UCL Discovery
UCL home » Library Services » Electronic resources » UCL Discovery

The Determination of Wind Terminal Velocities and Ionic Abundances from Infrared Fine-Structure Lines: the WC8 Component of γ Velorum

Barlow, MJ; Roche, PF; Aitken, DK; (1988) The Determination of Wind Terminal Velocities and Ionic Abundances from Infrared Fine-Structure Lines: the WC8 Component of γ Velorum. Monthly Notices of the Royal Astronomical Society , 232 (4) pp. 821-834. 10.1093/mnras/232.4.821. Green open access

[thumbnail of Barlow_Roche_Aitken88.pdf]
Preview
Text
Barlow_Roche_Aitken88.pdf - Published version

Download (1MB) | Preview

Abstract

The spectrum of γ Velorum has been observed with a resolving power of 330 in the 12−13μm spectral region. The 12.8 μm forbidden line of [Ne II] has a rectangular profile, as expected for an optically thin line formed at large radii. The wind terminal velocity implied by this profile is 1520±200kms−1⁠. This velocity, combined with the known radio flux, implies a mass loss rate of 8.8×10−5M⊙yr−1 for γ Vel. An analysis of the He I and He II recombination lines observed in the spectrum implies that the He+/He2+ ratio exceeds 6 in the 12 μm emitting region, confirming previous inferences that the degree of ionization decreases outwards in the wind. The flux measured in the [Ne II] line is used, along with the published [Ne III] 15.5 μm line flux, to rederive the abundance of neon in the wind of γ Vel, using improved analysis techniques. A Ne/He number ratio of 1.0±0.35×10−3 is found, a factor of 9 lower than previously estimated. This neon abundance is only slightly higher than would be expected for an initial cosmic abundance ratio. The large enhancement in the abundance of neon that is theoretically predicted for WC stars, due to the creation of 22Ne, is not present in the case of γ Vel.

Type: Article
Title: The Determination of Wind Terminal Velocities and Ionic Abundances from Infrared Fine-Structure Lines: the WC8 Component of γ Velorum
Open access status: An open access version is available from UCL Discovery
DOI: 10.1093/mnras/232.4.821
Publisher version: https://doi.org/10.1093/mnras/232.4.821
Language: English
Additional information: This version is the version of record. For information on re-use, please refer to the publisher’s terms and conditions.
UCL classification: UCL
UCL > Provost and Vice Provost Offices
UCL > Provost and Vice Provost Offices > UCL BEAMS
UCL > Provost and Vice Provost Offices > UCL BEAMS > Faculty of Maths and Physical Sciences
UCL > Provost and Vice Provost Offices > UCL BEAMS > Faculty of Maths and Physical Sciences > Dept of Physics and Astronomy
URI: https://discovery.ucl.ac.uk/id/eprint/10095253
Downloads since deposit
7Downloads
Download activity - last month
Download activity - last 12 months
Downloads by country - last 12 months

Archive Staff Only

View Item View Item