2009A&A...503..973L


Query : 2009A&A...503..973L

2009A&A...503..973L - Astronomy and Astrophysics, volume 503, 973-984 (2009/9-1)

Atmospheric velocity fields in tepid main sequence stars.

LANDSTREET J.D., KUPKA F., FORD H.A., OFFICER T., SIGUT T.A.A., SILAJ J., STRASSER S. and TOWNSHEND A.

Abstract (from CDS):

The line profiles of the stars with vesini below a few km/s can reveal direct signatures of local velocity fields such as convection in stellar atmospheres. This effect is well established in cool main sequence stars, and has been detected and studied in three A stars. This paper reports observations of main sequence B, A and F stars (1) to identify additional stars with sufficiently low values of vesini to search for spectral line profile signatures of local velocity fields and (2) to explore how the signatures of the local velocity fields in the atmosphere depend on stellar parameters such as effective temperature and peculiarity type. We have carried out a spectroscopic survey of B and A stars of low vesini at high resolution. Comparison of model spectra with those observed allows us to detect signatures of the local velocity fields such as asymmetric excess line wing absorption, best-fit vesini parameter values that are found to be larger for strong lines than for weak lines, and discrepancies between observed and modelled line profile shapes. Symptoms of local atmospheric velocity fields are always detected through a non-zero microturbulence parameter for main sequence stars having Te below about 10000K, but not for hotter stars. Direct line profile tracers of the atmospheric velocity field are found in six very sharp-lined stars in addition to the three reported earlier. Direct signatures of velocity fields are found to occur in A stars with and without the Am chemical peculiarities, although the amplitude of the effects seems larger in Am stars. Velocity fields are also directly detected in spectral line profiles of A and early F supergiants, but without significant line asymmetries. We confirm that several atmospheric velocity field signatures, particularly excess line wing absorption which is stronger in the blue line wing than in the red, are detectable in the spectral lines of main sequence A stars of sufficiently low ve sin i. We triple the sample of A stars known to show these effects, which are found both in Am and normal A stars. We argue that the observed line distortions are probably due to convective motions reaching the atmosphere. These data still have not been satisfactorily explained by models of atmospheric convection, including numerical simulations.

Abstract Copyright:

Journal keyword(s): convection - stars: atmospheres - stars: chemically peculiar - stars: abundances - stars: rotation - line: profiles

Simbad objects: 42

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Number of rows : 42
N Identifier Otype ICRS (J2000)
RA
ICRS (J2000)
DEC
Mag U Mag B Mag V Mag R Mag I Sp type #ref
1850 - 2022
#notes
1 HD 2421 SB* 00 28 13.6587644888 +44 23 40.108531657   5.207 5.173     A2Vs 80 0
2 HD 3883 ** 00 41 36.0369780076 +24 37 44.432978078   6.333 6.046     kA5hF1mF2 118 0
3 * 53 Tau a2* 04 19 26.0972533052 +21 08 32.310998300   5.413 5.482     B9Vsp 260 0
4 * del03 Tau a2* 04 25 29.38340 +17 55 40.4579   4.369 4.298 6.18 4.24 A2IV-Vs 388 0
5 * 13 Mon * 06 32 54.2284145046 +07 19 58.668312797 4.30 4.50 4.50 4.40 4.36 A0I 190 1
6 * gam Gem SB* 06 37 42.71050 +16 23 57.4095 1.98 1.92 1.92 1.86 1.87 A1.5IV+ 493 0
7 * alf CMa SB* 06 45 08.91728 -16 42 58.0171 -1.51 -1.46 -1.46 -1.46 -1.43 A0mA1Va 1445 0
8 * alf CMi SB* 07 39 18.11950 +05 13 29.9552 0.82 0.79 0.37 -0.05 -0.28 F5IV-V+DQZ 1800 0
9 HD 72660 * 08 34 01.6143548549 -02 09 05.594896178   5.797 5.792     A0V 120 0
10 * 40 Cnc BS* 08 40 11.4527985964 +19 58 16.085231072   6.62 6.61     A1V 145 0
11 * kap Cnc a2* 09 07 44.8101438776 +10 40 05.527005225 4.70 5.13 5.24     B8IIImnp 356 0
12 * tet UMa PM* 09 32 51.4338939 +51 40 38.281102 3.67 3.64 3.18 2.74 2.47 F7V 393 0
13 * eta Leo * 10 07 19.9518606 +16 45 45.580270 3.17 3.39 3.41 3.32 3.35 A0Ib 326 0
14 * o Leo SB* 11 55 40.5342459259 +15 38 48.556539104   5.632 5.522     A3V 156 0
15 * 8 Com * 12 19 19.1930734072 +23 02 04.821330146   6.416 6.220     A8m 130 0
16 HD 108642 SB* 12 28 38.1502568007 +26 13 37.024817133   6.71 6.54     A2m 139 0
17 * 22 Com * 12 33 34.2192186914 +24 16 58.742920851   6.363 6.243     A4Vm 143 0
18 * tet Vir ** 13 09 56.9843568248 -05 32 20.465727623   4.385 4.397     A1IVs 245 0
19 * 3 Cen ** 13 51 49.60136 -32 59 38.7067           B5III+B9IV 244 0
20 * sig Boo PM* 14 34 40.8171808483 +29 44 42.463685978 4.76 4.84 4.47 4.13 3.94 F4VkF2mF1 584 0
21 HD 132955 * 15 02 59.2752145072 -32 38 35.855774022 4.69 5.319 5.437     B3V 88 0
22 * gam Ser PM* 15 56 27.1826948 +15 39 41.820500 4.31 4.34 3.84 3.37 3.13 F6V 539 0
23 * omi Sco V* 16 20 38.1806792 -24 10 09.549111 5.99 5.40 4.57 3.69 2.93 A5II 247 0
24 * n Her * 16 32 35.6857867065 +05 31 16.396436559 5.39 5.57 5.63     B9.5III 113 0
25 HD 157486 * 17 25 02.6671440070 -34 41 45.832671247   6.170 6.142     ApSiCr 27 0
26 * iot Her bC* 17 39 27.8860861 +46 00 22.800110 2.940 3.630 3.800     B3IV 436 1
27 HD 170580 ** 18 30 05.1199518627 +04 03 55.270633622 6.29 6.80 6.69     B2V 97 0
28 HD 172910 Pu* 18 44 19.3590068 -35 38 31.154592 3.97 4.69 4.87 5.02 5.18 B2V 87 1
29 HD 174179 Be* 18 47 57.3737736182 +31 45 24.609739171 5.25 5.910 6.054     B3IVp 52 0
30 HD 175640 * 18 56 22.6598248501 -01 47 59.505133114 5.86 6.149 6.196     B9IIIpHgMnEu 141 0
31 * ksi01 Sgr * 18 57 20.4767796018 -20 39 22.871889929   5.140 5.054     B9/A0Ib 47 0
32 HD 178329 SB* 19 06 17.0359265622 +41 24 49.611093636 5.66 6.345 6.496     B3V 68 0
33 HD 178065 SB* 19 07 09.0290270150 +00 38 27.495717066 6.31 6.584 6.538     B9III 95 0
34 HD 181470 SB* 19 19 01.1490839163 +37 26 43.245158883 6.190 6.260 6.260     A0III 77 0
35 * nu. Aql * 19 26 31.0891514908 +00 20 18.860635125 5.71 5.31 4.72 4.21 3.77 F2Ib 129 0
36 * tet Cyg PM* 19 36 26.5343563 +50 13 15.964573 4.83 4.86 4.48 4.13 3.92 F3+V 333 1
37 * 46 Aql * 19 42 12.8124227379 +12 11 35.738183084   6.234 6.321     B9III 111 0
38 * 15 Vul a2* 20 01 06.0484585 +27 45 12.863884   4.829 4.651     A4III 230 0
39 * bet02 Cap ** 20 20 46.5502323959 -14 47 05.511257716   6.08 6.10     B9/A0III/IV 137 0
40 * 21 Peg * 22 03 19.0321963138 +11 23 11.575087477   5.762 5.822     B9.5V 140 0
41 * 32 Aqr SB* 22 04 47.4219684698 -00 54 22.846937982   5.519 5.271     A5IV 174 0
42 * omi Peg * 22 41 45.3989328992 +29 18 27.554214525 4.77 4.78 4.79 4.75 4.77 A1IV 273 0

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2021.11.28-16:54:47

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