J/MNRAS/517/1849 Analysis of Gaia RV standards (Boulkaboul+, 2022)
Analysis of Gaia radial-velocity standards:
stability and new substellar companion candidates.
Boulkaboul A., Damerdji Y., Morel T., Fremat Y., Soubiran C., Gosset E.,
Abdelatif T.E.
<Mon. Not. R. Astron. Soc. 517, 1849-1866 (2022)>
=2022MNRAS.517.1849B 2022MNRAS.517.1849B (SIMBAD/NED BibCode)
ADC_Keywords: Stars, fundamental ; Stars, standard ; Radial velocities ; Optical
Keywords: techniques: radial velocities - stars: activity -
(stars:) binaries: spectroscopic - stars: fundamental parameters
Abstract:
Our main aim is to test the non-variability of the radial velocity
(RV) of a sample of 2351 standard stars used for wavelength
calibration of the Radial Velocity Spectrometer (RVS) instrument
onboard Gaia . In this paper, we present the spectroscopic analysis of
these stars with the determination of their physical parameters by
matching observed and synthetic spectra. Weestimate the offset between
different instruments after determining the shift between measured and
archived RVs since the instrument pipelines use various numerical
masks. Through the confirmation of the stability of the target RVs, we
find 68 stars with a long-term variation having an acceleration that
exceeds 10m/s/yr. This suggests a barycentric reflex motion caused by
a companion. As activity phenomena may be the source of periodic and
trend-like RV variations in stars with putative planetary companions,
we analysed various activity indicators in order to check their
correlations to the RV changes. Among the trend stars, 18 have a trend
model scatter greater than 100m/s^ over a time span from 10 to 12 yr.
We also confirm that six stars with known substellar companions have a
total model scatter, 3σ, exceeding the threshold set by Gaia,
that is, 300m/s. In addition, TYC8963-01543-1, an SB2 star, has data
scatter σ=176.6m/s. Four more other stars are revealed to be
variable after combining data from different instruments. Despite the
presence of low-amplitude changes, a very large fraction of our sample
(98.8 per cent) appears suitable as RV calibrators for Gaia RVS.
Description:
We present stellar parameters and mean RV of 2351 stars determined
from spectra fitting of HARPS, SOPHIE, ELODIE, and NARVAL targets. We
tabulate the orthogonal regression coefficients of the fit between our
measured and T20 RVs.
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
table1.dat 118 3521 List of targets: coordinates, spectral type from
CS18 (Soubiran et al., 2018, Cat. J/A+A/616/A7)
table2.dat 97 3521 Stellar parameters of the best-fitting
synthetic spectra
table3.dat 78 840 Orthogonal regression coefficients of the fit
between our measured and T20 RVs
and number of analyzed spectra
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See also:
J/A+A/616/A7 : Gaia DR2 radial velocity standard stars catalog
(Soubiran+, 2018)
J/A+A/636/A74 : HARPS radial velocity database (Trifonov+, 2020)
Byte-by-byte Description of file: table1.dat
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Bytes Format Units Label Explanations
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1- 15 A15 --- Name HIP/TYC target name
18- 27 F10.6 deg RAdeg Right ascension (ICRS) at Epoch
30- 38 F9.5 deg DEdeg Declination (ICRS) at Epoch
41 A1 --- --- [J]
42- 47 F6.1 yr Epoch Specific epoch
50- 54 F5.2 mag Vmag Visual apparent magnitude
57- 71 A15 --- SpType Spectral type
74- 80 F7.2 d T Total time span
83- 88 F6.2 --- min(SNR) Minimum values of signal to noise ratio
91- 97 F7.2 --- max(SNR) Maximum values of signal to noise ratio
100-103 I4 --- Ninit Total number of analysed spectra
106-109 I4 --- N Final number of measurements after filtering
112-115 I4 --- Nadd Number of additional spectra compared to
CS18 (Soubiran et al., 2018, Cat. J/A+A/616/A7)
118 A1 --- Inst The instrument used (H, S, E, N for
HARPS, SOPHIE, ELODIE and NARVAL
respectively)
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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- 15 A15 --- Name HIP/TYC target name
18- 21 I4 K Teff ?=- Effective temperature
24- 26 F3.1 [cm/s2] logg ?=- Surface gravity
29- 33 F5.2 [-] [Fe/H] ?=- Metallicity
36- 39 F4.1 [-] [alpha/Fe] ?=- ratio of α elements
41 A1 --- l_vbroad Limit flag on vbroad
42- 47 F6.3 km/s vbroad ?=- rotation velocity
48 A1 --- n_vbroad [c]
49 A1 --- levbroad Limit flag on e_vbroad
50- 55 F6.3 km/s e_vbroad ?=- Uncertainty on vbroad
59- 67 F9.4 km/s RVmean ?=- This work mean measured RV
70- 75 F6.4 km/s e_RVmean ?=- Uncertainty on mean measured RV
78- 86 F9.4 km/s RVmedCS18 Median RV from CS18
89- 94 F6.4 km/s e_RVmedCS18 Uncertainty on median RV from CS18
97 A1 --- Inst [HSEN] The instrument used (1)
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Note (1): instrument used as follows:
H = HARPS
S = SOPHIE
E = ELODIE
N = NARVAL
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Byte-by-byte Description of file: table3.dat
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Bytes Format Units Label Explanations
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1- 15 A15 --- Name HIP/TYC target name
18- 23 F6.3 --- a-pre ?=- Slope HARPS fibre pre-upgrade
26- 30 F5.3 --- e_a-pre ?=- Error of slope pre-upgrade
33- 40 F8.3 km/s b-pre ?=- Y-intercept HARPS fibre pre-upgrade
43- 47 F5.3 km/s e_b-pre ?=- Error of Y-intercept pre-upgrade
50- 55 F6.3 --- a-post ?=- Slope HARPS fibre post-upgrade
58- 62 F5.3 --- e_a-post ?=- Error of slope post-upgrade
64- 71 F8.3 km/s b-post ?=- Y-intercept HARPS fibre post-upgrade
74- 78 F5.3 km/s e_b-post ?=- Error of Y-intercept post-upgrade
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Acknowledgements:
Amina Boulkaboul, boulkaboulamina(at)gmail.com
(End) Patricia Vannier [CDS] 31-Oct-2022