J/MNRAS/477/2276 Type II Cepheids abundances (Kovtyukh+, 2018)
Type II Cepheids: evidence for Na-O anticorrelation for BL Her type stars?
Kovtyukh V., Yegorova I., Andrievsky S., Korotin S., Saviane I.,
Lemasle B., Chekhonadskikh F., Belik S.
<Mon. Not. R. Astron. Soc., 477, 2276-2285 (2018)>
=2018MNRAS.477.2276K 2018MNRAS.477.2276K (SIMBAD/NED BibCode)
ADC_Keywords: Stars, variable ; Abundances
Keywords: stars: abundances - stars: BL Her type - stars: type II Cepheids -
stars: W Vir type
Abstract:
The chemical composition of 28 Population II Cepheids and one RR Lyrae
variable has been studied using high-resolution spectra. The chemical
composition of W Vir variable stars (with periods longer than 8 d) is
typical for the halo and thick disc stars. However, the chemical
composition of BL Her variables (with periods of 0.8-4 d) is
drastically different, although it does not differ essentially from
that of the stars belonging to globular clusters. In particular, the
sodium overabundance ([Na/Fe]~=0.4) is reported for most of these
stars, and the Na-O anticorrelation is also possible. The evolutionary
tracks for BL Her variables (with a progenitor mass value of 0.8 solar
masses) indicate that mostly helium-overabundant stars (Y=0.30-0.35)
can fall into the instability strip region. We suppose that it is the
helium overabundance that accounts not only for the existence of BL Her
variable stars but also for the observed abnormalities in the chemical
composition of this small group of pulsating variables.
Description:
Sixteen objects were observed with cross-dispersed Echelle
spectrograph UVES at the VLT (observing run 089.D-0489).
Twelve objects were observed with the 3.5-m telescope at the Apache
Point Observatory, with the ARC Echelle Spectrograph (ARCES).
Spectrum for one object (V553 Cen) was taken from the ESO archive. The
star was observed with the Echelle spectrograph HARPS at the ESO La
Silla 3.6-m telescope.
For some objects (with double lines in the spectrum or with emissions
in Fe lines), the chemical composition was not determined. For those
objects, the atmospheric parameters are missing in Table 1.
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
table1.dat 131 54 Details of observations and stellar parameters
for 29 stars
table3.dat 113 24 Relative to Fe abundances in T2C (C-Mn)
table4.dat 107 24 Relative to Fe abundances in T2C (Co-Eu)
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Byte-by-byte Description of file: table1.dat
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Bytes Format Units Label Explanations
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1- 18 A18 --- Star Star name
19 A1 --- n_Star [a] Note on Star (1)
20- 29 F10.7 d Per Period
31- 35 A5 --- Tel Telescope
37- 46 F10.4 d JD ?=- Julian date (JD-2400000)
48- 51 I4 s Exptime ?=- Exposure time
53- 57 F5.3 --- Phase ?=- Phase
59- 62 I4 K Teff ?=- Effective temperature
64- 67 F4.2 [cm/s2] logg ?=- Surface gravity
68- 70 F3.1 km/s Vt ?=- Microturbulent velocity
72- 76 F5.2 [-] [Fe/H] ?=- Metallicity
78-131 A54 --- Rem Remarks
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Note (1): a: Data on the spectra (KP Cyg) are given in the paper by
Andrievsky et al. (2010PASP..122..877A 2010PASP..122..877A).
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Byte-by-byte Description of file: table3.dat
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Bytes Format Units Label Explanations
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1- 18 A18 --- Star Star name
20- 29 F10.7 d Per Period
32- 36 F5.2 [-] [C/Fe] ?=- Abundance [C/Fe]
38- 42 F5.2 [-] [N/Fe] ?=- Abundance [N/Fe]
44- 48 F5.2 [-] [O/Fe] ?=- Abundance [O/Fe]
50- 54 F5.2 [-] [Na/Fe] ?=- Abundance [Na/Fe]
56- 60 F5.2 [-] [Mg/Fe] ?=- Abundance [Mg/Fe]
62- 66 F5.2 [-] [Al/Fe] ?=- Abundance [Al/Fe]
68- 72 F5.2 [-] [Si/Fe] ?=- Abundance [Si/Fe]
74- 77 F4.2 [-] [S/Fe] ?=- Abundance [S/Fe]
79- 83 F5.2 [-] [Ca/Fe] ?=- Abundance [Ca/Fe]
85- 89 F5.2 [-] [Sc/Fe] ?=- Abundance [Sc/Fe]
91- 95 F5.2 [-] [Ti/Fe] ?=- Abundance [Ti/Fe]
97-101 F5.2 [-] [V/Fe] ?=- Abundance [V/Fe]
103-107 F5.2 [-] [Cr/Fe] ?=- Abundance [Cr/Fe]
109-113 F5.2 [-] [Mn/Fe] ?=- Abundance [Mn/Fe]
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Byte-by-byte Description of file: table4.dat
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Bytes Format Units Label Explanations
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1- 18 A18 --- Star Star name
20- 29 F10.7 d Per Period
31- 35 F5.2 [-] [Fe/H] Metallicity
37- 41 F5.2 [-] [Co/Fe] ?=- Abundance [Co/Fe]
43- 47 F5.2 [-] [Ni/Fe] ?=- Abundance [Ni/Fe]
49- 53 F5.2 [-] [Cu/Fe] ?=- Abundance [Cu/Fe]
55- 59 F5.2 [-] [Zn/Fe] ?=- Abundance [Zn/Fe]
61- 65 F5.2 [-] [Y/Fe] ?=- Abundance [Y/Fe]
67- 71 F5.2 [-] [Zr/Fe] ?=- Abundance [Zr/Fe]
73- 77 F5.2 [-] [Ba/Fe] ?=- Abundance [Ba/Fe]
79- 83 F5.2 [-] [La/Fe] ?=- Abundance [La/Fe]
85- 89 F5.2 [-] [Ce/Fe] ?=- Abundance [Ce/Fe]
91- 95 F5.2 [-] [Nd/Fe] ?=- Abundance [Nd/Fe]
97-101 F5.2 [-] [Sm/Fe] ?=- Abundance [Sm/Fe]
103-107 F5.2 [-] [Eu/Fe] ?=- Abundance [Eu/Fe]
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History:
From electronic version of the journal
(End) Patricia Vannier [CDS] 04-Jun-2021