2017A&A...601A...6K


Query : 2017A&A...601A...6K

2017A&A...601A...6K - Astronomy and Astrophysics, volume 601A, 6-6 (2017/5-1)

Polarimetry of transiting planets: Differences between plane-parallel and spherical host star atmosphere models.

KOSTOGRYZ N.M., YAKOBCHUK T.M., BERDYUGINA S.V. and MILIC I.

Abstract (from CDS):

Context. To properly interpret photometric and polarimetric observations of exoplanetary transits, accurate calculations of center-to-limb variations of intensity and linear polarization of the host star are needed. These variations, in turn, depend on the choice of geometry of stellar atmosphere.
Aims. We want to understand the dependence of the flux and the polarization curves during a transit on the choice of the applied approximation for the stellar atmosphere: spherical and plane-parallel. We examine whether simpler plane-parallel models of stellar atmospheres are good enough to interpret the flux and the polarization light curves during planetary transits, or whether more complicated spherical models should be used.
Methods. Linear polarization during a transit appears because a planet eclipses a stellar disk and thus breaks left-right symmetry. We calculate the flux and the polarization variations during a transit with given center-to-limb variations of intensity and polarization.
Results. We calculate the flux and the polarization variations during transit for a sample of 405 extrasolar systems. Most of them show higher transit polarization for the spherical stellar atmosphere. Our calculations reveal a group of exoplanetary systems that demonstrates lower maximum polarization during the transits with spherical model atmospheres of host stars with effective temperatures of Teff=4400-5400K and surface gravity of logg=4.45-4.65 than that obtained with plane-parallel atmospheres. Moreover, we have found two trends of the transit polarization. The first trend is a decrease in the polarization calculated with spherical model atmosphere of host stars with effective temperatures Teff=3500-5100K, and the second shows an increase in the polarization for host stars with Teff=5100-7000K. These trends can be explained by the relative variation of temperature and pressure dependences in the plane-parallel and spherical model atmospheres.
Conclusions. For most cases of known transiting systems the plane-parallel approximation of stellar model atmospheres may be safely used for calculation of the flux and the polarization curves because the difference between two models is tiny. However, there are some examples where the spherical model atmospheres are necessary to get proper results, such as the systems with grazing transits, with Earth-size planets, or for the hot host stars with effective temperatures higher than 6000K.

Abstract Copyright: © ESO, 2017

Journal keyword(s): polarization - methods: numerical - planetary systems - planetary systems

Simbad objects: 15

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Number of rows : 15
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 HD 15082b Pl 02 26 51.0582746497 +37 33 01.737746137           ~ 292 1
2 * bet Per EB* 03 08 10.1324535 +40 57 20.328013 1.70 2.07 2.12 2.08 2.11 B8V 1188 1
3 HD 33643b Pl 05 13 10.9287552017 +33 19 05.403226195           ~ 43 0
4 HATS-6 * 05 52 35.2366980288 -19 01 53.970810276   16.664 15.160     M1V 19 0
5 HAT-P-54 * 06 39 35.5181974296 +25 28 57.156510144   14.832 13.505     ~ 18 0
6 HD 80606b Pl 09 22 37.5769478105 +50 36 13.434928660           ~ 301 1
7 WASP-43 PM* 10 19 38.0088913464 -09 48 22.605801336   13.4 12.4 12.08 11.10 K7V 122 1
8 Qatar 2 PM* 13 50 37.4100326640 -06 48 14.421574044   14.0   13.45   K5V 60 1
9 Kepler-447 Ro* 19 01 04.4556648384 +48 33 35.945205516           G5 41 0
10 Kepler-447b Pl 19 01 04.4557486819 +48 33 35.944635820           ~ 35 0
11 Kepler-45 Ro* 19 31 29.4966491088 +41 03 51.356401092     16.88 16.63   M1V 83 1
12 HD 189733 BY* 20 00 43.7129433648 +22 42 39.073143456 9.241 8.578 7.648 7.126 6.68 K2V 820 1
13 HD 189733b Pl 20 00 43.7130382888 +22 42 39.071811263           ~ 1304 1
14 WASP-80 PM* 20 12 40.1693365800 -02 08 39.187438476   12.810 11.939 11.510 10.279 K7V-M0V 57 1
15 HD 209458b Pl 22 03 10.7729598762 +18 53 03.548248479           ~ 1723 1

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2022.11.30-19:08:52

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