HD 153720 – A SB2 system with twin metallic-line components ^*,**

¹ Department of Astronomy, Sejong University, Seoul, 143-747, Korea e-mail: yua@arcsec.sejong.ac.kr; kangyw@sejong.ac.kr
² Odessa Astronomical Observatory, Odessa National University, Park Shevchenko, Odessa, 65014, Ukraine e-mail: yua@odessa.net; gopkavera@mail.ru
³ Deceased (Institute of Astronomy, Russian Academy of Sciences, Pyatnitskaya ul. 48, Moscow, 109017, Russia)
⁴ The W. J. McDonald Observatory, University of Texas, Austin, TX 78712, USA e-mail: dll@astro.as.utexas.edu
⁵ Department of Earth Science Education, Chonbuk National University, Chonju 561-756, Korea e-mail: chkim@astro.chonbuk.ac.kr

Received: 20 December 2003
Accepted: 25 May 2004

Abstract

We report the results of abundance determinations for the components of the SB2 star HD 153720 from high resolution () echelle high signal-to-noise spectra of the wavelength region 3595-10 260 Å  taken with the 2.7 m telescope of the McDonald Observatory We found the values of the atmospheric parameters of the primary to be effective temperature  = 7425 K and surface gravity  = 4.0 cgs, and of the secondary to be  = 7125 K and  = 3.9 cgs. The microturbulent velocity is  = 2.7  for both components, and the projected rotational velocity is   = 15   also for both components. The abundances of about 20 elements were determined with the method of spectrum synthesis. The components of HD 153720 are metallic-line stars. Possible inconsistencies between old and new measurements of radial velocities may be explained by the existence of third body in this system. A review of recent high resolution spectral observations of eight A4-F1 binaries shows that only one of these systems can be classified as normal.