Periodic Variations in RW Aur A: Non-axisymmetric Accretion
Abstract
Spectroscopic and photometric monitoring of the young star RW Aur was carried out at the Nordic Optical Telescope in 1995-1999. We discovered periodical modulations in many spectral features related to accretion of the circumstellar gas onto the star. The radial velocities of the photospheric lines and those of the narrow emission lines of He I vary in anti-phase, with a period of 2.77 days. The same period is found in the strengths of the red-shifted absorption features formed in the streams of the accreting gas. The strength of these accretion features correlates with the intensity of the He I line, which suggests that this line is formed in a hot shock at the footpoint of the acrretion column, where the gas hits the stellar surface at the infall velocity of 400 km s-1. The photospheric spectrum is highly veiled, presumably by continuum radiation of the hot spot, but the expected correlation between the veiling and the brightness of the star was not found. We suggest two models of a non-axisymmetric accretion, where the asymmetry is caused either by a low-mass companion orbiting the star, or by a misalignment of the magnetic and rotational axes of the star.
- Publication:
-
Astronomische Gesellschaft Meeting Abstracts
- Pub Date:
- 2000
- Bibcode:
- 2000AGM....17..P22P