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Academic literature on the topic 'Stellar associations'

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Published: 4 June 2021
Last updated: 30 July 2024

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Journal articles on the topic "Stellar associations"

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Kalloghlian, A. T. "Stellar associations." Astrophysics 52, no. 2 (April 2009): 157–67. http://dx.doi.org/10.1007/s10511-009-9066-4.

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Quillen, Alice C., Alex R. Pettitt, Sukanya Chakrabarti, Yifan Zhang, Jonathan Gagné, and Ivan Minchev. "Birth sites of young stellar associations and recent star formation in a flocculent corrugated disc." Monthly Notices of the Royal Astronomical Society 499, no. 4 (October 15, 2020): 5623–40. http://dx.doi.org/10.1093/mnras/staa3189.

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ABSTRACT With backwards orbit integration, we estimate birth locations of young stellar associations and moving groups identified in the solar neighbourhood that are younger than 70 Myr. The birth locations of most of these stellar associations are at a smaller galactocentric radius than the Sun, implying that their stars moved radially outwards after birth. Exceptions to this rule are the Argus and Octans associations, which formed outside the Sun’s galactocentric radius. Variations in birth heights of the stellar associations suggest that they were born in a filamentary and corrugated disc of molecular clouds, similar to that inferred from the current filamentary molecular cloud distribution and dust extinction maps. Multiple spiral arm features with different but near corotation pattern speeds and at different heights could account for the stellar association birth sites. We find that the young stellar associations are located in between peaks in the radial/tangential (UV) stellar velocity distribution for stars in the solar neighbourhood. This would be expected if they were born in a spiral arm, which perturbs stellar orbits that cross it. In contrast, stellar associations seem to be located near peaks in the vertical phase-space distribution, suggesting that the gas in which stellar associations are born moves vertically together with the low-velocity dispersion disc stars.
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Ivanov, G. R. "Stellar associations in M81." Monthly Notices of the Royal Astronomical Society 257, no. 1 (July 1, 1992): 119–24. http://dx.doi.org/10.1093/mnras/257.1.119.

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Moskal, E. V., and V. G. Surdin. "Dynamical models of stellar associations." Astronomical & Astrophysical Transactions 15, no. 1-4 (April 1998): 37–43. http://dx.doi.org/10.1080/10556799808201748.

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Kontizas, E., M. Kontizas, D. Gouliermis, A. Dapergolas, R. Korakitis, and D. H. Morgan. "Stellar Associations in the LMC." Symposium - International Astronomical Union 190 (1999): 410–16. http://dx.doi.org/10.1017/s007418090011842x.

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The stellar associations are defined as loose unbound concentrations of young stars with a bright OB stellar component, mainly located at the most recent star forming regions, representing the smallest units in the hierarchy of stellar systems in galaxies. The definition of the associations is discussed and the main properties of their stellar content are summarized. Using plates taken with the 1.2m UK Schmidt Telescope a method is developed to detect all stellar associations in the LMC and to find their spatial distribution relative to the LMC's recent star formation history. In 40% of the LMC region, the number of “single peak” associations has increased considerably (~ 3x). A very interesting result is that the faint limit, where the identified associations are revealed, varies by about 3 mag. This indicates not only extinction differences but also the presence of pre-main sequence stars at a wide range of masses.
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Efremov, Yu N., G. R. Ivanov, and N. S. Nikolov. "New Stellar Associations in M31." Symposium - International Astronomical Union 116 (1986): 389–90. http://dx.doi.org/10.1017/s0074180900149216.

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About twenty years ago van den Bergh (1964) recognized 188 OB associations in the Andromeda Nebula. He used plates taken by the 52-inches Tautenburgh Schmidt telescope in GDR. Later on Richter (1971) added 7 new associations in the south-western periphery of M31. Now we have the opportunity to continue the search of stellar associations in M31 with the 2m Ritchey-Chrétien (RC) telescope of the Bulgarian National Astronomical Observatory. The limiting magnitude of this telescope is approximately the same as that of the Tautenburg 2m Schmidt telescope but it possesses somewhat smaller field (1°x1°) with plate-scale 12.8 mm−1. That is why a new search of stellar associations in M31 by means of the 2m RC telescope is very efficient. Indeed, some previous inspections of the RC plates (Efremov, 1982) indicated some new associations in M31.
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Hatzidimitriou, Despina, Charles J. Lada, Ata Sarajedini, Russell D. Cannon, Kyle McC Cudworth, Gary S. Da Costa, LiCai Deng, Young-Wook Lee, Ata Sarajedini, and Monica Tosi. "COMMISSION 37: STAR CLUSTERS AND ASSOCIATIONS." Proceedings of the International Astronomical Union 4, T27A (December 2008): 277–79. http://dx.doi.org/10.1017/s1743921308025684.

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Star clusters are valuable tools for theoretical and observational astronomy across a wide range of disciplines from cosmology to stellar spectroscopy. For example, properties of globular clusters are used to constrain stellar evolutionary models, nucleosynthesis and chemical evolution, as well as the star formation and assembly histories of galaxies and the distribution of dark matter in present-day galaxies. Open clusters are widely used as stellar laboratories for the study of specific stellar phenomena (e.g., various emission-line stars, pulsating pre-MS stars, magnetic massive stars, binarity, stellar rotation, etc.). They also provide observational constraints on models of massive star evolution and of Galactic disk formation and chemical evolution.
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Wood, Mackenna L., Andrew W. Mann, Madyson G. Barber, Jonathan L. Bush, Reilly P. Milburn, Pa Chia Thao, Stephen P. Schmidt, Benjamin M. Tofflemire, and Adam L. Kraus. "A Lithium Depletion Age for the Carina Association." Astronomical Journal 166, no. 6 (November 15, 2023): 247. http://dx.doi.org/10.3847/1538-3881/ad03f3.

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Abstract The dispersed remnants of stellar nurseries, stellar associations, provide unparalleled samples of coeval stars critical for studies of stellar and planetary formation and evolution. The Carina Stellar Association is one of the closest stellar associations to Earth, and yet measurements of its age have varied from 13 to 45 Myr. We aim to update the age of Carina using the lithium depletion boundary (LDB) method. We obtain new measurements of the Li 6708 Å absorption feature in likely members using optical spectra from the Goodman High Throughput Spectrograph on SOAR and NRES on LCO. We detect the depletion boundary at M K ≃ 6.8 (M5). This age is consistent within uncertainties across six different models, including those that account for magnetic fields and spots. We also estimate the age through analysis of the group’s overall variability, and by comparing the association members’ color–magnitude diagram to stellar evolutionary models using a Gaussian Mixture Model, recovering ages consistent with the LDB. Combining these age measures we obtain an age for the Carina association of 41 − 5 + 3 Myr. The resulting age agrees with the older end of previous age measurements and is consistent with the lithium depletion age for the neighboring Tucana-Horologium moving group.
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Hodge, Paul. "Systems of Stellar Associations in Galaxies." Symposium - International Astronomical Union 116 (1986): 369–79. http://dx.doi.org/10.1017/s0074180900149186.

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This paper begins with an attempt to examine the problem of identifying stellar associations in galaxies in a consistent way, so that meaningful physical comparisons can be made for the population of stellar associations of different galaxies. A compilation of the existing data on associations in other galaxies is given and their properties compared. Questions relating to star formation in stellar associations are discussed, and then the issue of the initial mass function of core clusters, especially those located in giant HII regions, is briefly examined.
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de Geus, Eugène, and Tim de Zeeuw. "The Stellar Content of SCO OB2." Symposium - International Astronomical Union 115 (1987): 205–6. http://dx.doi.org/10.1017/s0074180900095553.

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The study of the stellar content of nearby OB associations is important for understanding the Initial Mass Function, the study of differential age effects and for a better knowledge of the ambient radiation field, which plays an important role in the interpretation of measurements of gas and dust. Unfortunately, even for the nearest OB associations membership is known very poorly. In most cases no main sequence members of spectral type later than B5 are known. Membership determination using colour-magnitude diagrams suffers from the large intrinsic distance spread. The large angular extent on the sky of most associations makes proper motion measurements difficult to compare because of problems connecting photographic plates with different plate centers. In order to remedy this situation a consortium called SPECTER has been formed at Leiden Observatory. It has been granted observing time on the HIPPARCOS satellite for measuring proper motions of about 10000 candidate members of the OB associations within 600 pc of the Sun. Candidates were selected according to spectral type (not later than F8) apparent magnitude, and location. In anticipation of the HIPPARCOS results, SPECTER will gather a variety of other data. We have nearly completed a program aimed at obtaining VBLUW-photometry (Lub and Pel 1977) of all candidate stars visible from the Southern Hemisphere. Here we discuss the preliminary results for the association Sco OB2.
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Dissertations / Theses on the topic "Stellar associations"

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An, Deokkeun. "Improving the Local Distance Scale from Empirically Calibrated Stellar Isochrones." The Ohio State University, 2008. http://rave.ohiolink.edu/etdc/view?acc_num=osu1218593380.

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Balog, Zoltan, Nick Siegler, G. H. Rieke, L. L. Kiss, James Muzerolle, R. A. Gutermuth, Cameron P. M. Bell, et al. "PROTOPLANETARY AND TRANSITIONAL DISKS IN THE OPEN STELLAR CLUSTER IC 2395." IOP PUBLISHING LTD, 2016. http://hdl.handle.net/10150/622451.

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We present new deep UBVRI images and high-resolution multi-object optical spectroscopy of the young (similar to 6-10 Myr old), relatively nearby (800 pc) open cluster IC 2395. We identify nearly 300 cluster members and use the photometry to estimate their spectral types, which extend from early B to middle M. We also present an infrared imaging survey of the central region using the IRAC and MIPS instruments on board the Spitzer Space Telescope, covering the wavelength range from 3.6 to 24 mu m. Our infrared observations allow us to detect dust in circumstellar disks originating over a typical range of radii from similar to 0.1 to similar to 10 au from the central star. We identify 18 Class II, 8 transitional disk, and 23 debris disk candidates, respectively, 6.5%, 2.9%, and 8.3% of the cluster members with appropriate data. We apply the same criteria for transitional disk identification to 19 other stellar clusters and associations spanning ages from similar to 1 to similar to 18 Myr. We find that the number of disks in the transitional phase as a fraction of the total with strong 24 mu m excesses ([8] - [24]. 1.5) increases from (8.4. +/- 1.3)% at similar to 3 Myr to (46. +/- 5)% at similar to 10 Myr. Alternative definitions of transitional disks will yield different percentages but should show the same trend.
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Grether, Daniel Andrew Physics Faculty of Science UNSW. "Statistical analyses of extrasolar planets and other close companions to nearby stars." Awarded by:University of New South Wales. School of Physics, 2006. http://handle.unsw.edu.au/1959.4/29182.

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We analyse the properties of extrasolar planets, other close companions and their hosts. We start by identifying a sample of the detected extrasolar planets that is minimally affected by the selection effects of the Doppler detection method. With a simple analysis we quantify trends in the surface density of this sample in the Msini-period plane. A modest extrapolation of these trends puts Jupiter in the most densely occupied region of this parameter space, thus suggesting that Jupiter is a typical massive planet rather than an outlier. We then examine what fraction of Sun-like (~ FGK) stars have planets. We find that at least ~25% of stars possess planets when we limit our analysis to stars that have been monitored the longest and whose low surface activity allow the most precise radial velocity measurements. The true fraction of stars with planets may be as large as ~100%. We construct a sample of nearby Sun-like stars with close companions (period < 5 years). By using the same sample to extract the relative numbers of stellar, brown dwarf and planetary companions, we verify the existence of a very dry brown dwarf desert and describe it quantitatively. Approximately 16% of Sun-like stars have close companions more massive than Jupiter: 11% +- 3% are stellar, <1% are brown dwarf and 5% +- 2% are giant planets. A comparison with the initial mass function of individual stars and free-floating brown dwarfs, suggests either a different spectrum of gravitational fragmentation in the formation environment or post-formation migratory processes disinclined to leave brown dwarfs in close orbits. Finally we examine the relationship between the frequency of close companions and the metallicity of their Sun-like hosts. We confirm and quantify a ~4 sigma positive correlation between host metallicity and planetary companions. In contrast we find a ~2 sigma anti-correlation between host metallicity and the presence of a stellar companion. Upon dividing our sample into FG and K sub-samples, we find a negligible anti-correlation in the FG sub-sample and a ~3 sigma anti-correlation in the K sub-sample. A kinematic analysis suggests that this anti-correlation is produced by a combination of low-metallicity, high-binarity thick disk stars and higher-metallicity, lower-binarity thin disk stars.
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Smilgys, Romas. "Formation of stars and stellar clusters in galactic environment." Thesis, University of St Andrews, 2018. http://hdl.handle.net/10023/13229.

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Star and stellar cluster formation in spiral galaxies is one of the biggest questions of astrophysics. In this thesis, I study how star formation, and the formation of stellar clusters, proceeds using SPH simulations. These simulations model a region of 400 pc and 107 solar masses. Star formation is modelled through the use of sink particles which represent small groups of stars. Star formation occurs in high density regions, created by galactic spiral arm passage. The spiral shock compresses the gas and generates high density regions. Once these regions attain sufficiently high density, self-gravity becomes dominant and drives collapse and star formation. The regions fragment hierarchically, forming local small groups of stars. These fall together to form clusters, which grow through subsequent mergers and large scale gas infall. As the individual star formation occurs over large distances before forming a stellar cluster, this process can result in significant age spreads of 1-2 Myrs. One protocluster is found to fail to merge due to the large scale tidal forces from the nearby regions, and instead expands forming a dispersed population of young stars such as an OB association.
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McCarthy, Kyle. "Characterizing the Nearest Young Moving Groups." UKnowledge, 2015. http://uknowledge.uky.edu/physastron_etds/30.

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Moving groups are associations of stars which originated from the same star forming region. These groups are typically young (< 200 Myr) since they have not dissipated into the galactic field population. Over the last 15 years, roughly 10 such moving groups have been found with distances < 150 pc (7 with distances < 100 pc), each with a unique velocity and position. This work first investigates the likelihood to resolve star from two moving groups (AB Doradus and Beta Pictoris) using high spacial resolution optical interferrometry and found 5 AB Doradus stars and 1 Beta Pictoris star with declinations > -30 could be spacially resolved. To more deeply characterize individual groups, we used the 2.7m telescope at the McDonald Observatory to observe 10 proposed AB Doradus stars and 5 proposed Octans-Near stars (3 probable members, 2 possible) with high resolution (R ~60,000) optical spectroscopy. Each group is characterized in three ways: (1) Chemical analysis to determine the homogeneity among members, (2) Kinematic traceback to determine the origin, and (3) Isochrone fitting to determine the age. We find the 8 stars in our AB Doradus sample are chemically homogeneous with [M/H] = -0.03 ± 0.06 dex, traceback to an age of 125 Myr, and the stars in this mass range are on the main sequence. The two deviants are a metal rich, potentially younger member and a metal poor, young star likely not associated with AB Doradus. In our Octans-Near sample, we find the 3 probable members have [M/H] = -0.06 ± 0.11, the stars do not trace back to a common origin, and the probable members are on the main sequence. In addition to these tests, we found that the probable members are slightly more lithium depleted than the Pleiades, implying an age between 125 and 200 Myr. Finally, we investigate systematic trends in fundamental stellar parameters from the use of different techniques. Preliminary results find differences in temperatures between interferrometric and spectroscopic techniques to be a function of temperature with a interferrometric temperatures being cooler by an average of 36 ± 115 K. We also calculated the chemical abundances as a function of condensation temperature for our moving group sample and predict 2 stars in AB Doradus could represent the initial star forming environment and discuss the implications for planet hosting stars in nearby moving groups. This updated characterization technique allows for a deeper understanding of the moving group environment. As future, high precision instruments emerge in astronomy (Jame Webb Space Telescope, GAIA, 30m class telescopes), moving groups are ideal targets since these associations will help us understand star forming regions, stellar evolution at young ages, constrain stellar evolutionary models, and identify planetary formation and evolution mechanisms.
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Miret, Roig Núria. "COSMIC-DANCE : A comprehensive census of nearby star forming regions." Thesis, Bordeaux, 2020. http://www.theses.fr/2020BORD0327.

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Comprendre comment se forment les étoiles est l’une des questions fondamentales auxquelles l’astronomie entend répondre. Malheureusement, nous ne pouvons pas étudier la formation stellaire en temps réel et différentes méthodes indirectes doivent être utilisées pour faire la lumière sur ce sujet. L’objectif principal de cette thèse est de déterminer la fonction de masse initiale, la distribution de masse des étoiles à leur naissance, dans différentes associations et régions de formation d’étoiles. La fonction de masse est le produit direct de la formation stellaire et constitue donc un paramètre d’observation fondamental pour contraindre les théories de formation stellaire et sous-estellaire. Nous nous sommes concentrés sur l’amas ouvert de 30 Ma IC 4665 et la région de formation d’étoiles de 1 - 10 Ma de Upper Scorpius (USC) et r Ophiuchi (r Oph). Nous avons combiné l’astrométrie et la photométrie de Gaia Data Release 2 avec nos observations au sol pour préparer un catalogue profond et étendu de chaque région. Ensuite, nous avons calculé les probabilités d’appartenance en utilisanttoute l’astrométrie et la photométrie disponibles et identifié les membres à haute probabilité. Nous avons utilisé la liste finale des membres pour estimer la distribution de magnitude, et les fonctions de luminosité et masse de ces associations. Alors que la première a l’avantage d’être indépendante des modèles d’évolution, tandis que les fonctions de luminosité et de masse peuvent être utilisées pour contraindre les mécanismes de formation d’étoiles. L’étude d’IC 4556 nous a permis d’identifier des objets sous-stellaires, sans pour autant pouvoir fournir un recensement complet dans ce domaine de masse. Dans USC et r Oph, nous avons identifié une population très riche d’objets sous-stellaires, significativement plus nombreux que les prédictions des modèles de formation par effondrement de coeurs moléculaires, suggérant que la formation de naines brunes et d’objets de masses planétaires isolés par des phénomènes d’éjection dans des systèmes planétaires a une contribution importante et du même ordre que l’effondrement des coeurs moléculaires à la population finale d’objets dans un amas. L’âge est un paramètre fondamental pour étudier la formation et l’évolution des étoiles pour plusieurs raisons: premièrement puisqu’il établit une échelle de temps sur laquelle placer les observations. Deuxièmement car il est essentiel pour convertir les luminosités en masses, avec l’aide de modèles d’évolution stellaire. Les incertitudes sur l’age de USC et r Oph se traduisant en erreurs importantes dans notre estimation de la fonction de masse, j’ai développé une stratégie d’étude de "l’âge dynamique" au moyen d’une analyse orbitale de traçage des mouvements des membres d’associations jeunes. J’ai ainsi mis au point une stratégie incluant i) les observations et la recherche de données dans les archives publiques, ii) la réduction et l’analyse des spectres échelles obtenus; iii) et l’analyse dynamique, pour déterminer l’âge d’une association. La méthodologie, développée avec l’association b Pictoris (b Pic), est prête à être appliquée à d’autres régions et en particulier à USC et r Oph. Les membres que nous avons identifiés sont par ailleurs d’excellentes cibles pour des études complémentaires telles que la recherche de disques (produit également fondamental de la formation stellaire), d’exoplanètes, de système multiples, mais aussi pour la caractérisation des atmosphères et propriétés physiques des naines brunes et des planètes errantes. [...]
Understanding how stars form is one of the fundamental questions which astronomy aims to answer. Currently, it is well accepted that the majority of stars form in groups and that their predominant mechanism of formation is the core-collapse. However, several mechanisms have been suggested to explain the formation of substellar objects, and their contribution is still under debate. The main goal of this thesis is to determine the initial mass function, the mass distribution of stars at birth time, in different associations and star-forming regions. The mass function constitutes a fundamental observational parameter to constrain stellar and substellar formation theories since different formation mechanisms predict different fraction of stellar and substellar objects. We used the Gaia Data Release 2 catalogue together with ground-based observations from the COSMIC-DANCe project to look for high probability members via a probabilistic model of the distribution of the observable quantities in both the cluster and background populations. We applied this method to the 30 Myr open cluster IC 4665 and the 1 - 10 Myr star-forming region Upper Scorpius (USC) and r Ophiuchi (r Oph). We found very rich populations of substellar objects which largely exceed the numbers predicted by core-collapse models. In USC, where our sensitivity is best, we found a large number of free-floating planets and we suggest that ejection from planetary systems must have a similar contribution than core-collapse in their formation. The age is a fundamental parameter to study the formation and evolution of stars and is essential to accurately convert luminosities to masses. For that, we also presented a strategy to study the dynamical traceback age of young local associations through an orbital traceback analysis. We applied this method to determine the age of the b Pictoris moving group and in the future, we plan to apply it to other regions such as USC. The members we identified with the membership analysis are excellent targets for follow-up studies such as a search for discs, exoplanets, characterisation of brown dwarfs and free-floating planets. I this thesis, we presented a search for discs hosted by members of IC 4665 and we found six excellent candidates to be imaged with ALMA or the JWST. The tools we developed, are ready to be used in other regions such as USC and r Oph, where we expect to find a larger number of disc-host stars
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Da, Rio Nicola, Jonathan C. Tan, Kevin R. Covey, Michiel Cottaar, Jonathan B. Foster, Nicholas C. Cullen, John Tobin, et al. "IN-SYNC. V. Stellar Kinematics and Dynamics in the Orion A Molecular Cloud." IOP PUBLISHING LTD, 2017. http://hdl.handle.net/10150/625776.

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The kinematics and dynamics of young stellar populations enable us to test theories of star formation. With this aim, we continue our analysis of the SDSS-III/APOGEE IN-SYNC survey, a high-resolution near-infrared spectroscopic survey of young clusters. We focus on the Orion A star-forming region, for which IN-SYNC obtained spectra of similar to 2700 stars. In Paper IV we used these data to study the young stellar population. Here we study the kinematic properties through radial velocities (vr). The young stellar population remains kinematically associated with the molecular gas, following a similar to 10 km s(-1) gradient along the filament. However, near the center of the region, the vr distribution is slightly blueshifted and asymmetric; we suggest that this population, which is older, is slightly in the foreground. We find evidence for kinematic subclustering, detecting statistically significant groupings of colocated stars with coherent motions. These are mostly in the lower-density regions of the cloud, while the ONC radial velocities are smoothly distributed, consistent with it being an older, more dynamically evolved cluster. The velocity dispersion sigma(v) varies along the filament. The ONC appears virialized, or just slightly supervirial, consistent with an old dynamical age. Here there is also some evidence for ongoing expansion, from a v(r)-extinction correlation. In the southern filament, sigma(v) is similar to 2-3 times larger than virial in the L1641N region, where we infer a superposition along the line of sight of stellar subpopulations, detached from the gas. In contrast, sv decreases toward L1641S, where the population is again in agreement with a virial state.
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ZOCCHI, ALICE. "OBSERVATIONAL TESTS ON THE DYNAMICS OF GLOBULAR CLUSTERS." Doctoral thesis, Università degli Studi di Milano, 2014. http://hdl.handle.net/2434/235122.

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Galactic globular clusters are nearly gas-free, self-gravitating stellar systems characterized by an apparently simple geometry, with finite size probably determined by tidal truncation. These unique properties make them excellent laboratories for studies of stellar dynamics, and ideal targets for N-body simulations. For a long time, they have been treated as spherically symmetric, nonrotating, isotropic systems. The spherical King (1966) models, constructed to match this physical picture, are usually considered as the correct zeroth-order dynamical reference model, and are sometimes successful in representing the observed characteristics of these systems. In reality, this simple physical picture suffers from a number of limitations, which become more evident now that much improved observations have become available. In particular, deviations from sphericity have been observed and should be explained. Three physical ingredients are expected to affect the observed morphologies of stellar systems: internal rotation, pressure anisotropy, and external tides. A proper identification of the physical ingredients that shape the internal dynamics of globular clusters will lead to draw conclusions on their origin, and on the origin of their host systems. In particular, a detailed characterization of the role played by internal rotation and pressure anisotropy in present-day globular clusters would be a crucial element to discriminate among different formation scenarios for this class of stellar systems; indeed, the main goal of this Thesis is to clarify the role of these two important dynamical factors. For the purpose of giving a detailed and more realistic description of globular clusters, dynamical studies are an important counterpart to the stellar populations analyses often carried out for these systems. Dynamical studies are meaningful only when both photometric and kinematic data are taken into account, but unfortunately for globular clusters the application of dynamical models is frequently carried out only in relation to the available photometric profiles. This Thesis addresses this issue, and strongly supports the view that accurate kinematic data are crucial to provide a satisfactory description of these systems.
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Kastner, Joel H., David A. Principe, Kristina Punzi, Beate Stelzer, Uma Gorti, Ilaria Pascucci, and Costanza Argiroffi. "M STARS IN THE TW HYA ASSOCIATION: STELLAR X-RAYS AND DISK DISSIPATION." IOP PUBLISHING LTD, 2016. http://hdl.handle.net/10150/621232.

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To investigate the potential connection between the intense X-ray emission from young low-mass stars and the lifetimes of their circumstellar planet-forming disks, we have compiled the X-ray luminosities (L-X) of M stars in the similar to 8 Myr old TW Hya Association (TWA) for which X-ray data are presently available. Our investigation includes analysis of archival Chandra data for the TWA binary systems TWA 8, 9, and 13. Although our study suffers from poor statistics for stars later than M3, we find a trend of decreasing L-X/L-bol with decreasing T-eff for TWA M stars, wherein the earliest-type (M0-M2) stars cluster near log(L-X/L-bol) approximate to -3.0 and then log(L-X/L-bol) decreases, and its distribution broadens, for types M4 and later. The fraction of TWA stars that display evidence for residual primordial disk material also sharply increases in this same (mid-M) spectral type regime. This apparent anticorrelation between the relative X-ray luminosities of low-mass TWA stars and the longevities of their circumstellar disks suggests that primordial disks orbiting early-type M stars in the TWA have dispersed rapidly as a consequence of their persistent large X-ray fluxes. Conversely, the disks orbiting the very lowest-mass pre-MS stars and pre-MS brown dwarfs in the Association may have survived because their X-ray luminosities and, hence, disk photoevaporation rates are very low to begin with, and then further decline relatively early in their pre-MS evolution.
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Nakamura, Toshio. "Expression of the Na+/Ca2+ exchanger emerges in hepatic stellate cells after activation in association with liver fibrosis." Kyoto University, 1998. http://hdl.handle.net/2433/182267.

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Books on the topic "Stellar associations"

1

Hungary) Star Clusters and Associations (6th 1989 Visegrád. Star clusters and associations. Budapest: Roland [sic] Eötvös University, 1990.

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Efremov, Yu N. Open clusters, associations and stellar complexes. Chur: Harwood Academic Publishers, 1989.

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Arp, Halton C. A catalogue of southern peculiar galaxies and associations. Cambridge: Cambridge University Press, 1987.

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A, Hunter D., Gallagher J. S, and United States. National Aeronautics and Space Administration., eds. IUE observations of luminous blue star associations in irregular galaxies. [Washington, D.C.?: National Aeronautics and Space Administration, 1986.

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1949-, Schwengel Hermann, ed. Wer bestimmt die Zukunft?: Wie die Verantwortlichen aus Politik, Wirtschaft und Gesellschaft die Weichen für eine gute gesellschaftliche Entwicklung stellen können. Frankfurt am Main: Lang, 2005.

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United States. National Aeronautics and Space Administration., ed. A deep PSPC observation of the Cyg OB2 association: Final report. [Washington, DC: National Aeronautics and Space Administration, 1995.

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United States. National Aeronautics and Space Administration., ed. A deep PSPC observation of the Cyg OB2 association: Final report. [Washington, D.C: National Aeronautics and Space Administration, 1995.

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United States. National Aeronautics and Space Administration., ed. A deep PSPC observation of the Cyg OB2 association: Final report. [Washington, D.C: National Aeronautics and Space Administration, 1995.

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United States. National Aeronautics and Space Administration., ed. A deep PSPC observation of the Cyg OB2 association: Final report. [Washington, DC: National Aeronautics and Space Administration, 1995.

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Arp, Halton C., and Barry F. Madore. Catalogue of Southern Peculiar Galaxies and Associations. University of Cambridge ESOL Examinations, 1987.

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Book chapters on the topic "Stellar associations"

1

Kalloghlian, A. T. "STELLAR ASSOCIATIONS." In Ambartsumian’s Legacy and Active Universe, 77–87. New York, NY: Springer New York, 2011. http://dx.doi.org/10.1007/978-1-4614-0182-7_5.

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Inglis, Michael. "Galactic Clusters and Stellar Associations." In The Patrick Moore Practical Astronomy Series, 123–37. Cham: Springer International Publishing, 2014. http://dx.doi.org/10.1007/978-3-319-11644-0_7.

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Inglis, Michael. "Galactic Clusters and Stellar Associations." In The Patrick Moore Practical Astronomy Series, 153–71. Cham: Springer International Publishing, 2023. http://dx.doi.org/10.1007/978-3-031-16805-5_7.

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Wilson, Christine D. "Ob Associations in Ngc 6822." In The Stellar Populations of Galaxies, 506. Dordrecht: Springer Netherlands, 1992. http://dx.doi.org/10.1007/978-94-011-2434-8_173.

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Mathieu, Robert D. "Overview of Collisional Stellar Dynamics." In Dynamics of Young Star Clusters and Associations, 137–46. Berlin, Heidelberg: Springer Berlin Heidelberg, 2015. http://dx.doi.org/10.1007/978-3-662-47290-3_10.

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Mirzoyan, L. V. "Stellar Associations and Regions of Star Formation." In Star Forming Regions, 200–201. Dordrecht: Springer Netherlands, 1987. http://dx.doi.org/10.1007/978-94-009-4782-5_77.

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Reid, I. Neill. "Stellar Kinematics and the Dynamical Evolution of the Disc." In Dynamics of Young Star Clusters and Associations, 259–77. Berlin, Heidelberg: Springer Berlin Heidelberg, 2015. http://dx.doi.org/10.1007/978-3-662-47290-3_17.

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Reipurth, Bo. "FU Orionis eruptions and early stellar evolution." In Flare Stars in Star Clusters, Associations and the Solar Vicinity, 229–51. Dordrecht: Springer Netherlands, 1990. http://dx.doi.org/10.1007/978-94-009-0607-5_49.

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Harutyunian, H. A., and V. S. Hayrapetyan. "On the Gamma-Activity of Stellar Flares." In Flare Stars in Star Clusters, Associations and the Solar Vicinity, 333–36. Dordrecht: Springer Netherlands, 1990. http://dx.doi.org/10.1007/978-94-009-0607-5_67.

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Parsamian, E. S., and G. B. Ohanian. "Slow Flares in Stellar Aggregates and Solar Vicinity." In Flare Stars in Star Clusters, Associations and the Solar Vicinity, 109–12. Dordrecht: Springer Netherlands, 1990. http://dx.doi.org/10.1007/978-94-009-0607-5_26.

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Conference papers on the topic "Stellar associations"

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Montes, D., J. López-Santiago, R. M. Martínez-Arnáiz, P. Guillout, A. Klutsch, R. Freire Ferrero, A. Frasca, E. Marilli, and Eric Stempels. "Post T Tauri stars in the solar neighborhood: isolated or members of young associations and moving groups." In COOL STARS, STELLAR SYSTEMS AND THE SUN: Proceedings of the 15th Cambridge Workshop on Cool Stars, Stellar Systems and the Sun. AIP, 2009. http://dx.doi.org/10.1063/1.3099274.

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López-Santiago, J., G. Micela, L. Affer, and Eric Stempels. "The 32 Ori association: a test for the star formation history in our vicinity." In COOL STARS, STELLAR SYSTEMS AND THE SUN: Proceedings of the 15th Cambridge Workshop on Cool Stars, Stellar Systems and the Sun. AIP, 2009. http://dx.doi.org/10.1063/1.3099187.

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Béjar, V. J. S., M. R. Zapatero Osorio, A. Pérez-Garrido, C. Álvarez, E. L. Martín, R. Rebolo, I. Villó-Pérez, A. Díaz-Sánchez, and Eric Stempels. "Discovery of a wide planetary-mass companion of a brown dwarf in the Upper Scorpius association." In COOL STARS, STELLAR SYSTEMS AND THE SUN: Proceedings of the 15th Cambridge Workshop on Cool Stars, Stellar Systems and the Sun. AIP, 2009. http://dx.doi.org/10.1063/1.3099150.

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Kurbatova, Natalia Viktorovna. "DAS PHÄNOMEN DER BERUFSERFAHRUNG UND IHRE ENTWICKLUNG BEIM KUNSTLEHRER." In Themed collection of papers from Foreign International Scientific Conference « Science in the Era of Challenges and Global Changes» Ьу НNRI «National development» in cooperation with AFP (Puerto Cabezas, Nicaragua). Мау 2023. - Caracas (Venezuela). Crossref, 2023. http://dx.doi.org/10.37539/230527.2023.35.10.026.

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The article actualizes the task of studying and developing the personal professional experience of a teacher of fine arts, presents some results of empirical studies, characterizes the actual types of professional experience, the development of which is focused on the implementation of additional professional programs based on the Academy of Watercolor and Fine Arts of Sergey Andriyaka and the Association of Teachers of the Subject Area " Art” of the city of Moscow, chaired by the author of the article. Der Artikel aktualisiert die Aufgabe, die persönliche Berufserfahrung eines Lehrers für bildende Künste zu studieren und weiterzuentwickeln, stellt einige Ergebnisse empirischer Forschung vor, charakterisiert die tatsächlichen Arten von Berufserfahrung, deren Entwicklung auf der Umsetzung zusätzlicher beruflicher Programme basiert der Akademie für Aquarell und bildende Künste von Sergey Andriyaka und der Vereinigung der Lehrer des Fachgebiets „Kunst“ der Stadt Moskau unter dem Vorsitz des Autors des Artikels.
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Kurbatova, Natalia Viktorovna. "BERUFSERFAHRUNG DER KUNSTLEHRER." In Themed collection of papers from Foreign international scientific conference «Joint innovation - joint development». Part 1. Ьу НNRI «National development» in cooperation with PS ofUA. June 2023. Crossref, 2023. http://dx.doi.org/10.37539/230629.2023.24.35.043.

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The article actualizes the task of studying and developing the personal professional experience of a teacher of fine arts, presents some results of empirical studies, characterizes the actual types of professional experience, the development of which is focused on the implementation of additional professional programs based on the Academy of Watercolor and Fine Arts of Sergey Andriyaka and the Association of Teachers of the Subject Area " Art” of the city of Moscow, chaired by the author of the article. Der Artikel aktualisiert die Aufgabe, die persönliche Berufserfahrung eines Lehrers für bildende Künste zu studieren und weiterzuentwickeln, stellt einige Ergebnisse empirischer Forschung vor, charakterisiert die tatsächlichen Arten von Berufserfahrung, deren Entwicklung auf der Umsetzung zusätzlicher beruflicher Programme basiert der Akademie für Aquarell und bildende Künste von Sergey Andriyaka und der Vereinigung der Lehrer des Fachgebiets „Kunst“ der Stadt Moskau unter dem Vorsitz des Autors des Artikels.
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Correia, Ana Luisa. "Abstract PO005: Hepatic stellate cells suppress NK cell sustained breast cancer dormancy." In Abstracts: AACR Virtual Special Conference: The Evolving Tumor Microenvironment in Cancer Progression: Mechanisms and Emerging Therapeutic Opportunities; in association with the Tumor Microenvironment (TME) Working Group; January 11-12, 2021. American Association for Cancer Research, 2021. http://dx.doi.org/10.1158/1538-7445.tme21-po005.

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Tan, Xiaomian, Yun Yun Gong, and J. Bernadette Moore. "OP03 Identification of microRNAs regulated by vitamin D and fatty acid treatment in immortalised hepatocytes and hepatic stellate cells through microRNA sequencing." In Abstracts of the British Association for the Study of the Liver Annual Meeting, 20–23 September 2022. BMJ Publishing Group Ltd and British Society of Gastroenterology, 2022. http://dx.doi.org/10.1136/gutjnl-2022-basl.16.

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Fenglio, J., A. Bini, R. Mega-Tejada, B. Kudryk, and K. L. Kaplan. "DISTRIBUTION AND IDENTIFICATION OF FIBRINOGEN, FIBRIN AND DEGRADATION PRODUCTS IN ATHEROSCLEROSIS BY MONOCLONAL ANTIBODIES." In XIth International Congress on Thrombosis and Haemostasis. Schattauer GmbH, 1987. http://dx.doi.org/10.1055/s-0038-1643081.

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Specimens from vascular surgery and from heart transplant recipients were examined. The tissues were stained with the avidin biotin complex-immunoperoxidase technique using specific monoclonal antibodies (MAbs) for fibrinogen and fibrin. MAb I8C6 detects fibrinogen and fibrin I, MAb T2G1 is specific for fibrin II, MAb GC4 recognizes fragments D and D-D and does not cross-react with fibrinogen. Polyclonal antisera for fibrinogen, albumin and IgG were used as controls or as markers of increased vessel wall permeability. Serial sections of each specimen were stained with all the antibodies and the distribution of the different antigens compared. In samples of 4 normal thoracic aortas fibrinogen was present in 3/14 sections from different areas. Fibrin II and degradation products were absent. In 7 fibrous plaques, fibrinogen, fibrin II and fragment D were present, distributed in strands or in focal deposits. In most cases a stellate, patchy pattern of distribution was observed for fibrinogen and fibrin II suggestive of association with vessel wall cells and macrophages. In 7 complicated plaques fibrin II was always associated with fibrinogen, fragment D, albumin and IgG in areas of thrombus and these antigens were also present around cholesterol crystals and calcium deposits. In less severely affected areas some fibrinogen was focally distributed and fragment D was associated with fibrin II in granulation tissue. In three coronaries, fibrinogen and fibrin II were distributed in areas of early or fibrous plaque in which no fragment D was detected. In all the samples albumin and IgG were associated with fibrinogen and fibrin deposits suggesting penetration of plasma proteins into the vessel wall. These results indicate that polymerization and degradation of fibrin might occur not only on the luminal surface, but also within the vessel wall with cellular participation, thus contributing to the evolution of the atherosclerotic lesion. The use of specific monoclonal antibodies has made it possible to distinguish the distribution of fibrinogen and fibrin I, fibrin II and fragments D and D-D in normal and atherosclerotic vessels.
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Firuzi, O., PP Che, M. Buijs, B. El Hassouni, C. Stefano, M. Löhr, R. Heuchel, L. Saso, GJ Peters, and E. Giovannetti. "PO-278 Assessment of the influence of stellate cells on primary pancreatic cancer cell growth and drug resistance in a spheroid model: MET inhibitors to the rescue." In Abstracts of the 25th Biennial Congress of the European Association for Cancer Research, Amsterdam, The Netherlands, 30 June – 3 July 2018. BMJ Publishing Group Ltd, 2018. http://dx.doi.org/10.1136/esmoopen-2018-eacr25.792.

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