Subjects: Astronomy >> Astrophysical processes submitted time 2023-06-07 Cooperative journals: 《天文学进展》
Abstract： Binary star systems or multi-star systems are a common result of stellar evolu#2;tion. Therefore, the dependence of the stellar multiplicity and other properties of the binary star system on the primary mass and the stellar formation environment play important role in stellar evolution. There are many ways to study binary stars, such as the light curves method, the velocity curves method, and the Hertzsprung-Russell diagram method. In re#2;cent years, with the emergence of many large-scale astronomical survey observations, we have obtained a large amount of photometric and spectral survey data. For these large-scale survey data, many statisical methods have been developed to study the properties of binary stars. We use the WISE eclipse binaries with the medium-resolution spectra of LAMOST DR7 and part of DR8, and obtained 151 short period solar-type stars, and then selected those with more than 9 observations and relatively uniform phase distribution. By ana#2;lyzing their radial velocities, the orbital parameters such as the orbital period, mass ratio, orbital eccentricity of this sample are obtained. We find that the period we obtained consis#2;tent with that given by WISE. Thus, we use the period of WISE as a known quantity to solve for other orbital parameters, which makes other orbital parameters more accurate. Among them, 23 stars were selected and the radial velocity curves are well fitted by binary models. The statistical properties of these parameters are consistent with the results of Ragavan et al. For stars with orbital period of less than 10 days, their mass-ratio basically covers the entire parameter space from 0.2 to 1, while their orbital eccentricities are very small, all smaller than 0.2.
Subjects: Astronomy >> Astrophysical processes submitted time 2023-06-07 Cooperative journals: 《天文学进展》
Abstract： The magnification effect provided by gravitational lensing overcomes the limita#2;tions of current observation instruments, allowing researchers to study faint objects at high redshift (z ≈ 4). Over the last decades, the sample of strong lenses has been mostly confined to optical bands. With the advent of (sub)millimeter wide field extragalactic surveys, about 200 strong lenses have been discovered in (sub)millimeter bands. Observations with high resolution and sensitivity from ALMA, NOEMA, and SMA, coupled with the flux boost from strong lensing, provide new windows to study galaxies at high redshift. Many works have investigated topics such as star formation, interstellar medium, and dynamic properties. The main objective of this paper is to review the current research status of galaxy-galaxy lensing in (sub)millimeter bands from the perspectives of observation samples, modeling methods, and scientific applications.
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