| Full text | |
| Author(s): |
Ortiz, Roberto
;
Guerrero, Martin A.
Total Authors: 2
|
| Document type: | Journal article |
| Source: | Monthly Notices of the Royal Astronomical Society; v. 461, n. 3, p. 3036-3046, SEP 21 2016. |
| Web of Science Citations: | 9 |
| Abstract | |
Although the majority of known binary asymptotic giant branch (AGB) stars are symbiotic systems (i.e. with a white dwarf as a secondary star), main-sequence companions of AGB stars can be more numerous, even though they are more difficult to find because the primary high luminosity hampers the detection of the companion at visual wavelengths. However, in the ultraviolet the flux emitted by a secondary with T-eff > 5500 similar to 6000 K may prevail over that of the primary, and then it can be used to search for candidates to binary AGB stars. In this work, theoretical atmosphere models are used to calculate the UV excess in the GALEX near- and far-UV bands due to a main-sequence companion. After analysing a sample of confirmed binary AGB stars, we propose as a criterium for binarity: (1) the detection of the AGB star in the GALEX far-UV band and/or (2) a GALEX near-UV observed-to-predicted flux ratio >20. These criteria have been applied to a volume-limited sample of AGB stars within 500 pc of the Sun; 34 out of the sample of 58 AGB stars (similar to 60 per cent) fulfill them, implying to have a main-sequence companion of spectral type earlier than K0. The excess in the GALEX near- and far-UV bands cannot be attributed to a single temperature companion star, thus suggesting that the UV emission of the secondary might be absorbed by the extended atmosphere and circumstellar envelope of the primary or that UV emission is produced in accretion flows. (AU) | |
| FAPESP's process: | 15/00890-1 - Weighting Binarity Among the Precursors of Planetary Nebulae in the Magellanic Clouds |
| Grantee: | Roberto Pereira Ortiz |
| Support Opportunities: | Scholarships abroad - Research |
| FAPESP's process: | 10/18835-3 - Planetary nebulae, stars and chemical evolution of stellar systems |
| Grantee: | Roberto Dell'Aglio Dias da Costa |
| Support Opportunities: | Research Projects - Thematic Grants |