J/A+A/597/A137 HD 123999 and Alpha Cen A and B OIFITS files (Kervella+, 2017)
The radii and limb darkenings of Alpha Centauri A and B.
Kervella P., Bigot L., Gallenne A., Thevenin F.
<Astron. Astrophys. 597, A137 (2017)>
=2017A&A...597A.137K 2017A&A...597A.137K (SIMBAD/NED BibCode)
ADC_Keywords: Interferometry ; Stars, bright ; Stars, double and multiple
Keywords: stars: individual: alpha Centauri - techniques: interferometric -
stars: solar-type - stars: fundamental parameters -
stars: binaries: visual
Abstract:
The photospheric radius is one of the fundamental parameters governing
the radiative equilibrium of a star. We report new observations of the
nearest solar-type stars Alpha Centauri A (G2V) and B (K1V) with the
VLTI/PIONIER optical interferometer. The combination of four
configurations of the VLTI enable us to measure simultaneously the
limb darkened angular diameter thetaLD and the limb darkening
parameters of the two solar-type stars in the near-infrared H band
(lambda=1.65um). We obtain photospheric angular diameters of
θLD(A)=8.502±0.038mas (0.43%) and
θLD(B)=5.999±0.025mas (0.42%), through the adjustment of a
power law limb darkening model. We find H band power law exponents of
α(A)=0.1404±0.0050 (3.6%) and α(B)=0.1545±0.0044
(2.8%), which closely bracket the observed solar value
(alpha☉=0.15027). Combined with the parallax pi=747.17±0.61mas
determined by Kervella et al. (2016), we derive linear radii of
RA=1.2234±0.0053R☉ (0.43%) and RB=0.8632±0.0037R☉
(0.43%). The power law exponents that we derive for the two stars
indicate a significantly weaker limb darkening than predicted by both
1D and 3D stellar atmosphere models. As this discrepancy is also
observed on the near-infrared limb darkening profile of the Sun, an
improvement of the calibration of stellar atmosphere models is clearly
needed. The reported PIONIER visibility measurements of Alpha Cen A
and B provide a robust basis to validate the future evolutions of
these models.
Description:
The files contain all the PIONIER calibrated interferometric data
obtained on Alpha Centauri A and B, as well as on the dimensional
calibrator HD 123999. The data files follow the OIFITS standard of
optical interferometry as defined by Pauls et al.
(2005PASP..117.1255P 2005PASP..117.1255P).
Objects:
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RA (2000) DE Designation(s)
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14 10 23.93 +25 05 30.0 HD 123999 = * 12 Boo
14 39 36.49 -60 50 02.4 alpha Cen A = HD 128620
14 39 35.06 -60 50 15.1 alpha Cen B = HD 128621
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File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
list.dat 139 13 List of OIFITS files
oifits/* . 13 Individual OIFITS files
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See also:
J/A+A/586/A35 : TZ For OIFITS files (Gallenne+, 2016)
Byte-by-byte Description of file: list.dat
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Bytes Format Units Label Explanations
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1- 11 A11 --- Name Star name
13- 21 F9.5 deg RAdeg OI target right ascension (J2000)
23- 31 F9.5 deg DEdeg OI target declination (J2000)
33- 36 I4 km EffWave1 First Effective wavelength
38- 41 I4 km EffWave2 Second Effective wavelength
43- 46 I4 km EffWave3 Third Effective wavelength
48- 51 I4 km EffWave4 Fourth Effective wavelength
53- 56 I4 km EffWave5 Fith Effective wavelength
58- 61 I4 km EffWave6 sixth Effective wavelength
63- 66 F4.1 km EffBand Effective band
68- 69 I2 Kibyte size Size of OIFITS file
71- 95 A25 --- FileName Name of OIFITS file, in subdirectory oifits
97-139 A43 --- Title Title of the OIFITS file
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Acknowledgements:
Pierre Kervella, pierre.kervella(at)obspm.fr
(End) Patricia Vannier [CDS] 12-Oct-2016