A Planetary Companion to the Hyades Giant ε Tauri

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

doi:10.1086/513503

Cited by 173 publications

(153 citation statements)

References 35 publications

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“…Endl et al 2006), whereas they seem more frequent around giant stars with respect to dwarf stars, with thier long orbital periods and rather high minimum masses (e.g. Sato et al 2007). Our considerations are, however, limited to NeptuneJupiter planets around dwarf stars at the cluster turn off, so are not affected by this problem.…”

Section: Radial Velocity Searches For Substellar Companions Around Olmentioning

confidence: 99%

VLT multi-epoch radial velocity survey toward NGC 6253

Montalto¹,

Villanova²,

Koppenhoefer³

et al. 2011

A&A

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Context. One of the most metal-rich open cluster of the Galaxy, NGC 6253 is a target of special interest in the search for extrasolar planets, the study of stellar populations, and the chemical/dynamical evolution of the Galactic disk. Aims. We present the results of two photometric campaigns and a VLT multi-epoch radial velocity survey toward the open cluster NGC 6253. We complement our analysis with photometric, proper motion, and radial velocity data available from previous studies of this cluster, and analyze three planetary candidates found in the field of NGC 6253. Methods. We derived homogeneous radial velocity measurements for stars located at the turn-off, sub-giant, red-giant branch, redclump, and blue straggler regions of the cluster. We also analyzed a comparison sample of surrounding field stars. Spectra were obtained with the UVES and GIRAFFE spectrographs at the VLT during three epochs in August 2008. Results. The three UVES measurements acquired for our brightest transiting candidate (V = 15.26) are all consistent within their errors (200 m/s), but were acquired at very similar orbital phases. The mean radial velocity of this object is not consistent with the cluster recession velocity, which rules out cluster membership except in the case of a binary system. This star is worth further analysis with high-precision spectroscopy. For our faintest candidate (V = 18.247), we were able to exclude the observed transits being caused by a close-by stellar companion, but more precise measurements will be needed to derive an orbital fit and to study other possible scenarios. For the remaining candidate, no measurements were acquired probably because of bad fiber positioning. The mean radial velocity of the cluster is (RV cl ± σ cl ) = (−29.11 ± 0.85) km s −1 . Using both radial velocities and proper motions, we identified 35 cluster members. Our results are in good agreement with past radial velocity and photometric measurements. Furthermore, using our photometry, astrometry, and spectroscopy we identified a new eclipsing binary system member of the cluster. Conclusions. We discussed the possibility of detecting substellar companions (brown dwarfs and planets) with the radial velocity technique (both with UVES/GIRAFFE and HARPS) around turn-off stars of old open cluster. We isolated 5 stars that are optimal targets for searching for planetary mass companions with HARPS. Our optimized strategy minimizes the observing time requested to isolate and followup on the best planetary candidates in cluster with high-precision spectrographs, an important aspect given the faint target stars.

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Section: Radial Velocity Searches For Substellar Companions Around Olmentioning

confidence: 99%

VLT multi-epoch radial velocity survey toward NGC 6253

Montalto¹,

Villanova²,

Koppenhoefer³

et al. 2011

A&A

View full text Add to dashboard Cite

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“…Planets do indeed exist in clusters. Giant planets have been detected around evolved stars belonging to open clusters (Lovis & Mayor 2007;Sato et al 2007), and around a pulsar in the globular cluster M4 (Thorsett et al 1999). It is therefore difficult to understand why no planets have been detected in 47 Tuc.…”

Section: Introductionmentioning

confidence: 99%

An HST search for planets in the lower main sequence of the globular cluster NGC 6397

Nascimbeni

Bedin

Piotto

et al. 2012

A&A

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Searches for planetary transits carried out in open and globular clusters have to date yielded only a handful of weak, unconfirmed candidates. These results have been interpreted as either being insignificant, or evidence that the cluster chemical or dynamical environment inhibits planetary formation or survival. Most campaigns have been limited by small sample statistics or systematics from ground-based photometry. We performed a search for transiting planets and variables in a deep stellar field of NGC 6397 imaged by HST-ACS over 126 orbits. We analyzed 5078 light curves, including a careful selection of 2215 cluster-member M0-M9 dwarfs. The light curves were corrected for systematic trends and inspected using several tools. No high-significance planetary candidate is detected. We compared this null detection with the most recent results from Kepler, showing that no conclusive evidence of lower planet incidence can be drawn. However, a very small photometric jitter is measured for early-M cluster members ( 2 mmag on 98% of them), which may be worth targeting in the near future with more optimized campaigns. Twelve variable stars are reported for the first time.

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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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A Planetary Companion to the Hyades Giant ε Tauri

Cited by 173 publications

References 35 publications

VLT multi-epoch radial velocity survey toward NGC 6253

VLT multi-epoch radial velocity survey toward NGC 6253

An HST search for planets in the lower main sequence of the globular cluster NGC 6397

A likely exoplanet orbiting the oscillating K-giantαArietis

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