Astronomy and Astrophysics – Astrophysics
Scientific paper
Dec 2005
adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2005a%26a...444..895s&link_type=abstract
Astronomy and Astrophysics, Volume 444, Issue 3, December IV 2005, pp.895-904
Astronomy and Astrophysics
Astrophysics
2
Techniques: Spectroscopic, Binaries: Spectroscopic, Stars: Wolf-Rayet
Scientific paper
The binary star HD 45166 has been observed since 1922 but its orbital period has not yet been found. It is considered a peculiar Wolf-Rayet star, and its assigned classification has varied. For this reason we included the object as a candidate V Sge star and performed spectroscopy in order to search for its putative orbital period. High-resolution spectroscopic observations show that the spectrum, in emission and in absorption, is quite rich. The emission lines have great diversity of widths and profiles. The full widths at half maximum vary from 70 km s-1 for the weakest lines up to 370 km s-1 for the most intense ones. The hydrogen and helium lines are systematically broader than the CNO lines. Assuming that HD 45166 is a double-line spectroscopic binary, it presents an orbital period of P = 1.596 ± 0.003 day, with an eccentricity of e = 0.18 ± 0.08. In addition, a search for periodicity using standard techniques reveals that the emission lines present at least two other periods, of 5 and 15 h. The secondary star has a spectral type of B7 V and, therefore, should have a mass of about M2 = 4.8 ~M&sun;. Given the radial velocity amplitudes, we determined the mass of the hot (primary) star as M1 = 4.2 ± 0.7~M&sun; and the inclination angle of the system, i = 0.77° ± 0.09°. As the eccentricity of the orbit is non zero, the Roche lobes increase and decrease as a function of the orbital phase. At periastron, the secondary star fills its Roche lobe. The distance to the star has been re-determined as d = 1.3 ± 0.2 kpc and a color excess of E(B-V)=0.155~±~0.007 has been derived. This implies an absolute B magnitude of -0.6 for the primary star and -0.7 for the B7 star. We suggest that the discrete absorption components (DACs) observed in the ultraviolet with a periodicity similar to the orbital period may be induced by periastron events.
Based on observations made at the 1.5 m ESO telescope at La Silla, Chile, and at Laboratório Nacional de Astrofísica/CNPq, Brazil.
Tables 2-5 are only available in electronic form at the CDS via anonymous ftp to cdsarc.u-strasbg.fr (130.79.128.5) or via http://cdsweb.u-strasbg.fr/cgi-bin/qcat?J/A+A/444/895
Oliveira Alexandre S.
Steiner Joao Evangelista
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