Retired a Stars and Their Companions. Vii. 18 New Jovian Planets

Johnson, John Asher; Clanton, Christian; Howard, Andrew W.; Bowler, Brendan P.; Henry, Gregory W.; Marcy, Geoffrey W.; Crepp, Justin R.; Endl, Michael; Cochran, William D.; MacQueen, Phillip J.; Wright, Jason T.; Isaacson, Howard

doi:10.1088/0067-0049/197/2/26

Cited by 156 publications

(128 citation statements)

References 80 publications

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“…5.4. In addition to β Pic b (orange square) and the HR 8799 planets (red circles), the giant planets detected around old A stars by Johnson et al (2010bJohnson et al ( , 2011 of separation and planet mass. Extreme AO data will determine if the transition from a flat or rising population of close orbit planets to a declining population of wide orbit planets is smooth or discontinuous and may discover a peak in the separation distribution.…”

Section: Fig 10mentioning

confidence: 99%

“…The results of RV surveys of the evolved counterparts of A-stars (Johnson et al 2007) have also provided intriguing results (Johnson et al 2010b;Bowler et al 2010a;Johnson et al 2011), with significant differences in the planet population compared to RV-detected exoplanets around lower mass stars. Statistical analysis of the results clearly shows a higher frequency of planets around more massive stars and larger masses for the detected planets .…”

Section: Introductionmentioning

confidence: 99%

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The International Deep Planet Survey

Vigan

Patience

Marois

et al. 2012

A&A

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Breakthrough direct detections of planetary companions orbiting A-type stars confirm the existence of massive planets at relatively large separations, but dedicated surveys are required to estimate the frequency of similar planetary systems. To measure the first estimation of the giant exoplanetary systems frequency at large orbital separation around A-stars, we have conducted a deep-imaging survey of young (8−400 Myr), nearby (19−84 pc) A-and F-stars to search for substellar companions in the ∼10−300 AU range. The sample of 42 stars combines all A-stars observed in previous AO planet search surveys reported in the literature with new AO observations from VLT/NaCo and Gemini/NIRI. It represents an initial subset of the International Deep Planet Survey (IDPS) sample of stars covering M-to B-stars. The data were obtained with diffraction-limited observations in H-and K s -band combined with angular differential imaging to suppress the speckle noise of the central stars, resulting in typical 5σ detection limits in magnitude difference of 12 mag at 1 , 14 mag at 2 and 16 mag at 5 which is sufficient to detect massive planets. A detailed statistical analysis of the survey results is performed using Monte Carlo simulations. Considering the planet detections, we estimate the fraction of A-stars having at least one massive planet (3−14 M Jup ) in the range 5−320 AU to be inside 5.9−18.8% at 68% confidence, assuming a flat distribution for the mass of the planets. By comparison, the brown dwarf (15−75 M Jup ) frequency for the sample is 2.0−8.9% at 68% confidence in the range 5−320 AU. Assuming power law distributions for the mass and semimajor axis of the planet population, the AO data are consistent with a declining number of massive planets with increasing orbital radius which is distinct from the rising slope inferred from radial velocity (RV) surveys around evolved A-stars and suggests that the peak of the massive planet population around A-stars may occur at separations between the ranges probed by existing RV and AO observations. Finally, we report the discovery of three new close M-star companions to HIP 104365 and HIP 42334.

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Section: Fig 10mentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

The International Deep Planet Survey

Vigan

Patience

Marois

et al. 2012

A&A

155

200

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“…However, some recent programs have been monitoring also more massive stars, such as evolved subgiants and giants (e.g., Hatzes et al 2006;Döllinger et al 2009;Niedzielski et al 2009;Johnson et al 2011;Sato et al 2013) as well as A-F-type mainsequence stars (e.g., Galland et al 2005;Guenther et al 2009;Hartmann et al 2010;Borgniet et al 2014). One of our targets was the roAp star HD 42659.…”

Section: Observations and Data Reductionmentioning

confidence: 99%

A radial-velocity survey of Ap stars with HARPS

Hartmann

Hatzes

2015

A&A

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Context. Chemically peculiar Ap stars are main-sequence stars of spectral type B8-F3 which show large overabundances of some chemical elements (e.g., Si, Sr, Cr), especially of rare-earth elements, compared to normal A-type stars. Furthermore, they have strong, global magnetic fields and low rotational velocities. Some Ap stars exhibit high-overtone, low-degree, non-radial p-mode pulsations with periods of 6-24 min and are called rapidly oscillating Ap (roAp) stars. Interestingly, no roAp star is known to be a spectroscopic binary (SB), while many non-oscillating Ap (noAp) stars are found in SB systems. Aims. The goal of this survey was to carry out a systematic search for sub-stellar and stellar companions around Ap stars. Methods. Between 2004 and 2009, we observed 65 chemically peculiar stars with the HARPS spectrograph at the 3.6-m telescope at the European Southern Observatory (La Silla, Chile). The radial-velocity (RV) measurements were obtained using a new software called HARPS-TERRA which is based on a least-squares matching of each individual spectrum to a high signal-to-noise ratio template for each star. Results. We find significant variability with a period of 93.2 days and a semi-amplitude of 11.85 km s −1 in the RVs of HD 42659, a star of our sample that belongs to the group of roAp stars. This variability is caused by a stellar companion with a minimum mass of 0.47 M in a slightly eccentric (e = 0.146) orbit at a separation of 0.55 AU.Conclusions. This detection makes HD 42659 the first confirmed SB around a roAp star in a relatively close orbit. It shows that tidal interactions in binaries do not necessarily inhibit pulsations in Ap stars.

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“…To make this dichotomy more quantitative we performed a decomposition by Gaussian mixture models. The parameter space of two Gaussian mixture models was explored using a Markov Chain Monte Carlo simulation and a maximum-likelihood approach to define the best-fit parameters (for details on the code see Nataf et al 2011, for an in-depth explanation of MCMCs see Johnson et al 2011b). The chosen confidence level is 68%.…”

Section: Bright and Faint Sample Starsmentioning

confidence: 99%

Constraining the structure and formation of the Galactic bulge from a field in its outskirts

Uttenthaler¹,

Schultheis²,

Nataf³

et al. 2012

A&A

133

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Context. The presence of two stellar populations in the Milky Way bulge has been reported recently, based on observations of giant and dwarf stars in the inner and intermediate bulge.Aims. We aim at studying the abundances and kinematics of stars in the outer Galactic bulge, thereby providing additional constraints on formation models of the bulge. Methods. Spectra of 401 red giant stars in a field at (l, b) = (0 • , −10 • ) were obtained with the FLAMES-GIRAFFE spectrograph at the VLT. Stars of luminosities down to below the two bulge red clumps are included in the data set. From these spectra we measured general metallicities, abundances of iron and the α-elements, and radial velocities of the stars. The abundances were derived from an interpolation and fitting procedure within a grid of COMARCS model atmospheres and spectra. These measurements as well as photometric data were compared to simulations with the Besançon and TRILEGAL models of the Galaxy. Results. We confirm the presence of two populations among our sample stars: i) a metal-rich one at [M/H] ∼ +0.3, comprising about 30% of the sample, with low velocity dispersion and low α-abundance, and ii) a metal-poor population at [M/H] ∼ −0.6 with high velocity dispersion and high α-abundance. The metallicity difference between the two populations, a systematically and statistically robust figure, is Δ[M/H] = 0.87 ± 0.03. The metal-rich population could be connected to the Galactic bar. We identify this population as the carrier of the double red clump feature. We do not find a significant difference in metallicity or radial velocity between the two red clumps, a small difference in metallicity being probably due to a selection effect and contamination by the metal-poor population. The velocity dispersion agrees well with predictions of the Besançon Galaxy model, but the metallicity of the "thick bulge" model component should be shifted to lower metallicity by 0.2 to 0.3 dex to well reproduce the observations. We present evidence that the metallicity distribution function depends on the evolutionary state of the sample stars, suggesting that enhanced mass loss preferentially removes metal-rich stars. We also confirm the decrease of α-element over-abundance with increasing metallicity. Conclusions. Our sample is consistent with the existence of two populations, one being a metal-rich bar, the second one being more like a metal-poor classical bulge with larger velocity dispersion.

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Retired a Stars and Their Companions. Vii. 18 New Jovian Planets

Cited by 156 publications

References 80 publications

The International Deep Planet Survey

The International Deep Planet Survey

A radial-velocity survey of Ap stars with HARPS

Constraining the structure and formation of the Galactic bulge from a field in its outskirts

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