Light element non-LTE abundances of lambda Bootis stars. II. Nitrogen and sulphur

Details Light element non-LTE abundances of lambda Bootis stars. II. Nitrogen and sulphur Light element non-LTE abundances of lambda Bootis stars. II. Nitrogen and sulphur

Sep 2001

adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2001a%26a...375..899k&link_type=abstract

Astronomy and Astrophysics, v.375, p.899-908 (2001)

Astronomy and Astrophysics

Astrophysics

18

Stars: Abundances, Stars: Atmospheres, Stars: Chemically Peculiar, Stars: Early-Type

Scientific paper

One of the main characteristics proclaimed for the group of the lambda Bootis stars is the apparent solar abundance of the light elements C, N, O and S. The typical abundance pattern is completed by the strong underabundances of the Fe-peak elements. In the first paper of this series, we have shown that carbon is less abundant than oxygen but both elements are still significantly more abundant than Fe-peak elements. The mean abundances, based on a detailed non-LTE investigation, were found -0.37 dex and -0.07 dex, respectively. As a further step, we now present non-LTE abundances of nitrogen and sulphur for thirteen members of the lambda Bootis group based on several spectral lines between 8590 Å, and 8750 Å. Furthermore, LTE abundances for calcium in the same spectral range were derived and compared with values from the literature. Similar to the mean abundances of carbon and oxygen, nearly solar values were found (-0.30 dex for nitrogen and -0.11 dex for sulphur) for our sample of program stars. Among our sample, one previously undetected binary system (HD 64491) was identified. From a statistical point of view, the abundances of the light elements range from slightly overabundant to moderately underabundant compared to the Sun. However, the individual objects always exhibit a similiar pattern, with the Fe-peak elements being significantly more underabundant than the light elements. No correlation of the derived abundances with astrophysical parameters such as the effective temperature, surface gravity or projected rotational velocity was found. Furthermore, the abundances of the light elements do not allow us to discriminate between any proposed theory. Based on observations obtained at BNAO Rozhen and Complejo Astronómico el Leoncito (CASLEO), operated under the agreement between the Consejo Nacional de Investigaciones Científicas y Técnicas de la República Argentina and the National Universities of La Plata, Córdoba y San Juan.

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