Molecular spectroscopy in sunspots - Theoretical interpretation of TiO line equivalent width measurements

Details Molecular spectroscopy in sunspots - Theoretical interpretation of TiO line equivalent width measurements Molecular spectroscopy in sunspots - Theoretical interpretation of TiO line equivalent width measurements

Jun 1980

adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=1980a%26as...40..277b&link_type=abstract

Astronomy and Astrophysics Supplement Series, vol. 40, June 1980, p. 277-287.

Astronomy and Astrophysics

Astrophysics

11

Molecular Spectra, Solar Spectra, Spectral Line Width, Sunspots, Line Spectra, Titanium Oxides, Umbras

Scientific paper

The analysis of a high resolution umbra spectrum has enabled us to identify and to measure 147 pure TiO lines in the spectral range 6 100-7 100 Å. On the basis of solar abundances and laboratory molecular data recently published, a theoretical interpretation was performed and four umbra models have been compared. The great temperature sensitivity of TiO allowed us to improve the temperature profile in the outer layers of umbra. Up to now, the classical method used to correct sunspot models upper layers has involved the following assumptions:
1) the line source function is equal to the Planck function
2) the sunspot umbra is of infinite lateral extent.
We have introduced a second possible line formation mechanism for unsaturated TiO lines: coherent scattering - and checked, with hypothesis 2), for any systematic difference in theoretical equivalent widths resulting from the pure absorption and pure scattering processes. The best interpretation was obtained on Stellmacher-Wiehr's model basis, improved by a slight temperature increase in the outer layers. Using numerical examples we suggest that coherent scattering is more likely than Local Thermodynamic Equilibrium (L.T.E.) for the TiO line formation process. The lateral influx of radiation from the penumbra into the umbra may now contribute to the source function of TiO lines, and hypothesis 2) is no longer valid. With the help of the average penumbra model of Kjeldseth Moe-Maltby, we have estimated the order of magnitude of this phenomenon (on the axis and out of axis) for an umbra supposed to be axi-symmetric. New arguments result from this estimation favouring the validity of Stellmacher-Wiehr's initial model.

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