scholarly journals The Formation of Binary Stars

2006 ◽  
Vol 2 (S240) ◽  
pp. 337-346
Author(s):  
C.J. Clarke
Keyword(s):  
Binary Stars ◽  
Binary Star ◽  
Vital Role ◽  
Physical Processes ◽  
Multiple Systems ◽  
Star Forming ◽  
Circumstellar Material ◽  
Low Mass ◽  
Body Level ◽  
Hydrodynamical Simulations

AbstractI argue that binary star statistics offer the best observational constraints on current hydrodynamical simulations of star forming clusters. In these simulations, clusters form hierarchically from the bottom up, and dynamical interactions, mediated by the presence of circumstellar material, play a vital role at the lowest (few body) level of the hierarchy. Such a scenario produces a rich array of complex multiple systems whose properties are in many respects consistent with observations. I however highlight two areas of current disagreement: the simulations over-produce low mass single stars and under-produce binaries with low mass ratios. It is currently unclear to what extent these shortcomings reflect numerical issues and to what extent the omission of relevant physical processes. I conclude with a theorist's wish list for observational diagnostics that would most meaningfully constrain future modeling efforts.

scholarly journals The effect of photoionizing feedback on the shaping of hierarchically-forming stellar clusters

2020 ◽  
Vol 499 (1) ◽  
pp. 668-680
Author(s):  
Alejandro González-Samaniego ◽  
Enrique Vazquez-Semadeni
Keyword(s):  
Star Formation ◽  
Early Stage ◽  
Stellar Clusters ◽  
Low Mass Stars ◽  
Transfer Scheme ◽  
Star Forming ◽  
Secondary Star ◽  
Low Mass ◽  
Hydrodynamical Simulations ◽  
Formation Efficiency

ABSTRACT We use two hydrodynamical simulations (with and without photoionizing feedback) of the self-consistent evolution of molecular clouds (MCs) undergoing global hierarchical collapse (GHC), to study the effect of the feedback on the structural and kinematic properties of the gas and the stellar clusters formed in the clouds. During this early stage, the evolution of the two simulations is very similar (implying that the feedback from low-mass stars does not affect the cloud-scale evolution significantly) and the star-forming region accretes faster than it can convert gas into stars, causing the instantaneous measured star formation efficiency (SFE) to remain low even in the absence of significant feedback. Afterwards, the ionizing feedback first destroys the filamentary supply to star-forming hubs and ultimately removes the gas from it, thus first reducing the star formation (SF) and finally halting it. The ionizing feedback also affects the initial kinematics and spatial distribution of the forming stars because the gas being dispersed continues to form stars, which inherit its motion. In the non-feedback simulation, the groups remain highly compact and do not mix, while in the run with feedback, the gas dispersal causes each group to expand, and the cluster expansion thus consists of the combined expansion of the groups. Most secondary star-forming sites around the main hub are also present in the non-feedback run, implying a primordial rather than triggered nature. We do find one example of a peripheral star-forming site that appears only in the feedback run, thus having a triggered origin. However, this appears to be the exception rather than the rule, although this may be an artefact of our simplified radiative transfer scheme.

scholarly journals A binary star formation mechanism through the fragmentation of prolate dense cores rotating end over end

1991 ◽  
Vol 147 ◽  
pp. 526-528
Author(s):  
Hans Zinnecker
Keyword(s):  
Star Formation ◽  
Formation Mechanism ◽  
Binary Stars ◽  
Binary Star ◽  
Initial Structure ◽  
Eccentric Orbit ◽  
Dense Cores ◽  
Molecular Core ◽  
Low Mass

I propose and briefly elaborate on a major new mechanism for the formation of wide, low-mass binary stars: the fragmentation of a collapsing, initially elongated dense molecular core rotating end over end. This initial structure will develop into two independent gravitationally bound stellar condensations orbiting each other in a rather eccentric orbit.

scholarly journals A binary star formation mechanism through the fragmentation of prolate dense cores rotating end over end

1991 ◽  
Vol 147 ◽  
pp. 526-528
Author(s):  
Hans Zinnecker
Keyword(s):  
Star Formation ◽  
Formation Mechanism ◽  
Binary Stars ◽  
Binary Star ◽  
Initial Structure ◽  
Eccentric Orbit ◽  
Dense Cores ◽  
Molecular Core ◽  
Low Mass

I propose and briefly elaborate on a major new mechanism for the formation of wide, low-mass binary stars: the fragmentation of a collapsing, initially elongated dense molecular core rotating end over end. This initial structure will develop into two independent gravitationally bound stellar condensations orbiting each other in a rather eccentric orbit.

scholarly journals AT 2018lqh and the Nature of the Emerging Population of Day-scale Duration Optical Transients

2021 ◽  
Vol 922 (2) ◽  
pp. 247
Author(s):  
E. O. Ofek ◽  
S. M. Adams ◽  
E. Waxman ◽  
A. Sharon ◽  
D. Kushnir ◽  
...  
Keyword(s):  
Neutron Star ◽  
Late Time ◽  
Half Maximum ◽  
Radioactive Elements ◽  
Stellar Envelope ◽  
Star Forming ◽  
Circumstellar Material ◽  
Photometric Observations ◽  
Merger Event ◽  
Low Mass

Abstract We report on the discovery of AT 2018lqh (ZTF 18abfzgpl)—a rapidly evolving extragalactic transient in a star-forming host at 242 Mpc. The transient g-band light curve’s duration above a half-maximum light is about 2.1 days, where 0.4/1.7 days are spent on the rise/decay, respectively. The estimated bolometric light curve of this object peaked at about 7 × 1042erg s−1—roughly 7 times brighter than the neutron star (NS)–NS merger event AT 2017gfo. We show that this event can be explained by an explosion with a fast (v ∼ 0.08 c) low-mass (≈0.07 M ⊙) ejecta, composed mostly of radioactive elements. For example, ejecta dominated by 56Ni with a timescale of t 0 ≅ 1.6 days for the ejecta to become optically thin for γ-rays fits the data well. Such a scenario requires burning at densities that are typically found in the envelopes of neutron stars or the cores of white dwarfs. A combination of circumstellar material (CSM) interaction power at early times and shock cooling at late times is consistent with the photometric observations, but the observed spectrum of the event may pose some challenges for this scenario. We argue that the observations are not consistent with a shock breakout from a stellar envelope, while a model involving a low-mass ejecta ramming into low-mass CSM cannot explain both the early- and late-time observations.

scholarly journals Binary Star Database BDB: New Developments and Applications

2018 ◽  
Author(s):  
Oleg Malkov ◽  
Aleksey Karchevsky ◽  
Pavel Kaygorodov ◽  
Dana Kovaleva ◽  
Nikolay Skvortsov
Keyword(s):  
Binary Stars ◽  
Binary Star ◽  
Stellar Systems ◽  
Database Integration ◽  
New Developments ◽  
Multiple Systems ◽  
Star Catalogue ◽  
Star Database

Binary star DataBase (BDB) is the database of binary/multiple systems of various observational types. BDB contains data on physical and positional parameters of 260,000 components of 120,000 stellar systems of multiplicity 2 to more than 20, taken from a large variety of published catalogues and databases. We describe the new features in organization of the database, integration of new catalogues and implementation of new possibilities available to users. The development of the BDB index-catalogue, Identification List of Binaries, is discussed. This star catalogue provides cross-referencing between most popular catalogues of binary stars. We describe ideas and methods for reliable cross-identification of different entities (systems, pairs, components) in binary and multiple stellar systems.

scholarly journals Astrometric confirmation of young low-mass binaries and multiple systems in the Chamaeleon star-forming regions

2012 ◽  
Vol 546 ◽  
pp. A63 ◽  
Author(s):  
N. Vogt ◽  
T. O. B. Schmidt ◽  
R. Neuhäuser ◽  
A. Bedalov ◽  
T. Roell ◽  
...  
Keyword(s):  
Multiple Systems ◽  
Star Forming ◽  
Star Forming Regions ◽  
Low Mass

scholarly journals Binary Stars in the Orion Nebula Cluster

2006 ◽  
Vol 2 (S240) ◽  
pp. 114-116
Author(s):  
Rainer Köhler ◽  
Monika G. Petr-Gotzens ◽  
Mark J. McCaughrean ◽  
Jerome Bouvier ◽  
Gaspard Duchêne ◽  
...  
Keyword(s):  
Adaptive Optics ◽  
Binary Stars ◽  
Main Sequence ◽  
Cluster Center ◽  
Orion Nebula ◽  
Low Mass Stars ◽  
Star Forming ◽  
Star Forming Regions ◽  
Low Mass ◽  
Guide Star

AbstractWe report on a high-spatial-resolution survey for binary stars in the periphery of the Orion Nebula Cluster, at 5–15 arcmin (0.65 – 2 pc) from the cluster center. We observed 228 stars with adaptive optics systems, in order to find companions at separations of 0.13 – 1.12 arcsec (60 – 500 AU), and detected 13 new binaries. Combined with the results of Petr (1998), we have a sample of 275 objects, about half of which have masses from the literature and high probabilities to be cluster members. We used an improved method to derive the completeness limits of the observations, which takes into account the elongated point spread function of stars at relatively large distances from the adaptive optics guide star. The multiplicity of stars with masses >2 M⊙ is found to be significantly larger than that of low-mass stars. The companion star frequency of low-mass stars is comparable to that of main-sequence M-dwarfs, less than half that of solar-type main-sequence stars, and 3.5 to 5 times lower than in the Taurus-Auriga and Scorpius-Centaurus star-forming regions. We find the binary frequency of low-mass stars in the periphery of the cluster to be the same or only slightly higher than for stars in the cluster core (< 3′ from θ1C Ori). This is in contrast to the prediction of the theory that the low binary frequency in the cluster is caused by the disruption of binaries due to dynamical interactions. There are two ways out of this dilemma: Either the initial binary frequency in the Orion Nebula Cluster was lower than in Taurus-Auriga, or the Orion Nebula Cluster was originally much denser and dynamically more active. A detailed report of this work has been published in Astronomy & Astrophysics (Köhler et al. 2006).

scholarly journals Hierarchical fragmentation in high redshift galaxies revealed by hydrodynamical simulations

2021 ◽  
Author(s):  
Baptiste Faure ◽  
Frédéric Bournaud ◽  
Jérémy Fensch ◽  
Emanuele Daddi ◽  
Manuel Behrendt ◽  
...  
Keyword(s):  
Gravitational Lensing ◽  
Hubble Space Telescope ◽  
High Redshift ◽  
High Redshift Galaxies ◽  
Star Forming ◽  
Low Mass ◽  
Hydrodynamical Simulations ◽  
Gas Clusters ◽  
Very High ◽  
Redshift Galaxies

Abstract High-redshift star-forming galaxies have very different morphologies compared to nearby ones. Indeed, they are often dominated by bright star-forming structures of masses up to 108 − 9 M⊙ dubbed «giant clumps». However, recent observations questioned this result by showing only low-mass structures or no structure at all. We use Adaptative Mesh Refinement hydrodynamical simulations of galaxies with parsec-scale resolution to study the formation of structures inside clumpy high-redshift galaxies. We show that in very gas-rich galaxies star formation occurs in small gas clusters with masses below 107 − 8 M⊙ that are themselves located inside giant complexes with masses up to 108 and sometimes 109 M⊙ . Those massive structures are similar in mass and size to the giant clumps observed in imaging surveys, in particular with the Hubble Space Telescope. Using mock observations of simulated galaxies, we show that at very high resolution with instruments like the Atacama Large Millimeter Array or through gravitational lensing, only low-mass structures are likely to be detected, and their gathering into giant complexes might be missed. This leads to the non-detection of the giant clumps and therefore introduces a bias in the detection of these structures. We show that the simulated giant clumps can be gravitationally bound even when undetected in mocks representative for ALMA observations and HST observations of lensed galaxies. We then compare the top-down fragmentation of an initially warm disc and the bottom-up fragmentation of an initially cold disc to show that the process of formation of the clumps does not impact their physical properties.

scholarly journals The MUSE Hubble Ultra Deep Field Survey

2018 ◽  
Vol 619 ◽  
pp. A27 ◽  
Author(s):  
Leindert A. Boogaard ◽  
Jarle Brinchmann ◽  
Nicolas Bouché ◽  
Mieke Paalvast ◽  
Roland Bacon ◽  
...  
Keyword(s):  
Star Formation ◽  
Formation Rate ◽  
Analytical Models ◽  
High Signal ◽  
Noise Emission ◽  
Star Forming ◽  
Low Mass ◽  
Hydrodynamical Simulations ◽  
Hubble Ultra Deep Field ◽  
Intrinsic Scatter

Star-forming galaxies have been found to follow a relatively tight relation between stellar mass (M*) and star formation rate (SFR), dubbed the “star formation sequence”. A turnover in the sequence has been observed, where galaxies with M* <  1010 M⊙ follow a steeper relation than their higher mass counterparts, suggesting that the low-mass slope is (nearly) linear. In this paper, we characterise the properties of the low-mass end of the star formation sequence between 7 ≤ log M*[M⊙]  ≤  10.5 at redshift 0.11 <  z  <   0.91. We use the deepest MUSE observations of the Hubble Ultra Deep Field and the Hubble Deep Field South to construct a sample of 179 star-forming galaxies with high signal-to-noise emission lines. Dust-corrected SFRs are determined from Hβ λ4861 and Hα λ6563. We model the star formation sequence with a Gaussian distribution around a hyperplane between logM*, logSFR, and log(1 + z), to simultaneously constrain the slope, redshift evolution, and intrinsic scatter. We find a sub-linear slope for the low-mass regime where log SFR [M⊙yr−1] = 0.83+0.07−0.06 log M*[M⊙]+1.74+0.66−0.68 log(1 + z), increasing with redshift. We recover an intrinsic scatter in the relation of σintr = 0.44+0.05−0.04, dex, larger than typically found at higher masses. As both hydrodynamical simulations and (semi-)analytical models typically favour a steeper slope in the low-mass regime, our results provide new constraints on the feedback processes which operate preferentially in low-mass halos.

scholarly journals Observations of Binary Protostellar Systems

2004 ◽  
Vol 221 ◽  
pp. 213-222
Author(s):  
Ralf Launhardt
Keyword(s):  
Star Formation ◽  
Binary Stars ◽  
Binary Star ◽  
High Angular Resolution ◽  
Multiple Systems ◽  
Direct Observations ◽  
Theoretical Predictions ◽  
Statistical Studies ◽  
Formation Phase ◽  
Key Questions

A major gap in our understanding of star formation concerns the origins of binary stars although there is growing evidence that most stars form in binary and multiple systems. While some theoretical predictions of fragmentation models are indirectly supported by statistical studies of evolved binary stars at shorter wavelengths, direct observations of the formation phase became only possible with the advance of large millimeter interferometers. Molecular line spectroscopy and dust continuum observations at high angular resolution can address some of the key questions in binary star formation theories. Observing methods and results of recent studies of binary protostellar systems are reviewed in this paper.

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