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

Döllinger, M. P.; Hatzes, A. P.; Pasquini, L.; Guenther, E. W.; Hartmann, Michael; Girardi, L.

doi:10.1051/0004-6361/200810837

Cited by 38 publications

(46 citation statements)

References 43 publications

(61 reference statements)

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“…In 2011, we observed two giant stars, 42 Dra (K1.5III: Döllinger et al 2009) and 14 And (K0III: Sato et al 2008), and one mainsequence star, υ And (F9V: Fuhrmann et al 1998). The observations provided measurements close to the zero or up to the second lobe of squared visibility.…”

Section: Vega Observationsmentioning

confidence: 87%

A new interferometric study of four exoplanet host stars:θ Cygni, 14 Andromedae,υAndromedae and 42 Draconis

Ligi¹,

Mourard²,

Lagrange³

et al. 2012

A&A

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Context. Since the discovery of the first exoplanet in 1995 around a solar-type star, the interest in exoplanetary systems has kept increasing. Studying exoplanet host stars is of the utmost importance to establish the link between the presence of exoplanets around various types of stars and to understand the respective evolution of stars and exoplanets. Aims. Using the limb-darkened diameter (LDD) obtained from interferometric data, we determine the fundamental parameters of four exoplanet host stars. We are particularly interested in the F4 main-sequence star, θ Cyg, for which Kepler has recently revealed solar-like oscillations that are unexpected for this type of star. Furthermore, recent photometric and spectroscopic measurements with SOPHIE and ELODIE (OHP) show evidence of a quasi-periodic radial velocity of ∼150 days. Models of this periodic change in radial velocity predict either a complex planetary system orbiting the star, or a new and unidentified stellar pulsation mode. Methods. We performed interferometric observations of θ Cyg, 14 Andromedae, υ Andromedae and 42 Draconis for two years with VEGA/CHARA (Mount Wilson, California) in several three-telescope configurations. We measured accurate limb darkened diameters and derived their radius, mass and temperature using empirical laws. Results. We obtain new accurate fundamental parameters for stars 14 And, υ And and 42 Dra. We also obtained limb darkened diameters with a minimum precision of ∼1.3%, leading to minimum planet masses of M sin i = 5.33 ± 0.57, 0.62 ± 0.09 and 3.79 ± 0.29 M Jup for 14 And b, υ And b and 42 Dra b, respectively. The interferometric measurements of θ Cyg show a significant diameter variability that remains unexplained up to now. We propose that the presence of these discrepancies in the interferometric data is caused either by an intrinsic variation of the star or an unknown close companion orbiting around it.

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Section: Vega Observationsmentioning

confidence: 87%

A new interferometric study of four exoplanet host stars:θ Cygni, 14 Andromedae,υAndromedae and 42 Draconis

Ligi¹,

Mourard²,

Lagrange³

et al. 2012

A&A

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“…If confirmed, the determined orbit of the 1.8 M Jup mass planet is fairly eccentric, e = 0.25 ± 0.03, but, up to now, 6 out of 22 companions around K-giants show more than 0.2 eccentricity: e = 0.7 of ι Dra (Frink et al 2002), e = 0.2 of K1 III star HD 47536 (Setiawan et al 2003,b), e = 0.27 of K1 II-III star HD 13189 (Hatzes et al 2005), e = 0.43 of K1 III star 4 UMa (Döllinger et al 2007), e = 0.38 of K1.5 III star 42 Dra (Döllinger et al 2009), and e = 0.46 of K2 III star HD 110014 (de Medeiros et al 2009). The eccentricity for the planetary orbit of α Ari is therefore not unusual among K-giants, and such eccentric modulation is difficult to produce by surface variations or stellar oscillations.…”

Section: Discussionmentioning

confidence: 99%

“…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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“…α Ari and 42 Dra are also host stars of confirmed Jupitersized planets (alf Ari b, M = 1.8±0.2 M J , a = 1.2 AU (Lee et al 2011) 9 ; 42 Dra b, M = 3.88±0.85 M J , a = 1.19 AU (Döllinger et al 2009) 10 ) , but for these stars any possible debris disk emis- Fig. 8.…”

Section: Intrinsic Fir Excessmentioning

confidence: 94%

Herschel-PACS photometry of faint stars for sensitivity performance assessment and establishment of faint FIR primary photometric standards

Klaas

Balog

Nielbock

et al. 2018

A&A

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Aims. Our aims are to determine flux densities and their photometric accuracy for a set of seventeen stars that range in flux from intermediately bright ( 2.5 Jy) to faint ( 5 mJy) in the far-infrared (FIR). We also aim to derive signal-to-noise dependence with flux and time, and compare the results with predictions from the Herschel exposure-time calculation tool. Methods. We obtain aperture photometry from Herschel-PACS high-pass-filtered scan maps and chop/nod observations of the faint stars. The issues of detection limits and sky confusion noise are addressed by comparison of the field-of-view at different wavelengths, by multi-aperture photometry, by special processing of the maps to preserve extended emission, and with the help of large-scale absolute sky brightness maps from AKARI. This photometry is compared with flux-density predictions based on photospheric models for these stars. We obtain a robust noise estimate by fitting the flux distribution per map pixel histogram for the area around the stars, scaling it for the applied aperture size and correcting for noise correlation.Results. For 15 stars we obtain reliable photometry in at least one PACS filter, and for 11 stars we achieve this in all three PACS filters (70, 100, 160 µm). Faintest fluxes, for which the photometry still has good quality, are about 10 -20 mJy with scan map photometry. The photometry of seven stars is consistent with models or flux predictions for pure photospheric emission, making them good primary standard candidates. Two stars exhibit source-intrinsic far-infrared excess: β Gem (Pollux), being the host star of a confirmed Jupiter-size exoplanet, due to emission of an associated dust disk, and η Dra due to dust emission in a binary system with a K1 dwarf. The investigation of the 160 µm sky background and environment of four sources reveals significant sky confusion prohibiting the determination of an accurate stellar flux at this wavelength. As a good model approximation, for nine stars we obtain scaling factors of the continuum flux models of four PACS fiducial standards with the same or quite similar spectral type. We can verify a linear dependence of signal-to-noise ratio (S/N) with flux and with square root of time over significant ranges. At 160 µm the latter relation is, however, affected by confusion noise. Conclusions. The PACS faint star sample has allowed a comprehensive sensitivity assessment of the PACS photometer. Accurate photometry allows us to establish a set of five FIR primary standard candidates, namely α Ari, ε Lep, ω Cap, HD 41047 and 42 Dra, which are 2 -20 times fainter than the faintest PACS fiducial standard (γ Dra) with absolute accuracy of <6%. For three of these primary standard candidates, essential stellar parameters are known, meaning that a dedicated flux model code may be run.

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

Cited by 38 publications

References 43 publications

A new interferometric study of four exoplanet host stars:θ Cygni, 14 Andromedae,υAndromedae and 42 Draconis

A new interferometric study of four exoplanet host stars:θ Cygni, 14 Andromedae,υAndromedae and 42 Draconis

A likely exoplanet orbiting the oscillating K-giantαArietis

Herschel-PACS photometry of faint stars for sensitivity performance assessment and establishment of faint FIR primary photometric standards

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