Relation between spectral indices and binary fractions in globular clusters

doi:10.1051/0004-6361/202245212

	Relation between spectral indices and binary fractions in globular clusters
	Zhang FH(张奉辉)1,2,4; Li LF(李立芳)1,2,4; Han ZW(韩占文)1,2,4; Gong XB(龚小波)1,2,3,4
刊名	ASTRONOMY & ASTROPHYSICS
	2023-10-30
卷号	679
关键词	binaries: general globular clusters: general stars: formation galaxies: stellar content galaxies: formation galaxies: fundamental parameters
ISSN号	0004-6361
DOI	10.1051/0004-6361/202245212
产权排序	第1完成单位
文献子类	Article
英文摘要	Context. We study the relation between the known binary fraction and spectral absorption feature index to judge whether (and potentially which) spectral absorption feature indices are suitable for determining the binary fraction.Aims. The determination of the binary fraction is important in studies of binary star formation, evolutionary population synthesis models, and other works. The number of binary stars is difficult to determine for nearly all stellar systems because the individual stars are need to be resolved photometrically or spectroscopically. By comparison, their integrated spectra or spectral absorption feature indices are relatively easy to obtain.Methods. We used Galactic globular clusters (GCs) as our sample since they have relatively accurate binary fraction measurements and spectroscopic observations along the radial direction. When studying the relation between binary fractions and the spectral absorption feature index, we used three types of binary fractions: one with a mass ratio of q > 0.5 (f(q > 0.5)) and two with a total binary fraction (the methods of counting (f(tot)(mf)) and fitting (f(tot)(mc))), calculated and obtained the equivalent widths or magnitudes of 46 spectral absorption feature indices at three spectral resolutions (FWHMLick/IDS, 5, and 15 & Aring;). Since the regions for the binary fraction measurements (photometric) and the spectroscopic observations are different, we used the method of constructing the radial binary-fraction profile to get the binary fractions corresponding to the regions in the spectroscopic observations. The construction of the radial binary-fraction profile was obtained by using the python curve_fit module to fit the measured and analytic binary fraction values. The analytic value was expressed by taking advantage of the King surface-density profile and the assumed forms with respect to the radial binary-fraction profile (linear, quadratic, exponential, and Gaussian).Results. We find that the low-resolution (15 & Aring;) spectrum is not suitable for this study and the binary fraction type would affect the results: f(q > 0.5) and f(tot)(mc) exhibit better correlations with the spectral absorption feature index than f(tot)(mf) and the difference in metallicity would significantly affect the above relationship. Finally, to eliminate the effects of metallicity, age, and dynamical evolution, we only used those GCs with multiple spectra observed among different regions. We find that OIII-1, OIII-2, H-gamma F, H-delta F, H-gamma A, H-delta A, H-beta, Ca4455, C(2)4668, and TiO1 indices have strong correlations with binary fraction. The two OIII indices are the most sensitive to the binary fraction, followed by four Balmer indices - the two narrower central bandpass Balmer indices (similar to 20 & Aring;, F-definition) are more sensitive than the wider two (similar to 40 & Aring;, A-definition) and, lastly, the Ca4455, C(2)4668, and TiO1 indices. Using the binary fraction-sensitive spectral absorption feature indices in combination with the age- and metallicity-sensitive spectral absorption feature indices, we can determine the ages or metallicities first. Then we can go on to obtain the binary fractions for those stellar systems in which the individual stars cannot be resolved (e.g., dense or distant stellar systems). Furthermore, we are then able to carry out further studies of binary star formation and improve evolutionary population synthesis models.
学科主题	天文学
URL标识	查看原文
出版地	17, AVE DU HOGGAR, PA COURTABOEUF, BP 112, F-91944 LES ULIS CEDEX A, FRANCE
资助项目	This work was funded by the National Natural Science Foundation of China (Nos. 11973081, 11773065, 11573062, 11521303, 12288102), the Youth Innovation Promotion Association of Chinese Academy of Sciences Foundation (No. 2012048, Y201624), and the Science R[11973081]; This work was funded by the National Natural Science Foundation of China (Nos. 11973081, 11773065, 11573062, 11521303, 12288102), the Youth Innovation Promotion Association of Chinese Academy of Sciences Foundation (No. 2012048, Y201624), and the Science R[11773065]; This work was funded by the National Natural Science Foundation of China (Nos. 11973081, 11773065, 11573062, 11521303, 12288102), the Youth Innovation Promotion Association of Chinese Academy of Sciences Foundation (No. 2012048, Y201624), and the Science R[11573062]; This work was funded by the National Natural Science Foundation of China (Nos. 11973081, 11773065, 11573062, 11521303, 12288102), the Youth Innovation Promotion Association of Chinese Academy of Sciences Foundation (No. 2012048, Y201624), and the Science R[11521303]; This work was funded by the National Natural Science Foundation of China (Nos. 11973081, 11773065, 11573062, 11521303, 12288102), the Youth Innovation Promotion Association of Chinese Academy of Sciences Foundation (No. 2012048, Y201624), and the Science R[12288102]; National Natural Science Foundation of China[2012048]; National Natural Science Foundation of China[Y201624]; Youth Innovation Promotion Association of Chinese Academy of Sciences Foundation[CMS-CSST-2021-A08]; China Manned Space Project[2021YFA1600403]; China Manned Space Project[2021YFA1600400]; National Key Ramp;D Program of China[202302AN360001]; International Centre of Supernovae, Yunnan Key Laboratory
WOS关键词	HORIZONTAL-BRANCH STARS ; STELLAR POPULATION SYNTHESIS ; SPACE-TELESCOPE OBSERVATIONS ; SUBDWARF-B-STARS ; MAIN-SEQUENCE ; SPECTROSCOPIC BINARIES ; CLOSE BINARIES ; CORE ; SEARCH ; I.
WOS研究方向	Astronomy & Astrophysics
语种	英语
出版者	EDP SCIENCES S A
WOS记录号	WOS:001096229100007
资助机构	This work was funded by the National Natural Science Foundation of China (Nos. 11973081, 11773065, 11573062, 11521303, 12288102), the Youth Innovation Promotion Association of Chinese Academy of Sciences Foundation (No. 2012048, Y201624), and the Science R[11973081, 11773065, 11573062, 11521303, 12288102] ; National Natural Science Foundation of China[2012048, Y201624] ; Youth Innovation Promotion Association of Chinese Academy of Sciences Foundation[CMS-CSST-2021-A08] ; China Manned Space Project[2021YFA1600403, 2021YFA1600400] ; National Key Ramp ; D Program of China[202302AN360001] ; International Centre of Supernovae, Yunnan Key Laboratory
内容类型	期刊论文
版本	出版稿
源URL	[http://ir.ynao.ac.cn/handle/114a53/26517]
专题	云南天文台_大样本恒星演化研究组
作者单位	1.Yunnan Observatories, Chinese Academy of Sciences, 396 Yangfangwang, Guandu District, Kunming 650216, PR China; 2.Key Laboratory for the Structure and Evolution of Celestial Objects, Chinese Academy of Sciences, 396 Yangfangwang, Guandu District, Kunming 650216, PR China; 3.University of Chinese Academy of Sciences, Beijing 100049, PR China; 4.International Centre of Supernovae, Yunnan Key Laboratory, Kunming 650216, PR China
推荐引用方式 GB/T 7714	Zhang FH,Li LF,Han ZW,et al. Relation between spectral indices and binary fractions in globular clusters[J]. ASTRONOMY & ASTROPHYSICS,2023,679.
APA	张奉辉,李立芳,韩占文,&龚小波.(2023).Relation between spectral indices and binary fractions in globular clusters.ASTRONOMY & ASTROPHYSICS,679.
MLA	张奉辉,et al."Relation between spectral indices and binary fractions in globular clusters".ASTRONOMY & ASTROPHYSICS 679(2023).