Accurate measurements of stellar positions and velocities are crucial for studying galactic and stellar dynamics.W aim to create a Cartesian catalog from Gaia DR3 to serve as a high-precision database for further rese...Accurate measurements of stellar positions and velocities are crucial for studying galactic and stellar dynamics.W aim to create a Cartesian catalog from Gaia DR3 to serve as a high-precision database for further research using stellar coordinates and velocities.To avoid the negative parallax values,we select 31,129,169 sources in Gaia DR3with radial velocity,where the fractional parallax error is less than 20%(0<σ■/■<0.2).To select the mos accurate and efficient method of propagating mean and covariance,we use the Monte Carlo results with 10^(7)samples (MC7) as the benchmark,and compare the precision of linear,second-order,and Monte Carlo erro propagation methods.By assessing the accuracy of propagated mean and covariance,we observe that second-orde error propagation exhibits mean deviations of at most 0.5%compared to MC7,with variance deviations of up to10%.Overall,this outperforms linear transformation.Though the Monte Carlo method with 10^(4) samples (MC4) i an order of magnitude slower than second-order error propagation,its covariance propagation accuracy reaches 1%whenσ■/■is below 15%.Consequently,we employ second-order error propagation to convert the mean astrometry and radial velocity into Cartesian coordinates and velocities in both equatorial and galactic systems fo30 million Gaia sources,and apply MC4 for covariance propagation.The Cartesian catalog and source code ar provided for future applications in high-precision stellar and galactic dynamics.展开更多
The Jiao Tong University Spectroscopic Telescope(JUST)is a 4.4-meter f/6.0 segmented-mirror telescope dedicated to spectroscopic observations.The JUST primary mirror is composed of 18 hexagonal segments,each with a di...The Jiao Tong University Spectroscopic Telescope(JUST)is a 4.4-meter f/6.0 segmented-mirror telescope dedicated to spectroscopic observations.The JUST primary mirror is composed of 18 hexagonal segments,each with a diameter of 1.1 m.JUST provides two Nasmyth platforms for placing science instruments.One Nasmyth focus fits a field of view of 10′and the other has an extended field of view of 1.2°with correction optics.A tertiary mirror is used to switch between the two Nasmyth foci.JUST will be installed at a site at Lenghu in Qinghai Province,China,and will conduct spectroscopic observations with three types of instruments to explore the dark universe,trace the dynamic universe,and search for exoplanets:(1)a multi-fiber(2000 fibers)medium-resolution spectrometer(R=4000-5000)to spectroscopically map galaxies and large-scale structure;(2)an integral field unit(IFU)array of 500 optical fibers and/or a long-slit spectrograph dedicated to fast follow-ups of transient sources for multi-messenger astronomy;(3)a high-resolution spectrometer(R~100000)designed to identify Jupiter analogs and Earth-like planets,with the capability to characterize the atmospheres of hot exoplanets.展开更多
Scheduled for launch in 2030,the enhanced X-ray Timing and Polarization(eXTP)telescope is a Chinese space-based mission aimed at studying extreme conditions and phenomena in astrophysics.eXTP will feature three main p...Scheduled for launch in 2030,the enhanced X-ray Timing and Polarization(eXTP)telescope is a Chinese space-based mission aimed at studying extreme conditions and phenomena in astrophysics.eXTP will feature three main payloads:Spectroscopy Focusing Array(SFA),Polarimetry Focusing Array(PFA),and a Wide-field Camera(W2C).This white paper outlines observatory science,incorporating key scientific advances and instrumental changes since the publication of the previous white paper.We will discuss perspectives of eXTP on the research domains of flare stars,supernova remnants,pulsar wind nebulae,cataclysmic variables,X-ray binaries,ultraluminous X-ray sources,active galactic nucleus(AGN),and pulsar-based positioning and timekeeping.展开更多
基金supported by the National Key R&D Program of China,No.2024YFA1611801 and No.2024YFC2207800the National Natural Science Foundation of China (NSFC) under Grant No.12473066supported by Shanghai Jiao Tong University 2030 Initiative.W.W.is supported by NSFC (Grant Nos.12022307 and 12273021)。
文摘Accurate measurements of stellar positions and velocities are crucial for studying galactic and stellar dynamics.W aim to create a Cartesian catalog from Gaia DR3 to serve as a high-precision database for further research using stellar coordinates and velocities.To avoid the negative parallax values,we select 31,129,169 sources in Gaia DR3with radial velocity,where the fractional parallax error is less than 20%(0<σ■/■<0.2).To select the mos accurate and efficient method of propagating mean and covariance,we use the Monte Carlo results with 10^(7)samples (MC7) as the benchmark,and compare the precision of linear,second-order,and Monte Carlo erro propagation methods.By assessing the accuracy of propagated mean and covariance,we observe that second-orde error propagation exhibits mean deviations of at most 0.5%compared to MC7,with variance deviations of up to10%.Overall,this outperforms linear transformation.Though the Monte Carlo method with 10^(4) samples (MC4) i an order of magnitude slower than second-order error propagation,its covariance propagation accuracy reaches 1%whenσ■/■is below 15%.Consequently,we employ second-order error propagation to convert the mean astrometry and radial velocity into Cartesian coordinates and velocities in both equatorial and galactic systems fo30 million Gaia sources,and apply MC4 for covariance propagation.The Cartesian catalog and source code ar provided for future applications in high-precision stellar and galactic dynamics.
基金This work is supported by“the Fundamental Research Funds for the Central Universities”,111 project No.B20019Shanghai Natural Science Foundation,grant No.19ZR1466800.
文摘The Jiao Tong University Spectroscopic Telescope(JUST)is a 4.4-meter f/6.0 segmented-mirror telescope dedicated to spectroscopic observations.The JUST primary mirror is composed of 18 hexagonal segments,each with a diameter of 1.1 m.JUST provides two Nasmyth platforms for placing science instruments.One Nasmyth focus fits a field of view of 10′and the other has an extended field of view of 1.2°with correction optics.A tertiary mirror is used to switch between the two Nasmyth foci.JUST will be installed at a site at Lenghu in Qinghai Province,China,and will conduct spectroscopic observations with three types of instruments to explore the dark universe,trace the dynamic universe,and search for exoplanets:(1)a multi-fiber(2000 fibers)medium-resolution spectrometer(R=4000-5000)to spectroscopically map galaxies and large-scale structure;(2)an integral field unit(IFU)array of 500 optical fibers and/or a long-slit spectrograph dedicated to fast follow-ups of transient sources for multi-messenger astronomy;(3)a high-resolution spectrometer(R~100000)designed to identify Jupiter analogs and Earth-like planets,with the capability to characterize the atmospheres of hot exoplanets.
基金supported by the China’s Space Origins Exploration Program,the National Natural Science Foundation of China(Grant Nos.12273010,12333007,12433004,12233002,12373041,and 12422306)the International Partnership Program of Chinese Academy of Sciences(Grant No.113111KYSB20190020)+9 种基金the Strategic Priority Research Program of the Chinese Academy of Sciences(Grant No.XDA15020100)the Spanish MICIU(Grant Nos.PID2021-124581OB-I0,PID2024-155316NB-I00,and 2021SGR00426)the Ramon y Cajal Fellowship(Grant Nos.RYC2021-032718-I,and RYC2018-025950-I)the European Union NextGenerationEU/PRTR,the Spanish MINECO(Grant Nos.PID2022-136828NB-C44,and PID2023-148661NB-I00)the E.U.FEDER Funds,the AGAUR/Generalitat de Catalunya(Grant No.SGR-386/2021)the Deutsche Forschungsgemeinschaft(DFG,German Research Foundation)-Projektnummer(Grant No.549824807)the Programma di Ricerca Fondamentale INAF 2023,the National SKA Program of China(Grant No.2020SKA0120300)the National Key R&D Program of China(Grant No.2021YFA0718500)the Xinjiang Tianchi Program,the Hong Kong Government under HKU(Grant No.17304524)the Bagui Scholars Program.
文摘Scheduled for launch in 2030,the enhanced X-ray Timing and Polarization(eXTP)telescope is a Chinese space-based mission aimed at studying extreme conditions and phenomena in astrophysics.eXTP will feature three main payloads:Spectroscopy Focusing Array(SFA),Polarimetry Focusing Array(PFA),and a Wide-field Camera(W2C).This white paper outlines observatory science,incorporating key scientific advances and instrumental changes since the publication of the previous white paper.We will discuss perspectives of eXTP on the research domains of flare stars,supernova remnants,pulsar wind nebulae,cataclysmic variables,X-ray binaries,ultraluminous X-ray sources,active galactic nucleus(AGN),and pulsar-based positioning and timekeeping.
