能评分系统:优10例,良4例。结论:机器人联合Starr骨盆复位架治疗C型骨盆环新鲜骨折操作简单、缩短了手术和麻醉时间、并发症少,降低了手术风险,实现了骨盆骨折的微创治疗。但对于陈旧性骨折,因骨折复位困难,该技术并不适用。对于螺钉进钉点区域粉碎的骨折,通道螺钉置入困难,建议采用其他方式固定。对于伴有骨盆外伤史或骨盆发育异常者,术前需仔细评估有无经皮螺钉通道,避免损伤神经、血管。