Search for brown-dwarf companions of stars

Sahlmann, J.; Ségransan, D.; Queloz, D.; Udry, S.; Santos, N. C.; Marmier, M.; Mayor, M.; Naef, D.; Pepe, F.; Zucker, S.

doi:10.1051/0004-6361/201015427

Cited by 213 publications

(332 citation statements)

References 76 publications

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“…The distinction between the two types of objects has been argued to be related to the deuteriumburning mass limit near 13 M Jup (Burrows et al 2001). The lack of a discontinuity in the mass distribution of companions to solar-type stars at the brown-dwarf regime (Udry & Santos 2007;Sahlmann et al 2011) suggests, however, that a distinction based on the formation mechanisms may be more representative (Chabrier et al 2014). The detection and characterisation of high-mass planets in systems where lower mass planets exist (e.g.…”

Section: Introductionmentioning

confidence: 99%

An extreme planetary system around HD 219828

Santos

Santerne

Faria

et al. 2016

A&A

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Context. With about 2000 extrasolar planets confirmed, the results show that planetary systems have a whole range of unexpected properties. This wide diversity provides fundamental clues to the processes of planet formation and evolution. Aims. We present a full investigation of the HD 219828 system, a bright metal-rich star for which a hot Neptune has previously been detected. Methods. We used a set of HARPS, SOPHIE, and ELODIE radial velocities to search for the existence of orbiting companions to HD 219828. The spectra were used to characterise the star and its chemical abundances, as well as to check for spurious, activity induced signals. A dynamical analysis is also performed to study the stability of the system and to constrain the orbital parameters and planet masses. Results. We announce the discovery of a long period (P = 13.1 yr) massive (m sin i = 15.1 M Jup ) companion (HD 219828 c) in a very eccentric orbit (e = 0.81). The same data confirms the existence of a hot Neptune, HD 219828 b, with a minimum mass of 21 M ⊕ and a period of 3.83 days. The dynamical analysis shows that the system is stable, and that the equilibrium eccentricity of planet b is close to zero. Conclusions. The HD 219828 system is extreme and unique in several aspects. First, ammong all known exoplanet systems it presents an unusually high mass ratio. We also show that systems like HD 219828, with a hot Neptune and a long-period massive companion are more frequent than similar systems with a hot Jupiter instead. This suggests that the formation of hot Neptunes follows a different path than the formation of their hot jovian counterparts. The high mass, long period, and eccentricity of HD 219828 c also make it a good target for Gaia astrometry as well as a potential target for atmospheric characterisation, using direct imaging or high-resolution spectroscopy. Astrometric observations will allow us to derive its real mass and orbital configuration. If a transit of HD 219828 b is detected, we will be able to fully characterise the system, including the relative orbital inclinations. With a clearly known mass, HD 219828 c may become a benchmark object for the range in between giant planets and brown dwarfs.

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Section: Introductionmentioning

confidence: 99%

An extreme planetary system around HD 219828

Santos

Santerne

Faria

et al. 2016

A&A

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“…The minimum mass of the companion was then found to be 19.2 M Jup (best solution), From the results of our high-contrast imaging study, we find that the radial-velocity companion detected by Sahlmann et al (2011) is compatible with the one seen in SPHERE images and so is actually a low-mass star (M5 spectral type) instead of a substellar companion. It implies an angle of 7 • for the inclination of the binary orbit, and therefore an almost face-on system.…”

Section: Hd 211847mentioning

confidence: 54%

“…All observations were performed in pupil-stabilized mode with the apodized pupil Lyot coronograph N-ALC-YJH-S (Soummer 2005), which uses a coronagraphic mask of diameter 185 mas. The IRDIS detector was dithered on a 4×4 pattern to reduce the effect of the residual flat-field noise.…”

Section: Instrument and Strategymentioning

confidence: 99%

“…In the radial-velocity discovery paper (Sahlmann et al 2011), the best-fit solution has a semi-major axis of 7.5±1.5au but other solutions between 4 and 50au cannot be excluded due to the incomplete time coverage of the orbit. The minimum mass of the companion was then found to be 19.2 M Jup (best solution), From the results of our high-contrast imaging study, we find that the radial-velocity companion detected by Sahlmann et al (2011) is compatible with the one seen in SPHERE images and so is actually a low-mass star (M5 spectral type) instead of a substellar companion.…”

Section: Hd 211847mentioning

confidence: 99%

“…A oneKeplerian model fit gives a period for the long-term companion of 3134±566 days and a reduced χ 2 of 5.93. There is some noise in the residuals that was interpreted as stellar noise in Sahlmann et al (2011). In the periodogram of residuals there are two main peaks at 18.5 and 2.016 days.…”

Section: Hd 211847mentioning

confidence: 99%

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Eccentricity in planetary systems and the role of binarity

Moutou

Vigan

Mesa

et al. 2017

A&A

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We explore the multiplicity of exoplanet host stars with high-resolution images obtained with VLT/SPHERE. Two different samples of systems were observed: one containing low-eccentricity outer planets, and the other containing high-eccentricity outer planets. We find that 10 out of 34 stars in the high-eccentricity systems are members of a binary, while the proportion is 3 out of 27 for circular systems. Eccentric-exoplanet hosts are, therefore, significantly more likely to have a stellar companion than circular-exoplanet hosts. The median magnitude contrast over the 68 data sets is 11.26 and 9.25, in H and K, respectively, at 0.30 arcsec. The derived detection limits reveal that binaries with separations of less than 50au are rarer for exoplanet hosts than for field stars. Our results also imply that the majority of high-eccentricity planets are not embedded in multiple stellar systems (24 out of 34), since our detection limits exclude the presence of a stellar companion. We detect the low-mass stellar companions of HD 7449 and HD 211847, both members of our high-eccentricity sample. HD 7449B was already detected by Rodigas et al. (2016) and our independent observation is in agreement with this earlier work. HD 211847's substellar companion, previously detected by the radial velocity method, is actually a low-mass star seen face-on. The role of stellar multiplicity in shaping planetary systems is confirmed by this work, although it does not appear as the only source of dynamical excitation.

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Extra-Solar Planetary Systems

Milone

Wilson

2013

Solar System Astrophysics

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Search for brown-dwarf companions of stars

Cited by 213 publications

References 76 publications

An extreme planetary system around HD 219828

An extreme planetary system around HD 219828

Eccentricity in planetary systems and the role of binarity

Extra-Solar Planetary Systems

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