J/A+A/658/A115 Proxima Cen ESPRESSO RV and FWHM (Faria+, 2022)
A candidate short-period sub-Earth orbiting Proxima Centauri.
Faria J.P., Suarez Mascareno A., Figueira P., Silva A.M., Damasso M.,
Demangeon O., Pepe F., Santos N.C., Rebolo R., Cristiani S., Adibekyan V.,
Alibert Y., Allart R., Barros S.C.C., Cabral A., D'Odorico V.,
Di Marcantonio P., Dumusque X., Ehrenreich D., Gonzalez Hernandez J.I.,
Hara N., Lillo-Box J., Lo Curto G., Lovis C., Martins C.J.A.P., Megevand D.,
Mehner A., Micela G., Molaro P., Nunes N.J., Palle E., Poretti E.,
Sousa S.G., Sozzetti A., Tabernero H., Udry S., Zapatero Osorio M.R.
<Astron. Astrophys. 658, A115 (2022)>
=2022A&A...658A.115F 2022A&A...658A.115F (SIMBAD/NED BibCode)
ADC_Keywords: Stars, dwarfs ; Exoplanets ; Radial velocities ; Optical
Keywords: techniques: radial velocities - stars: activity -
stars: individual: Proxima
Abstract:
Proxima Centauri is the closest star to the Sun. This small, low-mass,
mid M dwarf is known to host an Earth-mass exoplanet with an orbital
period of 11.2 days within the habitable zone, as well as a
long-period planet candidate with an orbital period of close to 5yr.
We report on the analysis of a large set of observations taken with
the ESPRESSO spectrograph at the aimed at a thorough evaluation of the
presence of a third low-mass planetary companion, which started
emerging during a previous campaign. Radial velocities (RVs) were
calculated using both a cross-correlation function (CCF) and a
template matching approach. The RV analysis includes a component to
model Proxima`s activity using a Gaussian process (GP). We use the
CCF's full width at half maximum to help constrain the GP, and we
study other simultaneous observables as activity indicators in order
to assess the nature of any potential RV signals. We detect a signal
at 5.12±0.04 days with a semi-amplitude of 39±7cm/s. The analysis
of subsets of the ESPRESSO data, the activity indicators, and
chromatic RVs suggest that this signal is not caused by stellar
variability but instead by a planetary companion with a minimum mass
of 0.26±0.05M☉ (about twice the mass of Mars) orbiting at
0.029 au from the star. The orbital eccentricity is well constrained
and compatible with a circular orbit.
Description:
To add to the 67 observations reported in SM2020, we obtained 52 new
ESPRESSO spectra of Proxima, for a total of 117 observations spread
over 99 individual nights from 2019-02-10 to 2021-05-06. The
measurements were taken in ESPRESSO`s high resolution mode (HR21) with
an exposure time of 900s. We used the Fabry Perot (FP) for
simultaneous calibration, which allows the instrumental drift to be
monitored with a precision better than 10cm/s.
We exclude three observations that were affected by instrumental
issues. On the night of 25 April 2019, there was a cooling water
temperature increase, which propagated inside the spectrograph. The
drift measured on the red detector was 0.007pixel (i.e. 3m/s). This
spectrum also shows a signal-to-noise ratio below 1. On the
observation of 31 July 2019, the FP exposure was saturated, most
likely due to an issue with the neutral density filters. In this
situation, the contamination by the FP light on the charge-coupled
device may be large, and the drift measurement is likely unreliable.
Finally, on the night of 10 April 2021, the reported temperature of
the atmospheric dispersion compensator (ADC) was 0K, revealing an
issue with the correction. The barycentric Julian days of these three
excluded spectra are 2458598.523839, 2458695.52992, and
2459314.583084.
In June 2019, ESPRESSO underwent an intervention to update the fibre
link, which improved the instrument's efficiency by up to 50% (Pepe et
al., 2021A&A...645A..96P 2021A&A...645A..96P). This intervention introduced an RV offset,
leading us to consider separate ESPRESSO18 and ESPRESSO19 datasets.
More recently, operations at Paranal were interrupted due to the
COVID-19 pandemic and ESPRESSO was taken out of operations between 24
March 2020 and 24 December 2020. This led to a large gap in the
observations after the initial campaign. Moreover, a change in one of
the calibration lamps after the ramp-up of the instrument is likely to
have introduced another RV offset. Therefore, we consider an
independent ESPRESSO21 dataset for data obtained after the ramp-up.
In summary, we have 114 available RVs, divided between ESPRESSO18 (50
points), ESPRESSO19 (15 points), and ESPRESSO21 (49 points) subsets.
Objects:
---------------------------------------------
RA (2000) DE Designation(s)
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14 29 42.95 -62 40 46.2 Proxima = Gl 551
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File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
table.dat 81 114 Proxima Cen ESPRESSO RV and FWHM
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See also:
J/A+A/534/A133 : Proxima Cen chromospheric emission lines (Fuhrmeister+, 2011)
J/A+A/603/A58 : Full spectrum of Proxima Centauri (Ribas+, 2017)
J/AJ/153/93 : MOST photometry of Proxima (Kipping+, 2017)
J/AJ/155/12 : Photometry of Proxima Centauri observed by BSST (Liu+, 2018)
J/A+A/626/A111 : Proxima Cen flare activity temporal changes (Pavlenko+, 2019)
J/AJ/157/226 : Proxima Centauri photometry from 2006 to 2017 (Feliz+, 2019)
J/A+A/638/A120 : SPHERE maps around Proxima Cen (Gratton+, 2020)
J/A+A/639/A77 : Proxima Cen RV, FWHM and fluxes (Suarez Mascareno+, 2020)
Byte-by-byte Description of file: table.dat
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Bytes Format Units Label Explanations
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1- 14 F14.6 d BJD Barycentric Julian date
16- 27 F12.5 m/s RV Radial velocity from CCF
29- 35 F7.5 m/s e_RV Uncertainty on radial velocity from CCF
37- 46 F10.5 m/s FWHM Full width at half maximum of the CCF
48- 54 F7.5 m/s e_FWHM Uncertainty on FWHM of the CCF
56- 67 F12.5 m/s RVTM Radial velocity from template-matching (TM)
69- 75 F7.5 m/s e_RVTM Uncertainty on radial velocity from TM
77- 81 A5 --- Subset Subset of ESPRESSO data (ESP18, ESP19 or ESP21)
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Acknowledgements:
Joao Faria, joao.faria(at)astro.up.pt
(End) Patricia Vannier [CDS] 21-Feb-2022