Study of the impact of the post-MS evolution of the host star on the orbits of close-in planets

Monthly Notices of the Royal Astronomical Society

2015

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A recent reanalysis of archival data has lead several authors to arrive at strikingly different conclusions for a number of planet-hosting candidate stars. In particular, some radial velocities measured using FEROS spectra have been shown to be inaccurate, throwing some doubt on the validity of a number of planet detections. Motivated by these results, we have begun the Reanalysis of Archival FEROS specTra (RAFT) program and here we discuss the first results from this work. We have reanalyzed FEROS data for the stars HD 11977, HD 47536, HD 70573, HD 110014 and HD 122430, all of which are claimed to have at least one planetary companion. We have reduced the raw data and computed the radial velocity variations of these stars, achieving a long-term precision of ∼ 10 m s −1 on the known stable star τ Ceti, and in good agreement with the residuals to our fits. We confirm the existence of planets around HD 11977, HD 47536 and HD 110014, but with different orbital parameters than those previously published. In addition, we found no evidence of the second planet candidate around HD 47536, nor any companions orbiting HD 122430 and HD 70573. Finally, we report the discovery of a second planet around HD 110014, with a minimum mass of 3.1 M Jup and a orbital period of 130 days. Analysis of activity indicators allow us to confirm the reality of our results and also to measure the impact of magnetic activity on our radial velocity measurements. These results confirm that very metal-poor stars down to [Fe/H]∼-0.7 dex, can indeed form giant planets given the right conditions.

Section: Radial Velocity Calculationcontrasting

confidence: 54%

Section: Radial Velocity Calculationmentioning

confidence: 99%

Section: S-index and Bisector Velocity Spanmentioning

confidence: 99%

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RAFT – I. Discovery of new planetary candidates and updated orbits from archival FEROS spectra

Soto

Monthly Notices of the Royal Astronomical Society

2015

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“…5 0± 0.21 2.42 ± 0.27 1.63 ± 0.22 R (R ) 8 . 9 3± 1.02 11.6 ± 1.4 5.92 ± 0.44 method (Baranne et al 1996), according to the method described in Jones et al (2013) and .…”

Section: Observations and Data Reductionmentioning

confidence: 99%

Giant planets around two intermediate-mass evolved stars and confirmation of the planetary nature of HIP 67851c

Rojo

et al. 2015

A&A

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Context. Precision radial velocities are required to discover and characterize exoplanets. Optical spectra that exhibit many hundreds of absorption lines can allow the m s −1 precision levels required for this work. After the main-sequence, intermediate-mass stars expand and rotate more slowly than their progenitors, thus, thousands of spectral lines appear in the optical region, permitting the search for Doppler signals in these types of stars. Aims. In 2009, we began the EXPRESS program, aimed at detecting substellar objects around evolved stars, and studying the effects of the mass and evolution of the host star on their orbital and physical properties. Methods. We obtained precision radial velocity measurements for the giant stars HIP 65891 and HIP 107773, from CHIRON and FEROS spectra. Also, we obtained new radial velocity epochs for the star HIP 67851, which is known to host a planetary system. Additionally, HIP 67851 is one of five giant stars that are known to host a planetary system having a close-in planet (a < 0.7 AU). Based on the evolutionary states of those five stars, we conclude that close-in planets do exist in multiple systems around subgiants and slightly evolved giants stars, but most likely they are subsequently destroyed by the stellar envelope during the ascent of the red giant branch phase.

“…Based on this method, Jones et al (2013) showed that it is possible to reach a long-term precision of ∼3 m s −1 using FEROS data. The main steps of this method are described below.…”

Section: Radial Velocity Calculationsmentioning

confidence: 99%

No evidence of the planet orbiting the extremely metal-poor extragalactic star HIP 13044

2014

A&A

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Context. The recent discovery of three giant planets orbiting the extremely metal-poor stars HIP 11952 and HIP 13044 have challenged theoretical predictions of the core-accretion model. According to this, the metal content of the protoplanetary disk from which giant planets are formed is a key ingredient for the early formation of planetesimals prior to the runaway accretion of the surrounding gas. Aims. We reanalyzed the original FEROS data that were used to detect the planets to prove or refute their existence, employing our new reduction and analysis methods. Methods. We applied the cross-correlation technique to FEROS spectra to measure the radial velocity variation of HIP 13044 and HIP 11952. We reached a typical precision of ∼35 m s −1 for HIP 13044 and ∼25 m s −1 for HIP 11952, which is significantly superior to the uncertainties presented previously. Results. We found no evidence of the planet orbiting the metal-poor extragalactic star HIP 13044. We show that given our radial velocity precision, and considering the large number of radial velocity epochs, the probability for a non-detection of the radial velocity signal recently claimed is lower than 10 −4 . Finally, we also confirm findings that the extremely metal-poor star HIP 11952 does not contain a system of two gas giant planets. These results reaffirm the expectations from the core-accretion model of planet formation.