J/A+A/645/A124 Inclinations for RGBs from Kepler asteroseismology (Gehan+, 2021)
Automated approach to measure stellar inclinations:
validation through large-scale measurements on the red giant branch.
Gehan C., Mosser B., Michel E., Cunha M.S.
<Astron. Astrophys. 645, A124 (2021)>
=2021A&A...645A.124G 2021A&A...645A.124G (SIMBAD/NED BibCode)
ADC_Keywords: Asteroseismology ; Stars, giant
Keywords: asteroseismology - methods: data analysis - techniques: photometric -
stars: interiors - stars: low-mass - stars: solar-type
Abstract:
Measuring stellar inclinations is fundamental to understand planetary
formation and dynamics as well as physical conditions during star
formation. Oscillation spectra of red giant stars exhibit mixed modes
that have both a gravity component from the radiative interior and a
pressure component from the convective envelope. Gravity-dominated
(g-m) mixed modes split by rotation are well separated inside
frequency spectra, making possible accurate measurements of stellar
inclinations.
This work aims at developing an automated and general approach to
measure stellar inclinations, that can be applied to any solar-type
pulsator for which oscillation modes are identified, and at validating
it using red giant branch stars observed by Kepler.
The stellar inclination impacts the visibility of oscillation modes
with azimuthal orders m=(-1,0,+1). We use the mean
height-to-background ratio of dipole mixed modes with different
azimuthal orders to measure stellar inclinations. The underlying
statistical distribution of inclinations is recovered in an unbiased
way using a probability density function for the stellar inclination
angle.
We derive stellar inclination measurements for 1140 stars on the red
giant branch, for which Gehan et al. (2018A&A...616A..24G 2018A&A...616A..24G, Cat.
J/A+A/616/A24) have identified the azimuthal order of dipole g-m mixed
modes. Raw measured inclinations exhibit strong deviation with respect
to isotropy which is expected for random inclinations over the sky.
When taking uncertainties into account, the reconstructed distribution
of inclinations actually follows the expected isotropic distribution
of the rotational axis.
This work highlights the biases that affect inclination measurements
and provides the way to infer their underlying statistical
distribution. When the star is seen either pole-on or equator-on,
measurements are challenging and result in a biased distribution.
Correcting biases that appear at the low- and high inclination regimes
allows us to recover the underlying inclination distribution.
Description:
Inclination angles, associated uncertainties and number of visible
rotational components in the oscillation spectrum of the stars
analysed in the paper. Each star is identified with its KIC number
(Kepler Input Catalog, Cat. V/133).
Inclination angles were measured for 1140 red giant branch stars
analysed by Gehan et al. (2018, Cat. J/A+A/616/A24) using
gravity-dominated mixed modes.
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
incl.dat 25 1140 Inclination angles and number of visible
rotational components
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See also:
V/133 : Kepler Input Catalog (Kepler Mission Team, 2009)
J/A+A/540/A143 : Oscillations of red giants observed by Kepler (Mosser+, 2012)
J/A+A/588/A87 : Seismic global parameters of 6111 KIC (Vrard+, 2016)
J/A+A/616/A24 : Rotation in RGBs from Kepler asteroseismology (Gehan+, 2018)
Byte-by-byte Description of file: incl.dat
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Bytes Format Units Label Explanations
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1- 8 I8 --- KIC KIC number
10- 13 F4.1 deg i Inclination angle
15- 18 F4.1 deg E_i Positive uncertainty on i
20- 23 F4.1 deg e_i Negative uncertainty on i
25 I1 --- Ncomp Number of visible rotational components
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Acknowledgements:
Charlotte Gehan, charlotte.gehan(at)astro.up.pt
References:
Mosser et al., Paper I 2015A&A...584A..50M 2015A&A...584A..50M
Vrad et al., Paper II 2016A&A...588A..87V 2016A&A...588A..87V, Cat. J/A+A/588/A87
Gehan et al., Paper III 2018A&A...616A..24G 2018A&A...616A..24G, Cat. J/A+A/616/A24
(End) Charlotte Gehan [IA/CAUP], Patricia Vannier [CDS] 04-Nov-2020