2013A&A...551A..30B


C.D.S. - SIMBAD4 rel 1.7 - 2020.02.27CET03:22:35

2013A&A...551A..30B - Astronomy and Astrophysics, volume 551A, 30-30 (2013/3-1)

Abundances determined using Si II and Si III in B-type stars: evidence for stratification.

BAILEY J.D. and LANDSTREET J.D.

Abstract (from CDS):

It is becoming clear that determination of the abundance of Si using lines of Si ii and Si iii can lead to quite discordant results in mid to late B-type stars. The difference between the Si abundances derived from the two ion states can exceed one dex in some cases. We have carried out a study intended to clarify which kinds of B stars exhibit this discrepancy, to try to identify regularities in the phenomenon, and to explore possible explanations such as abundance stratification by comparing models to observed spectra. We used spectra from the ESPaDOnS spectropolarimeter and FEROS spectrograph, supplemented with spectra from the ESO and ELODIE archives, of magnetic Bp, HgMn, and normal B-type stars ranging in effective temperature from about 10500 to 15000K. Using these spectra, we derived abundances using the spectrum synthesis program zeeman, which can take the influence of magnetic fields into account. For each star, accurate abundances of SiII, SiIII, Ti, Cr, and Fe were derived from two separate ∼100Å windows. SiII abundances were deduced from multiple lines, and SiIII abundances were found using λλ 4552, 4567, and 4574. All magnetic Bp stars in our sample show a discordance between the derived abundances of the first and second ions of silicon, with the latter being between 0.6-1.7dex higher. The same behaviour is observed in the non-magnetic stars but to a much smaller extent: SiIII is enhanced by between 0.3-0.8 dex compared to SiII. We do not detect the discrepancy in three stars, HD 22136 (normal), HD 57608 (HgMn) and HD 27295 (HgMn); these are the only stars in our sample for which the microturbulence parameter is significantly different from zero, and which therefore probably have convection occurring in their atmospheres. We find that vertical stratification of silicon in the atmospheres of B-type stars may provide an explanation of this phenomenon, but our detailed stratification models do not completely explain the discrepancies, which may, in part, be due to non-LTE effects.

Abstract Copyright:

Journal keyword(s): stars: abundances - stars: chemically peculiar - stars: magnetic field - stars: early-type

Simbad objects: 35

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Number of rows : 35

N Identifier Otype ICRS (J2000)
RA
ICRS (J2000)
DEC
Mag U Mag B Mag V Mag R Mag I Sp type #ref
1850 - 2020
#notes
1 V* BM Hyi a2* 01 44 32.9710852435 -61 01 07.340453580   6.71 6.79     ApSi 32 0
2 HD 22136 V* 03 35 58.4899212444 +47 05 27.702423822   6.842 6.873     B8V 84 0
3 * 53 Tau a2* 04 19 26.0972533052 +21 08 32.310998300   5.413 5.482     B9Vsp 253 0
4 V* V682 Mon a2* 06 28 10.7658829483 -04 53 56.509693156   7.85 7.97     ApSi 73 0
5 HD 47116 * 06 36 05.0599673467 -24 07 07.560687323   7.71 7.70     ApSi 27 0
6 * alf CMa SB* 06 45 08.91728 -16 42 58.0171 -1.51 -1.46 -1.46 -1.46 -1.43 A1V+DA 1383 0
7 * 12 CMa a2* 06 47 01.4837300198 -21 00 55.449397291 5.27 5.89 6.08     B7II/III 131 0
8 BD+00 1659 * 06 51 46.3783516269 +00 27 56.651249887   9.01 9.15     A0p 22 0
9 HD 57608 * 07 22 03.4786497202 +00 10 37.637188337 5.62 5.897 5.971     B9III 37 0
10 HD 61045 ** 07 36 47.1655875650 -14 33 41.764393795   7.92 7.98     B8pSi 49 0
11 V* OO Vel a2* 08 40 08.3509993324 -51 56 29.606819775   7.338 7.439     ApSi 35 0
12 V* KT Vel a2* 08 42 18.9920732 -53 06 00.201557 4.79 5.340 5.474     B9III(pSi) 93 0
13 * alf Pyx V* 08 43 35.5375544 -33 11 10.989788 2.65 3.50 3.68 3.76 3.93 B1.5III 195 0
14 * kap Cnc a2* 09 07 44.8101438776 +10 40 05.527005225 4.70 5.13 5.24     B8IIImnp 351 0
15 V* V424 Car a2* 10 02 39.8181995000 -59 57 54.677610604   9.74 9.86     ~ 33 1
16 HD 96446 Pu* 11 06 05.8217576741 -59 56 59.536118851 5.81 6.57 6.69     B2IIIp 148 0
17 V* HR Lup a2* 15 08 12.1245697358 -40 35 02.158712447 5.25 5.65 5.79     B8IVSi 150 1
18 V* NN Aps a2* 15 31 27.1149385254 -71 03 43.664320879   6.76 6.87     Ap(SiCrFe) 83 0
19 V* V933 Sco a2* 16 20 05.4924613867 -20 03 23.032932987   7.56 7.40     B9II/III 172 0
20 * iot Her bC* 17 39 27.8860861 +46 00 22.800110 2.940 3.630 3.800     B3IV 428 1
21 V* V970 Sco a2* 17 39 41.2403913936 -32 17 57.534800537   9.38 9.34     ~ 49 0
22 HD 162586 ** 17 53 19.58018 -34 43 50.9011   6.14 6.17     B3/5III 67 0
23 HD 170054 a2* 18 27 14.6918823386 +06 31 06.962976079   8.19 8.19     ~ 54 0
24 CPD-19 6897 SB* 18 31 44.5599309505 -19 07 13.583630219 10.5 10.59 10.18     ~ 32 0
25 HD 175640 * 18 56 22.6598248501 -01 47 59.505133114 5.86 6.149 6.196     B9IIIpHgMnEu 133 0
26 HD 178065 SB* 19 07 09.0290270150 +00 38 27.495717066 6.31 6.584 6.538     B9III 90 0
27 * 21 Aql a2* 19 13 42.7007857827 +02 17 37.292126394 4.67 5.08 5.15     B7III 225 0
28 * 46 Aql * 19 42 12.8124227379 +12 11 35.738183084   6.234 6.321     B9III 107 0
29 HD 192452 * 20 15 55.2669061891 -26 47 00.002316918   10.26 9.30     G8IIICNIII/IV 5 0
30 * bet02 Cap ** 20 20 46.5502323959 -14 47 05.511257716   6.08 6.10     B9/A0III/IV 132 0
31 * eps Del V* 20 33 12.7719198 +11 18 11.741187 3.43 3.90 4.03 4.05 4.18 B6IV 137 0
32 * 20 Cap a2* 20 59 36.1395419983 -19 02 07.005308649   6.12 6.25     ApSi 77 0
33 BD+49 3789 * 22 15 11.4027837712 +49 45 30.434693269   10.17 10.06     B7III 22 0
34 * iot And * 23 38 08.2012983 +43 16 05.064880 3.90 4.18 4.29 4.29 4.38 B8V 152 0
35 * i03 Aqr Pe* 23 51 21.3383201 -18 54 32.993729 4.62 5.04 5.18     A0VpSiSr 177 0

    Equat.    Gal    SGal    Ecl

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2020.02.27-03:22:35

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