The imprint of accretion on the UV spectrum of young stellar objects: an X-Shooter view

Manara, C. F.; Testi, L.

doi:10.1007/s10509-014-2055-z

Cited by 3 publications

(2 citation statements)

References 19 publications

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“…where M is the stellar mass, α is the parameter that characterises the viscosity and Ṁ is the accretion rate into the star, which has a typical value of 10 −10 M yr −1 for small stars (Manara & Testi 2014). The irradiation temperature profile is given by:…”

Section: Initial Discmentioning

confidence: 99%

Diverse outcomes of planet formation and composition around low-mass stars and brown dwarfs

Miguel

Cridland

Ormel

et al. 2019

Monthly Notices of the Royal Astronomical Society

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The detection of Earth-size exoplanets around low-mass stars -such as Proxima Centauri b and the TRAPPIST-1 system-provide an exceptional chance to improve our understanding of the formation of planets around M stars and brown dwarfs. We explore the formation of such planets with a population synthesis code based on a planetesimal-driven model previously used to study the formation of the Jovian satellites. Because the discs have low mass and the stars are cool, the formation is an inefficient process that happens at low periods, generating compact planetary systems. Planets can be trapped in resonances and we follow the evolution of the planets after the gas has dissipated and they undergo orbit crossings and possible mergers. We find that planet formation in the planetesimal accretion scenario is only possible around stars with masses M 0.07M sun and discs of M disc 10 −2 M sun . Hence, in order to form planets (M p 0.1M ⊕ ) around low-mass stars (0.05 M 0.25M sun ), relatively massive discs are required. Our results show that one third of the synthetic planetary systems have at least one planet with M p 1M ⊕ , but we are not able to form planets larger than 5M ⊕ , showing that planets such as GJ 3512b form with another, more efficient mechanism. We find that the large majority of the planets formed have a large water content and most of our synthetic planetary systems have 1, 2 or 3 planets, but planets with 4,5,6 and 7 planets are also common, confirming that compact planetary systems with many planets should be a relatively common outcome of planet formation around small stars. Our results provide information to guide current and future surveys and aid in the interpretation of TESS and PLATO data.

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Section: Initial Discmentioning

confidence: 99%

Diverse outcomes of planet formation and composition around low-mass stars and brown dwarfs

Miguel

Cridland

Ormel

et al. 2019

Monthly Notices of the Royal Astronomical Society

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“…A global solution is necessary to properly derive the parameters of pre-main-sequence stars. (Adapted from [74]).…”

Section: Globular Clustersmentioning

confidence: 99%

The GMOX science case: resolving galaxies through cosmic time

et al. 2016

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We present the key scientific questions that can be addressed by GMOX, a Multi-Object Spectrograph selected for feasibility study as a 4th generation instrument for the Gemini telescopes. Using commercial digital micromirror devices (DMDs) as slit selection mechanisms, GMOX can observe hundred of sources at R∼ 5000 between the U and K band simultaneously. Exploiting the narrow PSF delivered by the Gemini South GeMS MCAO module, GMOX can synthesize slits as small as 40mas reaching extremely faint magnitude limits, and thus enabling a plethora of applications and innovative science. Our main scientific driver in developing GMOX has been Resolving galaxies through cosmic time: GMOX 40mas slit (at GeMS) corresponds to 300 pc at z ∼ 1.5, where the angular diameter distance reaches its maximum, and therefore to even smaller linear scales at any other redshift. This means tha GMOX can take spectra of regions smaller than 300 pc in the whole observable Universe, allowing to probe the growth and evolution of galaxies with unprecedented detail. GMOXs multi-object capability and high angular resolution enable efficient studies of crowded fields, such as globular clusters, the Milky Way bulge, the Magellanic Clouds, Local Group galaxies and galaxy clusters. The wide-band simultaneous coverage and the very fast slit configuration mechanisms also make GMOX ideal for followup of LSST transients.

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Global multifluid simulations of the magnetorotational instability in radially stratified protoplanetary discs

Rodgers-Lee

Ray

Downes

2016

Mon. Not. R. Astron. Soc.

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The redistribution of angular momentum is a long standing problem in our understanding of protoplanetary disk (PPD) evolution. The magnetorotational instability (MRI) is considered a likely mechanism. We present the results of a study involving multifluid global simulations including Ohmic dissipation, ambipolar diffusion and the Hall effect in a dynamic, self-consistent way. We focus on the turbulence resulting from the non-linear development of the MRI in radially stratified PPDs and compare with ideal MHD simulations.In the multifluid simulations the disk is initially set up to transition from a weak Hall dominated regime, where the Hall effect is the dominant non-ideal effect but approximately the same as or weaker than the inductive term, to a strong Hall dominated regime, where the Hall effect dominates the inductive term. As the simulations progress a substantial portion of the disk develops into a weak Hall dominated disk. We find a transition from turbulent to laminar flow in the inner regions of the disk, but without any corresponding overall density feature.We introduce a dimensionless parameter, α RM , to characterise accretion with α RM 0.1 corresponding to turbulent transport. We calculate the eddy turnover time, t eddy , and compared this with an effective recombination timescale, t rcb , to determine whether the presence of turbulence necessitates non-equilibrium ionisation calculations. We find that t rcb is typically around three orders of magnitude smaller than t eddy . Also, the ionisation fraction does not vary appreciably. These two results suggest that these multifluid simulations should be comparable to single fluid non-ideal simulations.

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The imprint of accretion on the UV spectrum of young stellar objects: an X-Shooter view

Cited by 3 publications

References 19 publications

Diverse outcomes of planet formation and composition around low-mass stars and brown dwarfs

Diverse outcomes of planet formation and composition around low-mass stars and brown dwarfs

The GMOX science case: resolving galaxies through cosmic time

Global multifluid simulations of the magnetorotational instability in radially stratified protoplanetary discs

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