2009A&A...502..253C


Query : 2009A&A...502..253C

2009A&A...502..253C - Astronomy and Astrophysics, volume 502, 253-265 (2009/7-4)

Absolute dimensions of solar-type eclipsing binaries. II. V636 Centauri: a 1.05 m primary with an active, cool, oversize 0.85 m secondary.

CLAUSEN J.V., BRUNTT H., CLARET A., LARSEN A., ANDERSEN J., NORDSTROEM B. and GIMENEZ A.

Abstract (from CDS):

The influence of stellar activity on the fundamental properties of stars around and below 1M is not well understood. Accurate mass, radius, and abundance determinations from solar-type binaries exhibiting various levels of activity are needed for a better insight into the structure and evolution of these stars. We aim to determine absolute dimensions and abundances for the solar-type detached eclipsing binary V636 Cen, and to perform a detailed comparison with results from recent stellar evolutionary models. uvby light curves and uvbyβ standard photometry were obtained with the Stroemgren Automatic Telescope, radial velocity observations with the CORAVEL spectrometer, and high-resolution spectra with the FEROS spectrograph, all at ESO, La Silla. State-of-the-art methods were applied for the photometric and spectroscopic analyses. Masses and radii that are precise to 0.5% have been established for the components of V636 Cen. The 0.85M secondary component is moderately active with starspots and CaII H and K emission, and the 1.05M primary shows signs of activity as well, but at a much lower level. We derive a [Fe/H] abundance of -0.20±0.08 and similar abundances for Si, Ca, Ti, V, Cr, Co, and Ni. Corresponding solar-scaled stellar models are unable to reproduce V636 Cen, especially its secondary component, which is ∼10% larger and ∼400K cooler than predicted. Models adopting significantly lower mixing-length parameters l/Hp remove these discrepancies, seen also for other solar-type binary components. For the observed [Fe/H], Claret models for l/Hp=1.4 (primary) and 1.0 (secondary) reproduce the components of V636Cen at a common age of 1.35Gyr. The orbit is eccentric (e=0.135±0.001), and apsidal motion with a 40% relativistic contribution has been detected. The period is U=5270±335yr, and the inferred mean central density concentration coefficient, log(k2)=-1.61±0.05, agrees marginally with model predictions. The measured rotational velocities, 13.0±0.2 (primary) and 11.2±0.5 (secondary) km/s, are in remarkable agreement with the theoretically predicted pseudo-synchronous velocities, but are about 15% lower than the periastron values. V636Cen and 10 other well-studied inactive and active solar-type binaries suggest that chromospheric activity, and its effect on envelope convection, is likely to cause radius and temperature discrepancies, which can be removed by adjusting the model mixing length parameters downwards. Noting this, the sample may also lend support to theoretical 2D radiation hydrodynamics studies, which predict a slight decrease of the mixing length parameter with increasing temperature/mass for inactive main sequence stars. More binaries are, however, needed for a description/calibration in terms of physical parameters and level of activity.

Abstract Copyright:

Journal keyword(s): stars: evolution - stars: fundamental parameters - Stars: abundances - stars: activity - stars: binaries: eclipsing - techniques: spectroscopic

VizieR on-line data: <Available at CDS (J/A+A/502/253): tablea1.dat>

Simbad objects: 32

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Number of rows : 32
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* UV Psc EB* 01 16 55.1191752816 +06 48 42.131407176   9.73 9.01   8.223 G5(N) 250 0
2 V* AL Ari EB* 02 42 36.3432139104 +12 44 07.817263224   9.69 9.23     F8 29 0
3 BD+17 579 ** 03 34 58.54262 +17 42 38.0564           ~ 32 0
4 BD+17 579A EB* 03 34 58.5443892288 +17 42 38.054792700   11.07 10.14 9.65 8.940 G0V 29 0
5 HD 27130 SB* 04 17 38.9458465152 +16 56 52.187419068   9.075 8.315 8.79   G8V 242 0
6 V* AL Dor SB* 04 46 52.2556041408 -60 36 12.698691444   8.30 7.73     F8V 36 0
7 V* EW Ori SB* 05 20 09.1431629664 +02 02 40.004288664   10.47 9.78     F8 95 0
8 V* V1174 Ori Or* 05 34 27.8529220296 -05 41 37.875014808 16.506 15.070 14.305   12.367 M0 53 0
9 HD 37071 SB* 05 37 32.5090124664 +37 05 12.259074408   8.59 8.05     G0 67 0
10 V* HS Aur SB* 06 51 18.4766820936 +47 40 24.176766540   10.85 10.05     G5(N) 86 0
11 HD 49987 SB* 06 53 37.0214978376 +48 28 55.295848200   9.85 8.72     K0 2 0
12 V* NY Hya SB* 09 21 22.8118162032 -06 40 19.528523004   9.37 8.64     G5V 27 0
13 V* KY Hya SB* 09 22 43.5755817615 -18 10 39.900736735   11.191 10.501 10.416   ~ 6 0
14 V* ZZ UMa SB* 10 30 03.1946894976 +61 48 41.430038256   10.43 9.83     F8 72 0
15 V* UV Leo EB* 10 38 20.7691705464 +14 16 03.663229224   9.62 8.92 9.188 8.194 G0V(N) 259 0
16 V* UW LMi EB* 10 43 30.2042029080 +28 41 09.086259732   8.90 8.32     G0V(N) 39 0
17 V* QR Hya SB* 10 56 31.1510369784 -34 33 50.152797252   9.63 8.399   7.706 G1V 33 0
18 V* V963 Cen SB* 13 18 44.3568297792 -58 16 01.258922892   9.24 8.59     G2V 35 0
19 V* BH Vir RS* 13 58 24.8603543280 -01 39 38.954265912   10.29 9.68   9.047 F6/8V 199 0
20 V* V636 Cen EB* 14 16 57.9122377992 -49 56 42.372930480   9.70 9.09     G0V 92 0
21 * alf Cen ** 14 39 29.71993 -60 49 55.9990   0.4 -0.1     G2V+K1V 913 0
22 V* CV Boo SB* 15 26 19.5363381672 +36 58 53.433780492   11.61 10.99     G3V(N) 76 0
23 V* WZ Oph SB* 17 06 39.0447030672 +07 46 57.800710560   9.66 9.12     F8 120 0
24 V* FL Lyr EB* 19 12 04.8624983832 +46 19 26.867864388   9.91 9.36     F8V 202 0
25 NGC 6791 OpC 19 20 53 +37 46.7   10.52 9.5     ~ 987 0
26 V* V568 Lyr EB* 19 20 57.3346763352 +37 45 36.739962972   18.295   16.823   ~ 42 0
27 V* V442 Cyg EB* 20 27 52.3040139552 +30 47 28.346913456   10.18 9.70     F2 71 0
28 BD+34 4217 EB* 20 58 13.4532832464 +35 10 29.672620140     10.13     G9.5Ve+K3Ve 259 0
29 V* V1061 Cyg EB* 21 07 20.5201575864 +52 02 58.418010528   9.78 9.21     F8 76 0
30 V* VZ Cep SB* 21 50 11.1350311248 +71 26 38.249750076   10.19 9.72     F3+G4 45 0
31 V* RW Lac SB* 22 44 57.1033105152 +49 39 27.512902116   11.23 10.81     F2 71 0
32 V* RT And RS* 23 11 10.0984058784 +53 01 33.031339248   9.58 9.043 8.73   F8V+G0-K1-3V 367 0

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2023.02.04-09:20:26

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