J/A+A/625/A33 Radial velocity time series of HD 122563 (Creevey+, 2019)
First detection of oscillations in the Halo giant HD 122563:
Validation of seismic scaling relations and new parameters.
Creevey O., Grundahl F., Thevenin F., Corsaro E., Palle P.L., Salabert D.,
Pichon B., Collet R., Bigot L., Antoci V., Andersen M.F.
<Astron. Astrophys. 625, A33 (2019)>
=2019A&A...625A..33C 2019A&A...625A..33C (SIMBAD/NED BibCode)
ADC_Keywords: Asteroseismology ; Stars, giant ; Stars, population II ;
Stars, metal-deficient ; Stars, nearby ; Radial velocities
Keywords: asteroseismology - methods: observational -
stars: fundamental parameters - stars: individual: HD 122563 -
stars: distances - stars: Population II
Abstract:
The nearby metal-poor giant HD122563 is an important astrophysical
laboratory in which to test stellar atmospheric and interior physics.
It is also a benchmark star for which to calibrate methods to apply to
large scale surveys. Recently it has been remeasured using various
methodologies given the new high precision instruments at our
disposal. However, inconsistencies in the observations and models have
been found.
In order to better characterise this star using complementary
techniques we have been measuring its radial velocities since 2016
using the Hertzsprung telescope (SONG network node) in order to detect
oscillations.
In this work we report the first detections of sun-like oscillations
in this star, and to our knowledge, a detection in the most metal-poor
giant to date. We applied the classical seismic scaling relation to
derive a new surface gravity for HD122563 of logg=1.39±0.01dex.
Reasonable constraints on the mass imposed by its PopII giant
classification then yields a radius of 30.8±1.0R☉. By coupling
this new radius with recent interferometric measurements we infer a
distance to the star of 306±9pc. This result places it further away
than was previously thought and is inconsistent with the Hipparcos
parallax. Independent data from the Gaia mission corroborate the
distance hypothesis (dGDR2=290±5pc), and thus the updated
fundamental parameters.
We confirm the validity of the classical seismic scaling relation for
surface gravity in metal-poor and evolved star regimes. The remaining
discrepancy of 0.04dex between loggGDR2 (=1.43±0.03) reduces to
0.02dex by applying corrections to the scaling relations based on the
mean molecular weight and adiabatic exponent. The new constraints on
the HR diagram (L*v=381±26L☉) significantly reduce the
disagreement between the stellar parameters and evolution models,
however, a discrepancy of the order of 150K still exists. Fine-tuned
stellar evolution calculations show that this discrepancy can be
reconciled by changing the mixing-length parameter by an amount
(-0.35) that is in agreement with predictions from recent 3D
simulations and empirical results. Asteroseismic measurements are
continuing, and analysis of the full frequency data complemented by a
distance estimate promises to bring important constraints on our
understanding of this star and of the accurate calibration of the
seismic scaling relations in this regime.
Description:
Radial velocity time series of HD 122563 are presented. These data
were obtained using the Hertzsprung telescope, a node of the Stellar
Observations Network Group (SONG) network, located at the Observatorio
del Teide on Tenerife, Spain.
Objects:
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RA (2000) DE Designation(s)
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14 02 31.85 +09 41 09.9 HD 122563 = HIP 68594
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File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
table1.dat 50 387 Radial velocities of HD 122563
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See also:
J/ApJ/819/103 : Abundances of HD 122563 and HD 140283 (Afsar+, 2016)
Byte-by-byte Description of file: table1.dat
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Bytes Format Units Label Explanations
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1- 18 F18.10 d JD Barycentric Julian Date
19- 34 F16.6 m/s RV Barycentric corrected radial velocity
35- 50 F16.6 m/s e_RV Uncertainty on RV (1)
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Note (1): This is the uncertainty derived and assigned by the authors to each
radial velocity point.
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History:
From Orlagh Creevey, orlagh.creevey(at)oca.eu
Acknowledgements:
These data were obtained with the Hertzsprung SONG telescope operated
on the Spanish Observatorio del Teide on the island of Tenerife by the
Aarhus and Copenhagen Universities and by the Instituto de Astrofisica
de Canarias. Support for the construction of the Hertzsprung SONG
Telescope from the Instituto de Astrofisica de Canarias, the Villum
Foundation, the Carlsberg Foundation and the Independent Research Fund
Denmark is gratefully acknowledged.
(End) Patricia Vannier [CDS] 23-Apr-2019