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Vertical gradients of neutral winds observed by ICON and estimated by the Horizontal Wind Model during the geomagnetic storm on August 26−28,2021
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作者 JiaWei Wu Chao Xiong +1 位作者 YuYang Huang YunLiang Zhou 《Earth and Planetary Physics》 EI CAS 2025年第1期69-80,共12页
The Michelson Interferometer for Global High-resolution Thermospheric Imaging(MIGHTI)onboard the Ionospheric Connection Explorer(ICON)satellite offers the opportunity to investigate the altitude profile of thermospher... The Michelson Interferometer for Global High-resolution Thermospheric Imaging(MIGHTI)onboard the Ionospheric Connection Explorer(ICON)satellite offers the opportunity to investigate the altitude profile of thermospheric winds.In this study,we used the red-line measurements of MIGHTI to compare with the results estimated by Horizontal Wind Model 14(HWM14).The data selected included both the geomagnetic quiet period(December 2019 to August 2022)and the geomagnetic storm on August 26-28,2021.During the geomagnetic quiet period,the estimations of neutral winds from HWM14 showed relatively good agreement with the observations from ICON.According to the ICON observations,near the equator,zonal winds reverse from westward to eastward at around 06:00 local time(LT)at higher altitudes,and the stronger westward winds appear at later LTs at lower altitudes.At around 16:00 LT,eastward winds at 300 km reverse to westward,and vertical gradients of zonal winds similar to those at sunrise hours can be observed.In the middle latitudes,zonal winds reverse about 2-4 h earlier.Meridional winds vary more significantly than zonal winds with seasonal and latitudinal variations.According to the ICON observations,in the northern low latitudes,vertical reversals of meridional winds are found at 08:00-13:00 LT from 300 to 160 km and at around 18:00 LT from 300 to 200 km during the June solstice.Similar reversals of meridional winds are found at 04:00-07:00 LT from 300 to 160 km and at 22:00-02:00 LT from 270 to 200 km during the December solstice.In the southern low latitudes,meridional wind reversals occur at 08:00-11:00 LT from 200 to 160 km and at 21:00-02:00 LT from 300 to 200 km during the June solstice.During the December solstice,reversals of the meridional wind appear at 20:00-01:00 LT below 200 km and at 06:00-11:00 LT from 300 to 160 km.In the northern middle latitudes,the northward winds are dominant at 08:00-14:00 LT at 230 km during the June solstice.Northward winds persist until 16:00 LT at 160 and 300 km.During the December solstice,the northward winds are dominant from 06:00 to 21:00 LT.The vertical variations in neutral winds during the geomagnetic storm on August 26-28 were analyzed in detail.Both meridional and zonal winds during the active geomagnetic period observed by ICON show distinguishable vertical shear structures at different stages of the storm.On the dayside,during the main phase,the peak velocities of westward winds extend from a higher altitude to a lower altitude,whereas during the recovery phase,the peak velocities of the westward winds extend from lower altitudes to higher altitudes.The velocities of the southward winds are stronger at lower altitudes during the storm.These vertical structures of horizontal winds during the storm could not be reproduced by the HWM14 wind estimations,and the overall response to the storm of the horizontal winds in the low and middle latitudes is underestimated by HWM14.The ICON observations provide a good dataset for improving the HWM wind estimations in the middle and upper atmosphere,especially the vertical variations. 展开更多
关键词 horizontal neutral winds vertical gradients Ionospheric Connection Explorer satellite Horizontal Wind Model 14 geomagnetic storm
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Polarization variability arising from clumps in the winds of Wolf-Rayet stars 被引量:1
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作者 Qing-Kang Li Joseph E Cassinelli +1 位作者 John C. Brown Richard Ignace 《Chinese Journal of Astronomy and Astrophysics》 CSCD 2009年第5期558-576,共19页
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, bu... 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. 展开更多
关键词 stars mass loss -- stars Wolf-Rayet -- stars winds outflows
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High-Resolution Spectroscopy of Winds Associated with T Tauri Stars
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作者 Naoto Iguchi Yoichi Itoh 《Research in Astronomy and Astrophysics》 SCIE CAS CSCD 2016年第2期89-96,共8页
We carried out optical high-resolution spectroscopy of T Tauri stars using the Subaru Telescope. Using archived data from the Keck Telescope and the Very Large Telescope, we detected forbidden lines of [S II] at 4069A... We carried out optical high-resolution spectroscopy of T Tauri stars using the Subaru Telescope. Using archived data from the Keck Telescope and the Very Large Telescope, we detected forbidden lines of [S II] at 4069A, in addition to those of [O I] at 5577 A and 6300A, for 13 T Tauri stars. We consider that low-velocity components of these forbidden lines emanate from the wind associated with T Tauri stars. Using two flux ratios of the three lines, we simultaneously determined the hydrogen density and temperature of the winds. The winds ofT Tauri stars have a hydrogen density of 2.5 × 106 cm^-3 - 2.5 × 10^9 cm^-3 and a temperature of 10 800 -18 000 K. The mass loss rates by the wind are estimated to lie in the range from 2.0 × 10^-10 M⊙ yr-1 to 1.4× 10^-9 M⊙ yr-1. The mass loss rates are found to increase with increasing mass accretion rates. The ratio of the mass loss rate to the mass accretion rate is 0.001-0.1 for classical T Tauri stars and 0.1-1 for transitional disk objects. 展开更多
关键词 stars pre-main sequence -- stars emission lines
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Free Energy of Anisotropic Strangeon Stars 被引量:2
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作者 Shichuan Chen Yong Gao +1 位作者 Enping Zhou Renxin Xu 《Research in Astronomy and Astrophysics》 SCIE CAS CSCD 2024年第2期50-57,共8页
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... 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. 展开更多
关键词 (stars:)pulsars general-methods numerical-(stars:)gamma-ray bursts general
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Rotating Massive Strangeon Stars and X-Ray Plateau of Short GRBs 被引量:1
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作者 Xi-Yan Yang Xiao-Yu Lai +1 位作者 Wei-Wei Tan Ren-Xin Xu 《Research in Astronomy and Astrophysics》 SCIE CAS CSCD 2024年第3期47-57,共11页
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 rem... 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. 展开更多
关键词 dense matter-(stars) PULSARS general-(stars) gamma-ray burst GENERAL
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Spectroscopic Observations of Ten Galactic Wolf-Rayet Stars at Bosscha Observatory:Determination of Stellar Parameters and Mass-loss Rates
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作者 Hakim Luthfi Malasan Bakuh Danang Setyo Budi 《Research in Astronomy and Astrophysics》 SCIE CAS CSCD 2024年第9期7-27,共21页
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(2... 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. 展开更多
关键词 stars:massive stars:mass-loss stars:Wolf-Rayet stars:atmospheres stars:winds OUTFLOWS
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Analysis of X-Ray Emission from OB Stars. IV. About X-Ray Emission from Inhomogeneous Winds of OB Stars
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作者 Elizaveta Ryspaeva Alexander Kholtygin 《Research in Astronomy and Astrophysics》 SCIE CAS CSCD 2023年第10期387-405,共19页
We study the origin of X-ray emission from OB stars due to collisions of stellar winds and/or inhomogeneities in the winds. The low-resolution X-ray spectra of a big sample of OB stars were fitted by both the stationa... We study the origin of X-ray emission from OB stars due to collisions of stellar winds and/or inhomogeneities in the winds. The low-resolution X-ray spectra of a big sample of OB stars were fitted by both the stationary APEC/MEKAL models and by this model with an additional PSHOCK component describing the nonstationary X-ray emission. These spectra were also described by two-temperature PSHOCK models. More than ~50% of considered spectra can be described by the above-mentioned model combinations including the PSHOCK model and the quality of the fits appears to be better for O stars. The plasma temperature of the PSHOCK component is about 1–5 keV with the ionization timescale τ_(u)~ 10^(8)–10^(13)s cm^(-3). The temperature of the PSHOCK component increases with the momentum and kinetic energy of the stellar wind by a power law with an index ~0.12–0.14.Such dependencies were not revealed through modeling by the stationary APEC/MEKAL models only. At the same time the X-ray luminosity of OB stars depends on momentum and kinetic energy of their winds similarly either for stationary or for nonstationary models. We conclude that many O stars and some B stars can be sources of the nonstationary X-rays formed in their inhomogeneous stellar wind. 展开更多
关键词 stars:early-type stars:statistics X-rays:stars
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Revise Thermal Winds of Remnant Neutron Stars in Gamma-Ray Bursts
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作者 Shuang Du Tingting Lin +1 位作者 Shujin Hou Renxin Xu 《Research in Astronomy and Astrophysics》 SCIE CAS CSCD 2023年第9期142-147,共6页
It seems that the wealth of information revealed by the multi-messenger observations of the binary neutron star(NS)merger event,GW170817/GRB 170817A/kilonova AT2017gfo,places irreconcilable constraints to models of th... It seems that the wealth of information revealed by the multi-messenger observations of the binary neutron star(NS)merger event,GW170817/GRB 170817A/kilonova AT2017gfo,places irreconcilable constraints to models of the prompt emission of this gamma-ray burst(GRB).The observed time delay between the merger of the two NSs and the trigger of the GRB and the thermal tail of the prompt emission can hardly be reproduced by these models simultaneously.We argue that the merger remnant should be an NS(last for,at least,a large fraction of 1 s),and that the difficulty can be alleviated by the delayed formation of the accretion disk due to the absorption of high-energy neutrinos emitted by the NS and the delayed emergence of effective viscosity in the disk.Further,we extend the consideration of the effect of the energy deposition of neutrinos emitted from the NS.If the NS is the central object of a GRB with a distance and duration similar to that of GRB 170817A,thermal emission of the thermal bubble inflated by the NS after the termination of accretion may be detectable.If our scenario is verified,it would be of interest to investigate the cooling of nascent NSs. 展开更多
关键词 (stars )gamma-ray burst general-(stars )gamma-ray burst individual(.. ...)-stars NEUTRON
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An Asymmetric Galactic Stellar Disk Traced by OB-type Stars from LAMOST DR7
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作者 Xiaopeng Liu Hao Tian +4 位作者 Wenyuan Cui Linlin Li Jiaming Liu Zhenyan Huo Yawei Gao 《Research in Astronomy and Astrophysics》 SCIE CAS CSCD 2024年第6期38-51,共14页
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 ... 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. 展开更多
关键词 Galaxy:disk galaxies:spiral stars:early-type stars:massive
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On the Identification of N-rich Metal-poor Field Stars with Future Chinese Space Station Telescope
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作者 Jiajun Zhang Baitian Tang +6 位作者 Jiang Chang Xiangxiang Xue JoséGFernández-Trincado Chengyuan Li Long Wang Hao Tian Yang Huang 《Research in Astronomy and Astrophysics》 SCIE CAS CSCD 2024年第1期151-164,共14页
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... 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. 展开更多
关键词 stars:chemically peculiar stars:abundances techniques:photometric techniques:spectroscopic
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The Progenitors of Be-stars Paired with O-subdwarfs:The Spin-up of a Be Star at the Stage of Conservative Mass Exchange
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作者 Evgeny Staritsin 《Research in Astronomy and Astrophysics》 SCIE CAS CSCD 2024年第11期104-111,共8页
The spinning-up of the accreting component in the process of conservative mass exchange is considered in binary systems—progenitors of systems consisting of a main sequence Be-star and an O-subdwarf.During the mass e... The spinning-up of the accreting component in the process of conservative mass exchange is considered in binary systems—progenitors of systems consisting of a main sequence Be-star and an O-subdwarf.During the mass exchange,the meridional circulation transfers 80%-85%of the angular momentum that entered the accretor together with the accreted matter to the accretor surface.This angular momentum is removed from the accretor by the disk.When the mass exchange finishes,the accretor has a rotation typical of classical Be-type stars. 展开更多
关键词 (stars:)binaries(including multiple) close-stars emission-line-Be-(stars:)binaries general
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Probing the Galactic Halo with RR Lyrae Stars.VI.The Radial Velocity Curve Templates of RRc Stars
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作者 Yue Huang Min Fang +8 位作者 Gaochao Liu Xianzhong Zheng Sarah Ann Bird Yang Huang Jianrong Shi Jiangtao Wang Huawei Zhang Haijun Tian Haotong Zhang 《Research in Astronomy and Astrophysics》 SCIE CAS CSCD 2024年第7期118-134,共17页
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 ... 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. 展开更多
关键词 stars VARIABLES RR Lyrae-stars-techniques radial velocities
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Period–Luminosity Relationship forδScuti Stars Revisited
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作者 Atila Poro S.Javad Jafarzadeh +7 位作者 Roghaye Harzandjadidi Mohammad Madani Elnaz Bozorgzadeh Esfandiar Jahangiri Ahmad Sarostad Ailar Alizadehsabegh Maryam Hadizadeh Mohammad EsmaeiliVakilabadi 《Research in Astronomy and Astrophysics》 SCIE CAS CSCD 2024年第2期138-143,共6页
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%probabili... 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. 展开更多
关键词 stars VARIABLES delta Scuti--stars fundamental parameters-methods data analysis
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Prospect of Detecting Magnetic Fields from Strong-magnetized Binary Neutron Stars
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作者 Rundong Tang Xingyu Zhong +2 位作者 Ye Jiang Ping Shen Yu Wang 《Research in Astronomy and Astrophysics》 SCIE CAS CSCD 2024年第11期11-21,共11页
Binary neutron star mergers are unique sources of gravitational waves in multi-messenger astronomy.The inspira phase of binary neutron stars can emit gravitational waves as chirp signals.The present waveform models o ... Binary neutron star mergers are unique sources of gravitational waves in multi-messenger astronomy.The inspira phase of binary neutron stars can emit gravitational waves as chirp signals.The present waveform models o gravitational waves only considered the gravitational interaction.In this paper,we derive the waveform of th gravitational wave signal taking into account the presence of magnetic fields.We found that the electromagneti interaction and radiation can introduce different frequency-dependent power laws for both the amplitude and frequency of the gravitational wave.We show from the results of the Fisher information matrix that the third generation observation may detect magnetic dipole moments if the magnetic field is~10^(17)G. 展开更多
关键词 stars neutron-magnetic fields-gravitational waves
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Detecting short-term gravitational waves from post-merger hyper-massive neutron stars with a kilohertz detector
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作者 陈奕康 朱宗宏 《Chinese Physics B》 SCIE EI CAS CSCD 2024年第8期222-228,共7页
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-merg... 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. 展开更多
关键词 neutron star mergers gravitational waves
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Variable Stars in the 50BiN Open Cluster Survey.Ⅲ.NGC 884
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作者 Lin-Hong Wang Qian-Heng Nie +5 位作者 Kun Wang Xiao-Dian Chen Chun-Guang Zhang Li-Cai Deng Xiao-Bin Zhang Tian-Lu Chen 《Research in Astronomy and Astrophysics》 SCIE CAS CSCD 2024年第2期36-45,共10页
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 ... 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. 展开更多
关键词 stars variables general-(Galaxy:)open clusters and associations individual(… …)-(stars:)binaries GENERAL
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Understanding Simulated Causes of Damaging Surface Winds in a Derecho-Producing Mesoscale Convective System near the East China Coast Based on Convection-Permitting Simulations
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作者 Liping LUO Ming XUE +3 位作者 Xin XU Lijuan LI Qiang ZHANG Ziqi FAN 《Advances in Atmospheric Sciences》 SCIE CAS CSCD 2024年第11期2112-2130,共19页
A mesoscale convective system(MCS) occurred over the East China coastal provinces and the East China Sea on 30April 2021, producing damaging surface winds near the coastal city Nantong with observed speeds reaching 45... A mesoscale convective system(MCS) occurred over the East China coastal provinces and the East China Sea on 30April 2021, producing damaging surface winds near the coastal city Nantong with observed speeds reaching 45 m s^(–1). A simulation using the Weather Research and Forecasting model with a 1.5-km grid spacing generally reproduces the development and subsequent organization of this convective system into an MCS, with an eastward protruding bow segment over the sea. In the simulation, an east-west-oriented high wind swath is generated behind the gust front of the MCS. Descending dry rear-to-front inflows behind the bow and trailing gust front are found to feed the downdrafts in the main precipitation regions. The inflows help to establish spreading cold outflows and enhance the downdrafts through evaporative cooling. Meanwhile, front-to-rear inflows from the south are present, associated with severely rearward-tilted updrafts initially forming over the gust front. Such inflows descend behind(north of) the gust front, significantly enhancing downdrafts and near-surface winds within the cold pool. Consistently, calculated trajectories show that these parcels that contribute to the derecho originate primarily from the region ahead(south) of the east-west-oriented gust front, and dry southwesterly flows in the low-to-middle levels contribute to strong downdrafts within the MCS. Moreover, momentum budget analyses reveal that a large westward-directed horizontal pressure gradient force within the simulated cold pool produced rapid flow acceleration towards Nantong. The analyses enrich the understanding of damaging wind characteristics over coastal East China and will prove helpful to operational forecasters. 展开更多
关键词 damaging surface winds convection-permitting simulations mesoscale convective system gust front cold pool
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Dust Condensation of SiC, SiO in Asymptotic Giant Branch Stellar Winds-SiC Spectrum
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作者 Ruiqing Wu Chunhua Zhu +7 位作者 Guoliang Lu Shuming Yang Zhisen Meng Xiaojiao Zhang Xizhen Lu Jinlong Yu Wujin Chen Mengqiu Long 《Research in Astronomy and Astrophysics》 SCIE CAS CSCD 2024年第5期13-20,共8页
We have chosen the Large Scale Atomic/Molecular Massively Parallel Simulator (LAMMPS) code to calculate the coalescence of silicon carbide (SiC),silicon oxide dust (SiO) in the AGB stellar wind.LAMMPS is a classica mo... We have chosen the Large Scale Atomic/Molecular Massively Parallel Simulator (LAMMPS) code to calculate the coalescence of silicon carbide (SiC),silicon oxide dust (SiO) in the AGB stellar wind.LAMMPS is a classica molecular dynamics simulation code.At the same time,we consider the effect of temperature on the evolution of molecular dynamics.We also calculated the temperature change of non-spherical SiC,SiO dust coalescence.The condensation temperature range of SiC dust in the AGB stellar wind is[300–500]k and[900–1100]k for SiO Finally,the infrared spectrum of SiC was calculated using Gaussian 16 software.The 77SiC,70Si_(3)C_(3),and 121Si_(3)C_(3) models have clear characteristic peaks of infrared spectra responding at 5,8.6,11.3,15,19,and 37μm. 展开更多
关键词 stars AGB and post-AGB infrared ISM-(ISM:)dust-extinction
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Life Origin in the Milky Way Galaxy: III. Spatial Distribution of Overheated Stars in the Solar Neighborhood
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作者 Alexander N. Safronov 《Journal of High Energy Physics, Gravitation and Cosmology》 CAS 2024年第2期693-709,共17页
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 stell... 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). 展开更多
关键词 Stellar Nucleogenesis Ensemble-Averaged Stellar Reactor Overheated stars Chandrasekhar Stellar Limit Arm Spirality
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On the Surface Helium Abundance of B-type Hot Subdwarf Stars from the WD+MS Channel of Type Ia Supernovae
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作者 Rui-Jie Ji Xiang-Cun Meng Zheng-Wei Liu 《Research in Astronomy and Astrophysics》 SCIE CAS CSCD 2024年第5期21-27,共7页
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 m... 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. 展开更多
关键词 (stars:)subdwarfs-atomic processes-diffusion
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