The HARPS search for southern extra-solar planets

Astudillo-Defru, N.; Forveille, T.; Bonfils, X.; Ségransan, D.; Bouchy, F.; Delfosse, X.; Lovis, C.; Mayor, M.; Murgas, F.; Pepe, F.; Santos, N. C.; Udry, S.; Wünsche, A.

doi:10.1051/0004-6361/201630153

Cited by 137 publications

(94 citation statements)

References 60 publications

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“…The stars within 100 pc represent ∼ 67% of our HARPS sample. This collection of stars, are representative of a volume-limited, long-lasting HARPS surveys dedicated to solar-mass G-dwarf stars (Pepe et al 2004;Lo Curto et al 2010;Moutou et al 2011;Lo Curto et al 2013;Udry et al 2019), low-mass M-dwarfs Trifon Trifonov et al: A public HARPS radial velocity database corrected for systematic errors (Bonfils et al 2005;Mayor et al 2009;Forveille et al 2009;Bonfils et al 2013;Anglada-Escudé et al 2016;Astudillo-Defru et al 2017;Ribas et al 2018) and metal-poor stars (Santos et al 2011;Faria et al 2016;Mortier et al 2016), which all target nearby stars. The remaining ∼ 28% of the HARPS sample (with distance > 120 pc) are typically bright main sequence stars of spectral types A0 to F6, some fainter and more distant transiting planet hosts observed by more recent RV follow-up campaigns of transit planet candidates from the HATSouth (Bakos et al 2013;Brahm et al 2016;Henning et al 2018;Espinoza et al 2019), WASP-south (Pollacco et al 2006;Gillon et al 2009;Nielsen et al 2019), and the K2 extended mission (Howell et al 2014;Grziwa et al 2016;Johnson et al 2018), or evolved subgiant and giant branch stars of spectral types G8 IV − K4 III.…”

Section: The Harps Data and The Stellar Samplementioning

confidence: 99%

Public HARPS radial velocity database corrected for systematic errors

Trifonov

Tal-Or

Zechmeister

et al. 2020

A&A

166

193

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Context. The High Accuracy Radial velocity Planet Searcher (HARPS) spectrograph is mounted since 2003 at the ESO 3.6 m telescope in La Silla and provides state-of-the-art stellar radial velocity (RV) measurements with a precision down to ∼ 1 m s −1 . The spectra are extracted with a dedicated data-reduction software (DRS) and the RVs are computed by cross correlating with a numerical mask. Aims. The aim of this study is three-fold: (i) Create an easy access to the public HARPS RV data set. (ii) Apply the new public SpEctrum Radial Velocity AnaLyser (SERVAL) pipeline to the spectra, and produce a more precise RV data set. (iii) Check whether the precision of the RVs can be further improved by correcting for small nightly systematic effects. Methods. For each star observed with HARPS, we downloaded the publicly available spectra from the ESO archive, and recomputed the RVs with SERVAL. This was based on fitting each observed spectrum with a high signal-to-noise ratio template created by co-adding all the available spectra of that star. We then computed nightly zero points (NZPs) by averaging the RVs of quiet stars. Results. Analysing the RVs of the most RV-quiet stars, whose RV scatter is < 5 m s −1 , we find that SERVAL RVs are on average more precise than DRS RVs by a few percent. Investigating the NZP time series, we find three significant systematic effects, whose magnitude is independent of the software used for the RV derivation: (i) stochastic variations with a magnitude of ∼ 1 m s −1 ; (ii) longterm variations, with a magnitude of ∼ 1 m s −1 and a typical timescale of a few weeks; and (iii) 20-30 NZPs significantly deviating by few m s −1 . In addition, we find small ( 1 m s −1 ) but significant intra-night drifts in DRS RVs before the 2015 intervention, and in SERVAL RVs after it. We confirm that the fibre exchange in 2015 caused a discontinuous RV jump, which strongly depends on the spectral type of the observed star: from ∼ 14 m s −1 for late F-type stars, to ∼ −3 m s −1 for M dwarfs. The combined effect of extracting the RVs with SERVAL and correcting them for the systematics we find is an improved average RV precision: ∼ 5% improvement for spectra taken before the 2015 intervention, and ∼ 15% improvement for spectra taken after it. To demonstrate the quality of the new RV data set, we present an updated orbital solution of the GJ 253 two-planet system. Conclusions. Our NZP-corrected SERVAL RVs can be retrieved from a user-friendly, public database. It provides more than 212 000 RVs for about 3000 stars along with many auxiliary information, such as the NZP corrections, various activity indices, and DRS-CCF products.Differential RV from SERVAL corrected for BERV, SA, drift, (non-NZP corrected). (d) RV from DRS corrected for BERV, SA, drift, (non-NZP corrected). (e) Differential RV from SERVAL corrected for BERV, SA, drift, (non-NZP corrected, joint RV calculation with -pre and -post fibre upgrade data.) (f) Chromatic index from SERVAL. (g) Differential line width from SERVAL. (h) Hα index from SERV...

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Section: The Harps Data and The Stellar Samplementioning

confidence: 99%

Public HARPS radial velocity database corrected for systematic errors

Trifonov

Tal-Or

Zechmeister

et al. 2020

A&A

166

193

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“…This now amounts to almost 40 detections, which include a few Earth-mass planets and a few super-Earths located in the habitable zones of their host (e.g. Astudillo-Defru et al 2017b). M dwarfs have also been the focus of several other planet searches with spectacular discoveries, including Proxima Cen b (Anglada-Escudé et al 2016), TRAPPIST-1 planets (Gillon et al 2017), and LHS1140b (Dittmann et al 2017).…”

Section: Introductionmentioning

confidence: 99%

A temperate exo-Earth around a quiet M dwarf at 3.4 parsec

Bonfils

Astudillo-Defru

Díaz

et al. 2018

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The combination of high-contrast imaging and high-dispersion spectroscopy, which has successfully been use to detect the atmosphere of a giant planet, is one of the most promising potential probes of the atmosphere of Earth-size worlds. The forthcoming generation of extremely large telescopes (ELTs) may obtain sufficient contrast with this technique to detect O2 in the atmosphere of those worlds that orbit low-mass M dwarfs. This is strong motivation to carry out a census of planets around cool stars for which habitable zones can be resolved by ELTs, i.e. for M dwarfs within ∼5 parsecs. Our HARPS survey has been a major contributor to that sample of nearby planets. Here we report on our radial velocity observations of Ross 128 (Proxima Virginis, GJ447, HIP 57548), an M4 dwarf just 3.4 parsec away from our Sun. This source hosts an exo-Earth with a projected mass m sin i = 1.35M⊕ and an orbital period of 9.9 days. Ross 128 b receives ∼1.38 times as much flux as Earth from the Sun and its equilibrium ranges in temperature between 269 K for an Earth-like albedo and 213 K for a Venus-like albedo. Recent studies place it close to the inner edge of the conventional habitable zone. An 80-day long light curve from K2 campaign C01 demonstrates that Ross 128 b does not transit. Together with the All Sky Automated Survey (ASAS) photometry and spectroscopic activity indices, the K2 photometry shows that Ross 128 rotates slowly and has weak magnetic activity. In a habitability context, this makes survival of its atmosphere against erosion more likely. Ross 128 b is the second closest known exo-Earth, after Proxima Centauri b (1.3 parsec), and the closest temperate planet known around a quiet star. The 15 mas planet-star angular separation at maximum elongation will be resolved by ELTs (> 3λ/D) in the optical bands of O2.

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“…Furthermore, M dwarfs have become the most promising ground for the hunt for low-mass, rocky planets (e.g. Dressing & Charbonneau 2013;Sozzetti et al 2013;Astudillo-Defru et al 2017b), due to their more advantageous mass and radius ratios compared to solar-type stars. There is a solid evidence, arising both from HARPS and Kepler observations, that super Earths and Neptunes are commonly found in multiple systems (e.g.…”

Section: Introductionmentioning

confidence: 99%

The HADES RV Programme with HARPS-N at TNG

Pinamonti

Damasso

Marzari

et al. 2018

A&A

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We present 20 yr of radial velocity (RV) measurements of the M1 dwarf Gl15A, combining five years of intensive RV monitoring with the HARPS-N spectrograph with 15 yr of archival HIRES/Keck RV data. We have carried out an MCMC-based analysis of the RV time series, inclusive of Gaussian Process (GP) approach to the description of stellar activity induced RV variations. Our analysis confirms the Keplerian nature and refines the orbital solution for the 11.44-day period super Earth, Gl15A b, reducing its amplitude to 1.68, and successfully models a long-term trend in the combined RV dataset in terms of a Keplerian orbit with a period around 7600 days and an amplitude of 2.5, corresponding to a super-Neptune mass (M sin i = 36 +25 −18 M ⊕ ) planetary companion. We also discuss the present orbital configuration of Gl15A planetary system in terms of the possible outcomes of Lidov-Kozai interactions with the wide-separation companion Gl15B in a suite of detailed numerical simulations. In order to improve the results of the dynamical analysis, we have derived a new orbital solution for the binary system, combining our RV measurements with astrometric data from the WDS catalogue. The eccentric Lidov-Kozai analysis shows the strong influence of Gl15B on the Gl15A planetary system, which can produce orbits compatible with the observed configuration for initial inclinations of the planetary system between 75• and 90• , and can also enhance the eccentricity of the outer planet well above the observed value, even resulting in orbital instability, for inclinations around 0• and 15• −30• . The Gl15A system is the multi-planet system closest to Earth, at 3.56 pc, and hosts the longest period RV sub-Jovian mass planet discovered so far. Its orbital architecture constitutes a very important laboratory for the investigation of formation and orbital evolution scenarios for planetary systems in binary stellar systems.

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The HARPS search for southern extra-solar planets

Cited by 137 publications

References 60 publications

Public HARPS radial velocity database corrected for systematic errors

Public HARPS radial velocity database corrected for systematic errors

A temperate exo-Earth around a quiet M dwarf at 3.4 parsec

The HADES RV Programme with HARPS-N at TNG

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