scholarly journals The Properties of Open Cluster Binaries Based on High-Resolution Imaging Surveys

2001 ◽  
Vol 200 ◽  
pp. 181-190 ◽  
Author(s):  
Jenny Patience ◽  
Gaspard Duchêne
Keyword(s):  
High Resolution ◽  
Binary Star ◽  
Open Cluster ◽  
Stellar Rotation ◽  
Ratio Distribution ◽  
Resolution Imaging ◽  
Formation And Evolution ◽  
Stellar Masses ◽  
The Impact ◽  
Stellar Density

With known properties such as age, distance and stellar density, young clusters provide ideal samples for binary star studies. We summarize recent results from high-resolution multiplicity surveys of IC 348, α Per, the Pleiades, the Hyades, and Praesepe. The statistics of the resolved companions are used to address binary star formation and evolution in clusters. Over the ranges of ages, densities and stellar masses covered by the clusters, it is found that the binary fraction is correlated with stellar density rather than age, and that both the binary fraction and binary mass ratio distribution depend upon mass. The impact of companions on X-ray emission and stellar rotation is also discussed.

Planet Formation in Transition Discs

2020 ◽  
Author(s):  
Daniel Cummins ◽  
James Owen
Keyword(s):  
Large Scale ◽  
Planet Formation ◽  
Formation Processes ◽  
Primary Interest ◽  
Rapid Formation ◽  
Planetary Embryo ◽  
Large Scale Vortex ◽  
Resolution Imaging ◽  
Formation And Evolution ◽  
The Impact

<p>High-resolution imaging of protoplanetary discs has revealed their wealth of substructure. Perhaps the most striking observation has been the presence of large-scale crescent-shaped features, which have been interpreted as large quantities of dust trapped in anticyclonic vortices. Such regions of high dust-to-gas ratios are expected to promote planet formation processes, so understanding their formation and evolution is of primary interest.<br />Gas-only hydrodynamics simulations have demonstrated that the thermal feedback from a planetary embryo undergoing rapid formation by pebble accretion can trigger the generation a large-scale vortex. However, the ability for such a vortex to trap dust and the impact this has on the forming planet are yet to be investigated. I will present results from hydrodynamics simulations of a disc containing both gas and dust, showing the efficiency with which dust grains accumulate in a vortex, and discuss the consequences this has for the growth of the planetary embryo.</p>

scholarly journals Extended main sequence turnoffs in open clusters as seen by Gaia – II. The enigma of NGC 2509

2019 ◽  
Vol 491 (2) ◽  
pp. 2129-2136 ◽  
Author(s):  
M de Juan Ovelar ◽  
S Gossage ◽  
S Kamann ◽  
N Bastian ◽  
C Usher ◽  
...  
Keyword(s):  
Stellar Evolution ◽  
Main Sequence ◽  
Narrow Range ◽  
Open Cluster ◽  
Open Clusters ◽  
Stellar Rotation ◽  
Rotation Rates ◽  
Magnitude Diagram ◽  
Stellar Density

ABSTRACT We investigate the morphology of the colour–magnitude diagram (CMD) of the open cluster NGC 2509 in comparison with other Galactic open clusters of similar age using Gaia photometry. At ${\sim}900\,\rm {Myr}$ Galactic open clusters in our sample all show an extended main sequence turnoff (eMSTO) with the exception of NGC 2509, which presents an exceptionally narrow CMD. Our analysis of the Gaia data rules out differential extinction, stellar density, and binaries as a cause for the singular MSTO morphology in this cluster. We interpret this feature as a consequence of the stellar rotation distribution within the cluster and present the analysis with mesa Isochrones and Stellar Tracks (MIST) stellar evolution models that include the effect of stellar rotation on which we based our conclusion. In particular, these models point to an unusually narrow range of stellar rotation rates (Ω/Ωcrit, ZAMS = [0.4, 0.6]) within the cluster as the cause of this singular feature in the CMD of NGC 2509. Interestingly, models that do not include rotation are not as good at reproducing the morphology of the observed CMD in this cluster.

scholarly journals Assessing the impact of an invasive bryophyte on plant species richness using high resolution imaging spectroscopy

2020 ◽  
Vol 110 ◽  
pp. 105882
Author(s):  
Michael Ewald ◽  
Sandra Skowronek ◽  
Raf Aerts ◽  
Jonathan Lenoir ◽  
Hannes Feilhauer ◽  
...  
Keyword(s):  
Species Richness ◽  
High Resolution ◽  
Plant Species ◽  
Imaging Spectroscopy ◽  
Plant Species Richness ◽  
High Resolution Imaging ◽  
Resolution Imaging ◽  
The Impact

High resolution imaging of parsec-scale jets: the impact of the VSOP observations

1999 ◽  
Vol 43 (8-10) ◽  
pp. 741-745 ◽  
Author(s):  
A.P Lobanov ◽  
T.P Krichbaum ◽  
A Witzel ◽  
J.A Zensus
Keyword(s):  
High Resolution ◽  
High Resolution Imaging ◽  
Resolution Imaging ◽  
The Impact

scholarly journals Binary-driven stellar rotation evolution at the main-sequence turn-off in star clusters

2021 ◽  
Vol 502 (3) ◽  
pp. 4350-4358
Author(s):  
Weijia Sun ◽  
Richard de Grijs ◽  
Licai Deng ◽  
Michael D Albrow
Keyword(s):  
Main Sequence ◽  
Open Cluster ◽  
Open Clusters ◽  
Stellar Rotation ◽  
Main Sequence Stars ◽  
Number Ratio ◽  
Medium Resolution ◽  
Novel Method ◽  
Tight Correlation ◽  
The Impact

ABSTRACT The impact of stellar rotation on the morphology of star cluster colour–magnitude diagrams is widely acknowledged. However, the physics driving the distribution of the equatorial rotation velocities of main-sequence turn-off stars is as yet poorly understood. Using Gaia Data Release 2 photometry and new Southern African Large Telescope medium-resolution spectroscopy, we analyse the intermediate-age ($\sim 1\text{-}{\rm Gyr}$-old) Galactic open clusters NGC 3960, NGC 6134, and IC 4756 and develop a novel method to derive their stellar rotation distributions based on SYCLIST stellar rotation models. Combined with literature data for the open clusters NGC 5822 and NGC 2818, we find a tight correlation between the number ratio of slow rotators and the clusters’ binary fractions. The blue-main-sequence stars in at least two of our clusters are more centrally concentrated than their red-main-sequence counterparts. The origin of the equatorial stellar rotation distribution and its evolution remains as yet unidentified. However, the observed correlation in our open cluster sample suggests a binary-driven formation mechanism.

scholarly journals Enhancing and inhibiting star formation: high-resolution simulation studies of the impact of cold accretion, mergers and feedback on individual massive galaxies

2012 ◽  
Vol 8 (S295) ◽  
pp. 13-16 ◽  
Author(s):  
Leila C. Powell ◽  
Frederic Bournaud ◽  
Damien Chapon ◽  
Julien Devriendt ◽  
Volker Gaibler ◽  
...  
Keyword(s):  
Star Formation ◽  
High Resolution ◽  
Velocity Dispersion ◽  
Simulation Studies ◽  
Massive Galaxies ◽  
Hot Gas ◽  
Mass Assembly ◽  
Stellar Masses ◽  
The Impact ◽  
Significant Mass

AbstractThe quest for a better understanding of the evolution of massive galaxies can be broadly summarised with 2 questions: how did they build up their large (stellar) masses and what eventually quenched their star formation (SF)? To tackle these questions, we use high-resolution ramses simulations (Teyssier 2002) to study several aspects of the detailed interplay between accretion (mergers and cold flows), SF and feedback in individual galaxies. We examine SF in major mergers; a process crucial to stellar mass assembly. We explore whether the merger-induced, clustered SF is as important a mechanism in average mergers, as it is in extreme systems like the Antennae. We find that interaction-induced turbulence drives up the velocity dispersion, and that there is a correlated rise in SFR in all our simulated mergers as the density pdf evolves to have an excess of very dense gas. Next, we introduce a new study into whether mechanical jet feedback can impact upon the ability of hot gas haloes to provide a supply of fuel for SF during mergers and in their remnants. Finally, we briefly review our recent study, in which we examine the effect of supernova (SN) feedback on galaxies accreting via the previously overlooked cold-mode, by resimulating a stream-fed galaxy at z ~ 9. A far-reaching galactic wind results yet it cannot suppress the cold, filamentary accretion or eject significant mass in order to reduce the SFR, suggesting that SN feedback may not be as effective as is often assumed.

scholarly journals From the bulge to the outer disc: StarHorse stellar parameters, distances, and extinctions for stars in APOGEE DR16 and other spectroscopic surveys

2020 ◽  
Vol 638 ◽  
pp. A76 ◽  
Author(s):  
A. B. A. Queiroz ◽  
F. Anders ◽  
C. Chiappini ◽  
A. Khalatyan ◽  
B. X. Santiago ◽  
...  
Keyword(s):  
High Resolution ◽  
Spectroscopic Data ◽  
Galactic Plane ◽  
Broad Band ◽  
Photometric Data ◽  
Galactic Centre ◽  
Optical Photometry ◽  
Data Release ◽  
The Impact ◽  
Stellar Density

We combine high-resolution spectroscopic data from APOGEE-2 survey Data Release 16 (DR16) with broad-band photometric data from several sources as well as parallaxes from Gaia Data Release 2 (DR2). Using the Bayesian isochrone-fitting code StarHorse, we derived the distances, extinctions, and astrophysical parameters for around 388 815 APOGEE stars. We achieve typical distance uncertainties of ∼6% for APOGEE giants, ∼2% for APOGEE dwarfs, and extinction uncertainties of ∼0.07 mag, when all photometric information is available, and ∼0.17 mag if optical photometry is missing. StarHorse uncertainties vary with the input spectroscopic catalogue, available photometry, and parallax uncertainties. To illustrate the impact of our results, we show that thanks to Gaia DR2 and the now larger sky coverage of APOGEE-2 (including APOGEE-South), we obtain an extended map of the Galactic plane. We thereby provide an unprecedented coverage of the disc close to the Galactic mid-plane (|ZGal| < 1 kpc) from the Galactic centre out to RGal ∼ 20 kpc. The improvements in statistics as well as distance and extinction uncertainties unveil the presence of the bar in stellar density and the striking chemical duality in the innermost regions of the disc, which now clearly extend to the inner bulge. We complement this paper with distances and extinctions for stars in other public released spectroscopic surveys: 324 999 in GALAH DR2, 4 928 715 in LAMOST DR5, 408 894 in RAVE DR6, and 6095 in GES DR3.

Detection of brain micrometastases by high-resolution stereotactic magnetic resonance imaging and its impact on the timing of and risk for distant recurrences

2011 ◽  
Vol 115 (3) ◽  
pp. 499-504 ◽  
Author(s):  
Patrick Hanssens ◽  
Bengt Karlsson ◽  
Tseng Tsai Yeo ◽  
Ning Chou ◽  
Guus Beute
Keyword(s):  
High Resolution ◽  
Mr Imaging ◽  
Brain Metastases ◽  
Randomized Study ◽  
Distant Recurrence ◽  
Consecutive Series ◽  
High Resolution Imaging ◽  
Whole Brain Radiation ◽  
Resolution Imaging ◽  
The Impact

Object The aim of this study was to assess the order of micrometastases that can be detected with high-resolution MR imaging at the time of Gamma Knife surgery (GKS), and to estimate the impact this has on the time until and incidence of distant recurrences. Methods A consecutive series of 835 patients with brain metastases treated with GKS in a 7-year period, excluding patients in whom earlier brain metastases were treated with other modalities, were retrospectively analyzed. In all patients GKS was based on high Gd–dose (0.3 mmol/kg), high-resolution stereotactic MR imaging. These images were compared with the standard pretreatment MR images, and the difference in number of metastases found was analyzed. The distant recurrence rate following GKS was compared with that found in a prospective randomized study (Aoyama et al.) comparing radiosurgery to radiosurgery plus prophylactic whole-brain radiation therapy. Results New tumors were diagnosed in 40% (95% CI 36%–43%) of all patients as well as in the majority of patients with multiple lesions found on the diagnostic scan. The more tumors there were on the diagnostic scan, the higher the likelihood of detecting additional lesions with high-resolution imaging. It was calculated that approximately 50% of the micrometastases present at the time of GKS could be diagnosed with high-resolution imaging, which decreased the incidence of and delayed the time for the development of distant recurrences. Conclusions Additional brain metastases can be diagnosed in 40% of patients by using high-resolution imaging. Thus, radiosurgical treatments based on high-resolution stereotactic MR imaging decrease the incidence of and lengthen the time to distant recurrences.

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