Mass-ratio Distribution of Binaries from the LAMOST-MRS Survey

Abstract

Binary evolution leads to the formation of important objects that are crucial for the development of astrophysics, but the statistical properties of binary populations are still poorly understood. The LAMOST-MRS has provided a large sample of stars to study the properties of binary populations, especially for the mass-ratio distributions and binary fractions. We have devised a peak amplitude ratio (PAR) approach to derive the mass ratio of a binary system based on results obtained from its spectrum. By computing a cross-correlation function, we established a relation between the derived mass ratio and the PARs of the binary systems. By using spectral observations obtained from LAMSOT DR6 and DR7, we applied the PAR approach to form distributions of the derived mass ratio of the binary systems to the spectral types. We selected the mass ratio within the range of 0.6−1.0 to investigate the mass-ratio distribution. Through a power-law fitting, we obtained power index γ values of −0.42 ± 0.27, 0.03 ± 0.12, and 2.12 ± 0.19 for the A-, F-, and G-type stars identified in the sample, respectively. The derived γ-values display an increasing trend toward lower primary star masses, and G-type binaries tend to be twins more frequently. The close binary fractions (for P ≲ 150 days and q ≳ 0.6) in our sample for A, F, and G binaries are 7.6% ± 0.5%, 4.9% ± 0.2%, and 3.7% ± 0.1%, respectively. Note that the PAR approach can be applied to large spectroscopic surveys of stars.

Mass Ratio Distribution of Hierarchical Triple Systems from the LAMOST-MRS Survey

“…The LAMOST-MRS red and blue arms have respective wavelength ranges of 6300-6800 and 4950-5350 Å. We chose the spectra of the blue arm to detect triple-star candidates and measure their RVs, as they have more absorption lines (Li et al 2021(Li et al , 2022. Fernandez et al (2017) found that spectra with low signal-to-noise ratios (S/ Ns) posed a significant challenge for detecting ST candidates, and Li et al (2021) chose the blue arm spectra with S/Ns larger than 10.…”

“…Li et al (2021) used a cross-correlation function (CCF) and obtained 132 ST candidates from LAMOST-MRS DR7. We cross-matched Gaia DR3 with the STs and obtained their magnitudes in the Bp, G, and Rp bands (Gaia Collaboration et al 2018;Li et al 2022). Since the diameter of the LAMOST fiber is about 3″, we used the 3″ search cone to cross-match the spectrum of Gaia (Cui et al 2012).…”

“…Utilizing the CFI and ULySS algorithms, LASP can perform a two-stage spectral fitting process that efficiently inverts the stellar parameters, thereby extracting the stellar parameters of the LAMOST-MRS spectra (Koleva et al 2009). We utilized the LASP to determine the effective temperature and divide the ST candidates into various spectral types according to the Morgan-Keenan classification (Wu et al 2011;Luo et al 2015;Li et al 2022). Since the spectra of A-type stars are not very sensitive to their temperature, only temperatures below 8500 K are given.…”

Criteria for Dynamical Timescale Mass Transfer of Metal-poor Intermediate-mass Stars

“…The fraction of binaries including multiple stars is over half of all stellar systems (e.g., Duchêne & Kraus 2013;Moe & Di Stefano 2017;Li et al 2022), and it can be even up to 70% for massive stars (Sana et al 2012). The evolution of close binary stars can form X-ray binaries, pulsar binaries, type Ia supernovae, white dwarf/neutron star (NS)/stellar-mass black hole (BH) binaries, etc.…”

Criteria for Dynamical Timescale Mass Transfer of Metal-poor Intermediate-mass Stars

“…The fraction of binary including multiple stars is over half of stellar systems (e.g. Duchêne & Kraus 2013;Moe & Di Stefano 2017;Li et al 2022) and it can be even up to 70% for massive stars (Sana et al 2012). The evolution of close binary stars can form X-ray binaries, pulsar binaries, type Ia supernovae, white dwarf/neutron star (NS)/stellar-mass black hole (BH) binaries, etc.…”