J/AJ/114/341 Type II Cepheids (Gonzalez+ 1997)
Abundance analyses of type II Cepheids in globular clusters
Gonzalez G., Lambert D.L.
<Astron. J. 114, 341 (1997)>
=1997AJ....114..341G 1997AJ....114..341G
ADC_Keywords: Clusters, globular ; Stars, variable ; Abundances
Abstract:
We have determined the photospheric compositions of five luminous F-G
variables in globular clusters: V11 in M2, V42 in M5, V84 in M5, V2 in
M10, and V17 in M28, three of which are classified as RV Tau variable
stars. Unlike the recent findings that the photospheres of field RV
Tau variables have been altered by a gas-dust separation process, none
of these stars, except possibly V2 in M10, show such signs. We suggest
that either a smaller carbon abundance in the photosphere of a
globular cluster RV Tau star (compared to its field analogues) might
be a factor in the gas-dust separation process due to the lack of
sufficient carbon grain formation, or the stellar winds and their
efficacy as dust-grain separators is influenced by the metallicity of
the stellar envelope which, unlike the photosphere, is never subject
to alteration by a dust-gas separation. Our analysis is most complete
for V84, for which we have estimated the abundances of 19 chemical
elements. Compared to the other giants in M5, this star displays a
very large excess of Na and a deficit of O. This finding is consistent
with a recently proposed mechanism of Na production in the ON-cycling
region of metal-poor RGB stars. The value of [Al/Fe] for V84 is also
high (also consistent with ON-cycling), but a comparison with the
other cluster giants cannot be performed until Al is measured in their
spectra. The s-process elements are not significantly enhanced in the
atmosphere of V84 relative to the other cluster members.
(c) 1997 American Astronomical Society.
Objects:
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RA (2000) DE Designation(s)
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21 33 36. -00 50 Cl* NGC 7089 SAW V11
16 57 06. -04 05 Cl* NGC 6254 SAW V2
15 18 24.8 +02 02 54 Cl* NGC 5904 SAW V42
15 18 36.1 +02 04 17 Cl* NGC 5904 SAW V84
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File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
tables.dat 91 265 Individual abundance results using the model
atmospheres in Table 1
tables.tex 77 415 AASTeX version of tables.dat
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Byte-by-byte Description of file: tables.dat
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Bytes Format Units Label Explanations
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1- 7 A7 --- Object Object designation (1)
9- 13 A5 --- Species Ion species
16- 22 F7.2 0.1nm Lambda Wavelength
24- 27 F4.2 eV EP Low energy potential
30- 34 F5.2 --- log(gf) Oscillator strength
36- 43 A8 "DD/MM/YY" Date1 Observation date (2)
45- 47 I3 10-4nm EW1 ? Equivalent width for Date1
49- 53 F5.2 --- log(e1) ? Mean number density abundance
relative to H for Date1
55- 62 A8 "DD/MM/YY" Date2 Observation date (2)
64 A1 --- l_EW2 limit flag for EW2
65- 67 I3 10-4nm EW2 ? Equivalent width for Date2
69 A1 --- l_log(e2) limit flag for E2
70- 73 F4.2 --- log(e2) ? Mean number density abundance
relative to H for Date2
75- 82 A8 "DD/MM/YY" Date3 Observation date (2)
84- 86 I3 10-4nm EW3 ? Equivalent width for Date3
88- 91 F4.2 --- log(e3) ? Mean number density abundance
relative to H for Date3
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Note (1): Cluster name followed by the variable number.
Note (2): For M5 V84, 24/06/94 corresponds to 24&25 Jun 1994
26/06/94 corresponds to 26&27 Jun 1994
09/04/96 corresponds to 9&10 Apr 1996
For M28 V17, 10/06/95 corresponds to 10&12 Jun 1995
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Table1: Stellar parameters of the program stars derived from the
Fe-line analyses
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Model FeI FeII
Star UT Date S/N Teff logg [Fe/H] Xi1 loge N loge N
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M2 V11 17/06/92 65 5550, 0.2, -1.5 4.2 5.80±0.04 14 5.80±0.05 3
M2 V11 06/12/93 65 5250, -0.3, -1.5 4.0 5.85±0.03 22 5.85±0.02 3
M5 V42 29/04/94 70 5750, 0.5, -1.5 3.5 6.23±0.03 17 6.22±0.04 4
M5 V42 15/05/95 110 6250, 1.5, -1.5 3.5 6.32±0.02 12 6.32±0.04 5
M5 V84 24-25/06/94 130 5400, 0.3, -1.5 3.6 6.16±0.02 26 6.16±0.04 6
M5 V84 26-27/06/94 100 5500, 0.5, -1.5 3.5 6.34±0.03 18 6.37±0.05 5
M5 V84 09-10/04/96 75 5250, 1.1, -1.5 4.2 6.31±0.02 33 6.29±0.02 7
M10 V2 17/06/92 60 4750, 0.0, -2.0 4.0 5.52±0.03 18 5.49±0.02 3
M28 V17 10-12/06/95 90 4750, 0.3, -1.0 4.0 6.19±0.03 26 6.19±0.03 6
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Origin: AAS CD-ROM series, Volume 9, 1997 Lee Brotzman [ADS] 26-Sep-1997
(End) [CDS] 05-Feb-1998