Searching for chemical signatures of brown dwarf formation

Maldonado, J.; Villaver, E.

doi:10.1051/0004-6361/201630120

Cited by 24 publications

(31 citation statements)

References 82 publications

(123 reference statements)

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“…Ma & Ge (2014); Mata Sánchez et al (2014) showed that unlike gas-giant planet hosts, stars with brown dwarfs do not show metalenrichment. Maldonado & Villaver (2017) found that stars with low-mass brown dwarfs tend to show higher metallicities than stars hosting more massive brown dwarfs. Ma & Ge (2014); Maldonado & Villaver (2017) also discussed differences in the period-eccentricity distribution of massive and low-mass brown dwarfs.…”

Section: Discussionmentioning

confidence: 99%

“…Maldonado & Villaver (2017) found that stars with low-mass brown dwarfs tend to show higher metallicities than stars hosting more massive brown dwarfs. Ma & Ge (2014); Maldonado & Villaver (2017) also discussed differences in the period-eccentricity distribution of massive and low-mass brown dwarfs. This result fits well with our interpretation that more massive substellar objects tend to form more like stars.…”

Section: Discussionmentioning

confidence: 99%

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Connecting substellar and stellar formation: the role of the host star’s metallicity

Maldonado

Villaver

Eiroa

et al. 2019

A&A

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Context. Most of our current understanding of the planet formation mechanism is based on the planet metallicity correlation derived mostly from solar-type stars harbouring gas-giant planets. Aims. To achieve a far more reaching grasp on the substellar formation process we aim to analyse in terms of their metallicity a diverse sample of stars (in terms of mass and spectral type) covering the whole range of possible outcomes of the planet formation process (from planetesimals to brown dwarfs and low-mass binaries). Methods. Our methodology is based on the use of high-precision stellar parameters derived by our own group in previous works from high-resolution spectra by using the iron ionisation and equilibrium conditions. All values are derived in an homogeneous way, except for the M dwarfs where a methodology based on the use of pseudo equivalent widths of spectral features was used. Results. Our results show that as the mass of the substellar companion increases the metallicity of the host star tendency is to lower values. The same trend is maintained when analysing stars with low-mass stellar companions and a tendency towards a wide range of host star's metallicity is found for systems with low mass planets. We also confirm that more massive planets tend to orbit around more massive stars. Conclusions. The core-accretion formation mechanism for planet formation achieves its maximum efficiency for planets with masses in the range 0.2 and 2 M Jup . Substellar objects with higher masses have higher probabilities of being formed as stars. Low-mass planets and planetesimals might be formed by core-accretion even around low-metallicity stars.

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Section: Discussionmentioning

confidence: 99%

Section: Discussionmentioning

confidence: 99%

Connecting substellar and stellar formation: the role of the host star’s metallicity

Maldonado

Villaver

Eiroa

et al. 2019

A&A

Self Cite

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“…Solar abundances were used For cooler stars (later than F2), a different approach was used to calculate parameters. In those cases we have followed the procedure described in detail by Maldonado & Villaver (2017) and Maldonado et al (2018), which is based on the iron ionisation and excitation equilibrium, and match of the curve of growth conditions. Radial velocities (v rad ) were estimated by measuring the shift between the synthetic spectrum, which is computed using a database of rest wavelengths, and the observed spectrum, corrected for barycentric velocity.…”

Section: Stellar Parametersmentioning

confidence: 99%

Exocomets: A spectroscopic survey

Rebollido

Eiroa

Montesinos

et al. 2020

A&A

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Context. While exoplanets are now routinely detected, the detection of small bodies in extrasolar systems remains challenging. Since the discovery of sporadic events, which are interpreted to be exocomets (falling evaporating bodies) around β Pic in the early 1980s, only ∼20 stars have been reported to host exocomet-like events. Aims. We aim to expand the sample of known exocomet-host stars, as well as to monitor the hot-gas environment around stars with previously known exocometary activity. Methods. We have obtained high-resolution optical spectra of a heterogeneous sample of 117 main-sequence stars in the spectral type range from B8 to G8. The data were collected in 14 observing campaigns over the course of two years from both hemispheres. We analysed the Ca II K&H and Na I D lines in order to search for non-photospheric absorptions that originated in the circumstellar environment and for variable events that could be caused by the outgassing of exocomet-like bodies. Results. We detected non-photospheric absorptions towards 50% of the sample, thus attributing a circumstellar origin to half of the detections (i.e. 26% of the sample). Hot circumstellar gas was detected in the metallic lines inspected via narrow stable absorptions and/or variable blue- and red-shifted absorption events. Such variable events were found in 18 stars in the Ca II and/or Na I lines; six of them are reported in the context of this work for the first time. In some cases, the variations we report in the Ca II K line are similar to those observed in β Pic. While we do not find a significant trend in the age or location of the stars, we do find that the probability of finding CS gas in stars with larger v sin i is higher. We also find a weak trend with the presence of near-infrared excess and with anomalous (λ Boo-like) abundances, but this would require confirmation by expanding the sample.

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“…Interestingly, several studies suggest that BDs with masses above and bellow ∼ 42 M might have formed by different processes [e.g. 189,[238][239][240]. In particular, low-mass BDs can be formed by disk instability and the high-mass BDs via cloud fragmentation as stars [238].…”

Section: Very Massive Giants and Metallicitymentioning

confidence: 99%

Heavy Metal Rules. I. Exoplanet Incidence and Metallicity

Adibekyan

2019

Geosciences

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Discovery of only handful of exoplanets required to establish a correlation between giant planet occurrence and metallicity of their host stars. More than 20 years have already passed from that discovery, however, many questions are still under lively debate: What is the origin of that relation? what is the exact functional form of the giant planet -metallicity relation (in the metal-poor regime)?, does such a relation exist for terrestrial planets? All these question are very important for our understanding of the formation and evolution of (exo)planets of different types around different types of stars and are subject of the present manuscript. Besides making a comprehensive literature review about the role of metallicity on the formation of exoplanets, I also revisited most of the planet -metallicity related correlations reported in the literature using a large and homogeneous data provided by the SWEET-Cat catalog. This study lead to several new results and conclusions, two of which I believe deserve to be highlighted in the abstract: i) The hosts of sub-Jupiter mass planets (∼0.6 -0.9 M ) are systematically less metallic than the hosts of Jupiter-mass planets. This result might be related to the longer disk lifetime and higher amount of planet building materials available at high metallicities, which allow a formation of more massive Jupiter-like planets. ii) Contrary to the previous claims, our data and results do not support the existence of a breakpoint planetary mass at 4 M above and below which planet formation channels are different. However, the results also suggest that planets of the same (high) mass can be formed through different channels depending on the (disk) stellar mass i.e. environmental conditions.

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Searching for chemical signatures of brown dwarf formation

Cited by 24 publications

References 82 publications

Connecting substellar and stellar formation: the role of the host star’s metallicity

Connecting substellar and stellar formation: the role of the host star’s metallicity

Exocomets: A spectroscopic survey

Heavy Metal Rules. I. Exoplanet Incidence and Metallicity

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