Abundance studies of sdB stars using UV echelle HST/STIS 
spectroscopy

O'Toole, S. J.; Heber, U.

doi:10.1051/0004-6361:20053948

Cited by 99 publications

(110 citation statements)

References 27 publications

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“…Since the C ii/C iii abundances given in literature O'Toole & Heber 2006) do not show such high deviations, we conclude that the limited number of lines used in our study leads to those systematic shifts. Especially the C ii lines at 4267 Å are known to be very sensitive to NLTE effects (Nieva & Przybilla 2008).…”

Section: Comparison With Literature and Systematic Uncertaintiesmentioning

confidence: 47%

“…However, the abundance patterns of pulsating sdBs turned out to be the same as the ones of non-pulsating comparison stars with similar atmospheric parameters (Heber et al 2000;O'Toole & Heber 2006;Blanchette et al 2008).…”

Section: Abundance Patterns Of Sdb Sub-populationsmentioning

confidence: 85%

“…Lamontagne et al 1985Lamontagne et al , 1987O'Toole & Heber 2006) that the silicon abundance in sdB stars appears to drop sharply at T eff > 32 000 K. Fractionated winds have been invoked to explain this strange observation . The aluminium abundance were proposed to behave in a similar way.…”

Section: Other Trendsmentioning

confidence: 97%

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Hot subdwarf stars in close-up view

Geier

2013

A&A

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Context. Hot subdwarf B stars (sdBs) are considered to be core helium-burning stars with very thin hydrogen envelopes situated on or near the extreme horizontal branch. The formation of sdBs is still unclear as well as the chemical composition of their atmospheres. The observed helium depletion is attributed to atmospheric diffusion. Metal abundances have been determined for about a dozen sdBs only resulting in puzzling patterns with enrichment of heavy metals and depletion of lighter ones. Aims. We present a detailed metal abundance analysis of 106 sdBs. Methods. From high resolution spectra we measured elemental abundances of up to 24 different ions per star. A semi-automatic analysis pipeline was developed to calculate and fit LTE models to a standard set of spectral lines. Results. A general trend of enrichment was found with increasing temperature for most of the heavier elements. The lighter elements like carbon, oxygen, and nitrogen are depleted and less affected by temperature. Although there is considerable scatter from star to star, the general abundance patterns in most sdBs are similar. State-of-the-art diffusion models predict such patterns and are in qualitative agreement with our results. However, the highest enrichments measured cannot be explained with these models. Peculiar line shapes of the strongest metal lines in some stars indicate vertical stratification to be present in the atmospheres. Such effects are not accounted for in current diffusion models and may be responsible for some of the yet unexplained abundance anomalies.

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Section: Comparison With Literature and Systematic Uncertaintiesmentioning

confidence: 47%

Section: Abundance Patterns Of Sdb Sub-populationsmentioning

confidence: 85%

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Hot subdwarf stars in close-up view

Geier

2013

A&A

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“…In [4], the Ar III λ = 1002.097 Å spectral line has been used in the determination of abundance in hydrogen-rich subdwarf B stars. Ar III spectral lines were also observed by O'Toole and Heber [5] in the spectra of subdwarf B stars. Based on lines of Ar II, Heber and Edelmann [6] have reported abundances of argon in B subdwarfs.…”

Section: Introductionmentioning

confidence: 53%

Stark Widths of Ar II Spectral Lines in the Atmospheres of Subdwarf B Stars

Hamdi

Nessib

Dimitrijević

2017

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Stark broadening parameters are of interest for many problems in astrophysics and laboratory plasmas investigation. Ar II spectral lines are observed in many kinds of stellar atmospheres such as the atmospheres of B-Type stars and subdwarf B stars. In this work, we present theoretical Stark widths for Ar II spectral lines. We use the impact semiclassical perturbation approach. Our results are compared with the available experimental values. Finally, the importance of the Stark broadening mechanism is studied in atmospheric conditions of subdwarf B stars.

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“…The chemical composition of sdB stars is known to be highly peculiar, showing large deficiencies for the lighter elements (e.g. C and Si) on the one hand, and strong overabundances of heavy elements as deduced from UV and FUV spectra on the other (see O'Toole & Heber 2006;Blanchette et al 2008), while iron is found to be approximately solar in most sdBs. The line blocking of UV iron lines is responsible for most of the line blanketing affecting the temperature-density stratification of the model atmosphere.…”

Section: Computation Of Synthetic Line-profile Variationsmentioning

confidence: 99%

Interpreting the line-profile variations of subdwarf B pulsators: the case of PG 1336-018 (NY Virginis)

Vučković¹,

Østensen²,

Aerts

et al. 2009

A&A

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Aims. We analyze the high-resolution time-resolved VLT/uves spectra of PG 1336−018, a rapidly pulsating subdwarf B (sdB) primary in a close orbit with an M5 companion, with the aim to detect the pulsational signal of the primary in line-profile variations. Methods. After removing the dominant radial-velocity component inherent to the orbital motion and taking only out-of-eclipse data we computed cross-correlation functions (CCFs) for each individual spectrum and assumed these to approximate the average line profile. We computed predictions of line-profile variations for pulsating sdB stars and present their diagnostic value for mode identification. Results. We detect the pulsation mode at 5435 μHz in the line-profile variations of the CCFs which allows us to characterize the detected pulsation mode of PG 1336−018. Conclusions. We model the pulsational perturbations of synthetic spectra for a star with physical parameters like PG 1336−018 and confront them with the observed spectra. We find that low order Balmer lines can be used as diagnostic tool to identify pulsation modes. A detailed line-profile analysis of the perturbed time-series spectra excludes the = |m| = (3, 3), (1, 0), (2, 1) and (2, 0) modes, but does not allow a unique mode identification among the radial or sectoral dipole or quadrupole modes.

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Abundance studies of sdB stars using UV echelle HST/STIS spectroscopy

Cited by 99 publications

References 27 publications

Hot subdwarf stars in close-up view

Hot subdwarf stars in close-up view

Stark Widths of Ar II Spectral Lines in the Atmospheres of Subdwarf B Stars

Interpreting the line-profile variations of subdwarf B pulsators: the case of PG 1336-018 (NY Virginis)

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