Multiplicity of disc-bearing stars in Upper Scorpius and Upper Centaurus-Lupus

Kuruwita, Rajika; Ireland, Michael; Rizzuto, Aaron C.; Bento, J.; Federrath, Christoph

doi:10.1093/mnras/sty2108

Cited by 27 publications

(19 citation statements)

References 82 publications

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“…Overall, the influence of multiplicity on the disc lifetime has yet to be determined. Shorter circumstellar and circumbinary disc lifetimes are implied by the low disc frequency around binaries of separation a < 40 AU (Cieza et al 2009;Duchêne 2010;Kraus et al 2011); however, Kuruwita et al (2018) find that overall, the lifetime of discs in binaries may not vary significantly compared to disc lifetimes around single stars.…”

Section: Introductionmentioning

confidence: 61%

The dependence of episodic accretion on eccentricity during the formation of binary stars

Kuruwita

Federrath

Haugbølle

2020

A&A

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Context. Episodic accretion has been observed in short-period binaries, where bursts of accretion occur at periastron. The binary trigger hypothesis has also been suggested as a driver for accretion during protostellar stages. Aims. Our goal is to investigate how the strength of episodic accretion bursts depends on eccentricity. Methods. We investigate the binary trigger hypothesis in longer-period (> 20 yr) binaries by carrying out three-dimensional magnetohydrodynamical simulations of the formation of low-mass binary stars down to final separations of ∼10 AU, including the effects of gas turbulence and magnetic fields. We ran two simulations with an initial turbulent gas core of one solar mass each and two different initial turbulent Mach numbers, ℳ = σv/cs = 0.1 and ℳ = 0.2, for 6500 yr after protostar formation. Results. We observe bursts of accretion at periastron during the early stages when the eccentricity of the binary system is still high. We find that this correlation between bursts of accretion and passing periastron breaks down at later stages because of the gradual circularisation of the orbits. For eccentricities greater than e = 0.2, we observe episodic accretion triggered near periastron. However, we do not find any strong correlation between the strength of episodic accretion and eccentricity. The strength of accretion is defined as the ratio of the burst accretion rate to the quiescent accretion rate. We determine that accretion events are likely triggered by torques between the rotation of the circumstellar disc and the approaching binary stars. We compare our results with observational data of episodic accretion in short-period binaries and find good agreement between our simulations and the observations. Conclusions. We conclude that episodic accretion is a universal mechanism operating in eccentric young binary-star systems, independent of separation, and it should be observable in long-period binaries as well as in short-period binaries. Nevertheless, the strength depends on the torques and hence the separation at periastron.

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Section: Introductionmentioning

confidence: 61%

The dependence of episodic accretion on eccentricity during the formation of binary stars

Kuruwita

Federrath

Haugbølle

2020

A&A

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“…They found that the frequency of close binaries with a < 10 au, detectable by their survey, is compatible with solar-type stars in the field and does not differ substantially between the studied regions. Interestingly, they discovered a deficit of double-lined (largeq) pairs among disc-bearing stars, like those surveyed by Kuruwita et al (2018), that is recovered by the small-q single-lined systems with discs. Rebull et al (2018) also noted that multi-periodic stars in USco (large-q binaries) have a reduced incidence of discs.…”

Section: Discussionmentioning

confidence: 83%

“…No large radial velocity (RV) surveys of USco have been made so far to probe this regime. Kuruwita et al (2018) monitored RVs of 55 disc-bearing members of USco and estimated the frequency of spectroscopic binaries at 0.06 +0.07 −0.02 , like in the field and in other starforming regions (Duchêne & Kraus 2013). Presence of spectroscopic binaries in several northern associations and clusters (not including USco) has been probed by Kounkel et al (2019) using RV measurements from APOGEE.…”

Section: Discussionmentioning

confidence: 99%

Binary Stars in Upper Scorpius

Tokovinin

2019

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To address the statistics of binary stars in the 8-Myr old Upper Scorpius star formation region, we conducted speckle-interferometric survey of 614 association members more massive than 0.4 M ⊙ (spectral types earlier than M3V) based on the list of Luhman et al. (2018). We resolved 187 pairs, 55 of those are new discoveries. Using also the published data and the Gaia DR2, a catalog of 250 physical binaries is produced. We carefully estimated detection limits for each target and studied binary statistics in the separation range from 0. ′′ 06 to 20 ′′ (9 to 2800 au), as well as clustering at larger separations. The frequency of companions with mass ratios q > 0.3 in this separation range is 0.33±0.04 and 0.35±0.04 for early M and solar-type stars, respectively, larger by 1.62±0.22 and 1.39±0.18 times compared to field stars of similar masses. The excess is produced mostly by pairs closer than 100 au. At separations from 100 to 10 4 au, the separation distribution and companion fraction resemble those of solar-type stars in the field. However, unlike in the field, we see a relative deficit of equal-mass binaries at separations of ∼500 au, compared to smaller and larger separations. The distribution of q depends on the separation, with a preference of larger q and a larger fraction of twins with q > 0.95 at smaller separations. The binary population of Upper Scorpius differs from binaries in the field in several ways and suggests that binary statistics is not universal.

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“…For a system with a stellar companion external to the circumstellar disc, truncation occurs at 0.3-0.5 times the physical separation of the binary companion (see, for example, Papaloizou & Pringle 1977;Artymowicz & Lubow 1994). 1 A smaller disc also implies a shorter viscous dissipation timescale and previous infrared studies have shown that discs around medium-separation binaries do in fact have shorter lifetimes than those around single stars (Cieza et al 2009;Kuruwita et al 2018). In addition, Rosotti & Clarke (2018) found that secondary components of close binaries clear first due to the shorter viscous time scale associated with the smaller size of the disc, while for wide binaries the difference in photoevaporation rate permits a longer lifetime than tight systems.…”

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confidence: 99%

The effect of stellar multiplicity on protoplanetary discs: a near-infrared survey of the Lupus star-forming region

Zurlo

Cieza

Ansdell

et al. 2020

Monthly Notices of the Royal Astronomical Society

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We present results from a near-infrared (NIR) adaptive optics (AO) survey of pre-main-sequence stars in the Lupus Molecular Cloud with VLT/NACO to identify (sub)stellar companions down to ∼20 au separation and investigate the effects of multiplicity on circumstellar disc properties. We observe for the first time in the NIR with AO a total of 47 targets and complement our observations with archival data for another 58 objects previously observed with the same instrument. All 105 targets have millimetre ALMA data available, which provide constraints on disc masses and sizes. We identify a total of 13 multiple systems, including 11 doubles and 2 triples. In agreement with previous studies, we find that the most massive (Mdust > 50 M⊕) and largest (Rdust > 70 au) discs are only seen around stars lacking visual companions (with separations of 20–4800 au) and that primaries tend to host more massive discs than secondaries. However, as recently shown in a very similar study of >200 PMS stars in the Ophiuchus Molecular Cloud, the distribution of disc masses and sizes are similar for single and multiple systems for Mdust < 50 M⊕ and radii Rdust < 70 au. Such discs correspond to ∼80–90% of the sample. This result can be seen in the combined sample of Lupus and Ophiuchus objects, which now includes more than 300 targets with ALMA imaging and NIR AO data, and implies that stellar companions with separations > 20 au mostly affect discs in the upper 10% of the disc mass and size distributions.

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Multiplicity of disc-bearing stars in Upper Scorpius and Upper Centaurus-Lupus

Cited by 27 publications

References 82 publications

The dependence of episodic accretion on eccentricity during the formation of binary stars

The dependence of episodic accretion on eccentricity during the formation of binary stars

Binary Stars in Upper Scorpius

The effect of stellar multiplicity on protoplanetary discs: a near-infrared survey of the Lupus star-forming region

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