Speckle Interferometry of Two Low-mass Triple Systems in the Solar Neighbourhood

ABSTRACT In the last three decades several hundred nearby members of young stellar moving groups (MGs) have been identified, but there has been less systematic effort to quantify or characterize young stars that do not belong to previously identified MGs. Using a kinematically unbiased sample of 225 lithium-rich stars within 100 pc, we find that only 50 ± 10 per cent of young (≲125 Myr), low-mass (0.5 < M/M⊙ < 1.0) stars, are kinematically associated with known MGs. Whilst we find some evidence that five of the non-MG stars may be connected with the Lower Centaurus–Crux association, the rest form a kinematically ‘hotter’ population, much more broadly dispersed in velocity, and with no obvious concentrations in space. The mass distributions of the MG members and non-MG stars are similar, but the non-MG stars may be older on average. We briefly discuss several explanations for the origin of the non-MG population.

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Eccentricity distribution of wide low-mass binaries

Monthly Notices of the Royal Astronomical Society ◽

10.1093/mnras/staa1639 ◽

2020 ◽

Vol 496 (1) ◽

pp. 987-993 ◽

Cited By ~ 1

Author(s):

Andrei Tokovinin

Keyword(s):

Stellar Dynamics ◽

Statistical Information ◽

Solar Neighbourhood ◽

Wide Binary ◽

Eccentric Orbits ◽

Wide Pairs ◽

Low Mass ◽

Orbital Periods ◽

Relative Motions

ABSTRACT Distribution of eccentricities of very wide (up to 10 kau) low-mass binaries in the solar neighbourhood is studied using the catalogue of El-Badry and Rix (2018) based on Gaia. Direction and speed of relative motions in wide pairs contain statistical information on the eccentricity distribution, otherwise inaccessible owing to very long orbital periods. It is found that the eccentricity distribution is close to the linear (thermal) one f(e) = 2e. However, pairs with projected separations <200 au have less eccentric orbits, while f(e) for wide pairs with s > 1 kau appears to be slightly superthermal, with an excess of very eccentric orbits. Eccentricity of any wide binary can be constrained statistically using direction and speed of its motion. The thermal eccentricity distribution signals an important role of the stellar dynamics in the formation of wide binaries, although disc-assisted capture also can produce such pairs with eccentric orbits.

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A Radial velocity survey of spatially resolved young, low-mass binaries

Astronomy and Astrophysics ◽

10.1051/0004-6361/201732156 ◽

2018 ◽

Vol 618 ◽

pp. A5 ◽

Cited By ~ 2

Author(s):

Stephen Durkan ◽

Markus Janson ◽

Simona Ciceri ◽

Wolfgang Brandner ◽

Joshua Schlieder ◽

...

Keyword(s):

Radial Velocity ◽

Solar Neighborhood ◽

Activity Level ◽

Activity Levels ◽

Old Field ◽

Triple Systems ◽

Chromospheric Activity ◽

Low Mass ◽

Orbital Periods ◽

Moving Groups

The identification and characterisation of low-mass binaries is of importance for a range of astrophysical investigations. Low-mass binaries in young (∼10–100 Myr) moving groups (YMGs) in the solar neighborhood are of particular significance as they provide unique opportunities to calibrate stellar models and evaluate the ages and coevality of the groups themselves. Low-mass M-dwarfs have pre-main sequence life times on the order of ∼100 Myr and therefore are continually evolving along a mass-luminosity track throughout the YMG phase, providing ideal laboratories for precise isochronal dating, if a model-independent dynamical mass can be measured. AstraLux lucky imaging multiplicity surveys have recently identified hundreds of new YMG low-mass binaries, where a subsample of M-dwarf multiples have estimated orbital periods less than 50 yr. We have conducted a radial velocity survey of a sample of 29 such targets to complement the astrometric data. This will allow enhanced orbital determinations and precise dynamical masses to be derived in a shorter timeframe than possible with astrometric monitoring alone, and allow for a more reliable isochronal analysis. Here we present radial velocity measurements derived for our sample over several epochs. We report the detection of the three-component spectroscopic multiple 2MASS J05301858-5358483, for which the C component is a new discovery, and forms a tight pair with the B component. Originally identified as a YMG member, we find that this system is a likely old field interloper, whose high chromospheric activity level is caused by tidal spin-up of the tight BC pair. Two other triple systems with a tight pair exist in the sample, 2MASS J04244260-0647313 (previously known) and 2MASS J20163382-0711456, but for the rest of the targets we find that additional tidally synchronized companions are highly unlikely, providing further evidence that their high chromospheric activity levels are generally signatures of youth.

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Prevalent externally driven protoplanetary disc dispersal as a function of the galactic environment

Monthly Notices of the Royal Astronomical Society ◽

10.1093/mnras/stz2747 ◽

2019 ◽

Vol 491 (1) ◽

pp. 903-922 ◽

Cited By ~ 9

Author(s):

Andrew J Winter ◽

J M Diederik Kruijssen ◽

Mélanie Chevance ◽

Benjamin W Keller ◽

Steven N Longmore

Keyword(s):

Planet Formation ◽

Solar Neighbourhood ◽

Related Factor ◽

Low Mass Stars ◽

Stellar Feedback ◽

Low Mass ◽

Far Ultraviolet ◽

Birth Environment ◽

Stellar Density ◽

Key Questions

ABSTRACT The stellar birth environment can significantly shorten protoplanetary disc (PPD) lifetimes due to the influence of stellar feedback mechanisms. The degree to which these mechanisms suppress the time and mass available for planet formation is dependent on the local far-ultraviolet (FUV) field strength, stellar density, and ISM properties. In this work, we present the first theoretical framework quantifying the distribution of PPD dispersal time-scales as a function of parameters that describe the galactic environment. We calculate the probability density function for FUV flux and stellar density in the solar neighbourhood. In agreement with previous studies, we find that external photoevaporation is the dominant environment-related factor influencing local stellar populations after the embedded phase. Applying our general prescription to the Central Molecular Zone of the Milky Way (i.e. the central $\sim 250~\mbox{${\rm pc}$}$), we predict that $90{{\ \rm per\ cent}}$ of PPDs in the region are destroyed within 1 Myr of the dispersal of the parent molecular cloud. Even in such dense environments, we find that external photoevaporation is the dominant disc depletion mechanism over dynamical encounters between stars. PPDs around low-mass stars are particularly sensitive to FUV-induced mass-loss, due to a shallower gravitational potential. For stars of mass ∼1 M⊙, the solar neighbourhood lies at approximately the highest gas surface density for which PPD dispersal is still relatively unaffected by external FUV photons, with a median PPD dispersal time-scale of ∼4 Myr. We highlight the key questions to be addressed to further contextualize the significance of the local galactic environment for planet formation.

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Episodic accretion in binary protostars emerging from self-gravitating solar mass cores

Astronomy and Astrophysics ◽

10.1051/0004-6361/201732076 ◽

2018 ◽

Vol 614 ◽

pp. A53 ◽

Cited By ~ 2

Author(s):

R. Riaz ◽

S. Vanaverbeke ◽

D. R. G. Schleicher

Keyword(s):

Molecular Cloud ◽

Accretion Rate ◽

Solar Mass ◽

Multiple Systems ◽

Average Mass ◽

Triple Systems ◽

Large Spread ◽

Low Mass ◽

Over Time

Observations show a large spread in the luminosities of young protostars, which are frequently explained in the context of episodic accretion. We tested this scenario with numerical simulations that follow the collapse of a solar mass molecular cloud using the GRADSPH code, thereby varying the strength of the initial perturbations and temperature of the cores. A specific emphasis of this paper is to investigate the role of binaries and multiple systems in the context of episodic accretion and to compare their evolution to the evolution in isolated fragments. Our models form a variety of low-mass protostellar objects including single, binary, and triple systems in which binaries are more active in exhibiting episodic accretion than isolated protostars. We also find a general decreasing trend in the average mass accretion rate over time, suggesting that the majority of the protostellar mass is accreted within the first 105 years. This result can potentially help to explain the surprisingly low average luminosities in the majority of the protostellar population.

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Circumstellar disk fragmentation and the origin of massive planetary companions, brown dwarfs, and very low-mass stars

Proceedings of the International Astronomical Union ◽

10.1017/s174392131800827x ◽

2018 ◽

Vol 14 (S345) ◽

pp. 239-240 ◽

Cited By ~ 1

Author(s):

M. B. N. Kouwenhoven ◽

Yun Li ◽

D. Stamatellos ◽

S. P. Goodwin

Keyword(s):

Binary Systems ◽

Brown Dwarfs ◽

Mass Range ◽

Mass Function ◽

Initial Mass Function ◽

Low Mass Stars ◽

Triple Systems ◽

Low Mass ◽

Viable Mechanism

AbstractThe low-mass end of the initial mass function remains poorly understood. In this mass range, very low-mass stars, brown dwarfs, and massive planets are able to form through a variety of physical processes. Here, we study the long-term evolution of disk-fragmented systems around low-mass stars, for the epoch up to 10 Myr (the typical lifetime of an embedded cluster) and up to 10 Gyr (the age of the Milky Way). We carry out N-body simulations to study the decay of disk-fragmented systems and the resulting end products. Our simulations indicate rapid decay and frequent physical collisions during the first 10 Myr. We find that disk fragmentation provides a viable mechanism for explaining hierarchical triple systems, the brown dwarf desert, single and binary brown dwarfs, and very low-mass binary systems in the solar neighbourhood.

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FORMATION OF BLACK HOLE LOW-MASS X-RAY BINARIES IN HIERARCHICAL TRIPLE SYSTEMS

The Astrophysical Journal ◽

10.3847/2041-8205/822/2/l24 ◽

2016 ◽

Vol 822 (2) ◽

pp. L24 ◽

Cited By ~ 25

Author(s):

Smadar Naoz ◽

Tassos Fragos ◽

Aaron Geller ◽

Alexander P. Stephan ◽

Frederic A. Rasio

Keyword(s):

Black Hole ◽

X Ray ◽

Triple Systems ◽

Low Mass ◽

X Ray Binaries

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Abundances and Chemical Evolution of the Galactic Center

International Astronomical Union Colloquium ◽

10.1017/s0252921100067397 ◽

1977 ◽

Vol 45 ◽

pp. 79-101

Author(s):

Jean Audouze

Keyword(s):

Chemical Evolution ◽

Gamma Rays ◽

Molecular Clouds ◽

Galactic Center ◽

Solar Neighbourhood ◽

Interstellar Matter ◽

Low Mass Stars ◽

Element Abundances ◽

The Galaxy ◽

Low Mass

AbstractFrom observations of the galactic center using various techniques radioastronomy, millimeter waves (molecules) – infrared and gamma rays, the interstellar matter of this region* appears to have been strongly processed into stars : the gas density is much lower than in the solar neighbourhood. From CO measurements one knows that there are many molecular clouds such as SgrB2 where stars are forming now. From IR measurements, there are some indication that low mass stars are relatively more numerous in such regions than in the external regions of the galaxy. Finally the heavy element abundances show three important features (i) the possibility of strong enhancements in elements such as N and in a less extent 0 and Ne (the so called abundance gradients), (ii) Some specific enhancements of isotopes such43C,44N and also47O relative to42C,45N and43O (iii) Deuterium seems to have a lower abundance than in other parts of the galaxy such as the solar neighbourhood. Simple models of chemical evolution have been designed to account for such features and are rewiewed here.

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Low-mass visual binaries in the solar neighbourhood: The case of HD 141272

Astronomische Nachrichten ◽

10.1002/asna.200610770 ◽

2007 ◽

Vol 328 (6) ◽

pp. 521-526 ◽

Cited By ~ 7

Author(s):

T. Eisenbeiss ◽

A. Seifahrt ◽

M. Mugrauer ◽

T. O. B. Schmidt ◽

R. Neuhäuser ◽

...

Keyword(s):

Solar Neighbourhood ◽

Low Mass ◽

Visual Binaries

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The Milky Way evolution under the RAVE perspective

Proceedings of the International Astronomical Union ◽

10.1017/s1743921315008686 ◽

2015 ◽

Vol 11 (S317) ◽

pp. 320-323

Author(s):

Georges Kordopatis ◽

Keyword(s):

Radial Velocity ◽

Milky Way ◽

Solar Neighbourhood ◽

Low Mass Stars ◽

Medium Resolution ◽

Low Mass

AbstractThe RAdial Velocity Experiment (RAVE) collected from 2003 to 2013 medium resolution spectra for 5ċ105 low-mass stars of our Galaxy, improving our understanding of the Milky Way evolution and of its properties outside the Solar neighbourhood. This proceeding gives an overview of RAVE results obtained in the last two years.

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