J/A+A/575/A89 Center-to-limb polarization of FGK stars (Kostogryz+, 2015)
Center-to-limb polarization in continuum spectra of F, G, K stars.
Kostogryz N.M., Berdyugina S.V.
<Astron. Astrophys. 575, A89 (2015)>
=2015A&A...575A..89K 2015A&A...575A..89K
ADC_Keywords: Models, atmosphere ; Polarization ; Stars, late-type
Keywords: polarization - radiative transfer - scattering - stars: atmosphere -
methods: numerical
Abstract:
Scattering and absorption processes in stellar atmosphere act the
center-to-limb variations of the intensity (CLVI) and the linear
polarization (CLVP) of stellar radiation.
There are several theoretical and observational studies of CLVI using
different stellar models, however, most studies of CLVP have
concentrated on the solar atmosphere and have not considered the CLVP
in cooler non-gray stellar atmospheres at all. In this paper, we
present a theoretical study of the CLV of the intensity and the linear
polarization in continuum spectra of different spectral type stars.
We solve the radiative transfer equations for polarized light
iteratively assuming no magnetic field and considering a planeparallel
model atmospheres and various opacities.
Description:
The stellar parameters we considered here are the following: effective
temperature is in the range of 4500K-6900K with the step of 100K and
for logg=3.0, 3.5, 4.0, 4.5, 5.0. All calculations are made for such
wavelengths: 4000Å, 4500Å, 5000Å, 6000Å, 7000Å.
table1.dat:
Calculated center-to-limb variations of intensity (limb darkening) for
different stellar parameters with plane-parallel atmosphere model
approximation. All intensities are normalized to the intensity in the
center of stellar disks, therefore, in the centre of the disks
(mu=1.0), I(mu)/I(1.0)=1.0.
table2.dat:
Calculated center-to-limb variations of linear polarization (Stokes
parameter Q/I) for different stellar parameters with plane-parallel
atmosphere model approximation. The radiation coming from the centre
of the stellar disk is nonpolarized, so all values of Q/I(1.0)=0.0.
table3.dat:
Calculated polynomial coefficients of center-to-limb variations of
intensity (limb darkening) fits for different stellar parameters with
plane-parallel atmosphere model approximation.
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
table1.dat 83 625 Calculated center-to-limb variation of intensity
for different stellar parameters
table2.dat 113 625 Calculated center-to-limb variation of linear
polarization for different stellar parameters
table3.dat 52 625 Coefficients of polynomial fits of calculated limb
darkening curves for different stellar parameters
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See also:
J/AJ/106/2096 : Limb-darkening coefficients in binaries (Van Hamme 1993)
J/A+A/510/A21 : Stellar Limb-Darkening Coefficients (Sing, 2010)
J/A+A/529/A75 : Limb-darkening coefficients (Claret+, 2011)
J/A+A/546/A14 : Limb-darkening for CoRoT, Kepler, Spitzer (Claret+, 2012)
J/A+A/552/A16 : Limb-darkening for CoRoT, Kepler, Spitzer. II. (Claret+, 2013)
J/ApJ/766/3 : Limb-darkening coefficients for eclipsing WD (Gianninas+ 2013)
Byte-by-byte Description of file: table1.dat
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Bytes Format Units Label Explanations
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1- 4 I4 0.1nm lambda [4000/7000] Wavelength (Å)
6- 9 I4 K Teff [4500/6900] Effective temperature
11- 13 F3.1 [cm/s2] logg [3/5] Surface gravity
15- 20 F6.4 --- LD10 [0/1] Limb darkening at µ=0.10, I(µ)/I(1.0)
22- 27 F6.4 --- LD15 [0/1] Limb darkening at µ=0.15, I(µ)/I(1.0)
29- 34 F6.4 --- LD20 [0/1] Limb darkening at µ=0.20, I(µ)/I(1.0)
36- 41 F6.4 --- LD25 [0/1] Limb darkening at µ=0.25, I(µ)/I(1.0)
43- 48 F6.4 --- LD30 [0/1] Limb darkening at µ=0.30, I(µ)/I(1.0)
50- 55 F6.4 --- LD35 [0/1] Limb darkening at µ=0.35, I(µ)/I(1.0)
57- 62 F6.4 --- LD40 [0/1] Limb darkening at µ=0.40, I(µ)/I(1.0)
64- 69 F6.4 --- LD50 [0/1] Limb darkening at µ=0.50, I(µ)/I(1.0)
71- 76 F6.4 --- LD70 [0/1] Limb darkening at µ=0.70, I(µ)/I(1.0)
78- 83 F6.4 --- LD90 [0/1] Limb darkening at µ=0.90, I(µ)/I(1.0)
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Byte-by-byte Description of file: table2.dat
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Bytes Format Units Label Explanations
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1- 4 I4 0.1nm lambda [4000/7000] Wavelength (Å)
6- 9 I4 K Teff [4500/6900] Effective temperature
11- 13 F3.1 [cm/s2] logg [3/5] Surface gravity
15- 23 F9.7 --- NS10 [0/0.025] Normalized Stokes parameter Q/I
at µ=0.1, Q(µ)/I(µ)
25- 33 F9.7 --- NS15 [0/0.016] Normalized Stokes parameter Q/I
at µ=0.15, Q(µ)/I(µ)
35- 43 F9.7 --- NS20 [0/0.011] Normalized Stokes parameter Q/I
at µ=0.2, Q(µ)/I(µ)
45- 53 F9.7 --- NS25 [0/0.01] Normalized Stokes parameter Q/I
at µ=0.25, Q(µ)/I(µ)
55- 63 F9.7 --- NS30 [0/0.006] Normalized Stokes parameter Q/I
at µ=0.3, Q(µ)/I(µ)
65- 73 F9.7 --- NS35 [0/0.006] Normalized Stokes parameter Q/I
at µ=0.35, Q(µ)/I(µ)
75- 83 F9.7 --- NS40 [0/0.005] Normalized Stokes parameter Q/I
at µ=0.4, Q(µ)/I(µ)
85- 93 F9.7 --- NS50 [0/0.003] Normalized Stokes parameter Q/I
at µ=0.5, Q(µ)/I(µ)
95-103 F9.7 --- NS70 [0/0.001] Normalized Stokes parameter Q/I
at µ=0.7, Q(µ)/I(µ)
105-113 F9.7 --- NS90 [0/0.001] Normalized Stokes parameter Q/I
at µ=0.9, Q(µ)/I(µ)
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Byte-by-byte Description of file: table3.dat
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Bytes Format Units Label Explanations
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1- 4 I4 0.1nm lambda [4000/7000] Wavelength {lamdba} (Å)
6- 9 I4 K Teff [4500/6900] Effective temperature
11- 13 F3.1 [cm/s2] logg [3/5] Surface gravity
15- 20 F6.4 --- a1 [0.08/0.4] 1st polynomial coefficient a1 (1)
22- 28 F7.4 --- a2 [-0.4/0.6] 2nd polynomial coefficient a2 (1)
30- 35 F6.4 --- a3 [0.1/2.0] 3d polynomial coefficient a2 (1)
37- 43 F7.4 --- a4 [-1/0.2] 4th polynomial coefficient a4 (1)
45- 52 F8.6 --- sigma [0/0.000355] Deviation error of calculated
CLVI from polynomial fitted curves
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Note (1): coefficients of center-to-limb variations of the intensity
I(µ)/I(1) = Σai µi/2
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Acknowledgements:
Nadia Kostogryz, ,
Svetlana Berdyugina, ,
Kiepenheuer-Institut fuer Sonnenphysik
(End) N. Kostogryz, S. Berdyugina, [KIS], Patricia Vannier [CDS] 27-Feb-2015