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J/A+A/423/677 Oxygen abundances in chromospherically active stars (Morel+, 2004)

On the determination of oxygen abundances in chromospherically active stars. Morel T., Micela G. <Astron. Astrophys. 423, 677 (2004)> =2004A&A...423..677M
ADC_Keywords: Stars, variable ; Abundances Keywords: stars: abundances - stars: activity - line: formation Abstract: We discuss oxygen abundances derived from [O I] 6300 and the O I triplet in stars spanning a wide range in chromospheric activity level, and show that these two indicators yield increasingly discrepant results with higher chromospheric/coronal activity measures. While the forbidden and permitted lines give fairly consistent results for solar-type disk dwarfs, spuriously high O I triplet abundances are observed in young Hyades and Pleiades stars, as well as in individual components of RS CVn binaries (up to 1.8dex). The distinct behaviour of the [O I]-based abundances which consistently remain near-solar suggests that this phenomenon mostly results from large departures from LTE affecting the O I triplet at high activity level that are currently unaccounted for, but also possibly from a failure to adequately model the atmospheres of K-type stars. These results suggest that some caution should be exercised when interpreting oxygen abundances in active binaries or young open cluster stars. Description: Table 2 presents the oxygen abundances derived for a sample of RS CVn binaries and field subgiants from a curve-of-growth analysis using FEROS spectra and plane-parallel, line-blanketed LTE Kurucz atmospheric models. These observations are supplemented by literature data for Pleiades, Hyades and field FG dwarfs. Two activity indices derived from the Ca II H+K lines and the X-ray emission are also given. File Summary:
FileName Lrecl Records Explanations
ReadMe 80 . This file table2.dat 101 100 Oxygen abundances and activity indices refs.dat 111 26 References
See also: J/A+A/412/495 : Equivalent widths for 6 RS CVn systems (Morel+, 2003) J/A+A/426/1007 : Abundances of 8 single-lined active binaries (Morel+, 2004) Byte-by-byte Description of file: table2.dat
Bytes Format Units Label Explanations
1- 9 A9 --- Star Star name (1) 11- 14 I4 K Teff Effective temperature 16- 20 F5.2 [Sun] [Fe/H] Iron abundance (2) 22- 25 F4.2 [Sun] e_[Fe/H] Iron abundance uncertainty (2) 27- 31 F5.2 [Sun] [O/Fe]6300 ? Oxygen abundance yielded by [O I] 6300 (3) 33- 36 F4.2 [Sun] e_[O/Fe]6300 ? Uncertainty for the oxygen abundance yielded by [O I] 6300 (3) 38- 42 F5.2 [Sun] [O/Fe]trip ? Oxygen abundance yielded by the O I-7774 triplet (3) 44- 47 F4.2 [Sun] e_[O/Fe]trip ? Uncertainty for the oxygen abundance yielded by the O I-7774 triplet (3) 49 I1 --- r_[O/Fe]trip Reference code for the oxygen abundance data (in refs.dat file) 51- 55 F5.2 [---] log(R'HK) ? Activity index derived from the Ca II H+K lines (4) 57- 60 F4.2 [---] e_log(R'HK) ? Uncertainty for the activity index derived from the Ca II H+K lines (4) 62- 63 I2 --- r_log(R'HK) ? Reference code for the R'HK data (in refs.dat file) 65- 69 F5.2 [10-7W] logLX ? ROSAT X-ray luminosity (5) 71- 74 F4.2 [10-7W] e_logLX ? ROSAT X-ray luminosity uncertainty (5) 76- 80 F5.2 [---] logRX ? Activity index derived from the X-ray data (5) 82- 85 F4.2 [---] e_logRX ? Uncertainty for the activity index derived from the X-ray data (5) 87 I1 --- f_logRX ? X-ray detection flag (6) 89- 90 I2 --- r_logRX ? Reference code for the RX data (in refs.dat file)
Note (1): Identification for Pleiades and Hyades stars from Hertzsprung (HII, 1947AnLei..19a...1H) and van Bueren (VB, 1952BAN....11..385V), respectively. Note (2): We quote the mean cluster metallicity of the Pleiades and Hyades determined by King et al. (2000AJ....119..859K) and Cayrel, Cayrel de Strobel & Campbell (1985A&A...146..249C), respectively. Note (3): The [O/Fe] data from the literature were rescaled to our adopted iron and oxygen solar abundances (log(εsolarFe)=7.67 and log(εsolarO)=8.93), and corrected for departures from LTE in the case of the O I triplet (Gratton et al., 1999, Cat. J/A+A/350/955). The EWs of [O I] 6300 have been corrected for the contribution of Ni I 6300.339. We use the values of Schuler et al. (2004ApJ...602L.117S) derived without convective overshoot ('NOVER'). Note (4): For the RS CVn binaries and field subgiants, a blank indicates that the Ca II H+K profiles were not filled in by emission. The errors take into account the uncertainties in (V-R)0 and Teff. Note (5): Except for the open cluster stars and HD 118238 (130pc; Strassmeier et al., 1993A&A...268..671S), all luminosities were rescaled to the Hipparcos distances. For consistency with previous X-ray observations, the bolometric luminosities were computed adopting a mean distance to the Pleiades of 127pc (Crawford & Perry, 1976AJ.....81..419C). For the Hyades, we used the individual distances of Schwan (1991, Cat. J/A+A/243/386). No reddening and a mean extinction A(V)=0.12mag were assumed for the Hyades and Pleiades, respectively (Nissen, 1988A&A...199..146N). We used A(V)=0.26mag for HII 676 (Stauffer et al., 1994, Cat. J/ApJS/91/625). The bolometric corrections are taken from Flower (1996ApJ...469..355F). The errors take into account the uncertainties in the X-ray counts and in the distances. Note (6): X-ray detection flags. 0 = X-ray detected, 1 = upper limit.
Byte-by-byte Description of file: refs.dat
Bytes Format Units Label Explanations
1- 2 I2 --- Ref Reference code 4- 22 A19 --- BibCode BibCode 24- 51 A28 --- Aut Author's name 52-111 A60 --- Com Comments
Acknowledgements: Thierry Morel
(End) Patricia Vannier [CDS] 17-Jun-2004
The document above follows the rules of the Standard Description for Astronomical Catalogues.From this documentation it is possible to generate f77 program to load files into arrays or line by line

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