A detailed study of opacity in the upper atmosphere of Proxima Centauri

Francis Keenan, Damian Christian, Michail Mathioudakis, Shaun Bloomfield, J. Dupuis

Research output: Contribution to journalArticle

13 Citations (Scopus)


We present far-UV and UV spectroscopic observations of Proxima Centauri obtained as part of our continued investigation into the optically thin approximation assumed for the transition regions of late-type stars. Significant opacity is found in the C III lines during both the quiescent and flaring states of Proxima Cen, with up to 70% of the expected flux being lost in the latter. Our findings cast some doubt on the suitability of the C III lambda977 line for estimating the electron density in stellar atmospheres. However, the opacity has no significant effect on the observed line widths. We calculate optical depths for homogeneous and inhomogeneous geometries and estimate an electron density of 6 x 10(10) cm(-3) for the transition region using the O IV line ratios at 1400 Angstrom. The combination of electron density and optical depth indicates path lengths as low as approximate to 10 km, which are in excellent agreement with estimates of the small-scale structure seen in the solar transition region.
Original languageEnglish
Pages (from-to)1140-1146
Number of pages7
JournalAstrophysical Journal
Issue number2 I
Publication statusPublished - 10 Sep 2004

ASJC Scopus subject areas

  • Space and Planetary Science

Fingerprint Dive into the research topics of 'A detailed study of opacity in the upper atmosphere of Proxima Centauri'. Together they form a unique fingerprint.

Cite this