2014A&A...561A.147B


Query : 2014A&A...561A.147B

2014A&A...561A.147B - Astronomy and Astrophysics, volume 561A, 147-147 (2014/1-1)

Discovery of secular variations in the atmospheric abundances of magnetic Ap stars.

BAILEY J.D., LANDSTREET J.D. and BAGNULO S.

Abstract (from CDS):

The stars of the middle main sequence have relatively quiescent outer layers, and unusual chemical abundance patterns may develop in their atmospheres. The presence of chemical peculiarities reveal the action of such subsurface phenomena as gravitational settling and radiatively driven levitation of trace elements, and their competition with mixing processes such as turbulent diffusion. At present, little is known about the time evolution of these anomalous abundances, nor about the role that diffusion may play in maintaining them, during the main sequence lifetime of such a star. We want to establish whether abundance peculiarities change as stars evolve on the main sequence, and provide observational constraints to diffusion theory. We have performed spectral analysis of 15 magnetic Bp stars that are members of open clusters (and thus have well-known ages), with masses between about 3 and 4 M. For each star, we measured the abundances of He, O, Mg, Si, Ti, Cr, Fe, Pr and Nd. We have discovered the systematic time evolution of trace elements through the main-sequence lifetime of magnetic chemically peculiar stars as their atmospheres cool and evolve towards lower gravity. During the main sequence lifetime, we observe clear and systematic variations in the atmospheric abundances of He, Ti, Cr, Fe, Pr and Nd. For all these elements, except He, the atmospheric abundances decrease with age. The abundances of Fe-peak elements converge towards solar values, while the rare-earth elements converge towards values at least 100 times more abundant than in the Sun. Helium is always underabundant compared to the Sun, evolving from about 1% up to 10% of the solar He abundance. We have attempted to interpret the observed abundance variations in the context of radiatively driven diffusion theory, which appears to provide a framework to understand some, but not all, of the anomalous abundance levels and variations that we observe.

Abstract Copyright:

Journal keyword(s): stars: magnetic field - stars: chemically peculiar - stars: abundances - stars: atmospheres - stars: evolution

Simbad objects: 27

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Number of rows : 27
N Identifier Otype ICRS (J2000)
RA
ICRS (J2000)
DEC
Mag U Mag B Mag V Mag R Mag I Sp type #ref
1850 - 2023
#notes
1 V* V1356 Ori a2* 06 08 24.1247449056 +13 56 47.872901400   10.0 10.855 10.76   A0V 45 0
2 NGC 2169 OpC 06 08 30 +13 57.1   5.99 5.9     ~ 152 0
3 NGC 2232 OpC 06 27 33 -04 44.9           ~ 161 0
4 V* V682 Mon a2* 06 28 10.7659506576 -04 53 56.511231684   7.85 7.97     ApSi 86 0
5 NGC 2301 OpC 06 51 46 +00 27.9   6.30 6.0     ~ 149 0
6 BD+00 1659 * 06 51 46.3780372968 +00 27 56.650078872   9.01 9.15     A0p 28 0
7 NGC 2422 OpC 07 36 35 -14 29.3           ~ 233 0
8 HD 61045 ** 07 36 47.1653427840 -14 33 41.765206968   7.92 7.98     B8pSi 56 0
9 NGC 2451 Cl* 07 45.4 -37 58           ~ 156 1
10 V* OX Pup a2* 07 47 05.7565479792 -39 19 51.585710340   6.171 6.322     ApSi 81 0
11 IC 2391 OpC 08 41 10 -52 59.5           ~ 785 0
12 V* KT Vel a2* 08 42 18.9920732 -53 06 00.201557 4.79 5.340 5.474     B9III(pSi) 99 0
13 NGC 3114 OpC 10 02 13 -60 02.5   4.47 4.2     ~ 182 0
14 V* V424 Car a2* 10 02 39.8186174520 -59 57 54.678266820   9.74 9.86     B7/8 39 1
15 V* HZ Lup a2* 15 06 33.1978166352 -30 55 06.533677056   5.893 5.977     ApSi 102 0
16 V* HR Lup a2* 15 08 12.1238757000 -40 35 02.155417224 5.25 5.65 5.79     B8IVSi 162 1
17 NAME Upper Centaurus Lupus As* 15 24 -41.9           ~ 428 1
18 NAME Upper Sco Association As* 16 12 -23.4           ~ 1236 1
19 V* V933 Sco a2* 16 20 05.4927999744 -20 03 23.030685720   7.56 7.40     B9II/III 183 0
20 V* V958 Sco a2* 17 53 15.9791676888 -34 37 15.060028836   7.01 6.99     B8/9III 74 0
21 NGC 6475 OpC 17 53 47 -34 50.5           ~ 359 0
22 V* V951 Sco a2* 17 53 58.1358478008 -34 49 51.800052684   6.43 6.42     kB6hA0VHeA0pSiCr 97 0
23 CPD-19 6897 SB* 18 31 44.5599164880 -19 07 13.582426260 10.5 10.59 10.18     ~ 35 0
24 IC 4725 OpC 18 31 45 -19 06.8           ~ 208 0
25 NGC 7243 OpC 22 15 09 +49 49.8   6.54 6.4     ~ 110 0
26 BD+49 3789 * 22 15 11.4029031720 +49 45 30.438333648   10.17 10.06     B7III 27 0
27 AG+49 1940 * 22 15 38.8832130984 +49 57 16.214027796   10.05 10.09     A0Vp 31 0

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2022.11.28-12:18:13

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