J/A+A/690/A79 Barnard's star radial velocity curves (Gonzalez Hernandez+, 2024)
A sub-Earth-mass planet orbiting Barnard's star.
Gonzalez Hernandez J.I., Suarez Mascareno A., Silva A.M., Stefanov A.K.,
Faria J.P., Tabernero H.M., Sozzetti A., Rebolo R., Pepe F., Santos N.C.,
Cristiani S., Lovis C., Dumusque X., Figueira P., Lillo-Box J., Nari N.,
Benatti S., Hobson M.J., Castro-Gonzalez A., Allart R., Passegger V.M.,
Zapatero Osorio M.-R., Adibekyan V., Alibert Y., Allende Prieto C.,
Bouchy F., Damasso M., D'Odorico V., Di Marcantonio P., Ehrenreich D.,
Lo Curto G., Genova Santos R., Martins C.J.A.P., Mehner A., Micela G.,
Molaro P., Nunes N., Palle E., Sousa S.G., Udry S.
<Astron. Astrophys. 690, A79 (2024)>
=2024A&A...690A..79G 2024A&A...690A..79G (SIMBAD/NED BibCode)
ADC_Keywords: Stars, double and multiple ; Exoplanets ; Radial velocities ;
Optical
Keywords: techniques: radial velocity - techniques: spectroscopic -
planets and satellites: terrestrial planets - stars: activity -
stars: low-mass - stars: individual: GJ 699
Abstract:
ESPRESSO guaranteed time observations (GTO) at the 8.2m-VLT telescope
aimed at finding Earth-like exoplanets in the habitable zone of nearby
stars. Barnard's star is a primary target within the ESPRESSO GTO as
it is the second closest neighbour to our Sun after the alpha Centauri
stellar system.
We present here a large set of 156 ESPRESSO observations of
Barnard's star taken over four years with the goal of exploring
periods shorter than 50 days, thus including the habitable zone.
The analysis of ESPRESSO data using Gaussian process (GP) to model
stellar activity suggests a long-term activity cycle at 3200d and
confirms stellar activity due to rotation at 140d as the dominant
source of RV variations. These results are supported by adding
publicly available HARPS, HARPS-N and CARMENES data. ESPRESSO RVs do
not support the existence of the previously reported candidate planet
at 233 d. Results. ESPRESSO RVs reveal, after subtracting the GP
model, several short period candidate planet signals at periods 3.15d,
4.12d, 2.34d and 6.74d. We confirm the 3.15d signal as a sub-Earth
mass planet, with a semi-amplitude of 55±7cm/s, leading to a planet
minimum mass mpsini of 0.37±0.05M⊕, about three times the
mass of Mars. ESPRESSO RVs provide hints of a candidate system with
four sub-Earth mass planets in circular orbits with semi-amplitudes
from 20 to 47cm/s, thus corresponding to minimum masses in the range
0.17-0.32M⊕.
The sub-Earth mass planet at 3.1533±0.0006d is in a closely circular
orbit with a semi-major axis of 0.0229±0.0003AU, thus located inner
to the habitable zone of Barnard's star, with an equilibrium
temperature of 400K. The other three candidate signals will require
additional ESPRESSO observations to be confirmed as a compact
short-period planet system orbiting Barnard's star inner to its
habitable zone.
Description:
Table 5: Radial velocity (RV) and full width at half maximum (FWHM)
measurements of ESPRESSO datasets used in Fig. 12 (model E1e in Table
3 with prior and posterior parameters given in Table 6) in the paper.
ESPRESSO data is based on Guaranteed Time Observations collected at
the European Southern Observatory under ESO programmes 1102.C-0744,
1104.C-0350, 106.21M2.001, 106.21M2.004, 106.21M2.006, 108.22GM.001,
108.2254.001, 108.2254.003, 108.2254.004, 108.2254.006, 110.24CD.001,
110.24CD.003 by the ESPRESSO Consortium. Template-matching (TM) RVs
are computed with S-BART code (Silva et al., 2022A&A...663A.143S 2022A&A...663A.143S) and
FWHMs are computed from DRS cross-correlation function (CCF) profiles.
RVs are corrected for barycentric Earth radial velocity (BERV) and for
secular acceleration (SA).
Labels corresponding to the different spectra are given in column
Subset as E18 and E19 for ESPRESSO before and after the intervention
in June 2019 (Pepe et al., 2021A&A...645A..96P 2021A&A...645A..96P), respectively.
Both the RV and FHWM data have been corrected by subtracting the
median value of the measurements for each subset (E18 and E19).
Table D3: Radial velocity (RV) and full width at half maximum (FWHM)
measurements of all datasets used in Fig. D.5 (model L1 in Table 3
with prior and posterior parameters given in Table D.1) in the paper.
ESPRESSO data is based on Guaranteed Time Observations collected at
the European Southern Observatory under ESO programs 1102.C-0744,
1104.C-0350, 106.21M2.001, 106.21M2.004, 106.21M2.006, 108.22GM.001,
108.2254.001, 108.2254.003, 108.2254.004, 108.2254.006, 110.24CD.001,
110.24CD.003 by the ESPRESSO Consortium. HARPS ESO programs:
099.C-0880, 0101.D-0494, 1102.C-0339, 110.242T.001. HARPS-N programs:
CAT16A_109, CAT17A_38, CAT18A_115, CAT20A_121. CARMENES data are
provided in the public DR1 in Ribas et al. (2023A&A...670A.139R 2023A&A...670A.139R).
Template-matching (TM) RVs are computed with S-BART code (Silva et
al., 2022A&A...663A.143S 2022A&A...663A.143S) for ESPRESSO, HARPS and HARPS-N data, and
with SERVAL (Zechmeister et al., 2018A&A...609A..12Z 2018A&A...609A..12Z) code for
CARMENES data. RVs are corrected for barycentric Earth radial velocity
(BERV) and for secular acceleration (SA).
FWHMs are computed from DRS cross-correlation function (CCF) profiles
for ESPRESSO, HARPS and HARPS-N data, and with the RACCOON code
(Lafarga et al., 2020A&A...636A..36L 2020A&A...636A..36L) for CARMENES data.
Labels corresponding to the different spectra are given in column
Subset as CAR, E18, E19, H15 and HAN for CARMENES, ESPRESSO before and
after the intervention in June 2019 (Pepe et al.,
2021A&A...645A..96P 2021A&A...645A..96P), HARPS after the intervention in 2015 (Lo Curto
et al., 2015Msngr.162....9L 2015Msngr.162....9L) and HARPS-N, respectively.
Objects:
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RA (2000) DE Designation(s)
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17 57 48.49 +04 41 36.1 Barnard's star = HIP 87937
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File Summary:
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FileName Lrecl Records Explanations
--------------------------------------------------------------------------------
ReadMe 80 . This file
table5.dat 56 149 TM RV and CCF FHWM measurements of
ESPRESSO datasets
tabled3.dat 56 792 TM RV and CCF FHWM measurements of all datasets
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See also:
J/ApJ/764/131 : Long-term monitoring of Barnard's star velocity
(Choi+, 2013)
J/other/Nat/563.365 : Barnard's star radial velocity curve (Ribas+, 2018)
J/AJ/162/61 : Radial velocity follow up of Barnard's star with HPF
(Lubin+, 2021)
Byte-by-byte Description of file: table5.dat tabled3.dat
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Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 12 F12.6 d BJD Barycentric Julian date (BJD-2450000)
14- 22 E9.6 m/s RV Radial velocity from template-matching (TM)
24- 31 F8.6 m/s e_RV Radial velocity from template-matching (TM)
error
33- 42 F10.6 m/s FWHM Full width at half maximum of the CCF
44- 52 F9.6 m/s e_FWHM Full width at half maximum of the CCF error
54- 56 A3 --- Subset Subset of data (1)
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Note (1): Subset of data as follows:
E18 = ESPRESSO before intervention in June 2019
E19 = ESPRESSO after intervention in June 2019
H15 = HARPS after the intervention in 2015
HAN = HARPS-N
Car = CARMENES
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Acknowledgements:
Jonay I. Gonzalez Hernandez, jonay.gonzalez(at)iac.es
References:
Toledo-Padron et al., 2019MNRAS.488.5145T 2019MNRAS.488.5145T,
Stellar activity analysis of Barnard's Star: very slow rotation and
evidence for long-term activity cycle
Artigau et al., 2022AJ....164...84A 2022AJ....164...84A,
Line-by-line Velocity Measurements: an Outlier-resistant Method for
Precision Velocimetry
Fouque et ak., 2023A&A...672A..52F 2023A&A...672A..52F,
The SPIRou legacy survey. Rotation period of quiet M dwarfs from circular
polarization in near-infrared spectral lines: The SPIRou APERO analysis
(End) Patricia Vannier [CDS] 18-Sep-2024