J/ApJ/602/L117 Oxygen in Pleiades and M34 dwarfs (Schuler+, 2004)
Oxygen in open cluster dwarfs: Pleiades and M34.
Schuler S.C., King J.R., Hobbs L.M., Pinsonneault M.H.
<Astrophys. J., 602, L117-L120 (2004)>
=2004ApJ...602L.117S 2004ApJ...602L.117S
ADC_Keywords: Clusters, open ; Stars, late-type ; Stars, population II ;
Abundances
Keywords: open clusters and associations: individual (M34, Pleiades) -
stars: abundances - stars: atmospheres - stars: late-type -
stars: Population II
Abstract:
We analyze the high-excitation O I λ7774 triplet in
high-resolution, moderate signal-to-noise ratio spectra of 15 Pleiades
and eight M34 open cluster dwarfs over the effective temperature range
of 5048-6172K. Relative O abundances have been derived using model
atmospheres interpolated from four different sets of ATLAS9 grids. In
contrast to existing non-LTE (NLTE) predictions, a dramatic increase
in the O I triplet abundance with decreasing temperature is seen for
both clusters, regardless of the atmospheric model. S I abundances of
three Pleiades stars derived from the high-excitation λ6053
feature mimic the O I abundance behavior. O abundances have also been
derived from the [O I] λ6300 feature in three Pleiades stars;
the abundances exhibit a much lower mean value than do the cool dwarf
triplet results. Inasmuch as the [O I] abundances are presumed to be
free from NLTE effects, their mean values ([O/H]6300=+0.14) provide
the current best estimate of the Pleiades O abundance. Spreads in
[O/H]Trip at a given temperature are also seen in both clusters; no
correlation is found between the spreads and the chromospheric
emission measures.
Description:
Echelle spectra of the Pleiades stars were obtained with the 9.2m
Hobby-Eberly Telescope (HET) and the High Resolution Spectrograph
(HRS). The HET data presented herein were obtained on 22 separate
nights starting on 2002 August 23 UT and ending on 2003 February
17 UT.
Objects:
----------------------------------------------------------
RA (2000) DE Designation(s)
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03 47 00 +24 07.0 Pleiades = M 45
02 42 00 +42 47.0 M 34
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File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
table1.dat 77 25 Parameters and Abundances
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See also:
III/193 : Chemical Abundances in Late-Type Stars (Thevenin, 1998)
J/AJ/106/1059 : Lithium in the Pleiades (Soderblom+, 1993)
Byte-by-byte Description of file: table1.dat
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Bytes Format Units Label Explanations
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1- 8 A8 --- CName Cluster name
10- 17 A8 --- Name Object name
19- 23 F5.3 mag B-V ? The (B-V)0 color
25- 28 I4 K Teff Effective temperature
30- 33 F4.2 km/s xi Microturbulant velocity
35- 38 F4.2 [cm/s2] log(g) Log of the surface gravity
40- 44 F5.1 0.1pm EW7771 ? The 7771 triplet equivalent width (1)
46- 49 F4.1 0.1pm EW7774 ? The 7774 triplet equivalent width (1)
51- 54 F4.1 0.1pm EW7775 ? The 7775 triplet equivalent width (1)
56- 59 F4.2 [Sun] OVER The OVER [O/H] abundance (2)
61 A1 --- f_OVER [b] Indicates all abundances are log(N(O))
63- 66 F4.2 [Sun] NOVER The NOVER [O/H] abundance (2)
68- 71 F4.2 [Sun] MLT5 The MLT5 [O/H] abundance (2)
73- 76 F4.2 [Sun] CGM72 The CGM72 [O/H] abundance (2)
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Note (1): In units of milliAngstroems.
Note (2): Abundances:
OVER: Kurucz grid with convective overshoot based on the ATLAS9 code
NOVER: grid with no convective overshoot based on a modified version
of ATLAS9 (Castelli, Gratton, & Kurucz, 1997A&A...318..841C 1997A&A...318..841C)
MLT5: ATLAS9 grid computed with the mixing length parameter set to
α = 0.5
CGM72: grid computed with ATLAS9 modified based on the formulation
of Canuto, Goldman, & Mazzitelli (1996ApJ...473..550C 1996ApJ...473..550C)
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History:
From electronic version of the journal
(End) Greg Schwarz [AAS], Patricia Vannier [CDS] 16-Mar-2004