J/AJ/161/80 Excalibur calibration method; HD34411 RVs with EXPRESS (Zhao+, 2021)
Excalibur: a nonparametric, hierarchical wavelength calibration method for a
precision spectrograph.
Zhao L.L., Hogg D.W., Bedell M., Fischer D.A.
<Astron. J., 161, 80 (2021)>
=2021AJ....161...80Z 2021AJ....161...80Z
ADC_Keywords: Stars, G-type; Exoplanets; Spectra, optical; Radial velocities
Keywords: Exoplanet detection methods ; Radial velocity ;
Astronomical techniques ; Astronomical instrumentation ;
Spectrometers ; Computational methods
Abstract:
Excalibur is a nonparametric, hierarchical framework for precision
wavelength calibration of spectrographs. It is designed with the needs
of extreme-precision radial-velocity (EPRV) instruments in mind, which
require calibration or stabilization to better than 10-4pixels.
Instruments vary along only a few dominant degrees of freedom,
especially EPRV instruments that feature highly stabilized optical
systems and detectors. Excalibur takes advantage of this property by
using all calibration data to construct a low-dimensional
representation of all accessible calibration states for an instrument.
Excalibur also takes advantage of laser-frequency combs or etalons,
which generate a dense set of stable calibration points. This density
permits the use of a nonparametric wavelength solution that can adapt
to any instrument or detector oddities better than parametric models,
such as a polynomial. We demonstrate the success of this method with
data from the Extreme Precision Spectrograph (EXPRES), which uses a
laser-frequency comb. When wavelengths are assigned to laser comb
lines using excalibur, the rms of the residuals is about one-fifth
that of wavelengths assigned using polynomial fits to individual
exposures. Radial-velocity measurements of HD34411 show a reduction in
rms scatter over a 10 month time baseline from 1.17 to 1.05m/s.
Description:
We test excalibur-generated wavelengths on RV measurements using
Extreme Precision Spectrograph (EXPRES) observations of HD34411. We
use 114 observations of HD34411 taken between 2019 October 8 and 2020
March 5 with S/N of 250. Radial velocity measurements are derived
using a chunk-by-chunk, forward-modeling algorithm run by the EXPRES
team.
Objects:
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RA (2000) DE Designation(s)
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05 19 08.48 +40 05 56.6 HD34411 = * lam Aur
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File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
table1.dat 42 114 EXPRES radial velocities using excalibur Wavelengths
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See also:
J/A+A/468/1115 : Thorium and argon lines in the visible (Lovis+, 2007)
J/A+A/549/A109 : HARPS XXXI. The M-dwarf sample (Bonfils+, 2013)
J/A+A/560/A61 : A frequency Comb calibrated solar atlas (Molaro+, 2013)
J/ApJS/225/32 : Extended abundance analysis of cool stars (Brewer+, 2016)
J/AJ/153/208 : LCES HIRES/Keck RVel Exoplanet Survey (Butler+, 2017)
J/AJ/156/18 : APOGEE DR14:Binary comp. of evolved stars (Price-Whelan+,2018)
J/AJ/159/187 : First RVs with EXPRES spectrograph: 51Peg (Petersburg+, 2020)
J/A+A/639/A77 : Proxima Cen RV, FWHM and fluxes (Suarez Mascareno+, 2020)
Byte-by-byte Description of file: table1.dat
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Bytes Format Units Label Explanations
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1- 18 F18.12 d HJD [18764/19075] Heliocentric Julian Date; JD-2440000
20- 31 F12.9 m/s RVel [-3.42/3.66] Radial velocity
33- 42 F10.8 m/s e_RVel [0.27/0.59] Uncertainty in RVel
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History:
From electronic version of the journal
(End) Prepared by [AAS], Coralie Fix [CDS], 08-Apr-2021