Relation between spectral indices and binary fractions in GCs

Abstract

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. Results. We find that the low-resolution (15\,Å) spectrum is not suitable for this study and the binary fraction type would affect the results: $f$($q$>0.5) and $f$(tot)${}^{\mathrm{mc}}$ exhibit better correlations with the spectral absorption feature index than $f$(tot)${}^{\mathrm{mf}}$ 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${}_{\gamma \mathrm{F}}$, H${}_{\delta \mathrm{F}}$, H${}_{\gamma \mathrm{A}}$, H${}_{\delta \mathrm{A}}$, H${}_{\beta }$, Ca4455, C${}_2$4668, and TiO${}_1$ 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 ($\sim$20Å, F-definition) are more sensitive than the wider two ($\sim$40Å, A-definition) and, lastly, the Ca4455, C${}_2$4668, and TiO${}_1$ indices.

arXiv comment19 pages, 8 figures

References in corpus (40)

• Stellar population synthesis at the resolution of 2003
• Stellar Multiplicity
• Binary Population and Spectral Synthesis Version 2.1: construction, observational verification and new results
• The Origin of Subdwarf B Star (I): the Formation Channels
• Old Stellar Populations. VI. Absorption-Line Spectra of Galaxy Nuclei and Globular Clusters
• The origin of sdB stars (II)
• Reevaluating Old Stellar Populations
• The Hubble Space Telescope UV Legacy Survey of Galactic Globular Clusters. I. Overview of the Project and Detection of Multiple Stellar Populations
• The ACS Survey of Galactic Globular Clusters. XII. Photometric Binaries along the Main-Sequence
• Empirical calibration of the near-IR Ca II triplet - I. The stellar library and index definition
• MIUSCAT: extended MILES spectral coverage. I. Stellar populations synthesis models
• The properties of Galactic globular cluster sub-systems
• A Complete N-body Model of the Old Open Cluster M67
• The second and third parameters of the Horizontal Branch in Globular Clusters
• The Frequency of Binary Stars in the Core of 47 Tucanae
• The fraction of binary systems in the core of thirteen low-density Galactic globular clusters
• Ionizing spectra of stars that lose their envelope through interaction with a binary companion: role of metallicity
• A Library of Integrated Spectra of Galactic Globular Clusters
• Integrated Spectroscopy of Bulge Globular Clusters and Fields I. The Data Base and Comparison of Individual Lick Indices in Clusters and Bulge
• Multiple stellar populations in the Galactic globular cluster NGC 6752
• Inclusion of Binaries in Evolutionary Population Synthesis
• The binary fraction in the globular cluster NGC 6397
• Evolutionary Population Synthesis for Binary Stellar Populations
• Fabry-Perot Measurements of the Dynamics of Globular Cluster Cores: M15 (NGC~7078)
• The lack of close binaries among hot horizontal branch stars in NGC6752
• Formation of the Galactic Halo
• What a Local Sample of Spectroscopic Binaries can tell us about the Field-Binary Population
• The WAGGS project - I. The WiFeS Atlas of Galactic Globular cluster Spectra
• Spectroscopic Binaries in Globular Clusters. II. A Search for Long-Period Binaries in M22
• Effective action and motion of a cosmic string
• The Binary Populations of Eight Globular Clusters in the Outer Halo of the Milky Way
• A lack of close binaries among hot horizontal branch stars in globular clusters. II. NGC\,2808
• A lack of close binaries among hot horizontal branch stars in globular clusters - M80 and NGC5986
• SHOTGLAS I: The ultimate spectroscopic census of extreme horizontal branch stars in $\omega$ Centauri
• Can the third dredge-up extinguish hot-bottom burning in massive AGB stars?
• Dynamics of the Globular Cluster NGC 362
• Revisiting binary stars in population synthesis models
• Spectroscopic Binaries in Globular Clusters. I. A Search for Ultra-Hard Binaries on the Main Sequence in M4
• NH and Mg Index Trends in Elliptical Galaxies
• Uncertainties in the calibrations of star formation rate

Cited by in corpus (1)

• Determination method of binary fractions by the integrated spectrum