A HARPS RV search for planets around young nearby stars

Abstract

Context. Young nearby stars are good candidates in the search for planets with both radial velocity (RV) and direct imaging techniques. This, in turn, allows for the computation of the giant planet occurrence rates at all separations. The RV search around young stars is a challenge as they are generally faster rotators than older stars of similar spectral types and they exhibit signatures of magnetic activity (spots) or pulsation in their RV time series. Specific analyses are necessary to characterize, and possibly correct for, this activity. Aims. Our aim is to search for planets around young nearby stars and to estimate the giant planet (GP) occurrence rates for periods up to 1000 days. Methods. We used the HARPS spectrograph on the 3.6 m telescope at La Silla Observatory to observe 89 A − M young (< 600 Myr) stars. We used our SAFIR (Spectroscopic data via Analysis of the Fourier Interspectrum Radial velocities ) software to compute the RV and other spectroscopic observables. Then, we computed the companion occurrence rates on this sample. Results. We confirm the binary nature of HD177171, HD181321 and HD186704. We report the detection of a close low mass stellar companion for HIP36985. No planetary companion was detected. We obtain upper limits on the GP (< 13 MJup) and BD (∈ [13; 80] MJup) occurrence rates based on 83 young stars for periods less than 1000 days, which are set, 2 +3 −2 % and 1 +3 −1 %.

A SOPHIE RV search for giant planets around young nearby stars (YNS)

“…To filter the bad spectra we used the selection criteria used for the HARPS YNS survey (Grandjean et al 2020): S /N 550 nm 7 ∈ [80; 380], sec z < 3, and χ 2 < 10 ( Galland et al 2005b). For faint stars (V > 8.8 mag) we included spectra with S /N 550 nm down to 30 as it was the best compromise to include enough spectra to perform our analysis without degrading the RV uncertainties.…”

“…Details can be found in Tables A.1, A.3, A.2, and A.4 (Tables A.3 and A.4 being updated versions of Tables A.1 and A.2 presented in Grandjean et al 2020).…”

“…From our combined HARPS and SOPHIE sample of 119 stars, we computed the occurrence rates of GPs (1 to 13 M Jup ) and BDs 10 Assuming a circular orbit in the computation of the detection limits is common in the field of large RV surveys (Cumming et al 2008;Lagrange et al 2009;Borgniet et al 2017;Grandjean et al 2020) (13 to 80 M Jup ) around AF-type (B − V ∈ [−0.05 : 0.52[), FKtype (B − V ∈ [0.52 : 1.33[), and KM-type (B − V ≥ 1.33) stars, and for different ranges of periods: 1-10, 10-100, 100-1000, and 1-1000 days. We used the method described in Borgniet et al (2017) to compute the occurrence rates and to correct them from the estimated number of missed companions n miss derived from the search completeness.…”

The effects of granulation and supergranulation on Earth-mass planet detectability in the habitable zone around F6-K4 stars

“…The LPA method proposed in Meunier et al (2012) computes detection limits as a function of orbital period from a given RV time series, taking the power around the considered orbital period due to stellar contribution into account since stellar activity produces signal at some specific periods. This fast computing method has been used in several works (for example Lagrange et al 2013Lagrange et al , 2018Borgniet et al 2017Borgniet et al , 2019Lannier et al 2017;Grandjean et al 2020). Here, we recall the method in brief, which is also illustrated in the upper panel of Fig.…”

The impact of unresolved magnetic spots on high-precision radial velocity measurements

“…As a result, even though some studies focus on young stars (e.g. Lagrange et al 2013;Grandjean et al 2020), the majority of studies are directed towards older and less active stars. One example of a young star that has been extensively observed with the radial velocity technique is Eridani.…”