Analysis of δ Librae including Hipparcos astrometry |
| |
| Authors: | V Bak&#;&#; E Budding A Erdem H Bak&#;&#; O Demircan P Hadrava |
| |
| Institution: | Çanakkale Onsekiz Mart University Observatory, Terzio lu Kampüsü, Çanakkale, Turkey 17040;Carter Observatory, Wellington, New Zealand;Astronomickýústav, Akademie věd ?eskérepubliky, CZ-251 65, Ond?ejov, Czech Republic |
| |
| Abstract: | New spectroscopy of the classical Algol system δ Lib, combined with high-quality optical and infrared photometry, provides the basis for a good understanding of the close binary system's main parameters. Detailed analysis of the photometry reveals the significant role of a third light source, pointing to the existence of a companion to the eclipsing system of mass ～1 M⊙ .
We review the methodology of applying high-accuracy positional information, available from the Hipparcos Intermediate Astrometric Data archive, to stars that may have such companions. Analysis of the astrometry of δ Lib also points to a third star similar to the one already identified by Worek from radial-velocity data, although with slightly revised parameters. O–C data do not contradict this, but their general precision (while confirming the close pair's Algol status) fails to allow a decision on the third orbit parameters: Worek's or revised ones. Taking the photometry, spectroscopy and astrometry together, however, the existence of a third star of comparable mass to the Sun, as a relatively close companion to the eclipsing binary (～4 au), is confirmed. |
| |
| Keywords: | binaries: close stars: individual: δ Lib |
|
|
