J/A+A/690/A125 Gaia parallax uncertainties and RHD simulations (Beguin+, 2024)
Retrieving stellar parameters and dynamics of AGB stars with Gaia parallax
measurements and CO5BOLD RHD simulations.
Beguin E,. Chiavassa A., Ahmad A., Freytag B., Uttenthaler S.
<Astron. Astrophys. 690, A125 (2024)>
=2024A&A...690A.125B 2024A&A...690A.125B (SIMBAD/NED BibCode)
ADC_Keywords: Stars, giant ; Parallaxes, trigonometric ; Models ;
Effective temperatures
Keywords: hydrodynamics - astrometry - parallaxes - stars: AGB and post-AGB -
stars: atmospheres
Abstract:
The complex dynamics of asymptotic giant branch (AGB) stars and the
resulting stellar winds have a significant impact on the measurements
of stellar parameters and amplify their uncertainties.
Three-dimensional (3D) radiative hydrodynamic (RHD) simulations of
convection suggest that convection-related structures at the surface
of AGB star affect the photocentre displacement and the parallax
uncertainty measured by Gaia. We explore the impact of the convection
on the photocentre variability and aim to establish analytical laws
between photocentre displacement and stellar parameters to retrieve
such parameters from the parallax uncertainty. We used a selection of
31 RHD simulations with CO5BOLD and the post-processing radiative
transfer code Optim3D to compute intensity maps in the Gaia G band
[320-1050nm]. From these maps, we calculated the photocentre position
and temporal fluctuations. We then compared the synthetic standard
deviation to the parallax uncertainty of a sample of 53 Mira stars
observed with Gaia. The simulations show a displacement of the
photocentre across the surface ranging from 4 to 13% of the
corresponding stellar radius, in agreement with previous studies. We
provide an analytical law relating the pulsation period of the
simulations and the photocentre displacement as well as the pulsation
period and stellar parameters. By combining these laws, we retrieve
the surface gravity, the effective temperature, and the radius for the
stars in our sample. Our analysis highlights an original procedure to
retrieve stellar parameters by using both state-of-the-art 3D
numerical simulations of AGB stellar convection and parallax
observations of AGB stars. This will help us refine our understanding
of these giants.
Description:
The table A.2 contains star information from the Gaia archive
(name, parallax...) or from computations, for example: the pulsation
period and luminosity through the study of light curves and spectral
energy distribution. Thanks to state-of-the-art simulations of AGB
convection, we were able to compare photocentre displacement with GDR3
parallax uncertainty and to provide analytical laws between stellar
parameters and parallax uncertainty. We then gave a direct estimation
of the Miras' stellar parameters (temperature, radius, surface
gravity) from the parallax uncertainty in table A.3.
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
tablea1.dat 84 31 RHD simulation parameters
tablea2.dat 65 53 Parameters of the sample Miras
tablea3.dat 109 53 Stellar parameters of the Miras inferred
from the simulations
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See also:
I/355 : Gaia DR3 Part 1. Main source (Gaia Collaboration, 2022)
J/A+A/622/A120 : Mass loss from Miras with and without Tc (Uttenthaler, 2019)
Byte-by-byte Description of file: tablea1.dat
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Bytes Format Units Label Explanations
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1- 2 I2 --- Id Model identification number (1)
4- 15 A12 --- Sim Simulation name
17- 19 F3.1 Msun M* Stellar mass
21- 25 I5 Lsun L* Average emitted luminosity
27- 29 I3 Rsun R* Average approximate stellar radius
31- 34 I4 K Teff Effective temperature
36- 40 F5.2 [cm/s2] logg Surface gravity
42- 46 F5.2 yr tavg Stellar time used for the averaging of
the rest of the quantities
48- 50 I3 d P Pulsation period
52- 54 I3 d e_P Pulsation period error
56- 61 F6.3 au Px Time-averaged position Px
62 A1 --- n_Px [a] Note on Px (2)
64- 69 F6.3 au Py Time-averaged position Py
70 A1 --- n_Py [a] Note on Px (2)
72- 76 F5.3 au sigP Standard deviation of the photocentre
displacement in AU
77 A1 --- n_sigP [a] Note on Px sigP (2)
79- 83 F5.2 --- sipPp Standard deviation of the photocentre
displacement in percentage of stellar radius
84 A1 --- n_sipPp [a] Note on Px (2)
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Note (1): The simulations 1-12 are the new models presented in this work;
the simulations 13-23 are presented in Ahmad et al. (2023A&A...669A..49A 2023A&A...669A..49A)
and the simulations 24-31 are presented in Freytag et al.
(2012JCoPh.231..919F 2012JCoPh.231..919F) and Chiavassa et al. (2018A&A...617L...1C 2018A&A...617L...1C).
Note (2): a: data come from the previous analysis of Chiavassa et al.
(2018A&A...617L...1C 2018A&A...617L...1C).
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Byte-by-byte Description of file: tablea2.dat
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Bytes Format Units Label Explanations
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1- 8 A8 --- Name Miras' name
10- 12 I3 d Pobs Pulsation period obtained from light curves (1)
14- 18 F5.3 --- RUWE RUWE
20- 21 I2 --- Nper Number of visibility periods used in the
astrometric solution (2)
23- 25 I3 --- Ngood Total number of good observations along-scan
(astrometricngoodobsal) by Gaia to compute
the astrometric solution
27- 30 I4 Lsun L* Luminosity
32- 36 I5 Lsun e_L* Negative luminosity uncertainty
38- 41 I4 Lsun E_L* Positive luminosity uncertainty
43- 47 F5.3 mas plx Gaia DR3 parallax
49- 53 F5.3 mas plxcorr Corrected Gaia DR3 parallax according to
Lindegren et al. (2021A&A...649A...4L 2021A&A...649A...4L)
55- 59 F5.3 mas e_plx Parallax uncertainty
61- 65 A5 --- Pop Population membership based on a study of
stellar total space velocity according to
Chen et al. (2021ApJ...909..115C 2021ApJ...909..115C),
halo stars are more metal poor
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Note (1): From Merchan-Benitez et al. (2023A&A...672A.165M 2023A&A...672A.165M,
Cat. J/A+A/672/A165). Pulsation period uncertainty is assumed to be 2:4% of
the corresponding
Note (2): a visibility period consists of a group of observations separated from
other groups by at least 4 days. A high number of periods is a indicator of a
well-observed source while a value smaller than 10 indicates that the
calculated parallax could be more vulnerable to errors
(visibilityperiodsused in the Gaia archive).
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Byte-by-byte Description of file: tablea3.dat
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Bytes Format Units Label Explanations
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1- 8 A8 --- Name Name of the Mira star
10- 12 I3 d Pobs Pulsation period (1)
14- 18 F5.3 --- RUWE Goodness of the astrometry fit
from Gaia DR3
20- 21 I2 --- Nper Nb of visibility periods for astrometry
from Gaia DR3
23- 25 I3 --- Ngood Total nb of good observations along-scan
from Gaia DR3
27- 30 I4 Lsun L* Computed luminosity value (2)
32- 35 I4 Lsun e_L* Negative luminosity uncertainty (2)
37- 40 I4 Lsun E_L* Positive luminosity uncertainty (2)
43- 47 F5.3 mas plx Gaia DR3 parallax
49- 53 F5.3 mas plxcorr Corrected parallax, see Lindegren et al.,
2021A&A...649A...4L 2021A&A...649A...4L
55- 59 F5.3 mas e_plx GDR3 parallax uncertainty
61- 65 A5 --- Pop Population membership, see Chen et al.,
2021ApJ...909..115C 2021ApJ...909..115C, Cat. J/ApJ/909/115
67- 69 I3 d P10 Pulsation period inferred from simulations
at 1.0M☉
71- 72 I2 % DP10 Relative difference between Pobs and P10
74- 76 I3 d P15 Pulsation period inferred from simulations
at 1.5M☉
78- 79 I2 % DP15 Relative difference between Pobs and P15
81- 85 F5.2 [cm/s2] logg10 Surface gravity from simulations
at 1.0M☉
87- 91 F5.2 [cm/s2] logg15 Surface gravity from simulations
at 1.5M☉
93- 95 I3 Rsun R10 Radius inferred from simulations
at 1.0M☉
97- 99 I3 Rsun R15 Radius inferred from simulations
at 1.5M☉
101-104 I4 K Teff10 Effective temperature from simulations
at 1.0M☉
106-109 I4 K Teff15 Effective temperature from simulations
at 1.5M☉
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Note (1): Pulsation periods were taken mainly from Templeton et al.
(2005AJ....130..776T 2005AJ....130..776T, Cat. J/AJ/130/776) where available, or were also
collected from VizieR. See Section 3.1 for more details. In particular, the
period variability is assumed to be of the order of 2.4% of the respective
pulsation period (Merchan-Benitez et al., 2023A&A...672A.165M 2023A&A...672A.165M,
Cat. J/A+A/672/A165).
Note (2): The luminosities were computed from a numerical integration under the
photometric spectral energy distribution between the B-band and the IRAS 60um
band or, if available, the Atari 90um band. See Section 3.1 for more details.
Here, the lower bound of the luminosity is L*-e_L* and the upper bound
is L*+E_L*.
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Acknowledgements:
Elysabeth Beguin, elysabeth.beguin(at)oca.eu
(End) Patricia Vannier [CDS] 04-Sep-2024