Filter and export

Publications

What is a Publication?
7 Publications visible to you, out of a total of 7
Simulated analogues I: apparent and physical evolution of young binary protostellar systems

Abstract (Expand)

ABSTRACT Protostellar binaries harbour complex environment morphologies. Observations represent a snapshot in time, and projection and optical depth effects impair our ability to interpret them. Careful …to interpret them. Careful comparison with high-resolution models that include the larger star-forming region can help isolate the driving physical processes and give context in the time domain to the observations. We carry out four zoom-in simulations with au scale resolution that result in three binaries and a single star. For the first time ever, we follow the detailed evolution of a protobinary in a full molecular cloud context until a circumbinary disc forms. We investigate the gas dynamics around the young stars and extract disc sizes. Using radiative transfer, we obtain the evolutionary tracer Tbol of the binary systems. We find that the centrifugal radius in prestellar cores is a poor estimator of the resulting disc size due to angular momentum transport at all scales. For binaries, the disc sizes are regulated periodically by the binary orbit, having larger radii close to the apastron. The bolometric temperature differs systematically between edge-on and face-on views and shows a high-frequency time dependence correlated with the binary orbit and a low-frequency time dependence with larger episodic accretion events. These oscillations can cause the appearance of the system to change rapidly from class 0 to class I and, for short periods, even bring it to class II. The highly complex structure in early stages, as well as the binary orbit itself, affects the classical interpretation of protostellar classes, and the direct translation to evolutionary stages has to be done with caution and include other evolutionary indicators such as the extent of envelope material.

Authors: Vito Tuhtan, Rami Al-Belmpeisi, Mikkel Bregning Christensen, Rajika Kuruwita, Troels Haugbølle

Date Published: 1st Nov 2024

Publication Type: Journal

Simulated analogues II: a new methodology for non-parametric matching of models to observations

Abstract (Expand)

ABSTRACT Star formation is a multiscale problem, and only global simulations that account for the connection from the molecular cloud-scale gas flow to the accreting protostar can reflect the observed …r can reflect the observed complexity of protostellar systems. Star-forming regions are characterized by supersonic turbulence, and as a result, it is not possible to simultaneously design models that account for the larger environment and in detail reproduce observed stellar systems. Instead, the stellar inventories can be matched statistically, and the best matches found that approximate specific observations. Observationally, a combination of single-dish telescopes and interferometers are now able to resolve the nearest protostellar objects on all scales from the protostellar core to the inner $10\, \mathrm{au}$. We present a new non-parametric methodology which uses high-resolution simulations and post-processing methods to match simulations and observations using deep learning. Our goal is to perform a down-selection from large data sets of synthetic images to a ranked list of best-matching candidates with respect to the observation. This is particularly useful for binary and multiple stellar systems that form in turbulent environments. The objective is to accelerate the rate at which we can do such comparisons, remove biases from hand-picking matches, and contribute to identifying the underlying physical processes that drive the creation and evolution of observed protostellar systems.

Authors: Rami Al-Belmpeisi, Vito Tuhtan, Mikkel Bregning Christensen, Rajika Kuruwita, Troels Haugbølle

Date Published: 1st Nov 2024

Publication Type: Journal

Protostellar spin-up and fast rotator formation through binary star formation

Abstract (Expand)

Context. Many fast-rotating stars (rotation periods of < 2 days) are found to be unresolved binaries with separations of tens of AU. This correlation between fast rotators and binarity leads to the …ween fast rotators and binarity leads to the question of whether the formation of binary stars inherently produces fast rotators. Aims. Our goal is to understand the spin evolution of protostars and whether the formation of companions plays a role in spinning up stars. Methods. We used magneto-hydrodynamic simulations to study the formation of multiple star systems from turbulent and non-turbulent protostellar cores. We tracked the angular momentum accreted by individual star and inner disc systems by using a sink (star) particle technique. We ran a resolution study to extrapolate protostellar properties. Results. We find in all simulations that the primary star can experience a spin-up event correlated with the formation of companions, namely fragmentation into binaries or higher-order systems. The primary star can spin up by up to 84% of its pre-fragmentation angular momentum and by up to 18% of its pre-fragmentation mass-specific angular momentum. The mechanism for the spin-up is gravitational disc instabilities in the circumstellar disc around the primary star, which leads to the accretion of material with high specific angular momentum. The simulations that experience the strongest disc instabilities fragment to form companions. Simulations with weaker spin-up events experience disc instabilities triggered by a companion flyby, and the disc instability in these cases typically does not produce further fragments (i.e. they remain binary systems). Conclusions. The primary star in multiple star systems can end up with a higher spin than single stars. This is because gravitational instabilities in the circumstellar disc around the primary star can trigger a spin-up event. In the strongest spin-up events, the instability is likely to cause disc fragmentation and the formation of companions. This spin-up mechanism, coupled with shorter disc lifetimes due to truncated circumstellar discs (and thus short spin-down times), may help produce fast rotators.

Authors: Rajika L. Kuruwita, Christoph Federrath, Marina Kounkel

Date Published: 1st Oct 2024

Publication Type: Journal

Orbital architectures of planet-hosting binaries – III. Testing mutual inclinations of stellar and planetary orbits in triple-star systems

Abstract (Expand)

ABSTRACT Transiting planets in multiple-star systems, especially high-order multiples, make up a small fraction of the known planet population but provide unique opportunities to study the environments … to study the environments in which planets would have formed. Planet-hosting binaries have been shown to have an abundance of systems in which the stellar orbit aligns with the orbit of the transiting planet, which could give insights into the planet formation process in such systems. We investigate here if this trend of alignment extends to planet-hosting triple-star systems. We present long-term astrometric monitoring of a novel sample of triple-star systems that host Kepler transiting planets. We measured orbit arcs in 21 systems, including 12 newly identified triples, from a homogeneous analysis of our Keck adaptive optics data and, for some systems, Gaia astrometry. We examine the orbital alignment within the nine most compact systems ($\lesssim 500$ au), testing if either (or both) of the stellar orbits align with the edge-on orbits of their transiting planets. Our statistical sample of triple systems shows a tendency toward alignment, especially when assessing the alignment probability using stellar orbital inclinations computed from full orbital fits, but is formally consistent with isotropic orbits. Two-population tests where half of the stellar orbits are described by a planet-hosting-binary-like moderately aligned distribution give the best match when the other half (non-planet-hosting) has a Kozai-like misaligned distribution. Overall, our results suggest that our sample of triple-star planet-hosting systems are not fully coplanar systems and have at most one plane of alignment.

Authors: Elise L Evans, Trent J Dupuy, Kendall Sullivan, Adam L Kraus, Daniel Huber, Michael J Ireland, Megan Ansdell, Rajika L Kuruwita, Raquel A Martinez, Mackenna L Wood

Date Published: 1st Oct 2024

Publication Type: Journal

Observations of high-order multiplicity in a high-mass stellar protocluster

Abstract (Expand)

Abstract The dominant mechanism forming multiple stellar systems in the high-mass regime ( M *  ≳ 8  M ⊙ ) remained unknown because direct imaging of multiple protostellar systems at early phases of … ⊙ ) remained unknown because direct imaging of multiple protostellar systems at early phases of high-mass star formation is very challenging. High-mass stars are expected to form in clustered environments containing binaries and higher-order multiplicity systems. So far only a few high-mass protobinary systems, and no definitive higher-order multiples, have been detected. Here we report the discovery of one quintuple, one quadruple, one triple and four binary protostellar systems simultaneously forming in a single high-mass protocluster, G333.23–0.06, using Atacama Large Millimeter/submillimeter Array high-resolution observations. We present a new example of a group of gravitationally bound binary and higher-order multiples during their early formation phases in a protocluster. This provides the clearest direct measurement of the initial configuration of primordial high-order multiple systems, with implications for the in situ multiplicity and its origin. We find that the binary and higher-order multiple systems, and their parent cores, show no obvious sign of disk-like kinematic structure. We conclude that the observed fragmentation into binary and higher-order multiple systems can be explained by core fragmentation, indicating its crucial role in establishing the multiplicity during high-mass star cluster formation.

Authors: Shanghuo Li, Patricio Sanhueza, Henrik Beuther, Huei-Ru Vivien Chen, Rolf Kuiper, Fernando A. Olguin, Ralph E. Pudritz, Ian W. Stephens, Qizhou Zhang, Fumitaka Nakamura, Xing Lu, Rajika L. Kuruwita, Takeshi Sakai, Thomas Henning, Kotomi Taniguchi, Fei Li

Date Published: 15th Jan 2024

Publication Type: Journal

The contribution of binary star formation via core fragmentation on protostellar multiplicity

Abstract (Expand)

Context. Observations of young multiple star systems find a bimodal distribution in companion frequency and separation. The origin of these peaks has often been attributed to binary formation via core …been attributed to binary formation via core and disc fragmentation. However, theory and simulations suggest that young stellar systems that form via core fragmentation undergo significant orbital evolution. Aims. We investigate the influence of the environment on the formation and orbital evolution of multiple star systems, and how core fragmentation contributes to the formation of close (20 − 100 AU) binaries. We use multiple simulations of star formation in giant molecular clouds and compare them to the multiplicity statistics of the Perseus star-forming region. Methods. Simulations were run with the adaptive mesh refinement code RAMSES with sufficient resolution to resolve core fragmentation beyond 400 AU and dynamical evolution down to 16.6 AU, but without the possibility of resolving disc fragmentation. The evolution of the resulting stellar systems was followed over millions of years. Results. We find that star formation in lower gas density environments is more clustered; however, despite this, the fractions of systems that form via dynamical capture and core fragmentation are broadly consistent at ∼40% and ∼60%, respectively. In all gas density environments, we find that the typical scale at which systems form via core fragmentation is 10 3 − 3.5  AU. After formation, we find that systems that form via core fragmentation have slightly lower inspiral rates (∼10 −1.68  AU yr −1 measured over the first 10 000 yr) compared to dynamical capture (∼10 −1.32  AU yr −1 ). We then compared the simulation with the conditions most similar to the Perseus star-forming region to determine whether the observed bimodal distribution can be replicated. We find that it can be replicated, but it is sensitive to the evolutionary state of the simulation. Conclusions. Our results indicate that a significant number of low-mass close binaries with separations from 20 − 100 AU can be produced via core fragmentation or dynamical capture due to efficient inspiral, without the need for a further contribution from disc fragmentation.

Authors: Rajika L. Kuruwita, Troels Haugbølle

Date Published: 1st Jun 2023

Publication Type: Journal

Discovery of a septuple protostellar system--implications for the origin of extreme high-order multiplicity

Abstract (Expand)

Stellar multiple systems play a pivotal role in cluster dynamics and stellar evolution, leading to intense phenomena like X-ray binaries, gamma-ray bursts, Type Ia supernova, and stellar mergers. … However, their origin remains poorly understood, and there are no direct observations of multiple systems with more than five members during the early stages of star formation. We report the discovery of a septuple protostellar system embedded in a Keplerian disk within the high-mass star-forming region NGC6334IN. The stability analysis reveals that the disk is dynamically unstable, aligning with the observed separations of the septuple system originating from disk fragmentation. These findings suggest that the septuple system formed via fragmentation of a gravitationally unstable disk, shedding new light on the formation of extreme high-order multiplicity in cluster environments.

Authors: Shanghuo Li, Henrik Beuther, Andr'e Oliva, Vardan G Elbakyan, Stella S. R Offner, Rolf Kuiper, Keping Qiu, Xing Lu, Patricio Sanhueza, Huei-Ru Chen, Zhang Qizhou, Fernando A Olguin, Chang Won Lee, Ralph Pudritz, Shuo Kong, Rajika L. Kuruwita, Qiuyi Luo, Junhao Liu

Date Published: No date defined

Publication Type: Unpublished

Powered by
 (v.1.15.2)
About HITS Publication SEEK | About HITS-Publication-SEEK | Funding and Programmes | Credits
Copyright © 2008 - 2024 The University of Manchester and HITS gGmbH