THE HARPS-TERRA PROJECT. I. DESCRIPTION OF THE ALGORITHMS, PERFORMANCE, AND NEW MEASUREMENTS ON A FEW REMARKABLE STARS OBSERVED BY HARPS

By G. Anglada-Escudé, R. P. Butler. 2012

253 citations recorded by the source corpus.

Doppler spectroscopy has uncovered or confirmed all the known planets orbiting nearby stars. Two main techniques are used to obtain precision Doppler measurements at optical wavelengths. The first approach is the gas cell method, which consists of least-squares matching of the spectrum of iodine imprinted on the spectrum of the star. The second method relies on the construction of a stabilized spectrograph externally calibrated in wavelength. The most precise stabilized spectrometer in operation is the High Accuracy Radial velocity Planet Searcher (HARPS), operated by the European Southern Observatory in La Silla Observatory, Chile. The Doppler measurements obtained with HARPS are typically obtained using the cross-correlation function (CCF) technique. This technique consists of multiplying the stellar spectrum by a weighted binary mask and finding the minimum of the product as a function of the Doppler shift. It is known that CCF is suboptimal in exploiting the Doppler information in the stellar spectrum. Here we describe an algorithm to obtain precision radial velocity measurements using least-squares matching of each observed spectrum to a high signal-to-noise ratio template derived from the same observations. This algorithm is implemented in our software HARPS-TERRA (Template-Enhanced Radial velocity Re-analysis Application). New radial velocity measurements on a representative sample of stars observed by HARPS are used to illustrate the benefits of the proposed method. We show that, compared with CCF, template matching provides a significant improvement in accuracy, especially when applied to M dwarfs.

Subfields: Astronomy and Astrophysics

View Paper: https://www.semanticscholar.org/paper/3794514bc650929a7a16732333332b3437dcff94

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Citations in the corpus

The planet search programme at the ESO CES and HARPS - IV. The search for Jupiter analogues around solar-like stars (2012, methodology): “We note that, combining the RVs of HARPS and all the RVs given in Benedict et al. (2006), Anglada-Escudé & Butler (2012) could also not confirm the planet solution, though, without evaluating the significance, they suggested another best fitting, similar longperiod. α Men: Eggenberger et al. (2007)…”
The CARMENES Search for Exoplanets around M Dwarfs: A Low-mass Planet in the Temperate Zone of the Nearby K2-18 (2018, methodology): “Following the approach by Anglada-Escudé & Butler (2012), a high signal-to-noise ratio spectrum is constructed by a suitable combination of the observed spectra and used as a template to measure the RVs.”
A dynamically-packed planetary system around GJ 667C with three super-Earths in its habitable zone (2013, methodology): “…obtained using the PFS/Magellan spectrograph between June 2011 and October 2011 using the Iodine cell technique, and 22 HIRES/Keck Doppler measurements (both RV sets are provided in Anglada-Escudé & Butler 2012) that have lower precision but allow extending the time baseline of theobservations.”
Spectrum radial velocity analyser (SERVAL). High-precision radial velocities and two alternative spectral indicators (2017, methodology): “Hence naive coadding would require either some kind of resampling or interpolation of the observations onto a common wavelength grid (e.g. Anglada-Escudé & Butler 2012), which leads to difficulties in applying the data uncertainties, or calculating some form of bin means, which ignores the local…”
A BCool magnetic snapshot survey of solar-type stars (2013, background): “…K-star (K2V according to the SIMBAD data base) and a possible planet hosting star (Hatzes et al. 2000; Butler et al. 2006; Benedict et al. 2006; Anglada-Escudé & Butler 2012) and as such its magnetic field properties are of significant interest in the study of the impact of magnetic activity…”
High-cadence spectroscopy of M-dwarfs. I. Analysis of systematic effects in HARPS-N line profile measurements on the bright binary GJ 725A+B (2016, methodology): “…limit, it is unlikely that the 0.8 - 0.9 m s−1 (reported lower noise limit in HARPS-ESO observations by Pepe et al. 2011, and of a handful of very quiet M dwarfs, e.g. GJ 699 and GJ 588, by Anglada-Escudé & Butler 2012) is an universal limit for Doppler measurements. c© 2015 RAS ar X iv :1 60 4.”
THE Hα EMISSION OF NEARBY M DWARFS AND ITS RELATION TO STELLAR ROTATION (2016, methodology): “We use a 5th-order Legendre polynomial to account for the continuum mismatch (e.g Anglada-Escudé & Butler 2012).”
Chromospheric activity catalogue of 4454 cool stars (2018, methodology): “This method consists of measuring the surface flux RHK by co-adding all available spectra into a template spectra with a high signal-to-noise ratio (S/N) using the HARPS-TERRA software (Anglada-Escudé & Butler 2012).”
Barycentric Corrections at 1 cm s-1 for Precise Doppler Velocities (2014, methodology): “In this method, shifts are usually measured with a cross-correlation technique (Baranne et al. 1996; Pepe et al. 2002), although occasionally forwardmodeling is used (Anglada-Escudé & Butler 2012).”