Planetary Companions around Three Intermediate-Mass G and K Giants: 18 Delphini, ξ Aquilae, and HD 81688

Sato, Bun’ei; Izumiura, Hideyuki; Toyota, Eri; Kambe, Eiji; Ikoma, Masahiro; Omiya, Masashi; Masuda, Seiji; Takeda, Yoichi; Murata, Daisuke; Itoh, Yoichi; Ando, Hiroyasu; Yoshida, Michitoshi; Kokubo, Eiichiro; Ida, Shigeru

doi:10.1093/pasj/60.3.539

Cited by 121 publications

(62 citation statements)

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“…After the detection of the first few planets around evolved stars, it was noticed that they are not found in orbits interior to ∼0.7 AU (e.g., Johnson et al 2007;Sato et al 2008). Nowadays, more than 100 exoplanets have been discovered around such stars (including subgiants), and the paucity of short-period systems is still present.…”

Section: Orbital Distributionmentioning

confidence: 99%

“…This observational result has been attributed to be due to the dynamical interaction between the host stars and their planets. Different authors have studied this effect, showing that close-in planets spiral inward due to the loss of orbital angular momentum, which is mainly transferred and dissipated in the stellar convective envelope (e.g., Livio & Soker, 1983;Rasio et al 1996;Sato et al 2008;Schröder & Connon Smith 2008;Villaver & Livio 2009;Kunitomo, et al 2011). As a result of the tidal decay, close-in planets are not expected to be found, at least, around post-RGB stars.…”

Section: Orbital Distributionmentioning

confidence: 99%

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The properties of planets around giant stars

Jones

Jenkins

Bluhm

et al. 2014

A&A

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Context. More than 50 exoplanets have been found around giant stars, revealing different properties when compared to planets orbiting solar-type stars. In particular, they are super-Jupiters and are not found orbiting interior to ∼0.5 AU. Aims. We are conducting a radial velocity study of a sample of 166 giant stars aimed at studying the population of close-in planets orbiting giant stars and how their orbital and physical properties are influenced by the post-MS evolution of the host star. Methods. We have collected multiepoch spectra for all of the targets in our sample. We have computed precision radial velocities from FECH/CHIRON and FEROS spectra, using the I 2 cell technique and the simultaneous calibration method, respectively. Results. We present the discovery of a massive planet around the giant star HIP 105854. The best Keplerian fit to the data leads to an orbital distance of 0.81 ± 0.03 AU, an eccentricity of 0.02 ± 0.03 and a projected mass of 8.2 ± 0.2 M J . With the addition of this new planet discovery, we performed a detailed analysis of the orbital properties and mass distribution of the planets orbiting giant stars. We show that there is an overabundance of planets around giant stars with a ∼ 0.5−0.9 AU, which might be attributed to tidal decay. Additionally, these planets are significantly more massive than those around MS and subgiant stars, suggesting that they grow via accretion either from the stellar wind or by mass transfer from the host star. Finally, we show that planets around evolved stars have lower orbital eccentricities than those orbiting solar-type stars, which suggests that they are either formed in different conditions or that their orbits are efficiently circularized by interactions with the host star.

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Section: Orbital Distributionmentioning

confidence: 99%

Section: Orbital Distributionmentioning

confidence: 99%

The properties of planets around giant stars

Jones

Jenkins

Bluhm

et al. 2014

A&A

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“…It is true that planets move outwards because of the mass-loss of the star, but this effect is not strong enough to explain the complete lack of planets within 0.5 AU. A third possibility is that intermediate-mass stars have close-in planets when they are on the main sequence but that these are engulfed when the star becomes a giant star (Sato et al 2008). Calculations by Villaver & Livio (2009) show that tidal interaction can lead to the engulfment of close-in planets by evolved stars.…”

Section: The Frequency Of Planets Orbiting A-type Starsmentioning

confidence: 99%

Multi-object spectroscopy of stars in the CoRoT fields

Sebastian

Guenther

Schaffenroth

et al. 2012

A&A

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Context. Observations of giant stars indicate that the frequency of giant planets is much higher for intermediate-mass stars than for solar-like stars. Up to now all known planets of giant stars orbit at relatively far distances from their host stars. It is not known whether intermediate-mass stars also had many close-in planets when they were on the main sequence, which were then engulfed when the star became a giant star. To understand the formation and evolution of planets it is therefore important to find out whether main-sequence stars of intermediate-mass have close-in planets or not. Aims. A survey for transiting planets of intermediate-mass stars would be ideal to solve this question, because the detection of transiting planets is not affected by the rapid rotation of these stars. With CoRoT it is possible to detect transiting planets around stars up to a spectral type B4V. As a first step for an efficient survey we need to identify intermediate-mass stars in the CoRoT-fields, which can then be used as an input list. Methods. To compile the input list we derived the spectral types of essentially all O, B and A stars down to 14.5 mag in the CoRoT fields IRa01, LRa01, LRa02 taken with the multi-object spectrograph AAOmega. We determined the spectral types by comparing the spectra with template spectra from a library. Results. In total we identify 1856 A and B stars that have been observed with CoRoT. Using multiple spectra of these stars, we find that the accuracy of the resulting spectral classification is 1.61 ± 0.14 sub-classes for A and B stars. Conclusions. Given the number of planets that have been detected in these fields amongst late-type stars, we estimate that there are one to four transiting planets of intermediate-mass stars waiting to be discovered. Our survey not only allows us to carry out a dedicated planet search programme but is also essential for any types of studies of the light curves of early-type stars in the CoRoT database. We also show that it would be possible to extend the survey to all fields that CoRoT has observed using photometrically determined spectral types.

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“…This makes giant stars suitable targets for extrasolar planet detection with the RV method. Frink et al (2002) discovered the first planetary companion around the K-giant star ι Dra (K2 III), and thereafter, several companions around K-giant stars have been reported using the precise RV method (Setiawan 2003;Setiawan et al 2003;Mitchell et al 1234;Hatzes et al 2005Hatzes et al , 2006Reffert et al 2006;Johnson et al 2007Johnson et al , 2008Döllinger et al 2007Döllinger et al , 2009de Medrios et al 2009;and Sato et al 2007and Sato et al , 2008aand Sato et al ,b, 2010. However, in K-giants the velocity variations caused by planetary companions can be blended with the stellar pulsations and surface activities, which complicates identification of planetary companions.…”

Section: Introductionmentioning

confidence: 99%

A likely exoplanet orbiting the oscillating K-giantαArietis

Lee

Mkrtichian

Han

et al. 2011

A&A

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Aims. To search for extrasolar planets around intermediate-mass stars, we are conducting a precise RV survey around K-giants. Methods. We present high-accuracy RV measurements of α Ari made from November 2003 to February 2010. This star belongs to our sample of 55 K-giants studied for extrasolar planet and pulsation searches using the fiber-fed Bohyunsan Observatory Echelle Spectrograph (BOES) attached to the 1.8-m telescope at Bohyunsan Optical Astronomy Observatory (BOAO) in Korea.Results. We find a planetary companion with long-period and low-amplitude radial velocity (RV) variations in oscillating K2 III star α Ari (HD 12929). We do not find the correlation between RV variations and chromospheric activity indicators (Ca II H & K region, Hα line). The bisector analysis also shows that the bisector velocity span (BVS) does not show any obvious correlation with RV variation but has periodic component that may be attributed to the rotation of the star. If the RV variation is indeed caused by a planetary companion, an orbital solution with a period of P = 381 days, a semi-amplitude of K = 41 m s −1 , and an eccentricity of e = 0.25 fits the data best. Assuming a possible stellar mass of M = 1.5 M , we estimate the minimum mass for the planetary companion of m 2 sin i = 1.8 M Jup with an orbital semi-major axis of 1.2 AU. Conclusions. Our finding of a likely exoplanet in α Ari supports searching for extrasolar planets around giant stars with multiperiodic oscillations.

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Planetary Companions around Three Intermediate-Mass G and K Giants: 18 Delphini, ξ Aquilae, and HD 81688

Cited by 121 publications

References 50 publications

The properties of planets around giant stars

The properties of planets around giant stars

Multi-object spectroscopy of stars in the CoRoT fields

A likely exoplanet orbiting the oscillating K-giantαArietis

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