arXiv subjects

Xiao-Long Wang

Publications and source records attributed to Xiao-Long Wang.

14 recordsLinked to original sources

arXiv2026

OB stars identified in LAMOST Data Release 10

A large sample of OB stars plays an important role in studying the stellar parameters of massive stars, as well as the formation and evolution of the Milky Way. With the help of the Large Sky Area Multi-Object Fiber Spectroscopic Telescope (LAMOST) Data Release 10 (DR10), we are able to construct a large sample of OB stars with spectroscopic data. In this study, we identify 48,463 spectra of 34,550 OB stars from LAMOST DR10, based on the Hertzsprung-Russell (H-R) diagram constructed with Gaia DR3 data and spectral line indices measured from LAMOST DR10 low-resolution spectra. Among these, 6907 OB stars are newly identified. We use the MKCLASS tool to derive the spectral subtypes of the OB sample. The spatial distribution of 25,287 OB stars and the Toomre diagram of 20,397 OB stars indicate that the majority of these stars are located in the Galactic disk. Based on their peculiar velocities, we identify 1960 runaway star candidates.

astro-ph.SR↗

arXiv2026

Identifying and Determining Atmospheric Parameters of BHB Stars Based on LAMOST DR11

Large catalogs of blue horizontal-branch (BHB) stars are essential for studying substructures and kinematics of the Galactic halo. And accurate determination of atmospheric parameters for BHB stars provides insight into stellar evolution. In this work, we perform a systematic search for BHB stars based on LAMOST DR11, and identify $13\,988$ BHB spectra, corresponding to $10\,236$ unique BHB stars. We estimate an identification rate of $\sim80\%-90\%$, and a contamination rate of $\lesssim10\%$ for our sample. Atmospheric parameters for these BHB stars are estimated via the data-driven method named the Stellar LAbel Machine (SLAM). We demonstrate the necessity of including color indices in the spectral labeling to effectively break the degeneracy between effective temperature and surface gravity. We note a bump in the distribution of [Fe/H], and most of these metal-rich BHB stars belong to the disk population. We also provide a list of 4282 blue straggler (BS) stars with determined atmospheric parameters.

astro-ph.SR↗

arXiv2026

Investigation of projected rotational velocities of Be-type stars in LAMOST DR7

Stellar rotation plays a key role in the transfer of angular momentum, and a large sample of Be-type stars with reliable projected rotational velocities is crucial for understanding their formation and evolution. In this work, we derive the projected rotational velocities ($v$\,sin\,$i$) of 479 Be-type stars using the Fourier transform method, based on their LAMOST Medium-resolution Survey (MRS) spectra. Our results suggest that the Fourier transform method can provide reliable $v$\,sin\,$i$ values for Be-type stars by analyzing the \ion{He}{1}\,lines at 4922, 5015, 5047, and 6678 \,Åin their LAMOST MRS spectra. A K-S test indicates that Be-type stars with different H$α$ emission line morphologies exhibit different $v$\,sin\,$i$ distributions, and Be-type stars with double-peaked emission have a higher fraction of rapid rotators than those with single-peak emission. The $v$\,sin\,$i$ distributions of our Be-type stars in the field, OB associations, and clusters show no significant differences. The deconvolved $v$\,sin\,$i$ distribution of our entire Be-type star sample does not exhibit a bimodal distribution but rather a single peak at $v\approx260$\,km$\cdot$s$^{-1}$. Based on the analysis of 105 stars in our sample, we find that the mean equatorial rotational velocity is 0.74 times the critical velocity. Furthermore, we investigate the relationship between $v$\,sin\,$i$ and the H$α$ peak separation velocity for Be-type stars exhibiting double-peak H$α$ emission lines, using Pearson and Spearman rank correlation coefficients.

astro-ph.SR↗

arXiv2026

The Structure of an 80 pc Long Massive Filament

Using new Institut de Radioastronomie Millimétrique (IRAM) 30m telescope $\rm N_2H^+$, $\rm C^{18}O$ $J$=1-0 and Atacama Pathfinder Experiment (APEX) telescope $\rm ^{13}CO$ and $\rm C^{18}O$ $J$=2-1 maps together with archival far-infrared continuum data, and $\rm ^{12}CO$, and $\rm ^{13}CO$ $J$=1-0 data, we present a comprehensive analysis of the massive filament CFG024.00$+$0.48 (G24) across clump-to-cloud scales. Our results show that G24 is an $\sim$80 pc giant filament with a total mass of $\sim$$10^5$ M$_{\odot}$. In the different tracers the filament width is measured to be about $\sim$2 times the beam size of the observations, as expected for power-law density distributions, giving beam-deconvolved widths in the range from 0.8 to 2.8 pc. We determine a line-of-sight thickness of $\sim$2.2 pc demonstrating that G24 is not an edge-on, flatten structure. The virial parameter obtained from line mass ($α_{\rm line,vir}=M_{\rm line,vir}/M_{\rm line}$) from the $\rm C^{18}O$ (1-0) data is 0.85, and that obtained from $Herschel$-based H$_2$ column density is 0.52, suggesting G24 is globally close to virial equilibrium. The distribution of the 40 dust clumps appears to have a ''two-tier'' fragmentation pattern. For the clump groups, the separation, with a mean/median of 3.68/3.46 pc, is very close to expected length associated with the maximum fragmentation growth rate of $λ_{\rm max}=3.55 \pm0.32$ pc estimated for the dust. However, the longitudinal centroid velocity profiles of $\rm C^{18}O$ and $\rm N_2H^+$ show oscillation patterns with wavelengths of 9.8$\pm$0.1 pc and 9.9$\pm$0.1 pc, respectively. This is $\sim$2 times larger than the corresponding values of $λ_{\rm max}$ of 4.96$\pm$0.63 pc and 4.65$\pm$1.34 pc, respectively. This suggests that the velocity structure is not dominated by flows directly associated with the fragmentation seen in the dust emission.

astro-ph.GA↗

arXiv2025

The MALATANG survey: star formation, dense gas, and AGN feedback in NGC 1068

We aim to investigate the interplay between dense molecular gas, star formation, and active galactic nucleus (AGN) feedback in the luminous infrared galaxy (LIRG) NGC 1068 at sub-kiloparsec scales. We present the HCN (4-3) and HCO$^+$ (4-3) maps of NGC 1068, obtained with JCMT as part of the Mapping the dense molecular gas in the strongest star-forming galaxies (MALATANG) project, and perform spatially resolved analyses of their correlations with infrared luminosity and soft X-ray emission. Spatially resolved relations between the luminosities of infrared dust emission and dense molecular gas tracers ($L_{\rm IR}-L'_{\rm dense}$) are found to be nearly linear, without clear evidence of excess contributions from AGN activity. The spatially resolved X-ray emission ($L^{\rm gas}_{0.5-2\,\mathrm{keV}}$) displays a radially-dependent twofold correlation with the star formation rate (SFR), suggesting distinct gas-heating mechanisms between the galaxy center and the outer regions. A super-linear scaling is obtained in galactic center regions with SFR surface density ($Σ_{\rm SFR}$) $>$ 8.2 $\times$ 10$^{-6}$ $M_\odot$ yr$^{-1}$ kpc$^{-2}$: log($L^{\rm gas}_{0.5-2\,\mathrm{keV}}$/erg s$^{-1}$) = 2.2 log(SFR/$M_\odot$ yr$^{-1}$) + 39.1. We further found a statistically significant super-linear correlation ($β= 1.34$ $\pm$ 0.86) between $L^{\rm gas}_{0.5-2\,\mathrm{keV}}$/SFR and HCN(4-3)/CO(1-0) intensity ratio, whereas no such trend is seen for HCO$^+$(4-3)/CO(1-0) or CO(3-2)/CO(1-0). These findings indicate that AGN feedback does not dominate star formation regulation on sub-kiloparsec scales, and that the excitation of dense gas traced by HCN (4-3) may be more directly influenced by high-energy feedback processes compared to HCO$^+$ (4-3) and CO (3-2).

astro-ph.GA↗

arXiv2025

Identification of OB associations using the LAMOST-Gaia OB star sample

OB associations, as an intermediate stage between Galactic clusters and field stars, play an important role in understanding the star formation process, early stellar evolution, and Galactic evolution. In this work, we construct a large sample of OB stars with 6D phase space parameters ($l, b, d, V_{\rm los}, pmra ,pmdec$) by combining the distances from Bailer-Jones et al. (2021), radial velocities derived from low-resolution spectra of the Large Sky Area Multi-Object Fiber Spectroscopic Telescope (LAMOST), and proper motions from the \textit{Gaia} Data Release 3 (DR3). This sample includes 19,933 OB stars, most of which are located within 6\,kpc of the Sun. Using 6D phase space parameters and friends-of-friends clustering algorithm, we identify 67 OB associations and 112 OB association candidates, among them, 49 OB associations and 107 OB association candidates are newly identified. The Galactic rotation curve derived using 67 OB association members is relatively flat in the range of Galactocentric distances 7$<$$R$$<$13\,kpc. The angular rotation velocity at solar Galactocentric distance of $R_\odot$ =8.34\,kpc is $Ω_0$ = 29.05$\pm$0.55\,km\,s$^{-1}$\,kpc$^{-1}$. The spatial distribution of the 67 OB associations indicates that they are mainly located at low Galactic latitudes and near spiral arms of the Milky Way. Additionally, we estimate the velocity dispersions and sizes of these 67 OB associations. Our results show that the velocity dispersions decrease as Galactocentric distances increase, while their sizes increase as Galactocentric distances increase.

astro-ph.GA↗

arXiv2025

Multiple generation star formation in Cepheus Flare

We present an analysis of the young stellar moving group ASCC 127 using Gaia DR3 data, significantly expanding its membership to 3,971 stars -- double the number identified in previous studies. Using kinematic and distance criteria, ASCC 127 is divided into five subgroups (Groups 1-5) with ages spanning from 15 to 32 Myr. Groups 1-5 are spatially linked to the Cepheus Flare star-forming region, revealing potential evidence of four sequential star formation episodes at approximately 32 Myr, 20 Myr, 15 Myr, and 7 Myr. Through dust and gas mapping, we identify a spatial cavity extending several tens of parsecs, which may have resulted from feedback processes such as supernovae associated with earlier generations of stars in the region. This structure, along with the larger Loop III feature, indicates that feedback from massive stars likely influenced the interstellar medium (ISM). By integrating young stellar populations with ISM studies, we provide a detailed picture of the feedback-driven star formation history in the Cepheus Flare region.

astro-ph.SR↗

arXiv2025

LAMOST Reveals Long-lived Protoplanetary Disks

While both observations and theories demonstrate that protoplanetary disks are not expected to live much longer than $\sim$10 Myr, several examples of prolonged disks have been observed in the past. In this work, we perform a systematic search for aged YSOs still surrounded by protoplanetary disks in the M star catalog from the LAMOST archive. We identify 14 sources older than 10 Myr, still surrounded by protoplanetary disks and with ongoing accretion activities, significantly improving the census of the category known as the Peter Pan disks. The stellar parameters, variability and accretion properties of these objects, as well as their spatial distribution, are investigated. Nearly all of these objects are distributed far away from nearby associations and star forming regions, but show evidence of being members of open clusters. Investigating the correlation between mass accretion rates and stellar masses, we find these long-lived disks accrete at systematically lower levels, compared to their younger counterparts with similar stellar masses. Studying the evolution of mass accretion rates with stellar ages, we find these aged disks follow similar trend as young ones.

astro-ph.GA↗

arXiv2024

DarkSHINE Baseline Design Report: Physics Prospects and Detector Technologies

DarkSHINE is a newly proposed fixed-target experiment initiative to search for the invisible decay of Dark Photon via missing energy/momentum signatures, based on the high repetition rate electron beam to be deployed/delivered by the Shanghai High repetition rate XFEL and Extreme light facility (SHINE). This report elaborates the baseline design of DarkSHINE experiment by introducing the physics goals, experimental setups, details of each sub-detector system technical designs, signal and backgground modelings, expected search sensitivities and future prospects, which mark an important step towards the further prototyping and technical demonstrations.

physics.ins-det↗

arXiv2024

The Value-added Catalog of OB Stars in LAMOST DR7

In this work, we update the catalog of OB stars based on the Large Sky Area Multi-Object Fiber Spectroscopic Telescope (LAMOST) data release 7 and modified the OB stars selection criterion the spectral line indices space. The new catalog includes 37,778 spectra of 27,643 OB stars, of which 3827 OB stars are newly identified. The spectral subclasses of 27,643 OB stars are obtained using the automatic classification code MKCLASS. We find that the modified OB star selection criteria can better improve the completeness of late B-type stars by analyzing their spectral classification results given by MKCLASS. We also identify 3006 Be-type stars or candidates by examining the Balmer lines in their spectra and find that the frequency of our Be-type stars (10.9\%) is consistent with previous results. The spatial distribution of OB stars indicates that they are mainly located in the Galactic disk. This new catalog of OB stars will provide valuable data for studying the structure and evolution of the Milky Way.

astro-ph.SR↗

arXiv2024

Visualization for physics analysis improvement and applications in BESIII

Modern particle physics experiments usually rely on highly complex and large-scale spectrometer devices. In high energy physics experiments, visualization helps detector design, data quality monitoring, offline data processing, and has great potential for improving physics analysis. In addition to the traditional physics data analysis based on statistical methods, visualization provides unique intuitive advantages in searching for rare signal events and reducing background noises. By applying the event display tool to several physics analyses in the BESIII experiment, we demonstrate that visualization can benefit potential physics discovery and improve the signal significance. With the development of modern visualization techniques, it is expected to play a more important role in future data processing and physics analysis of particle physics experiments.

physics.data-an↗

arXiv2024

Rotation effect on the spectral function of heavy vector mesons in holographic QCD

Exploring heavy vector mesons of the $ J / ψ$ and $ Υ( 1 S )$ is crucial for understanding the quark gluon plasma (QGP) formed in heavy ion collisions. The influences of rotational effect on the properties of the $ J / ψ$ and the $ Υ( 1 S )$ are investigated by incorporating rotation medium into the holographic QCD. It is found that temperature, chemical potential, and rotational radius effects enhance the dissociation process of the $ J / ψ$ and the $ Υ( 1 S )$ states within the medium. This rotation-induced effect is more significant for heavy vector mesons in the transverse direction than that of the longitudinal direction. The first holographic study on the influence of the radius of a homogeneous rotating system on the vector meson spectrum is proposed. It is found that increasing in rotation radius promotes the dissociation of vector mesons of the $ J / ψ$ and $ Υ( 1 S )$. We also find that the dissociation perpendicular to the direction of rotational angular velocity is more significant than that parallel to it at large rational radius.

hep-ph↗

arXiv2023

Variability of Young Stellar Objects in the Perseus Molecular Cloud

We present an analysis of 288 young stellar objects (YSOs) in the Perseus Molecular Cloud that have well defined $g$ and $r$-band lightcurves from the Zwicky Transient Facility. Of the 288 YSOs, 238 sources (83% of our working sample) are identified as variables based on the normalized peak-to-peak variability metric, with variability fraction of 92% for stars with disks and 77% for the diskless populations. These variables are classified into different categories using the quasiperiodicity ($Q$) and flux asymmetry ($M$) metrics. Fifty-three variables are classified as strictly periodic objects that are well phased and can be attributed to spot modulated stellar rotation. We also identify 22 bursters and 25 dippers, which can be attributed to accretion burst and variable extinction, respectively. YSOs with disks tend to have asymmetric and non-repeatable lightcurves, while the YSOs without disks tend to have (quasi)periodic lightcurves. The periodic variables have the steepest change in $g$ versus $g-r$, while bursters have much flatter changes than dippers in $g$ versus $g-r$. Periodic and quasiperiodic variables display the lowest variability amplitude. Simple models suggest that the variability amplitudes of periodic variables correspond to changes of the spot coverage of 30% to 40%, burster variables are attributed to accretion luminosity changes in the range of $L_{\rm acc}/L_{\star}=0.1-0.3$, and dippers are due to variable extinction with $A_{V}$ changes in the range of $0.5-1.3\;$mag.

astro-ph.SR↗

arXiv2022

Distributed YSOs in the Perseus Molecular Cloud from the Gaia and LAMOST Surveys

Identifying the young optically visible population in a star-forming region is essential for fully understanding the star formation event. In this paper, We identify 211 candidate members of the Perseus molecular cloud based on Gaia astronomy. We use LAMOST spectra to confirm that 51 of these candidates are new members, bringing the total census of known members to 856. The newly confirmed members are less extincted than previously known members. Two new stellar aggregates are identified in our updated census. With the updated member list, we obtain a statistically significant distance gradient of $\rm 4.84\;pc\;deg^{-1}$ from west to east. Distances and extinction corrected color-magnitude diagrams indicate that NGC 1333 is significantly younger than IC 348 and the remaining cloud regions. The disk fraction in NGC 1333 is higher than elsewhere, consistent with its youngest age. The star formation scenario in the Perseus molecular cloud is investigated and the bulk motion of the distributed population is consistent with the cloud being swept away by the Per-Tau Shell.

astro-ph.GA↗