J/A+A/586/A87 Center-to-limb polarization of FGK stars (Kostogryz+, 2016)
Center-to-limb variation of intensity and polarization in continuum spectra of
FGK stars for spherical atmospheres.
Kostogryz N.M., Milic I., Berdyugina S.V., Hauschildt P.H.
<Astron. Astrophys. 586, A87 (2016)>
=2016A&A...586A..87K 2016A&A...586A..87K (SIMBAD/NED BibCode)
ADC_Keywords: Models, atmosphere ; Polarization ; Stars, late-type
Keywords: polarization - radiative transfer - scattering - stars: atmosphere -
methods: numerical
Abstract:
One of the necessary parameters needed for the interpretation of the
light curves of transiting exoplanets or eclipsing binary stars (as
well as interferometric measurements of a star or microlensing events)
is how the intensity and polarization of light changes from the center
to the limb of a star. Scattering and absorption processes in the
stellar atmosphere affect both the center-to-limb variation of
intensity (CLVI) and polarization (CLVP). In this paper, we present a
study of the CLVI and CLVP in continuum spectra, taking into
consideration the different contributions of scattering and absorption
opacity for a variety of spectral type stars with spherical
atmospheres.
We solve the radiative transfer equation for polarized light in the
presence of a continuum scattering, taking into consideration the
spherical model of a stellar atmosphere. To cross-check our results,
we developed two independent codes that are based on Feautrier and
short characteristics methods, respectively,
We calculate the center-to-limb variation of intensity (CLVI) and
polarization (CLVP) in continuum for the Phoenix grid of spherical
stellar model atmospheres for a range of effective temperatures
(4000-7000K), gravities (logg=1.0-5.5), and wavelengths
(4000-7000Å). In addition, we present several tests of our codes
and compare our calculations for the solar atmosphere with published
photometric and polarimetric measurements. We also show that our two
codes provide similar results in all considered cases.
Description:
Calculated center-to-limb variations of intensity (limb darkening) for
different stellar parameters with spherical 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. The parameters of spherical Phoenix
stellar model atmospheres we considered here are the following:
effective temperature is in the range of 4000K-7000K with the step
of 100K and for logg=1.0-5.5 with the step of 0.5. All calculations
are made for such wavelengths: 4000Å, 4500Å, 5000Å, 6000Å,
7000Å. We also present the position of the stellar limb and
calculated stellar radius.
Calculated center-to-limb variations of polarization (CLVP) for
different stellar parameters with spherical 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. The parameters of spherical Phoenix model
atmosphere we considered here are the following: effective temperature
is in the range of 4000K-7000 K with the step of 100K and for
logg=1.0-5.5 with the step of 0.5. All calculations are made for such
wavelengths: 4000Å, 4500Å, 5000Å, 6000Å, 7000Å. We also
present the position of the stellar limb.
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
table1.dat 114 1549 Calculated center-to-limb variation of intensity
for different stellar parameters
table2.dat 108 1550 Calculated center-to-limb variation of
polarization for different stellar parameters
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See also:
J/A+A/575/A89 : Center-to-limb polarization of FGK stars (Kostogryz+, 2015)
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
6- 9 I4 K Teff [4000/7000] Effective temperature
11- 13 F3.1 --- logg [1/5.5] Surface gravity
15- 18 F4.2 --- mulimb [0.03/0.37] Position of the stellar limb
20- 24 F5.2 km Rstar Calculated stellar radius
26- 33 E8.3 --- LD01 [0/1] Limb darkening at µ=0.01, I(mu)/I(1.0)
35- 42 E8.3 --- LD04 [0/1] Limb darkening at µ=0.04, I(mu)/I(1.0)
44- 51 E8.3 --- LD09 [0/1] Limb darkening at µ=0.09, I(mu)/I(1.0)
53- 60 E8.3 --- LD16 [0/1] Limb darkening at µ=0.16, I(mu)/I(1.0)
62- 69 E8.3 --- LD24 [0/1] Limb darkening at µ=0.24, I(mu)/I(1.0)
71- 78 E8.3 --- LD35 [0/1] Limb darkening at µ=0.35, I(mu)/I(1.0)
80- 87 E8.3 --- LD46 [0/1] Limb darkening at µ=0.46, I(mu)/I(1.0)
89- 96 E8.3 --- LD58 [0/1] Limb darkening at µ=0.58, I(mu)/I(1.0)
98-105 E8.3 --- LD72 [0/1] Limb darkening at µ=0.72, I(mu)/I(1.0)
107-114 E8.3 --- LD86 [0/1] Limb darkening at µ=0.86, I(mu)/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
6- 9 I4 K Teff [4000/7000] Effective temperature
11- 13 F3.1 --- logg [1/5.5] Surface gravity
15- 18 F4.2 --- mulimb [0.03/0.37] Position of the stellar limb
20- 27 F8.6 --- LD01 [0/1] Limb darkening at µ=0.01, I(mu)/I(1.0)
29- 36 F8.6 --- LD04 [0/1] Limb darkening at µ=0.04, I(mu)/I(1.0)
38- 45 F8.6 --- LD09 [0/1] Limb darkening at µ=0.09, I(mu)/I(1.0)
47- 54 F8.6 --- LD16 [0/1] Limb darkening at µ=0.16, I(mu)/I(1.0)
56- 63 F8.6 --- LD24 [0/1] Limb darkening at µ=0.24, I(mu)/I(1.0)
65- 72 F8.6 --- LD35 [0/1] Limb darkening at µ=0.35, I(mu)/I(1.0)
74- 81 F8.6 --- LD46 [0/1] Limb darkening at µ=0.46, I(mu)/I(1.0)
83- 90 F8.6 --- LD58 [0/1] Limb darkening at µ=0.58, I(mu)/I(1.0)
92- 99 F8.6 --- LD72 [0/1] Limb darkening at µ=0.72, I(mu)/I(1.0)
101-108 F8.6 --- LD86 [0/1] Limb darkening at µ=0.86, I(mu)/I(1.0)
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Acknowledgements:
Nadia Kostogryz, kostogryz(at)kis.uni-freiburg.de
Kiepenheuer-Institut fuer Sonnenphysik
(End) Nadia Kostogryz [KIS], Patricia Vannier [CDS] 27-Jan-2016