EDP Sciences
Free access
Volume 382, Number 1, January IV 2002
Page(s) 312 - 318
Section The Sun
DOI http://dx.doi.org/10.1051/0004-6361:20011582

A&A 382, 312-318 (2002)
DOI: 10.1051/0004-6361:20011582

Center-to-limb-variation of the G-band lines at 430.5 nm

K. Langhans and W. Schmidt

Kiepenheuer-Institut für Sonnenphysik, Schöneckstr. 6, 79104 Freiburg, Germany

(Received 10 September 2001 / Accepted 8 November 2001 )

We measure the center-to-limb-variation of the CH lines in the wavelength range from 430.40 to 430.61 nm (G-band) for both quiet sun and for the cooler atmophere of sunspot umbrae at different heliographic positions. The limb effect of the CH lines is about 650 ms -1 at $\mu=0.1$ with a slope similar to weak Fe lines. We investigate the behaviour of the CH abundance in the range of optical depth ( $\tau=-0.05$ to $\tau=-0.25$) that is accessible by center-to-limb observations. The CH abundance decreases with height in accordance with recent numerical models.

Key words: Sun: atmosphere, photosphere

Offprint request: K. Langhans, kai@kis.uni-freiburg.de

© ESO 2002