J/MNRAS/298/332 Chromospheric activity-age relation (Rocha-Pinto+ 1998)
Metallicity effects on the chromospheric activity-age relation for
late-type dwarfs
Rocha-Pinto H.J., Maciel W.J.
<Mon. Not. R. Astron. Soc. 298, 332 (1998)>
=1998MNRAS.298..332R 1998MNRAS.298..332R
ADC_Keywords: Stars, late-type ; Stars, ages ; Abundances, [Fe/H]
Keywords: stars: activity - stars: chromospheres -
stars: fundamental parameters - stars: late-type
Abstract:
We show that there is a relationship between the age excess, defined
as the difference between the stellar isochrone and chromospheric
ages, and the metallicity as measured by the index [Fe/H] for
late-type dwarfs. The chromospheric age tends to be lower than the
isochrone age for metal-poor stars, and the opposite occurs for
metal-rich objects. We suggest that this could be an effect of
neglecting the metallicity dependence of the calibrated chromospheric
emission-age relation. We propose a correction to account for this
dependence. We also investigate the metallicity distributions of these
stars, and show that there are distinct trends according to the
chromospheric activity level. Inactive stars have a metallicity
distribution which resembles the metallicity distribution of solar
neighbourhood stars, while active stars appear to be concentrated in
an activity strip on the log(R'HK)*[Fe/H] diagram. We provide some
explanations for these trends, and show that the chromospheric
emission-age relation probably has different slopes on the two sides
of the Vaughan-Preston gap.
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
tablea1.dat 61 730 Stellar data for sample B
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Byte-by-byte Description of file: tablea1.dat
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Bytes FormatUnits Label Explanations
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1- 6 I6 --- HD HD (Cat. III/135) number
7 A1 --- m_HD [ABC] Multiplicity index on HD
9- 14 F6.3 --- logR'HK logR'HK index (measurement of the
chromospheric emission)
16- 22 F7.4 [Sun] [Fe/H] Metallicity
24- 29 F6.4 [K] logTeff Effective temperature
31- 37 F7.4 mag DVMAG Differential absolute V magnitude
39- 45 F7.4 [yr] logtiso ? Isochrone age
47- 53 F7.4 [yr] logtce ? Chromospheric age (tce=-1.50logR'HK+2.25)
55- 61 F7.4 [yr] Dlogt ? Age excess (logtis - logtce)
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History: Prepared via OCR at CDS.
(End) James Marcout, Patricia Bauer [CDS] 17-Feb-2000