A giant exoplanet orbiting a very-low-mass star challenges planet formation models

Surveys have shown that super-Earth and Neptune-mass exoplanets are more frequent than gas giants around low-mass stars, as predicted by the core accretion theory of planet formation. We report the discovery of a giant planet around the very-low-mass star GJ 3512, as determined by optical and near-infrared radial-velocity observations. The planet has a minimum mass of 0.46 Jupiter masses, very high for such a small host star, and an eccentric 204-day orbit. Dynamical models show that the high eccentricity is most likely due to planet-planet interactions. We use simulations to demonstrate that the GJ 3512 planetary system challenges generally accepted formation theories, and that it puts constraints on the planet accretion and migration rates. Disk instabilities may be more efficient in forming planets than previously thought.

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Multi-Wavelength High-Resolution Spectroscopy for Exoplanet Detection: Motivation, Instrumentation and First Results

Geosciences ◽

10.3390/geosciences8080289 ◽

2018 ◽

Vol 8 (8) ◽

pp. 289 ◽

Cited By ~ 1

Author(s):

Serena Benatti

Keyword(s):

High Resolution ◽

Near Infrared ◽

Giant Planet ◽

High Resolution Spectroscopy ◽

M Dwarfs ◽

Low Mass Stars ◽

First Results ◽

Multi Wavelength ◽

Low Mass ◽

Rocky Planets

Exoplanet research has shown an incessant growth since the first claim of a hot giant planet around a solar-like star in the mid-1990s. Today, the new facilities are working to spot the first habitable rocky planets around low-mass stars as a forerunner for the detection of the long-awaited Sun-Earth analog system. All the achievements in this field would not have been possible without the constant development of the technology and of new methods to detect more and more challenging planets. After the consolidation of a top-level instrumentation for high-resolution spectroscopy in the visible wavelength range, a huge effort is now dedicated to reaching the same precision and accuracy in the near-infrared. Actually, observations in this range present several advantages in the search for exoplanets around M dwarfs, known to be the most favorable targets to detect possible habitable planets. They are also characterized by intense stellar activity, which hampers planet detection, but its impact on the radial velocity modulation is mitigated in the infrared. Simultaneous observations in the visible and near-infrared ranges appear to be an even more powerful technique since they provide combined and complementary information, also useful for many other exoplanetary science cases.

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Terrestrial planet formation in extra-solar planetary systems

Proceedings of the International Astronomical Union ◽

10.1017/s1743921308016645 ◽

2007 ◽

Vol 3 (S249) ◽

pp. 233-250 ◽

Cited By ~ 2

Author(s):

Sean N. Raymond

Keyword(s):

Final Stage ◽

Planet Formation ◽

Giant Planet ◽

Terrestrial Planet ◽

Circumstellar Disks ◽

Giant Planets ◽

Terrestrial Planets ◽

Low Mass Stars ◽

Low Mass ◽

Rocky Planets

AbstractTerrestrial planets form in a series of dynamical steps from the solid component of circumstellar disks. First, km-sized planetesimals form likely via a combination of sticky collisions, turbulent concentration of solids, and gravitational collapse from micron-sized dust grains in the thin disk midplane. Second, planetesimals coalesce to form Moon- to Mars-sized protoplanets, also called “planetary embryos”. Finally, full-sized terrestrial planets accrete from protoplanets and planetesimals. This final stage of accretion lasts about 10-100 Myr and is strongly affected by gravitational perturbations from any gas giant planets, which are constrained to form more quickly, during the 1-10 Myr lifetime of the gaseous component of the disk. It is during this final stage that the bulk compositions and volatile (e.g., water) contents of terrestrial planets are set, depending on their feeding zones and the amount of radial mixing that occurs. The main factors that influence terrestrial planet formation are the mass and surface density profile of the disk, and the perturbations from giant planets and binary companions if they exist. Simple accretion models predicts that low-mass stars should form small, dry planets in their habitable zones. The migration of a giant planet through a disk of rocky bodies does not completely impede terrestrial planet growth. Rather, “hot Jupiter” systems are likely to also contain exterior, very water-rich Earth-like planets, and also “hot Earths”, very close-in rocky planets. Roughly one third of the known systems of extra-solar (giant) planets could allow a terrestrial planet to form in the habitable zone.

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Low-mass Star Formation: Observations

Proceedings of the International Astronomical Union ◽

10.1017/s1743921311000123 ◽

2010 ◽

Vol 6 (S270) ◽

pp. 25-32 ◽

Cited By ~ 1

Author(s):

Neal J. Evans

Keyword(s):

Star Formation ◽

Molecular Clouds ◽

Planet Formation ◽

Mass Star ◽

Low Mass Stars ◽

Chemical Changes ◽

Open Questions ◽

Low Mass ◽

Over Time ◽

The Imf

AbstractI briefly review recent observations of regions forming low mass stars. The discussion is cast in the form of seven questions that have been partially answered, or at least illuminated, by new data. These are the following: where do stars form in molecular clouds; what determines the IMF; how long do the steps of the process take; how efficient is star formation; do any theories explain the data; how are the star and disk built over time; and what chemical changes accompany star and planet formation. I close with a summary and list of open questions.

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High-redshift quasar selection from the CFHQSIR survey

Astronomy and Astrophysics ◽

10.1051/0004-6361/201833488 ◽

2018 ◽

Vol 617 ◽

pp. A127 ◽

Cited By ~ 2

Author(s):

S. Pipien ◽

J.-G. Cuby ◽

S. Basa ◽

C. J. Willott ◽

J.-C. Cuillandre ◽

...

Keyword(s):

Near Infrared ◽

High Redshift ◽

Selection Procedure ◽

Absolute Magnitude ◽

Big Bang ◽

Mass Star ◽

Wide Field ◽

Galactic Latitude ◽

Low Mass Stars ◽

Low Mass

Being observed only one billion years after the Big Bang, z ∼ 7 quasars are a unique opportunity for exploring the early Universe. However, only two z ∼ 7 quasars have been discovered in near-infrared surveys: the quasars ULAS J1120+0641 and ULAS J1342+0928 at z = 7.09 and z = 7.54, respectively. The rarity of these distant objects, combined with the difficulty of distinguishing them from the much more numerous population of Galactic low-mass stars, requires using efficient selection procedures. The Canada-France High-z Quasar Survey in the Near Infrared (CFHQSIR) has been carried out to search for z ∼ 7 quasars using near-infrared and optical imaging from the Canada-France Hawaii Telescope (CFHT). Our data consist of ∼130 deg2 of Wide-field Infrared Camera (WIRCam) Y-band images up to a 5σ limit of YAB ∼ 22.4 distributed over the Canada-France-Hawaii Telescope Legacy Survey (CFHTLS) Wide fields. After follow-up observations in J band, a first photometric selection based on simple colour criteria led us to identify 36 sources with measured high-redshift quasar colours. However, we expect to detect only ∼2 quasars in the redshift range 6.8 < z < 7.5 down to a rest-frame absolute magnitude of M1450 = −24.6. With the motivation of ranking our high-redshift quasar candidates in the best possible way, we developed an advanced classification method based on Bayesian formalism in which we model the high-redshift quasars and low-mass star populations. The model includes the colour diversity of the two populations and the variation in space density of the low-mass stars with Galactic latitude, and it is combined with our observational data. For each candidate, we compute the probability of being a high-redshift quasar rather than a low-mass star. This results in a refined list of the most promising candidates. Our Bayesian selection procedure has proven to be a powerful technique for identifying the best candidates of any photometrically selected sample of objects, and it is easily extendable to other surveys.

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Discovery of a stellar companion to HD 131399A

Astronomy and Astrophysics ◽

10.1051/0004-6361/201730978 ◽

2017 ◽

Vol 608 ◽

pp. L9 ◽

Cited By ~ 1

Author(s):

A.-M. Lagrange ◽

M. Keppler ◽

H. Beust ◽

L. Rodet ◽

N. Meunier ◽

...

Keyword(s):

High Resolution ◽

Binary System ◽

Planet Formation ◽

Giant Planet ◽

Dynamical Evolution ◽

Young Stars ◽

Circumstellar Disk ◽

Mass Star ◽

Low Mass

Context. The giant exoplanets imaged on wide orbits (≥10 au) around young stars challenge the classical theories of planet formation. The presence of perturbing bodies could have played a role in the dynamical evolution of the planets once formed. Aims. We aim to search for close companions to HD 131399, a star around which a giant planet has been discovered, at a projected separation of about 80 au. The star also appears to be a member of a wide (320 au) binary system. Methods. We recorded HARPS high resolution spectra in January 2017. Results. We find that HD 131399A is probably seen close to pole-on. We discover a low mass star companion that orbits with a period of about 10 days on a misaligned orbit. Even though the companion does not have an impact on the current dynamical evolution of the planet, it could have played a role in its setting and in clearing the circumstellar disk from which the planet may originate.

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Planet formation around M dwarfs via disc instability

Astronomy and Astrophysics ◽

10.1051/0004-6361/201936954 ◽

2020 ◽

Vol 633 ◽

pp. A116

Author(s):

Anthony Mercer ◽

Dimitris Stamatellos

Keyword(s):

Planet Formation ◽

M Dwarfs ◽

Low Mass Stars ◽

Dwarf Stars ◽

Low Mass ◽

Protostellar Discs ◽

Stellar Masses ◽

M Dwarf Stars ◽

Core Accretion ◽

M Dwarf

Context. Around 30 per cent of the observed exoplanets that orbit M dwarf stars are gas giants that are more massive than Jupiter. These planets are prime candidates for formation by disc instability. Aims. We want to determine the conditions for disc fragmentation around M dwarfs and the properties of the planets that are formed by disc instability. Methods. We performed hydrodynamic simulations of M dwarf protostellar discs in order to determine the minimum disc mass required for gravitational fragmentation to occur. Different stellar masses, disc radii, and metallicities were considered. The mass of each protostellar disc was steadily increased until the disc fragmented and a protoplanet was formed. Results. We find that a disc-to-star mass ratio between ~0.3 and ~0.6 is required for fragmentation to happen. The minimum mass at which a disc fragment increases with the stellar mass and the disc size. Metallicity does not significantly affect the minimum disc fragmentation mass but high metallicity may suppress fragmentation. Protoplanets form quickly (within a few thousand years) at distances around ~50 AU from the host star, and they are initially very hot; their centres have temperatures similar to the ones expected at the accretion shocks around planets formed by core accretion (up to 12 000 K). The final properties of these planets (e.g. mass and orbital radius) are determined through long-term disc-planet or planet–planet interactions. Conclusions. Disc instability is a plausible way to form gas giant planets around M dwarfs provided that discs have at least 30% the mass of their host stars during the initial stages of their formation. Future observations of massive M dwarf discs or planets around very young M dwarfs are required to establish the importance of disc instability for planet formation around low-mass stars.

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Pebble-driven planet formation around very low-mass stars and brown dwarfs

Astronomy and Astrophysics ◽

10.1051/0004-6361/202037720 ◽

2020 ◽

Vol 638 ◽

pp. A88 ◽

Cited By ~ 2

Author(s):

Beibei Liu ◽

Michiel Lambrechts ◽

Anders Johansen ◽

Ilaria Pascucci ◽

Thomas Henning

Keyword(s):

Mass Fraction ◽

Planet Formation ◽

Water Mass ◽

Giant Planet ◽

Brown Dwarfs ◽

Mass Range ◽

Protoplanetary Disk ◽

Low Mass Stars ◽

Streaming Instability ◽

Low Mass

We conduct a pebble-driven planet population synthesis study to investigate the formation of planets around very low-mass stars and brown dwarfs in the (sub)stellar mass range between 0.01 M⊙ and 0.1 M⊙. Based on the extrapolation of numerical simulations of planetesimal formation by the streaming instability, we obtain the characteristic mass of the planetesimals and the initial mass of the protoplanet (largest body from the planetesimal populations), in either the early self-gravitating phase or the later non-self-gravitating phase of the protoplanetary disk evolution. We find that the initial protoplanets form with masses that increase with host mass and orbital distance, and decrease with age. Around late M-dwarfs of 0.1 M⊙, these protoplanets can grow up to Earth-mass planets by pebble accretion. However, around brown dwarfs of 0.01 M⊙, planets do not grow to the masses that are greater than Mars when the initial protoplanets are born early in self-gravitating disks, and their growth stalls at around 0.01 Earth-mass when they are born late in non-self-gravitating disks. Around these low-mass stars and brown dwarfs we find no channel for gas giant planet formation because the solid cores remain too small. When the initial protoplanets form only at the water-ice line, the final planets typically have ≳15% water mass fraction. Alternatively, when the initial protoplanets form log-uniformly distributed over the entire protoplanetary disk, the final planets are either very water rich (water mass fraction ≳15%) or entirely rocky (water mass fraction ≲5%).

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SpS1-Dust and gas clearing in transitional disks

Proceedings of the International Astronomical Union ◽

10.1017/s1743921310010483 ◽

2009 ◽

Vol 5 (H15) ◽

pp. 521-521

Author(s):

Joanna M. Brown

Keyword(s):

Planet Formation ◽

Giant Planet ◽

Circumstellar Disks ◽

Spectral Energy ◽

Mass Star ◽

Infrared Observations ◽

Star Forming ◽

Star Forming Regions ◽

Disk Material ◽

Low Mass

Understanding how disks dissipate is essential to studies of planet formation. Infrared observations of young stars demonstrate that optically-thick circumstellar disks disappear from around half the stars in low-mass star-forming regions by an age of 3 Myr and are almost entirely absent in 10 Myr old associations (e.g. Haisch et al., 2001). Accretion ceases on the same approximate timescale (e.g. Calvet et al. 2005). The disappearence of gas and dust - planetary building material - places stringent limits on the timescales of giant planet formation. During this crucial interval, planet(esimal)s form and the remaining disk material is accreted or dispersed. Mid-infrared spectrophotometry of protoplanetary disks has revealed a small sub-class of objects in the midst of losing their disk material. These disks have spectral energy distributions (SEDs) suggestive of large inner gaps with low dust content, often interpreted as a signature of young planets. Such objects are still rare although Spitzer surveys have significantly increased the number of known transitional objects (e.g. Brown et al. 2007, D'Alessio et al., 2005). However, spectrophotometric signatures are indirect and notoriously difficult to interpret as multiple physical scenarios can result in the same SED. Recent direct imaging from millimeter interferometry has confirmed the presence of large inner holes in transitional disks, providing additional constraints and lending confidence to current SED interpretations (Brown et al. 2008, Brown et al. 2009, Andrews et al. 2009, Isella et al., 2009).

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