Natalie Behara

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Context. Balmer lines serve as important indicators of stellar effective temperatures in late-type stellar spectra. One of their modelling uncertainties is the influence of convective flows on their shape. Aims. We aim to characterize the influence of convection on the wings of Balmer lines. Methods. We perform a differential comparison of synthetic Balmer(More)
Context. The lithium abundance predicted by the standard big bang nucleosynthesis with the baryonic density accurately measured from the fluctuations of the cosmic microwave background is a factor of three higher than that observed in metal-poor dwarf stars of the Galactic halo, the so-called Spite Plateau. Most Globular Clusters are believed to host a(More)
We describe an opacity sampled version of the LTE model atmosphere code sterne with revised continuous opacities. In particular, we examine the results of replacing the existing treatment of the continuous opacities which followed the method of Kurucz (1970, SAOSR, No. 309) and Peach (1970, MNRAS, 73, 1), with photoionization cross-sections from the Opacity(More)
We present a detailed analysis of all the known Hot DQ white dwarfs in the Fourth Data Release of the Sloan Digital Sky Survey (SDSS) recently found to have carbon dominated atmospheres. Our spectroscopic and photometric analysis reveals that these objects all have effective temperatures between ∼ 18,000 and 24,000 K. The surface composition is found to be(More)
Approximately 20% of very metal-poor stars ([Fe/H] < –2.0) are strongly enhanced in carbon ([C/Fe] > +1.0). Such stars are referred to as carbon-enhanced metal-poor (CEMP) stars. We present a chemical abundance analysis based on high resolution spectra acquired with UVES at the VLT of three dwarf CEMP stars: SDSS J1349-0229, SDSS J0912+0216 and SDSS(More)
We give a progress report about the activities within the CIFIST Team related to the search for extremely metal-poor stars in the Sloan Digital Sky Survey’s spectroscopic catalog. So far the search has provided 25 candidates with metallicities around or smaller −3. For 15 candidates high resolution spectroscopy with UVES at the VLT has confirmed their(More)
We carried out an extensive observational study of the Slowly Pulsating B (SPB) star, HD 25558. The ≈2000 spectra obtained at different observatories, the ground-based and MOST satellite light curves revealed that this object is a double-lined spectroscopic binary with an orbital period of about nine years. The observations do not allow the inference of an(More)
We present a detailed analysis of the carbon and nitrogen abundances of two dwarf carbon-enhanced metal-poor (CEMP) stars: SDSS J1349-0229 and SDSS J0912+0216. We also report the oxygen abundance of SDSS J1349-0229. These stars are metal-poor, with [Fe/H] < –2.5, and were selected from our ongoing survey of extremely metal-poor dwarf candidates from the(More)
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