J/A+A/549/A110 Metal abundances of sdB stars (Geier, 2013)
Hot subdwarf stars in close-up view.
III. Metal abundances of subdwarf B stars.
Geier S.
<Astron. Astrophys. 549, A110 (2013)>
=2013A&A...549A.110G 2013A&A...549A.110G
ADC_Keywords: Stars, subdwarf ; Stars, B-type ; Stars, atmospheres ; Abundances
Keywords: stars: atmospheres - subdwarfs
Abstract:
Hot subdwarf B stars (sdBs) are considered to be core helium-burning
stars with very thin hydrogen envelopes situated on or near the
extreme horizontal branch (EHB). The formation of sdBs is still
unclear as well as the chemical composition of their atmospheres. The
observed helium depletion is attributed to atmospheric diffusion.
Metal abundances have been determined for about a dozen sdBs only
resulting in puzzling patterns with enrichment of heavy metals and
depletion of lighter ones. In this paper we present a detailed metal
abundance analysis of 106 sdBs. From high resolution spectra we
measured elemental abundances of up to 24 different ions per star. A
semi-automatic analysis pipeline was developed to calculate and fit
LTE models to a standard set of spectral lines. A general trend of
enrichment was found with increasing temperature for most of the
heavier elements. The lighter elements like carbon, oxygen and
nitrogen are depleted and less affected by temperature. Although there
is considerable scatter from star to star, the general abundance
patterns in most sdBs are similar. State-of-the-art diffusion models
predict such patterns and are in qualitative agreement with our
results. However, the highest enrichments measured cannot not be
explained with these models. Peculiar line shapes of the strongest
metal lines in some stars indicate vertical stratification to be
present in the atmospheres. Such effects are not accounted for in
current diffusion models and may be responsible for some of the yet
unexplained abundance anomalies.
Description:
Metal abundances of 106 field sdB stars are given (Table A.1-A.3).
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
abund.dat 301 106 Metal abundances
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See also:
J/A+A/442/1023 : Radial velocity of 17 bright subdwarf B (Edelmann+, 2005)
J/A+A/513/A6 : NOT survey of subdwarf B stars (Ostensen+, 2010)
Byte-by-byte Description of file: abund.dat
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Bytes Format Units Label Explanations
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1- 13 A13 --- Name Star name
15- 24 A10 --- n_Name Variability or peculiarity (1)
26- 30 I5 K Teff Effective temperature
32 A1 --- l_HeI/II Upper limit flag on HeI/II
33- 37 F5.2 --- HeI/II He abundance
39 A1 --- l_CII Upper limit flag on CII
40- 43 F4.2 --- CII ?=- CII abundance
45- 48 F4.2 --- e_CII ?=- uncertainty of CII
50 A1 --- l_CIII Upper limit flag on CIII
51- 54 F4.2 --- CIII ?=- CIII abundance
56- 59 F4.2 --- e_CIII ?=- uncertainty of CIII
61 A1 --- l_NII Upper limit flag on NII
62- 65 F4.2 --- NII ?=- NII abundance
67- 70 F4.2 --- e_NII ?=- uncertainty of NII
72 A1 --- l_NIII Upper limit flag on NIII
73- 76 F4.2 --- NIII ?=- NIII abundance
78- 81 F4.2 --- e_NIII ?=- uncertainty of NIII
83 A1 --- l_OII Upper limit flag on OII
84- 87 F4.2 --- OII ?=- OII abundance
89- 92 F4.2 --- e_OII ?=- uncertainty of OII
94 A1 --- l_NeII Upper limit flag on NeII
95- 98 F4.2 --- NeII ?=- NeII abundance
100-103 F4.2 --- e_NeII ?=- uncertainty of NeII
105 A1 --- l_MgII Upper limit flag on MgII
106-109 F4.2 --- MgII ?=- MgII abundance
111-114 F4.2 --- e_MgII ?=- uncertainty of MgII
116 A1 --- l_AlIII Upper limit flag on AlIII
117-120 F4.2 --- AlIII ?=- AlIII abundance
122-125 F4.2 --- e_AlIII ?=- uncertainty of AlIII
127 A1 --- l_SiIII Upper limit flag on SiIII
128-131 F4.2 --- SiIII ?=- SiIII abundance
133-136 F4.2 --- e_SiIII ?=- uncertainty of SiIII
138 A1 --- l_SiIV Upper limit flag on SiIV
139-142 F4.2 --- SiIV ?=- SiIV abundance
144-147 F4.2 --- e_SiIV ?=- uncertainty of SiIV
149 A1 --- l_PIII Upper limit flag on PIII
150-153 F4.2 --- PIII ?=- PIII abundance
155-158 F4.2 --- e_PIII ?=- uncertainty of PIII
160 A1 --- l_SII Upper limit flag on SII
161-164 F4.2 --- SII ?=- SII abundance
166-169 F4.2 --- e_SII ?=- uncertainty of SII
171 A1 --- l_SIII Upper limit flag on SIII
172-175 F4.2 --- SIII ?=- SIII abundance
177-180 F4.2 --- e_SIII ?=- uncertainty of SIII
182 A1 --- l_ArII Upper limit flag on ArII
183-186 F4.2 --- ArII ?=- ArII abundance
188-191 F4.2 --- e_ArII ?=- uncertainty of ArII
193 A1 --- l_KII Upper limit flag on KII
194-197 F4.2 --- KII ?=- KII abundance
199-202 F4.2 --- e_KII ?=- uncertainty of KII
204 A1 --- l_CaIII Upper limit flag on CaIII
205-208 F4.2 --- CaIII ?=- CaIII abundance
210-213 F4.2 --- e_CaIII ?=- uncertainty of CaIII
215 A1 --- l_ScIII Upper limit flag on ScIII
216-219 F4.2 --- ScIII ?=- ScIII abundance
221-224 F4.2 --- e_ScIII ?=- uncertainty of ScIII
226 A1 --- l_TiIII Upper limit flag on TiIII
227-230 F4.2 --- TiIII ?=- TiIII abundance
232-235 F4.2 --- e_TiIII ?=- uncertainty of TiIII
237 A1 --- l_TiIV Upper limit flag on TiIV
238-241 F4.2 --- TiIV ?=- TiIV abundance
243-246 F4.2 --- e_TiIV ?=- uncertainty of TiIV
248 A1 --- l_VIII Upper limit flag on VIII
249-252 F4.2 --- VIII ?=- VIII abundance
254-257 F4.2 --- e_VIII ?=- uncertainty of VIII
259 A1 --- l_CrIII Upper limit flag on CrIII
260-263 F4.2 --- CrIII ?=- CrIII abundance
265-268 F4.2 --- e_CrIII ?=- uncertainty of CrIII
270 A1 --- l_FeIII Upper limit flag on FeIII
271-274 F4.2 --- FeIII ?=- FeIII abundance
276-279 F4.2 --- e_FeIII ?=- uncertainty of FeIII
281 A1 --- l_CoIII Upper limit flag on CoIII
282-285 F4.2 --- CoIII ?=- CoIII abundance
287-290 F4.2 --- e_CoIII ?=- uncertainty of CoIII
292 A1 --- l_ZnIII Upper limit flag on ZnIII
293-296 F4.2 --- ZnIII ?=- ZnIII abundance
298-301 F4.2 --- e_ZnIII ?=- uncertainty of ZnIII
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Note (1): Notes as follows:
r = Radial velocity variable sdB
1 = Long-period pulsator of sdBVs-type
s = Short-period pulsator of sdBVr-type
p(X) = Peculiar line profiles detected for lines of ion X
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Acknowledgements:
Stephan Geier, sgeier (at)eso.org
References:
Geier et al., Paper I 2010A&A...519A..25G 2010A&A...519A..25G
Geier & Heber, Paper II 2012A&A...543A.149G 2012A&A...543A.149G
(End) Stephan Geier [ESO Garching, Germany], Patricia Vannier [CDS] 26-Nov-2012