2004/03/11 by A. S. Oliveira, Alexandre S. Oliveira, J. E. Steiner · 1 citation
Physics and Astronomy · #Astronomy and Astrophysical Research #Astrophysical Phenomena and Observations #Gamma-ray bursts and supernovae #astro-ph
paper · pdf · doi:10.1111/j.1365-2966.2004.07817.x
published as Mon.Not.Roy.Astron.Soc. 351 (2004) 685 · 12 pages, 11 EPS figures, preprint of an article accepted for publication in Monthly Notices of The Royal Astronomical Society
arxiv created 2004/03/11 · openalex publication_date 2004/06/21 · arxiv updated 2009/12/01 · openalex created_date 2016/06/24 · openalex updated_date 2026/07/28
We confirm the orbital period of WX Cen ≡ WR 48c determined by Diaz & Steiner and refined its value to Porb= 0.416 961 5(±22) d. The light curve of this object has a peak-to-peak variation of approximately 0.32 mag. It is non-sinusoidal in the sense that it has a V-shaped narrow minimum, similar to the ones seen in V Sge, V617 Sgr and in compact binary supersoft sources (CBSS). Most of the emission lines in the optical spectrum are due to Balmer, He ii, C iv, N v, O v and O vi. An analysis of the He ii Pickering series decrement shows that the system has significant amount of hydrogen. The emission lines of He ii 4686 Å became weaker between the 1991 and 2000/2002 observations, indicating distinct levels of activity. The spectra of WX Cen show variable absorption features in the Balmer lines with V=−2900 km s−1 and in emission with V=±3500 km s−1. These highly variable features remind us of the satellite emission lines found in the spectra of CBSS. We estimate the colour excess as E(B−V) = 0.63 on the basis of the observed diffuse interstellar band at 5780 Å. Given the distance–colour excess relation in the direction of WX Cen, this implies a distance of 2.8 ± 0.3 kpc. Interstellar absorption of the Na i D lines show components at −4.1 km s−1, which corresponds to the velocity of the Coalsack, and three other components at −23.9, −32.0 and −39.0 km s−1. These components are also seen with similar strengths in field stars that have distances between 1.8 and 2.7 kpc. The intrinsic colour of WX Cen is (B−V)0=−0.2 and the absolute magnitude is MV=−0.5. Extended red wings in the strong emission lines are seen. A possible explanation is that the system has a spill-over stream similar to what is seen in V617 Sgr. We predict that when observed in opposite phase, blue wings would be observed. A puzzling feature that remains to be explained is the highly variable red wing (V∼ 700 km s−1) of the O vi emission lines as well as of the red wings of the H and He lines. The velocity of the satellite-like feature is consistent with the idea that the central star is a white dwarf with a mass of M∼ 0.9 M⊙. With the high accretion rate under consideration, the star may become a Type Ia supernova (SN Ia) in a time-scale of 5 × 106 yr.