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The Hierarchical Structure of the Open Cluster NGC 752 认领 引用
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作者 Delong Jia Heng Yu +1 位作者 Zhengyi Shao Lu Li 《Research in Astronomy and Astrophysics》 SCIE CAS CSCD 2026年第4期93-103,共11页
The structure of open clusters provides key insights into their evolution and the dynamics of the Milky Way.Using Gaia DR3 data,we applied a hierarchical clustering algorithm to the open cluster NGC 752 based on the k... The structure of open clusters provides key insights into their evolution and the dynamics of the Milky Way.Using Gaia DR3 data,we applied a hierarchical clustering algorithm to the open cluster NGC 752 based on the kinematical information and identified four substructures corresponding to different stages of disintegration.The cluster exhibits a pronounced signature of mass segregation.Its outer members show a clear expansion trend with a velocity of 0.25 km s−1in the plane of the sky.In addition,the system shows a projected rotational pattern with an angular velocity of approximately 0.03 rad Myr−1.We also identified a correlation between the escape times of disturbed members and the epochs at which the cluster crossed the Galactic disk,highlighting the role of Galactic tidal forces in accelerating cluster dissolution.We conclude that hierarchical clustering based on projection bounding energy is effective for studying the internal structure of star clusters,but it has limitations when dealing with unconstrained structures such as tidal tails. 展开更多
关键词 (Galaxy:)open clusters and associations NGC 752-methods data analysis-stars kinematics and dynamics
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Balmer Decrement and IRX Break in Tracing Dust Attenuation at Scales of Individual Star-forming Regions in NGC 628 认领 引用
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作者 Man Qiao Mingfeng Liu +10 位作者 Zongfei Lyu Shuang Liu Chao Yang Dongdong Shi Fangxia An Zhizheng Pan Wenhao Liu Binyang Liu Run Wen Yuheng Zhang Xianzhong Zheng 《Research in Astronomy and Astrophysics》 SCIE CAS CSCD 2025年第8期128-139,共12页
We investigate the relationships between infrared excess(IRX = LIR/LUV) and Balmer decrement(Hα/Hβ) as indicators of dust attenuation for 609 H II regions at scales of ~50–200 pc in NGC 628, utilizing data from Ast... We investigate the relationships between infrared excess(IRX = LIR/LUV) and Balmer decrement(Hα/Hβ) as indicators of dust attenuation for 609 H II regions at scales of ~50–200 pc in NGC 628, utilizing data from AstroSat, the James Webb Space Telescope(JWST) and Multi Unit Spectroscopic Explorer. Our findings indicate that about three-fifths of the sample H II regions reside within the regime occupied by local star-forming galaxies(SFGs) along the dust attenuation correlation described by their corresponding color excess parameters E(B-V)IRX= 0.51 E(B-V)Hα/Hβ. Nearly 27% of the sample exhibits E(B-V)IRX> E(B-V)Hα/Hβ, while a small fraction(~13%) displays significantly lower E(B-V)IRXcompared to E(B-V)Hα/Hβ. These results suggest that the correlation between the two dust attenuation indicators no longer holds for spatially resolved H II regions. Furthermore, the ratio of E(B-V)IRXto E(B-V)Hα/Hβremains unaffected by various physical parameters of the H II regions, including star formation rate(SFR), SFR surface density, infrared luminosity(LIR),LIRsurface density, stellar mass, gas-phase metallicity, circularized radius, and the distance to the galactic center.We argue that the ratio is primarily influenced by the evolution of the surrounding interstellar medium of the starforming regions, transitioning from an early dense and thick phase to the late blown-away stage. 展开更多
关键词 (ISM:)dust extinction galaxies:ISM galaxies:individual(NGC 628) galaxies:star formation
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河外星系NGC 0925中HⅡ区氧元素丰度估计研究 认领 引用
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作者 李林林 吴啟明 +1 位作者 毛业伟 莫诗茵 《广州大学学报（自然科学版）》 CAS 2025年第3期31-41,共11页
氧元素丰度是揭示星系化学演化的关键指针。利用光谱发射线估计氧元素丰度是最常用的方法。然而,不同方法对同一目标源氧元素丰度的估计存在显著差异,给氧元素丰度估计和星系化学演化研究带来很大的不确定性。该研究基于国家天文台2.16... 氧元素丰度是揭示星系化学演化的关键指针。利用光谱发射线估计氧元素丰度是最常用的方法。然而,不同方法对同一目标源氧元素丰度的估计存在显著差异,给氧元素丰度估计和星系化学演化研究带来很大的不确定性。该研究基于国家天文台2.16m望远镜对河外星系NGC0925中HⅡ区的观测数据,利用不同方法得到HⅡ区的氧元素丰度,比较并量化不同方法间的偏差程度,并借助贝叶斯统计方法探讨氧元素丰度估计中的关键发射线。观测得到的光谱发射线一共7条:[OⅡ]λ3727、[OⅢ]λ5007、[NⅡ]λ6583、[SⅡ]λλ6717,6731、Hα和Hβ,该研究采用的氧元素估计方法包括最常用的4种强线单指针法N2、O3N2、N2O2、R23和1种贝叶斯多发射线统计法NebulaBayes,其中,贝叶斯统计方法中通过调配发射线组合又得到27种估计值。研究结果表明,不同方法得到的氧元素丰度的平均值约为8.3,最大值和最小值分别为9.068和7.179。经过比较分析,发现在输入全部7条发射线时,贝叶斯方法与N2方法的氧元素丰度结果高度一致(~8.36,偏差只有0.085dex),而与R23方法(氧元素丰度的结果为8.112)的偏差最大,为0.33dex;在所有7条发射线中,[OⅡ]λ3727与[NⅡ]λ6583是氧元素估计中的关键发射线,如果缺失会导致很大的偏差(|Δ|>0.3dex),同时这两条关键发射线的缺失将失去对电离态的约束,导致贝叶斯统计中后验概率分布可能趋于极端值而使误差范围显著扩大。非关键发射线如[SⅡ]λλ6717,6731缺失仅引起的偏差很小(|Δ|≤0.1dex),此时输出的误差较小且误差的上下限相等。该研究的结果对氧元素丰度方法的精确定标提供了观测上的指示性参照,同时建议在氧元素丰度的实际测定中需要优先确保[OⅡ]λ3727与[NⅡ]λ6583光谱发射线的观测覆盖,并推荐结合贝叶斯多线统计联合约束以降低系统误差,为高精度星系化学演化建模提供方法论方面的指导。 展开更多
关键词 氧元素丰度 HⅡ区 光谱学观测研究 谱线和波段 恒星形成 个源星系(NGC 0925)
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Chemical Tagging of Tidal Tail Star Candidates of NGC 6362 认领 引用
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作者 Andrés E.Piatti 《Research in Astronomy and Astrophysics》 SCIE CAS CSCD 2025年第8期39-46,共8页
The inner Milky Way disk globular cluster NGC 6362 appears to exhibit tidal tails composed of stars that have proper motions and positions in the color–magnitude diagram similar to those of cluster stars. Because rec... The inner Milky Way disk globular cluster NGC 6362 appears to exhibit tidal tails composed of stars that have proper motions and positions in the color–magnitude diagram similar to those of cluster stars. Because recent results seem also to show that these stars are distributed across the regions least affected by interstellar absorption and reproduce the observed composite star field density map, we carried out a detailed spectroscopic analysis of a number of chemical element abundances of tidal tail star candidates in order to investigate the relationship between them and NGC 6362. From European Southern Observatory's VLT@FLAMES spectra we found that the red giant branch stars selected as the cluster's tidal tail stars neither have overall metallicities nor abundances of Mg, Ca, Sc, Ti, Cr, Ni and Ba similar to the cluster's ones. Moreover, they are mainly alike to stars that belong to the Milky Way thick disk, some of them could be part of the thin disk and a minor percentage could belong to the Milky Way halo star population. On the other hand, since the resulting radial velocities do not exhibit a distribution function similar to that of the cluster's stars, we concluded that looking for kinematic properties similar to those of the cluster would not seem to be as suitable of an approach for selecting the cluster's tidal tail stars as previously thought. 展开更多
关键词 methods:observational techniques:spectroscopic (Galaxy:)globular clusters:general (Galaxy:)globular clusters:individual(NGC 6362)
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基于50BiN望远镜的疏散星团NGC 7789的变星搜寻研究 认领 引用
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作者 叶倩 王坤 彭宇慧 《西华师范大学学报（自然科学版）》 2025年第1期79-85,共7页
基于西华师范大学50BiN望远镜获得的长时序测光观测数据,在疏散星团NGC 7789及其周围的20′×20′视场中搜寻到19颗变星,其中10颗是本次观测发现的。基于变星在NGC 7789颜色星等图上的位置、星团成员星概率和Gaia视差,对这19颗变星... 基于西华师范大学50BiN望远镜获得的长时序测光观测数据,在疏散星团NGC 7789及其周围的20′×20′视场中搜寻到19颗变星,其中10颗是本次观测发现的。基于变星在NGC 7789颜色星等图上的位置、星团成员星概率和Gaia视差,对这19颗变星的星团成员星性质进行初步分析。结果表明,17颗变星可能是星团成员,2颗可能是场星。根据变星光变曲线的形状,周期的长度以及在颜色星等图上的位置,对这19颗变星的分类进行了初步讨论。结果表明,13颗是短周期变星(3颗δ Scuti, 7颗食双星、3颗未知类型变星),6颗是长周期变星。研究扩大了星团变星的样本数量,为开展单个变星的星震学研究和星团变星的统计研究奠定了基础。 展开更多
关键词 50BiN 疏散星团 变星 NGC 7789 δScuti
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Detection of the Farthest Globular Cluster NGC 6715 and Two Other GCs in Gamma-Rays with Fermi-LAT 认领 引用 被引量：1
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作者 Min Yuan Chongyang Ren +2 位作者 Pengfei Zhang Zejun Jiang Li Zhang 《Research in Astronomy and Astrophysics》 SCIE CAS CSCD 2022年第11期137-146,共10页
In this paper,~12 yr long-term Pass 8 data from Fermi Large Area Telescope for the 157 globular clusters are carefully re-analyzed.Besides the 31 globular clusters reported in the fourth Fermi Large Area Telescope cat... In this paper,~12 yr long-term Pass 8 data from Fermi Large Area Telescope for the 157 globular clusters are carefully re-analyzed.Besides the 31 globular clusters reported in the fourth Fermi Large Area Telescope catalog Data Release 2,NGC 1851 is identified as a gamma-ray emitter and the significant gamma-ray emissions from NGC 6715 and NGC 6723 are detected.Especially NGC 6715 is located at a distance of 26.8 kpc,so far it is the farthest globular cluster detected in gamma-rays.A detailed analysis for these three globular clusters has been performed,but their gamma-ray pulsation emissions or flux variabilities are not found.The numbers of millisecond pulsars(MSPs)in these globular clusters are estimated under the assumption that each MSP inside globular clusters emits a similar amount of gamma-rays.Some possible origins of gamma-ray emission from globular clusters,such as MSPs,pulsar binary systems and/or dark matter,are discussed. 展开更多
关键词 (Galaxy:)globular clusters:individual(NGC6715 NGC1851 NGC6723)
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Clumpy metal concentrations in elliptical galaxies NGC 4374 and NGC 4636 认领 引用
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作者 Hai-Guang Xu Jun-Hua Gu +3 位作者 Li-Yi Gu Zhong-Li Zhang Yu Wang Tao An 《Research in Astronomy and Astrophysics》 SCIE CAS 2010年第3期220-226,共7页
We present a high spatial resolution study of metal distributions in the nearby, gas-rich elliptical galaxies NGC 4374 and NGC 4636 with the Chandra ACIS archive data. We define the hardness ratio HRFeL as the ratio o... We present a high spatial resolution study of metal distributions in the nearby, gas-rich elliptical galaxies NGC 4374 and NGC 4636 with the Chandra ACIS archive data. We define the hardness ratio HRFeL as the ratio of the emission in 0.65- 1.4 keV to that in 0.3-0.6 keV and 1.4-3.5 keV （after the magnesium and silicon lines are excluded）, and HRcont as the ratio of the emission in 1.4-3.5keV to that in 0.3- 0.6 keV, so that the HRFeL and HRcont maps can be used to trace the iron abundance and gas temperature distributions, respectively. By applying the a Trous wavelet algorithm to the obtained emission hardness ratio maps, we reveal that the HRFeL distributions are highly irregular, exhibiting strong spatial variations on 0.1-1 Re scales, which do not follow the HRcont distributions. Since the effect of temperature variation is small, we conclude that most of the high-HRFeL regions are very likely to possess higher abundances than the ambient gas. We also find that these high-HRFeL substructures are not associated with either the LMXB or globular cluster populations, thus their origins should be related to AGN activity or mergers. 展开更多
关键词 galaxies： elliptical and lenticular cD -- galaxies： individual （NGC 4374 NGC 4636） -- galaxies： ISM -- ISM： abundances -- X-rays： galaxies
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Star formation properties in barred galaxies (SFB) Ⅱ. NGC 2903 and NGC 7080 认领 引用
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作者 Zhi-Min Zhou Chen Cao Hong Wu 《Research in Astronomy and Astrophysics》 SCIE CAS CSCD 2012年第3期235-248,共14页
Stellar bars are important for the secular evolution of disk galaxies because they can drive gas into the galactic central regions. To investigate the star formation properties in barred galaxies, we presented a multi... Stellar bars are important for the secular evolution of disk galaxies because they can drive gas into the galactic central regions. To investigate the star formation properties in barred galaxies, we presented a multi-wavelength study of two barred galaxies： NGC 2903 and NGC 7080. We performed the three-component bulge-diskbar decomposition using the 3.6 μm images, and identified the bulges in the two galaxies as pseudobulges. Based on the narrowband Hα images, the star formation clumps were identified and analyzed. The clumps in the bulge regions have the highest surface densities of star formation rates in both galaxies, while the star formation activities in the bar of NGC 2903 are more intense than those in the bar of NGC 7080. Finally, we compared our results with the scenario of bar-driven secular evolution in previous studies, and discussed the possible evolutionary stages of the two galaxies. 展开更多
关键词 galaxies： evolution—galaxies： individual （NGC 2903 NGC 7080）—galaxies： star formation—galaxies： structure
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Comptonization and Reprocessing Processes in Accretion Disks: Applications to the Seyfert 1 Galaxies NGC 5548 and NGC 4051 认领 引用
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作者 Fan Zhang Xue-Bing Wu 《Chinese Journal of Astronomy and Astrophysics》 2006年第2期165-174,共10页
Simultaneous multi-wavelength observations have revealed complex variability in AGNs. To explain the variability we considered a theoretical model consisting of an inner hot comptonizing corona and an outer thin accre... Simultaneous multi-wavelength observations have revealed complex variability in AGNs. To explain the variability we considered a theoretical model consisting of an inner hot comptonizing corona and an outer thin accretion disk, with interactions between the two components in the form of comptonization and reprocessing. We found that the variability of AGNs is strongly affected by the parameters of the model, namely, the truncated disk radius rmin, the corona radius rs, the temperature KTe and the optical depth TO of the corona. We applied this model to the two best observed Seyfert 1 galaxies, NGC 5548 and NGC 4051. Our model can reproduce satisfactory the observed SEDs. Our fits indicate that NGC 5548 may have experienced dramatic changes in physical parameters between 1989-1990 and 1998, and that NGC 4051 has a much larger truncated disk radius （700 Schwarzschild radii） than NGC 5548 （several tens of Schwarzschild radii）. Since we adopted a more refined treatment of the comptonization process rather than simply assuming a cut-off power law, our results should be more reasonable than the previous ones. 展开更多
关键词 accretion - accretion disks - galaxies： active - galaxies： individual （NGC 5548 NGC 4051） - galaxies： Seyfert - X-rays： galaxies
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疏散星团NGC1750和NGC1758的研究 Ⅰ.自行和成员判定 认领 引用
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作者 田凯平 《中国科学院上海天文台年刊》 2000年第0期48-57,共10页
利用历元差最大达 6 8年的 2 0张底片 ,得到了金牛座暗星云 1° .5× 1° .5范围内的 540颗恒星的相对自行 ,其精度为 0 .6 7mas/a ;并根据该运动学资料以及改进后的最大似然法成功地确定了NGC1750和NGC1758两个星团的分布... 利用历元差最大达 6 8年的 2 0张底片 ,得到了金牛座暗星云 1° .5× 1° .5范围内的 540颗恒星的相对自行 ,其精度为 0 .6 7mas/a ;并根据该运动学资料以及改进后的最大似然法成功地确定了NGC1750和NGC1758两个星团的分布参数和它们的成员概率。 展开更多
关键词 NGC1750 NGC1758 自行 成员判定
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疏散星团NGC1750和NGC1758的研究 Ⅱ.照相测光和天体物理性质 认领 引用
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作者 田凯平 《中国科学院上海天文台年刊》 2000年第0期58-71,共14页
利用上海天文台 1.56m反射望远镜 1992～ 1993年拍摄的测光底片的PDS测量结果 ,采用P .B .Stetson所提供的照相星等归算方法 ,得到了 789颗恒星的B ,V星等 ,并与GJTR的测光结果进行了比较。同时在已经得出疏散星团NGC1750和NGC1758天区... 利用上海天文台 1.56m反射望远镜 1992～ 1993年拍摄的测光底片的PDS测量结果 ,采用P .B .Stetson所提供的照相星等归算方法 ,得到了 789颗恒星的B ,V星等 ,并与GJTR的测光结果进行了比较。同时在已经得出疏散星团NGC1750和NGC1758天区恒星的自行和测光结果的基础上 ,确定了两个星团包括面密度、半径、HR图、距离、年龄、光度函数和质量函数等在内的基本参数 ,并对运动学特征也进行了讨论。从而 ,进一步证实了这一天区确实存在着两个独立的动力学系统。 展开更多
关键词 NGC1750 NGC1758 照相测光 天体物理性质
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NGC收录护理临床实践指南方法学分析 认领 引用 被引量：2
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作者 孙月 陈吉 +3 位作者 布优祥 于丽萍 王波 田金徽 《护理学杂志》 CSCD 北大核心 2018年第14期99-100,104,共2页
目的分析美国国立指南文库(National Guideline Clearinghouse,NGC)收录的护理临床实践指南现状,以期对我国护理临床实践指南的开发和应用提供借鉴。方法检索NGC网站获取护理临床实践指南,并提取护理临床实践指南基本信息和方法学内容,... 目的分析美国国立指南文库(National Guideline Clearinghouse,NGC)收录的护理临床实践指南现状,以期对我国护理临床实践指南的开发和应用提供借鉴。方法检索NGC网站获取护理临床实践指南,并提取护理临床实践指南基本信息和方法学内容,并将数据输入Excel,使用STATA12.0软件进行数据统计分析。结果共收录268部指南,均含有护理相关内容。发布机构最多的是医学协会或学会、主要针对用户为护士和执业医师、260部(97.01%)基于系统评价、246部(91.79%)采用评级指标进行证据的质量和推荐强度的评估、264部(98.51%)采用专家共识的方法给予指南制定建议。结论 NGC收录的护理临床实践指南在证据选择/收集、证据质量和推荐强度的评估以及制定建议的方法学方面仍需进一步完善。 展开更多
关键词 NGC 临床护理指南 方法学
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A study of variable stars in the open cluster NGC 1582 and its surrounding field 认领 引用 被引量：4
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作者 Fang-Fang Song Ali Esamdin +4 位作者 Lu Ma Jin-Zhong Liu Yu Zhang Hu-Biao Niu Tao-Zhi Yang 《Research in Astronomy and Astrophysics》 SCIE CAS CSCD 2016年第10期35-44,共10页
This paper presents Charge-Coupled Device time-series photometric observations of the open cluster NGC 1582 and its surrounding field with Johnson B, V and R filters by using the Nanshan 1 m telescope administered by ... This paper presents Charge-Coupled Device time-series photometric observations of the open cluster NGC 1582 and its surrounding field with Johnson B, V and R filters by using the Nanshan 1 m telescope administered by Xinjiang Astronomical Observatory. 19 variable stars and three variable candi- dates were detected in a 45＇ - 48.75＇ field around the cluster. 12 of the variable stars are newly-discovered variable objects. The physical properties, classifications and memberships of these 22 objects are studied through their light curves, their positions on the color-magnitude diagram and with archival data from the Naval Observatory Merged Astrometric Dataset. Among these objects, five are eclipsing binary systems, six are pulsating variable stars including one known 6 Scuti star and one newly-discovered RR Lyrae star. The distance to the RR Lyrae star is estimated to be 7.9 - 0.3 kpc, indicating that the star is located far behind the cluster. Four variable stars are probable members of the cluster, and 13 of the 22 objects are confirmed to be field stars. 展开更多
关键词 NGC 1582 -- open cluster -- variable stars -- multi-color observation -- magnitude
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NGC4151的长期光变行为 认领 引用 被引量：6
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作者 樊军辉 苏成悦 《天文学报》 CAS 北大核心 1998年第3期251-255,共5页
本文收集了NGC4151近90年的光学资料，并用Jurkevich分析方法对其进行了光变周期分析其光变存在一个14．04±0．8年的长周期，且该天体的谱型与源的亮度强烈相关。
关键词 光变 周期 NGC4151 长期光变行为 Seyfert星系
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登革病毒(NGC株)C与prM全长基因的扩增与克隆 认领 引用 被引量：6
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作者 葛春喜 陈观今 黄炯烈 《中国人兽共患病杂志》 北大核心 2002年第1期5-7,共3页
目的　从登革病毒 (NGC株 )中快速分离基因组RNA ,RT -PCR扩增及克隆C和 prM全长基因 ,从而为研究蚊虫细胞对登革病毒的细胞内免疫研究奠定基础。方法　以Trizol试剂从C6 / 36细胞培养上清中提取基因组RNA ,RT -PCR扩增全长C和 prM基因 ... 目的　从登革病毒 (NGC株 )中快速分离基因组RNA ,RT -PCR扩增及克隆C和 prM全长基因 ,从而为研究蚊虫细胞对登革病毒的细胞内免疫研究奠定基础。方法　以Trizol试剂从C6 / 36细胞培养上清中提取基因组RNA ,RT -PCR扩增全长C和 prM基因 ,T -A重组入pGEM -T载体 ,重组质粒的双酶切、PCR与测序鉴定。 结果与结论　应用Trizol试剂从蚊细胞培养液上清中快速分离到高纯度和完整登革病毒RNA基因组 ,成功扩增与克隆出全长登革病毒C和 展开更多
关键词 登革病毒 NGC株 prM基因 C基因 RT-PCR
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Three pulsars discovered by FAST in the globular cluster NGC 6517 with a pulsar candidate sifting code based on dispersion measure to signal-to-noise ratio plots 认领 引用 被引量：1
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作者 Zhichen Pan Xiao-Yun Ma +6 位作者 Lei Qian Lin Wang Zhen Yan Jin-Tao Luo Scott M.Ransom Duncan R.Lorimer Peng Jiang 《Research in Astronomy and Astrophysics》 SCIE CAS CSCD 2021年第6期314-320,共7页
We report the discovery of three new pulsars in the globular cluster(GC)NGC 6517,namely NGC 6517 E,F and G,made with the Five-hundred-meter Aperture Spherical radio Telescope(FAST).The spin periods of NGC 6517 E,F and... We report the discovery of three new pulsars in the globular cluster(GC)NGC 6517,namely NGC 6517 E,F and G,made with the Five-hundred-meter Aperture Spherical radio Telescope(FAST).The spin periods of NGC 6517 E,F and G are 7.60 ms,24.89 ms and 51.59 ms,respectively.Their dispersion measures are 183.29,183.713 and 185.3 pc cm-3,respectively,all slightly larger than those of the previously known pulsars in this cluster.The spin period derivatives are at the level of 1×10-18s s-1,which suggests these are recycled pulsars.In addition to the discovery of these three new pulsars,we updated the timing solutions of the known isolated pulsars,NGC 6517 A,C and D.The solutions are consistent with those from Lynch et al.but with smaller timing residuals.From the timing solution,NGC6517 A,B(position from Lynch et al.),C,E and F are very close to each other on the sky and only a few arcseconds from the optical core of NGC 6517.With currently published and unpublished discoveries,nine pulsars have been discovered in NGC 651,ranking it 6 thfor GCs with the most known pulsars.The discoveries take advantage of the high sensitivity of FAST and a new algorithm used to check and filter possible candidate signals. 展开更多
关键词 Pulsar-Globular Clusters Individual NGC 6517-methods analytical-surveys-FAST
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基于DBSCAN聚类算法的疏散星团NGC 188的3维运动学成员判定 认领 引用 被引量：2
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作者 高新华 王超 +1 位作者 顾晓清 徐守坤 《天文学报》 CAS CSCD 北大核心 2017年第5期65-72,共8页
利用疏散星团NGC 188所在天区的1046颗恒星样本的高精度3维(3D)运动学数据(自行和视向速度)测试了DBSCAN(Density-Based Spatial Clustering of Applications with Noise)聚类算法的成员判定效果.为了避免自行和视向速度的单位不一致带... 利用疏散星团NGC 188所在天区的1046颗恒星样本的高精度3维(3D)运动学数据(自行和视向速度)测试了DBSCAN(Density-Based Spatial Clustering of Applications with Noise)聚类算法的成员判定效果.为了避免自行和视向速度的单位不一致带来的影响,在数据预处理阶段将3个分量的数据统一标准化至[0,1]区间.利用第k个最近邻点距离方法分析了1046颗恒星样本在标准化无量纲3D速度空间的分布特征,再根据第k个最近邻点距离随k值的变化趋势确定了DBSCAN聚类算法的输入参数(Eps,MinPts),最后利用DBSCAN聚类算法分离出497颗3D运动学成员星.分析结果表明得到的3D运动学成员星是可靠的. 展开更多
关键词 疏散星团和星协 个别 NGC 188 恒星 运动学与动力学 技术 视向速度 赫罗图与颜色-星等图
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The first CCD photometric study of the open cluster NGC 744 认领 引用 被引量：1
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作者 Kun Wang Li-Cai Deng +4 位作者 Zhi-Quan Luo Zheng-Zhou Yan Qi-Li Liu Jin-Jiang Sun Qiang Zhou 《Research in Astronomy and Astrophysics》 SCIE CAS CSCD 2018年第11期89-96,共8页
We present the first CCD photometric observations of open cluster NGC 744, as part of the 50 BiN Open Cluster Survey. The color-magnitude diagrams of this cluster were derived from absolute BV RI photometry on a good ... We present the first CCD photometric observations of open cluster NGC 744, as part of the 50 BiN Open Cluster Survey. The color-magnitude diagrams of this cluster were derived from absolute BV RI photometry on a good photometric night. A brief isochrone fitting gives a distance modulus of(m-M)V= 11.58±0.2 and a reddening of E(B-V) = 0.35±0.05 with an age of log t = 8.30±0.05.By carefully examining the BV time-series data, we discovered four new variable stars in a 20′×20′field around the cluster. We classified them as three eclipsing binary stars and one δ Scuti pulsating star,mainly based on the light-curve shape, the detected periods and the positions on the color-magnitude diagrams. 展开更多
关键词 open clusters and associations: individual(NGC 744) stars: variables: general
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恒星形成区NGC7538中的分子氢发射(英文) 认领 引用 被引量：1
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作者 姚永强 陈亚峰 +3 位作者 杨戟 石井未来 长田哲也 佐藤修二 《天文学报》 CAS 北大核心 2000年第1期1-14,共14页
报告在NGC7538 中利用H2(2 .12 μm) 发射线观测新发现的两个喷流和18 个近红外HH 天体.在IRS13 星云中观测到了强H2 发射壳层结构环绕在星云的北边.星云中红外源的UV 辐射场和外流活动都可能导致这一H2 发射.在IRS13 星云的南边和... 报告在NGC7538 中利用H2(2 .12 μm) 发射线观测新发现的两个喷流和18 个近红外HH 天体.在IRS13 星云中观测到了强H2 发射壳层结构环绕在星云的北边.星云中红外源的UV 辐射场和外流活动都可能导致这一H2 发射.在IRS13 星云的南边和东边探测到了5 个H2 knots.在IRS1 南边发现的H2 喷流暗示该区域有一个南北向的外流.在IRS11 星团的周围发现了9 个H2 knots.在西北东南方向和东北方向上各有一对H2 knots 与IRS11成直线排列.另外两个纤维状H2 knots 似乎由IRS11 在东北方向上发射出来.在IRS11 星团的东南观测到3 个H2 knots,其中的两个似是一条弯曲H2 结构上的亮节点.在邻近IRS9 的西边发现了两个明亮的H2 团块,它们的排列与IRS9 IRN1 星云的西南走向一致.在IRS9东南方向探测到了一个高准直的团块状喷流,与IRS9 星云的南向分支IRN 2 走向一致.在IRS9 以北～1′处还发现了一个不可分辨的H2 knot 和弥漫的H2 发射.分析发现许多H2 发射在形态上与分子线毫米观测的线翼发射的空间特征相一致.观测结果证明在3 个恒星形成区,即IRS13 ,IRS9 和IRS11 。 展开更多
关键词 红外成像 HH天体 恒星形成 NGC7538 分子氢发射
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3D cluster members and near-infrared distance of open cluster NGC 6819 认领 引用 被引量：4
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作者 Xin-Hua Gao Shou-Kun Xu Li Chen 《Research in Astronomy and Astrophysics》 SCIE CAS CSCD 2015年第12期2193-2203,共11页
In order to obtain clean members of the open cluster NGC 6819, the proper motions and radial velocities of 1691 stars are used to construct a three-dimensional （3D） velocity space. Based on the DBSCAN clustering alg... In order to obtain clean members of the open cluster NGC 6819, the proper motions and radial velocities of 1691 stars are used to construct a three-dimensional （3D） velocity space. Based on the DBSCAN clustering algorithm, 537 3D cluster members are obtained. From the 537 3D cluster members, the average radial velocity and absolute proper motion of the cluster are Vr = ＋2.30 ±0.04 km s-1 and （PMRA, PMDec） = （-2.5 ±0.5, -4.3 ± 0.5） mas yr-1, respectively. The proper motions, radial velocities, spatial positions and color-magnitude diagram of the 537 3D members indicate that our membership determination is effective. Among the 537 3D cluster members, 15 red clump giants can be easily identified by eye and are used as reliable standard candles for the distance estimate of the cluster. The distance modulus of the cluster is determined to be （m - M）0 -- 11.86 ± 0.05 mag （2355 ±54 pc）, which is quite consistent with published values. The uncertainty of our distance mod- ulus is dominated by the intrinsic dispersion in the luminosities of red clump giants （--0.04 mag）. 展开更多
关键词 open clusters and associations： individual （NGC 6819） -- Hertzsprung-Russell and C-M diagrams -- stars： kinematics and dynamics -- stars： distances
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