Determination of the temperatures of selected ISO flux calibration
 stars using the Infrared Flux Method

Blackwell, D. E.; Lynas-Gray, A. E.

doi:10.1051/aas:1998202

Cited by 122 publications

(142 citation statements)

References 10 publications

(13 reference statements)

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“…Tomkin et al 1992;Blackwell & Lynas-Gray 1998;Fulbright 2000;Nissen et al 2002;Gratton et al 2003;Reddy et al 2006;Masana et al 2006;Sousa et al 2011). The most discrepant T eff is from the work of Reddy et al (2006).…”

Section: Hd 126681mentioning

confidence: 99%

GaiaFGK benchmark stars: new candidates at low metallicities

Hawkins

Jofré

Heiter

et al. 2016

A&A

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Context. We have entered an era of large spectroscopic surveys in which we can measure, through automated pipelines, the atmospheric parameters and chemical abundances for large numbers of stars. Calibrating these survey pipelines using a set of "benchmark stars" in order to evaluate the accuracy and precision of the provided parameters and abundances is of utmost importance. The recent proposed set of Gaia FGK benchmark stars has up to five metal-poor stars but no recommended stars within −2.0 < [Fe/H] < −1.0 dex. However, this metallicity regime is critical to calibrate properly. Aims. In this paper, we aim to add candidate Gaia benchmark stars inside of this metal-poor gap. We began with a sample of 21 metalpoor stars which was reduced to 10 stars by requiring accurate photometry and parallaxes, and high-resolution archival spectra. Methods. The procedure used to determine the stellar parameters was similar to the previous works in this series for consistency. The difference was to homogeneously determine the angular diameter and effective temperature (T eff ) of all of our stars using the Infrared Flux Method utilizing multi-band photometry. The surface gravity (log g) was determined through fitting stellar evolutionary tracks. The [Fe/H] was determined using four different spectroscopic methods fixing the T eff and log g from the values determined independent of spectroscopy. Results. We discuss, star-by-star, the quality of each parameter including how it compares to literature, how it compares to a spectroscopic run where all parameters are free, and whether Fe i ionisation-excitation balance is achieved.Conclusions. From the 10 stars, we recommend a sample of five new metal-poor benchmark candidate stars which have consistent T eff , log g, and [Fe/H] determined through several means. These stars, which are within −1.3 < [Fe/H] < −1.0, can be used for calibration and validation purpose of stellar parameter and abundance pipelines and should be of highest priority for future interferometric studies.

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Section: Hd 126681mentioning

confidence: 99%

GaiaFGK benchmark stars: new candidates at low metallicities

Hawkins

Jofré

Heiter

et al. 2016

A&A

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“…To compute the luminosity of β Hyi we used the same value for the bolometric flux as North et al (2007), F bol = (2.019 ± 0.05) × 10 9 W m −2 (Blackwell & Lynas-Gray 1998, the uncertainty on F bol is from di Benedetto 1998) and the revised Hipparcos parallax (van Leeuwen 2007). Adopting L = 3.842 × 10 26 W with an uncertainty of 0.4% (Bahcall et al 2001), we found L = 3.494 ± 0.087 L for β Hyi.…”

Section: Non-seismic Datamentioning

confidence: 99%

“…The combination of these two values gives a direct measure of β Hyi's radius with high accuracy. Moreover, since the bolometric flux of this star is known (Blackwell & Lynas-Gray 1998), its position in the HertzprungRussell (HR) diagram is, in principle, well-constrained. Frandsen (1987) and Edmonds & Cram (1995) made unsuccessful attempts to detect stellar oscillations in β Hyi, placing upper limits on the p-mode amplitudes.…”

Section: Introductionmentioning

confidence: 99%

Asteroseismic modelling of the solar-type subgiant starβ Hydri

Brandão

Doğan

Christensen‐Dalsgaard

et al. 2011

A&A

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Context. Comparing models and data of pulsating stars is a powerful way to understand the stellar structure better. Moreover, such comparisons are necessary to make improvements to the physics of the stellar models, since they do not yet perfectly represent either the interior or especially the surface layers of stars. Because β Hydri is an evolved solar-type pulsator with mixed modes in its frequency spectrum, it is very interesting for asteroseismic studies. Aims. The goal of the present work is to search for a representative model of the solar-type star β Hydri, based on up-to-date nonseismic and seismic data. Methods. We present a revised list of frequencies for 33 modes, which we produced by analysing the power spectrum of the published observations again using a new weighting scheme that minimises the daily sidelobes. We ran several grids of evolutionary models with different input parameters and different physics, using the stellar evolutionary code ASTEC. For the models that are inside the observed error box of β Hydri, we computed their frequencies with the pulsation code ADIPLS. We used two approaches to find the model that oscillates with the frequencies that are closest to the observed frequencies of β Hydri: (i) we assume that the best model is the one that reproduces the star's interior based on the radial oscillation frequencies alone, to which we have applied the correction for the near-surface effects; (ii) we assume that the best model is the one that produces the lowest value of the chi-square (χ 2 ), i.e. that minimises the difference between the observed frequencies of all available modes and the model predictions, after all model frequencies are corrected for near-surface effects. Results. We show that after applying a correction for near-surface effects to the frequencies of the best models, we can reproduce the observed modes well, including those that have mixed mode character. The model that gives the lowest value of the χ 2 is a post-mainsequence model with a mass of 1.04 M and a metallicity slightly lower than that of the Sun. Our results underscore the importance of having individual frequencies to constrain the properties of the stellar model.

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“…The effective temperature (T eff ) for Vir was calculated using the colors (R − I) (Hoffleit & Jaschek 1982) and (V − K) (Johnson et al 1966) with the metallicity independent relations by McWilliam (1990), for (R − I) and (V − K), and by Blackwell & Lynas-Gray (1998), for (V − K). A mean T eff was then calculated for the (V − K) index, using the two calibrations, and this value was averaged with the T eff given by the (R − I) index.…”

Section: The Differential Analysismentioning

confidence: 99%

Abundance analysis of barium and mild barium stars

Smiljanić¹,

Mello²,

Silva³

2007

A&A

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Aims. We compare and discuss abundances and trends in normal giants, mild barium, and barium stars, searching for differences and similarities between barium and mild barium stars that could help shed some light on the origin of these similar objects. Also, we search for nucleosynthetic effects possibly related to the s-process that were observed in the literature for elements like Cu in other types of s-process enriched stars. Methods. High signal to noise, high resolution spectra were obtained for a sample of normal, mild barium, and barium giants.Atmospheric parameters were determined from the Fe i and Fe ii lines. Abundances for Na, Mg, Al, Si, Ca, Sc, Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Zn, Sr, Y, Zr, Ba, La, Ce, Nd, Sm, Eu, and Gd, were determined from equivalent widths and model atmospheres in a differential analysis, with the red giant Vir as the standard star. Results. The different levels of s-process overabundances of barium and mild barium stars were earlier suggested to be related to the stellar metallicity. Contrary to this suggestion, we found in this work no evidence of barium and mild barium having a different range in metallicity. However, comparing the ratio of abundances of heavy to light s-process elements, we found some evidence that they do not share the same neutron exposure parameter. The exact mechanism controlling this difference is still not clear. As a by-product of this analysis we identify two normal red giants misclassified as mild barium stars. The relevance of this finding is discussed. Concerning the suggested nucleosynthetic effects possibly related to the s-process, for elements like Cu, Mn, V and Sc, we found no evidence for an anomalous behavior in any of the s-process enriched stars analyzed here. However, further work is still needed since a clear [Cu/Fe] vs. [Ba/Fe] anticorrelation exists for other s-process enriched objects.

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Determination of the temperatures of selected ISO flux calibration stars using the Infrared Flux Method

Cited by 122 publications

References 10 publications

GaiaFGK benchmark stars: new candidates at low metallicities

GaiaFGK benchmark stars: new candidates at low metallicities

Asteroseismic modelling of the solar-type subgiant starβ Hydri

Abundance analysis of barium and mild barium stars

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