J/A+A/666/A196 Proxima telluric-corrected ESPRESSO RV (Allart+, 2022)
Automatic model-based telluric correction for the ESPRESSO data reduction
software Model description and application to radial velocity computation.
Allart R., Lovis C., Faria J., Dumusque X., Sosnowska D., Figueira P.,
Silva A.M., Mehner A., Pepe F., Cristiani S., Rebolo R., Santos N.C.,
Adibekyan V., Cupani G., Di Marcantonio P., D'Odorico V.,
Gonzalez Hernandez J.I., Martins C.J.A.P., Milakovic D., Nunes N.J.,
Sozzetti A., Suarez Mascareno A., Tabernero H., Zapatero Osorio M.R.
<Astron. Astrophys., 666, A196 (2022)>
=2022A&A...666A.196A 2022A&A...666A.196A (SIMBAD/NED BibCode)
ADC_Keywords: Stars, dwarfs ; Exoplanets ; Radial velocities ; Optical
Keywords: radiative transfer - methods: data analysis -
techniques: radial velocities - techniques: spectroscopic -
planets and satellites: detection
Abstract:
Ground-based high-resolution spectrographs are key instruments for
several astrophysical domains, such as exoplanet studies.
Unfortunately, the observed spectra are contaminated by the Earth's
atmosphere and its large molecular absorption bands. While different
techniques (forward radiative transfer models, principle component
analysis (PCA), or other empirical methods) exist to correct for
telluric lines in exoplanet atmospheric studies, in radial velocity
(RV) studies, telluric lines with an absorption depth of >2% are
generally masked, which poses a problem for faint targets and M dwarfs
as most of their RV content is present where telluric contamination is
important.
We propose a simple telluric model to be embedded in the Echelle
SPectrograph for Rocky Exoplanets and Stable Spectroscopic
Observations (ESPRESSO) data reduction software (DRS). The goal is to
provide telluric-free spectra and enable RV measurements through the
cross-correlation function technique (and others), including spectral
ranges where telluric lines fall. Methods. The model is a line-by-line
radiative transfer code that assumes a single atmospheric layer. We
use the sky conditions and the physical properties of the lines from
the HITRAN database to create the telluric spectrum. This
high-resolution model is then convolved with the instrumental
resolution and sampled to the instrumental wavelength grid. A subset
of selected telluric lines is used to robustly fit the spectrum
through a Levenberg-Marquardt minimization algorithm.
We computed the model to the H2O lines in the spectral range of
ESPRESSO. When applied to stellar spectra from A0- to M5-type stars,
the residuals of the strongest water lines are below the 2%
peak-to-valley (P2V) amplitude for all spectral types, with the
exception of M dwarfs, which are within the pseudo-continuum. We then
determined the RVs from the telluric-corrected ESPRESSO spectra of Tau
Ceti and Proxima. We created telluric-free masks and compared the
obtained RVs with the DRS RVs. In the case of Tau Ceti, we identified
that micro-telluric lines introduce systematics up to an amplitude of
58cm/s and with a period of one year if not corrected. For Proxima,
the impact of micro-telluric lines is negligible due to the low flux
below 5900Å. For late-type stars, the gain in spectral content at
redder wavelengths is equivalent to a gain of 25% in photon noise or a
factor of 1.78 in exposure time. This leads to better constraints on
the semi-amplitude and eccentricity of Proxima d, which was recently
proposed as a planet candidate. Finally, we applied our telluric model
to the O2 γ-band and we obtained residuals below the 2% P2V
amplitude.Conclusions. We propose a simple telluric model for
high-resolution spectrographs to correct individual spectra and to
achieve precise RVs. The removal of micro-telluric lines, coupled with
the gain in spectral range, leads to more precise RVs. Moreover, we
showcase that our model can be applied to other molecules, and thus to
other wavelength regions observed by other spectrographs, such as
NIRPS.
Description:
We reprocessed Proxima's CCFs presented in Faria et al.
(2022A&A...658A.115F 2022A&A...658A.115F, Cat. J/A+A/658/A115) on the telluric-corrected
ESPRESSO spectra.
Objects:
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RA (2000) DE Designation(s)
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14 29 42.94 -62 40 46.1 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
rv.dat 55 117 Proxima telluric-corrected ESPRESSO RV data
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See also:
J/A+A/639/A77 : Proxima Cen RV, FWHM and fluxes (Suarez Mascareno+, 2020)
J/A+A/658/A115 : Proxima Cen ESPRESSO RV and FWHM (Faria+, 2022)
Byte-by-byte Description of file: rv.dat
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Bytes Format Units Label Explanations
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1- 16 F16.8 d BJD Barycentric Julian date
18- 34 F17.13 km/s RV Radial velocity from CCF
36- 55 F20.18 km/s e_RV Uncertainty on radial velocity from CCF
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Acknowledgements:
Romain Allart, romain.allart(at)umontreal.ca
(End) Patricia Vannier [CDS] 25-Feb-2023