Precise Radial Velocities of Giant Stars. II. Pollux and Its Planetary Companion

Reffert, S.; Quirrenbach, A.; Mitchell, D.; Albrecht, S.; Hekker, S.; Fischer, Debra A.; Marcy, Geoffrey W.; Butler, R. Paul

doi:10.1086/507516

Cited by 105 publications

(81 citation statements)

References 20 publications

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“…We have continuously monitored the RVs of 373 G-and K-giant stars for more than a decade, resulting in several published planet detections (Frink et al 2002;Reffert et al 2006;Quirrenbach et al 2011;Mitchell et al 2013;Trifonov et al 2014). Typical masses in our sample are between ∼1-3 M and we reached RV precisions of ∼5-8 m s −1 .…”

Section: Observationsmentioning

confidence: 85%

Precise radial velocities of giant stars

Ortiz

Reffert

Trifonov

et al. 2016

A&A

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Context. For over 12 yr, we have carried out a precise radial velocity (RV) survey of a sample of 373 G-and K-giant stars using the Hamilton Échelle Spectrograph at the Lick Observatory. There are, among others, a number of multiple planetary systems in our sample as well as several planetary candidates in stellar binaries. Aims. We aim at detecting and characterizing substellar and stellar companions to the giant star HD 59686 A (HR 2877, HIP 36616). Methods. We obtained high-precision RV measurements of the star HD 59686 A. By fitting a Keplerian model to the periodic changes in the RVs, we can assess the nature of companions in the system. To distinguish between RV variations that are due to non-radial pulsation or stellar spots, we used infrared RVs taken with the CRIRES spectrograph at the Very Large Telescope. Additionally, to characterize the system in more detail, we obtained high-resolution images with LMIRCam at the Large Binocular Telescope. Results. We report the probable discovery of a giant planet with a mass of m p sin i = 6.92 +0.18 −0.24 M Jup orbiting at a p = 1.0860 +0.0006 −0.0007 au from the giant star HD 59686 A. In addition to the planetary signal, we discovered an eccentric (e B = 0.729 +0.004 −0.003 ) binary companion with a mass of m B sin i = 0.5296 +0.0011 −0.0008 M orbiting at a close separation from the giant primary with a semi-major axis of a B = 13.56 +0.18 −0.14 au. Conclusions. The existence of the planet HD 59686 Ab in a tight eccentric binary system severely challenges standard giant planet formation theories and requires substantial improvements to such theories in tight binaries. Otherwise, alternative planet formation scenarios such as second-generation planets or dynamical interactions in an early phase of the system's lifetime need to be seriously considered to better understand the origin of this enigmatic planet.

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Section: Observationsmentioning

confidence: 85%

Precise radial velocities of giant stars

Ortiz

Reffert

Trifonov

et al. 2016

A&A

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“…They discovered long-period RV variations in three K giants and they proposed two viable hypotheses for these variations in radial velocity: substellar companions or rotational modulation. Recently Hatzes et al (2006) and Reffert et al (2006) confirmed that the initial RV variations found by Hatzes & Cochran (1993) in β Gem were in fact due to a planetary companion. Since the first unequivocal discovery of the first extrasolar planet around the K giant HD 137 759 (ι Dra) by Frink et al (2002), several giant stars have been found to host giant planets (Setiawan et al 2003a(Setiawan et al ,b, 2005Sato et al 2003;Hatzes et al 2005).…”

Section: Introductionmentioning

confidence: 84%

Planetary companion candidates around the K giant stars 42 Draconis and HD 139 357

Döllinger¹,

Hatzes

Pasquini³

et al. 2009

A&A

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Context. For the past 3 years we have been monitoring 62 K giant stars using precise stellar radial velocity (RV) measurements with the 2 m Alfred Jensch Telescope of the Thüringer Landessternwarte Tautenburg (TLS). Aims. To probe the dependence of planet formation on stellar mass by finding planets around intermediate-mass giant stars. Methods. We present high accuracy RV measurements of the K1.5 III star 42 Dra and the K4 III star HD 139357. The wavelength reference for the RV measurements was provided by an iodine absorption cell placed in the optical path of the spectrograph. Results. Our measurements reveal that the time series of the radial velocity of 42 Dra shows a periodic variation of 479.1 days with a semiamplitude of K = 112.5 m s −1 . An orbital solution yields a mass function of f (m) = (5.29 ± 0.62) × 10 −8 solar masses (M ) and an eccentricity of e = 0.38 ± 0.06. From our template spectra, taken without the iodine cell, we determine a metallicity of −0.46 ± 0.04 dex and a stellar mass of 0.98 ± 0.06 M for this star. HD 139 357 shows periodic RV variations of 1125.7 days with a semiamplitude K = 159.9 m s −1 . An orbital solution yields an eccentricity, e = 0.10 ± 0.02 and mass function, f (m) = (4.79 ± 0.57) × 10 −7 M . An iron abundance of −0.13 ± 0.04 dex is obtained, and a stellar mass of 1.31 ± 0.24 M for the parent star is derived. An analysis of the HIPPARCOS photometry as well as our Hα core flux measurements reveal no variability with the radial velocity period. Keplerian motion is the most likely explanation for the observed radial velocity variations for these stars. Conclusions. The K giant stars 42 Dra and HD 139 357 host extrasolar planets with "minimum masses" of 3.88 ± 0.85 Jupiter masses M Jup and 9.76 ± 2.15 M Jup , respectively.

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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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Precise Radial Velocities of Giant Stars. II. Pollux and Its Planetary Companion

Cited by 105 publications

References 20 publications

Precise radial velocities of giant stars

Precise radial velocities of giant stars

Planetary companion candidates around the K giant stars 42 Draconis and HD 139 357

A likely exoplanet orbiting the oscillating K-giantαArietis

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