Relevant bibliographies by topics / Pre-main-sequence

Academic literature on the topic 'Pre-main-sequence'

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Published: 4 June 2021
Last updated: 14 March 2023

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Journal articles on the topic "Pre-main-sequence"

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Duchêne, Gaspard. "Pre-main sequence disks." Proceedings of the International Astronomical Union 6, S270 (May 2010): 45–48. http://dx.doi.org/10.1017/s1743921311000159.

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AbstractIn this contribution, I briefly review our empirical knowledge of disks around ≲2M⊙ pre-main sequence (T Tauri) stars, focusing first on the dichotomic question of their frequency before moving on to some more detailed disk properties (overall orientation, total mass, outer radius). Finally, I conclude with a brief discussion of disks around embedded protostars, which will play in the next few years a major role in testing star formation theory and simulations.
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Masson, Colin R. "Pre-main-sequence outflows." Astrophysics and Space Science 224, no. 1-2 (February 1995): 99–108. http://dx.doi.org/10.1007/bf00667830.

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D’Antona, Francesca. "The Pre - Main Sequence." International Astronomical Union Colloquium 137 (1993): 395–409. http://dx.doi.org/10.1017/s0252921100018157.

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AbstractThe Pre-Main-Sequence (pre-MS) is defined as the phase following the protostellar stage and ending with the ignition of hydrogen in the stellar core. Models in hydrostatic and thermal equilibrium such as typical “Hayashi track” models are basically adequate to describe the internal structure of pre-MS stars, although for a fraction of pre-MS objects there can be phases of accretion also at late stages, which may influence the surface abundances of light elements.The interior evolution of pre-MS structures is focused in the two main stages’ of Deuterium and Lithium burning for the low mass (M ≤ 1.5M⊙) stars. The location in the HR diagram of theoretical tracks is still subject to large uncertainty, even more apparent today that new opacities and treatment of turbulent convection are available, and the results can be internally compared. Uncertainties amount to a factor ~ two for mass and age determination of individual objects, and affect the absolute location for both the D-burning and the Li-burning regions. Qualitative constraints, such as that there can not be Li-depletion at L ≥ L⊙, remain valid. Abundances of7Li at the surface of pre-MS stars, if measured at a stage which can definitely be considered previous to the possible occurrence of nuclear burning, and, consequently, previous to other depletion mechanism which may occur later on, provide constraints on galactic evolution of this element of cosmological interest.
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Scicluna, P., G. Rosotti, J. E. Dale, and L. Testi. "Old pre-main-sequence stars." Astronomy & Astrophysics 566 (June 2014): L3. http://dx.doi.org/10.1051/0004-6361/201423654.

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Mathieu, Robert D. "Pre-Main-Sequence Binary Stars." Annual Review of Astronomy and Astrophysics 32, no. 1 (September 1994): 465–530. http://dx.doi.org/10.1146/annurev.aa.32.090194.002341.

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Bouy, Hervé. "Pre-main sequence multiple systems." Proceedings of the International Astronomical Union 6, S270 (May 2010): 41–44. http://dx.doi.org/10.1017/s1743921311000147.

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AbstractIt is now well established that the majority of young stars are found in multiple systems, so that any theory of stellar formation must account for their existence and properties. Studying the properties of multiple star systems therefore represents a very powerful approach to place observational constraints on star formation theories. Additionally, multiple systems offer other advantages. They provide the most accurate and unambiguous way to measure masses, using orbital fitting and Kepler's laws, and even the stellar radius in the special case of eclipsing binaries. They also allow to compare the properties of 2 coeval objects with different masses, providing important tests for the evolutionary models.
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Zwintz, K. "Asteroseismology of pre-main sequence stars." Communications in Asteroseismology 159 (2009): 59–60. http://dx.doi.org/10.1553/cia159s59.

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Hartmann, Lee, Gregory Herczeg, and Nuria Calvet. "Accretion onto Pre-Main-Sequence Stars." Annual Review of Astronomy and Astrophysics 54, no. 1 (September 19, 2016): 135–80. http://dx.doi.org/10.1146/annurev-astro-081915-023347.

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Marconi, Marcella, and Francesco Palla. "Pre-Main-Sequence A-type stars." Proceedings of the International Astronomical Union 2004, IAUS224 (July 2004): 69–79. http://dx.doi.org/10.1017/s1743921304004399.

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Zwintz, Konstanze. "Pulsation in pre-main sequence stars." Proceedings of the International Astronomical Union 11, A29B (August 2015): 552–59. http://dx.doi.org/10.1017/s1743921316006116.

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AbstractAsteroseismology has been proven to be a successful tool to unravel details of the internal structure for different types of stars in various stages of evolution well after birth. We can now show that it has similar power for pre-main sequence (pre-MS) objects. Pre-MS stars with masses between ~1 and 6 solar masses that have recently been formed and gain their energy mainly from gravitational contraction can become vibrationally unstable during their evolution to the main sequence. Within the past ~15 years, several dozens of pulsating pre-MS stars were discovered using data obtained from ground and from space. Depending on their masses, pre-MS stars can show three different types of pulsations: (i) δ Scuti type p-mode pulsations, (ii) γ Doradus like g-mode oscillations and (iii) g-mode Slowly Pulsating B star pulsations.Our asteroseismic investigations yielded new insights into the connection between the pulsations and early stellar evolution: We revealed a relation between the stars' oscillatory behavior and their relative evolutionary stages that might lead us to a model-independent determination of the stars' fundamental parameters. With this we will be able to put constraints on theoretical models and help to answer some of the yet open questions in early stellar evolution.
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Dissertations / Theses on the topic "Pre-main-sequence"

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Burhan, Mehmet. "Vibrational Stability Of Pre-main Sequence Stars." Master's thesis, METU, 2004. http://etd.lib.metu.edu.tr/upload/12604705/index.pdf.

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In this study, vibrational properties and stability of delta-Scuti like pulsating pre-main sequence stars have been investigated. Studies were held in the mass range 2-4 Mo and limited to radial linear adiabatic pulsations. Numerical computations were performed by the oscillation program written by Kirbiyik &
Al-Murad (1993). The models were selected to be at the latest phases of the pre-main sequence evolution where the luminosity starts to increase. We have limited our calculations upto the end of the radiative inner regions, since at the surface of the star, our adiabatic perturbation computation does not perfectly fit to the relatively thin non-adiabatic convective envelope of the star. The results of the stability analysis showed that the PMS models undergo an instability whose time period is a function of mass. Instability Strip of pulsating PMS stars was re-drawn with comparison to M. Marconi &
F.Palla (1998). The effect of gravitational contraction on stability was also investigated.
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Hutchinson, Mark Gerard. "Observational studies of pre-main sequence stars." Thesis, Keele University, 1988. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.716860.

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Giarrusso, Marina. "Lithium and age of pre-main sequence stars." Doctoral thesis, Università di Catania, 2016. http://hdl.handle.net/10761/3892.

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The expectation to date the age of low mass pre-main sequence stars from lithium has been tested by comparing the observed lithium and the predicted abundance by evolutionary models. The test, in this thesis, has been applied on a sample of binary systems whose components have a well known mass or whose mass ratio has been exactly established. The common metallicity and the coevality of the two components of a system are strong constraints to determine the age on the basis of evolutionary codes. To achieve reliable results, by an observational campaign, I have doubled the sample of stars presenting the necessary information for the analysis. Stellar parameters have been determined with the most precise and accurately tested techniques: high resolution spectroscopy along a very large wavelength range and numerical solution of the radiative transfer equation. As to the evolutionary code, I have implemented FRANEC with the very accurate reaction rates as determined with the most reliable experimental technique, the Trojan Horse Method. Since for PMS stars the agreement between observed and predicted lithium abundance can be obtained just tuning the external convective efficiency, I have computed a database of models for different values of the mixing length parameter. Age determination of stars has been carried out by adopting what is nowadays believed to be the most powerful statistical method in the field, the Bayesian analysis. I have extended in an original way this statistical method from binary system with known masses to the most common double lined spectroscopic binaries.
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Rolph, C. D. "Imaging polarimetry of pre- and post- main sequence objects." Thesis, Durham University, 1990. http://etheses.dur.ac.uk/6257/.

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In the first part of this thesis an automated polarimeter is described, and details are given of a dedicated CCD camera system based on a personal computer. The quality of the data produced by these instruments is demonstrated by the results presented in the succeeding chapters. Polarimetric observations of nebulae associated with two pre-MS objects, HH83/Rel7 and GL2591, and two post-MS objects, IRAS 07131-0147 and OH 231.8+4.2, are presented and discussed with reference to previous observations. In each case the location of the exciting source is determined and a simple model is described which explains the observed characteristics of the system. Both HH83/Rel7 and GL2591 are shown to be illuminated by nearby IRAS sources which have no optical counterparts. The nebula associated with HH83/Rel7 is caused by the reflection of radiation off the insides of the walls of a cavity excavated in the dark cloud by outflows from the IRS, and is crossed by a narrow unpolarised jet seen in emission-line radiation. The nebula associated with GL2591 is illuminated at optical wavelengths by both the IRS and a second, visible, source, and is composed of material ejected by the IRS in a discrete period of mass loss. IRAS 07131-0147 and OH 231.8+4.2 are shown to be stars which have evolved off the AGB and which will soon become the central stars of planetary nebulae. The protoplanetary nebulae which have formed as a result of the action of the fast stellar wind on the extended RGE around each star are bipolar and axially symmetric. The fast wind is shown to have ceased in the case of IRAS 07131-0147, but that related to OH 231.8+4.2 is still carrying material away from the star in a highly collimated fashion, producing narrow dusty filaments along the axes of the cavities. High levels of polarisation are measured in both nebulae, which indicates that the scattering particles are much smaller than those in the ISM.A brief comparison of the pre- and post-MS nebulae shows that the two phases of stellar evolution are linked by a number of observationally similar characteristics, and it is thought that similar processes may occur at opposite ends of the evolutionary track. Most notably, circumstellar discs appear to be common at various stages in the stellar life-cycle.
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Padgett, Deborah Lynne Oke J. Beverley. "Photospheric abundance analysis of low mass pre-main sequence stars /." Diss., Pasadena, Calif. : California Institute of Technology, 1992. http://resolver.caltech.edu/CaltechETD:etd-09202008-104122.

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Moe, Maxwell, and Kaitlin M. Kratter. "Dynamical Formation of Close Binaries during the Pre-main-sequence Phase." IOP PUBLISHING LTD, 2018. http://hdl.handle.net/10150/627100.

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Solar-type binaries with short orbital periods (P-close equivalent to 1-10. days; a less than or similar to 0.1. au) cannot form directly via fragmentation of molecular clouds or protostellar disks, yet their component masses are highly correlated, suggesting interaction during the pre-main-sequence (pre-MS) phase. Moreover, the close binary fraction of pre-MS stars is consistent with that of their MS counterparts in the field (F-close = 2.1%). Thus, we can infer that some migration mechanism operates during the early pre-MS phase (tau less than or similar to 5 Myr) that reshapes the primordial separation distribution. We test the feasibility of this hypothesis by carrying out a population synthesis calculation which accounts for two formation channels: Kozai-Lidov (KL) oscillations and dynamical instability in triple systems. Our models incorporate (1) more realistic initial conditions compared to previous studies, (2) octupole-level effects in the secular evolution, (3) tidal energy dissipation via weak-friction equilibrium tides at small eccentricities and via non-radial dynamical oscillations at large eccentricities, and (4) the larger tidal radius of a pre-MS primary. Given a 15% triple-star fraction, we simulate a close binary fraction from KL oscillations alone of F-close approximate to 0.4% after tau = 5. Myr, which increases to F-close 0.8% by tau = 5. Gyr. Dynamical ejections and disruptions of unstable coplanar triples in the disk produce solitary binaries with slightly longer periods P approximate to 10-100. days. The remaining approximate to 60% of close binaries with outer tertiaries, particularly those in compact coplanar configurations with log P-out (days) approximate to 2-5 (a(out) < 50 au), can be explained only with substantial extra energy dissipation due to interactions with primordial gas.
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Johnstone, Colin Philip. "Magnetic fields and X-ray emission in pre-main sequence stars." Thesis, University of St Andrews, 2012. http://hdl.handle.net/10023/3596.

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In this thesis, I use numerical models of stellar coronae to investigate coronal magnetic fields, X-ray emission, and accretion geometries of classical T Tauri stars. This is based on recently published Zeeman-Doppler Imaging (ZDI) magnetograms. I also investigate the effects of time-variable eclipsing of stellar flares on their observed lightcurves. I investigate how our ability to model stellar magnetic processes is affected by missing magnetic flux in observed ZDI magnetograms and find that the loss of unresolved small-scale field regions has a significant effect on our ability to model magnetically confined X-ray emitting coronae. However, it has little effect on predicted large scale field structures. I survey the sample of classical T Tauri stars with existing ZDI magnetograms and find that the field complexity is correlated with field strength and stellar rotation rate, such that rapidly rotating stars have weak complex fields, and slowly rotating stars have strong simple fields. It is not clear whether this is a result of the finite resolution of the ZDI technique, magnetic star-disc interactions, or the evolution of pre-main sequence stars. Using observed X-ray emission measures and temperatures for each of these stars, I model the closed X-ray emitting coronae and find that they typically extend several stellar radii from the stellar surface. The coronal extent is primarily determined by the complexity of the magnetic field, with simple fields extending a large distance from the stellar surface, and more complex fields being truncated closer to the stellar surface. Using observed mass accretion rates, I predict circumstellar disc truncation radii for these stars and find that they are typically several stellar radii from the stellar surface, with the locations of accretion footpoints being a strong function of the field strengths and complexities. In several cases, the disc is truncated significantly outside the maximum radius at which the corona can extend. This result is significant as studies into magnetospheric accretion generally assume that the magnetic field has a closed geometry at the inner edge of the disc. The lightcurve of a typical stellar flare consists of a single impulsive rise phase followed by a slower exponential decay. However, a large number of the observed flares do not possess typical morphologies, and instead show multiple rise phases, or large dips in their lightcurves. Using the largest flares observed by the Chandra Orion Ultradeep Project, I show that these atypical lightcurves could have been caused by the time variable eclipsing of typical flares due to the rotation of the host stars. However, this interpretation is unable to account for the large number of atypical lightcurves in the COUP flare sample, and so other physical mechanisms must be involved. Significantly, I find that most flares that are eclipsed by their host stars still retain typical lightcurves showing no obvious signs of eclipsing.
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Shen, Nancy. "Coronal properties of pre-main sequence stars in the Orion Trapezium Cluster." Thesis, Massachusetts Institute of Technology, 2012. http://hdl.handle.net/1721.1/78488.

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Thesis (S.B.)--Massachusetts Institute of Technology, Dept. of Physics, 2012.
Cataloged from PDF version of thesis.
Includes bibliographical references (p. 47-48).
Most of the young stars in the Orion Trapezium Cluster are much more peculiar in X-rays than expected, considering their structure, environment, and age. Highly resolved X-ray spectra provide many more details in order to study these peculiarities, specifically with respect to abundances and accretion signatures. We analyzed the high resolution X-ray spectra of six young stars in Orion using data from the Chandra X-Ray Observatory. We fit plasma models to the spectra, calculated temperature-insensitive elemental abundances from individual spectral line fits, determined common elemental abundances to refit the data, and computed confidence maps for pairs of model parameters. These results may provide insights into the physical properties and processes that cause certain stars to exhibit high temperatures in X-rays. This may lead to a better understanding of stellar structure and evolution in young stars.
by Nancy Shen.
S.B.
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Esau, Claire Frances. "Radiative-transfer modelling of the circumstellar environments of pre-main-sequence stars." Thesis, University of Exeter, 2015. http://hdl.handle.net/10871/22080.

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Circumstellar discs of pre-main sequence stars undergo different processes depending on the nature of the circumstellar environment, which is governed by stellar mass. I have performed numerical simulations of the circumstellar regions of classical T~Tauri stars (CTTs) and Herbig~Ae (HAe) stars using the radiative transfer code TORUS in order to test the paradigm of magnetospheric accretion in CTTs, and to ascertain the nature of the material in the inner regions of HAe discs. The process of magnetospheric accretion (MA) involves disc material attaching to stellar magnetic field lines and impacting the photosphere, producing accretion shocks. When the magnetic field is inclined to the star, disc warps form which periodically occult the photosphere. With specific reference to the CTTs AA Tau I perform three-dimensional MA models to study this variability. By comparing synthetic photometry with observational data I show that the geometry of the system can be constrained. I go on to study Balmer line profiles in the context of MA and disc wind outflows. I present three-dimensional models of a system comprising the star, magnetosphere, disc, and disc wind, producing synthetic line profiles and images. Using these profiles I perform time-series fitting to observational data and demonstrate that the mass accretion rate, mass loss rate, and magnetosphere temperature can be constrained. I show that there is a degeneracy between wind temperature and wind acceleration which require alternative methods to constrain further. While an outflow model alternative to a sole disc wind may produce better fits to observations, MA models reproduce various observational features well. Finally I test the hypothesis that refractory grains produce the innermost emission in HAe discs. Focussing on the HAe stars MWC 275 and AB Aur, I perform radiative equilibrium modelling to create synthetic images of these objects from which interferometric visibility profiles are produced. I show that the temperatures at which these refractory grains are required to survive are too high to be physically plausible. I also find that silicate dust is shielded when sufficiently high mass fractions of refractory grains are used, enabling the silicates to survive interior to the classical sublimation radius. While refractory dust may provide a significant contribution to the emission observed in these inner regions, this alone is not sufficient.
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Jose, Jessy, Jinyoung S. Kim, Gregory J. Herczeg, Manash R. Samal, John H. Bieging, Michael R. Meyer, and William H. Sherry. "STAR FORMATION IN W3—AFGL 333: YOUNG STELLAR CONTENT, PROPERTIES, AND ROLES OF EXTERNAL FEEDBACK." IOP PUBLISHING LTD, 2016. http://hdl.handle.net/10150/621216.

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One of the key questions in the field of star formation is the role of stellar feedback on the subsequent star formation process. The W3 giant molecular cloud complex at the western border of the W4 super bubble is thought to be influenced by the massive stars in W4. This paper presents a study of the star formation activity within AFGL. 333, a similar to 104 M-circle dot cloud within W3, using deep JHK(s) photometry obtained from the NOAO Extremely Wide Field Infrared Imager combined with Spitzer IRAC and MIPS photometry. Based on the infrared excess, we identify 812 candidate young stellar objects (YSOs) in the complex, of which 99 are Class I and 713 are Class II sources. The stellar density analysis of YSOs reveals three major stellar aggregates within AFGL. 333, namely AFGL. 333 Main, AFGL. 333 NW1 and AFGL. 333 NW2. The disk fraction within AFGL. 333 is estimated to be similar to 50%-60%. We use the extinction map made from the H - K-s colors of the background stars and CO data to understand the cloud structure and to estimate the cloud mass. From the stellar and cloud mass associated with AFGL. 333, we infer that the region is currently forming stars with an efficiency of similar to 4.5% and at a rate of similar to 2-3M(circle dot) Myr(-1) pc(-2). In general, the star formation activity within AFGL. 333 is comparable to that of nearby low mass star-forming regions. We do not find any strong evidence to suggest that the stellar feedback from the massive stars of nearby W4 super bubble has affected the global star formation properties of the AFGL. 333 region.
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Books on the topic "Pre-main-sequence"

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United States. National Aeronautics and Space Administration., ed. Pre-main sequence stars in the chamaeleon cloud and pre-main sequence stars in the Rho Ophiuchi cloud core: Final technical report for NASA grant NAG 5-1678. [Washington, DC: National Aeronautics and Space Administration, 1993.

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United States. National Aeronautics and Space Administration., ed. Pre-main sequence stars in the chamaeleon cloud and pre-main sequence stars in the Rho Ophiuchi cloud core: Final technical report for NASA grant NAG 5-1678. [Washington, DC: National Aeronautics and Space Administration, 1993.

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United States. National Aeronautics and Space Administration., ed. Soft X-ray observations of pre-main sequence stars in the Chamaeleon dark cloud. University Park, PA: Pennsylvania State University, Office of Sponsored Programs, 1988.

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United States. National Aeronautics and Space Administration., ed. Soft X-ray observations of pre-main sequence stars in the Chamaeleon dark cloud. University Park, PA: Pennsylvania State University, Office of Sponsored Programs, 1988.

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Space Telescope Science Institute (U.S.) and United States. National Aeronautics and Space Administration., eds. Radio and infrared properties of young stars. Baltimore, MD: Space Telescope Science Institute, 1987.

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ESO, Workshop on Low Mass Star Formation and Pre-main Sequence Objects (1989 Garching bei München Germany). ESO Workshop on Low Mass Star Formation and Pre-Main Sequence Objects, Garching bei München, 11-13 July 1989. Garching bei München, Germany: European Southern Observatory, 1989.

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Caillault, Jean-Pierre. Annual report for an X-ray search for PMS stars in translucent molecular clouds. [Washington, DC: National Aeronautics and Space Administration, 1994.

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Caillault, Jean-Pierre. Annual report for an x-ray search for PMS stars in traslucent molecular clouds. [Washington, DC: National Aeronautics and Space Administration, 1994.

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Caillault, Jean-Pierre. Annual report for an x-ray search for PMS stars in traslucent molecular clouds. [Washington, DC: National Aeronautics and Space Administration, 1994.

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National Aeronautics and Space Administration (NASA) Staff. Infalling Envelopes and Pre-Main Sequence Disks. Independently Published, 2018.

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Book chapters on the topic "Pre-main-sequence"

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Reipurth, Bo. "Pre-Main Sequence Binaries." In Formation and Evolution of Low Mass Stars, 305–18. Dordrecht: Springer Netherlands, 1988. http://dx.doi.org/10.1007/978-94-009-3037-7_20.

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Stahler, Steven. "Star, Pre-Main-Sequence." In Encyclopedia of Astrobiology, 1573. Berlin, Heidelberg: Springer Berlin Heidelberg, 2011. http://dx.doi.org/10.1007/978-3-642-11274-4_1269.

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Kippenhahn, Rudolf, Alfred Weigert, and Achim Weiss. "Pre-Main-Sequence Contraction." In Astronomy and Astrophysics Library, 323–28. Berlin, Heidelberg: Springer Berlin Heidelberg, 2012. http://dx.doi.org/10.1007/978-3-642-30304-3_28.

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Kippenhahn, Rudolf, and Alfred Weigert. "Pre-Main-Sequence Contraction." In Astronomy and Astrophysics Library, 266–70. Berlin, Heidelberg: Springer Berlin Heidelberg, 1990. http://dx.doi.org/10.1007/978-3-642-61523-8_28.

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Stahler, Steven W. "Pre-main-sequence Star." In Encyclopedia of Astrobiology, 2008–9. Berlin, Heidelberg: Springer Berlin Heidelberg, 2015. http://dx.doi.org/10.1007/978-3-662-44185-5_1269.

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Bisnovatyi-Kogan, G. S. "Pre-main Sequence Evolution." In Stellar Physics, 25–59. Berlin, Heidelberg: Springer Berlin Heidelberg, 2002. http://dx.doi.org/10.1007/978-3-662-22639-1_2.

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Masson, Colin R. "Pre-Main-Sequence Outflows." In Circumstellar Matter 1994, 99–108. Dordrecht: Springer Netherlands, 1995. http://dx.doi.org/10.1007/978-94-011-0147-9_19.

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Bodenheimer, Peter H. "Pre-Main-Sequence Evolution." In Astronomy and Astrophysics Library, 279–310. Berlin, Heidelberg: Springer Berlin Heidelberg, 2011. http://dx.doi.org/10.1007/978-3-642-15063-0_8.

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Kogure, Tomokazu, and Kam-Ching Leung. "Pre-main Sequence Stars." In The Astrophysics of Emission-Line Stars, 423–501. New York, NY: Springer New York, 2007. http://dx.doi.org/10.1007/978-0-387-68995-1_7.

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Mathieu, Robert D. "Pre-main-sequence Binaries." In Dynamics of Young Star Clusters and Associations, 191–202. Berlin, Heidelberg: Springer Berlin Heidelberg, 2015. http://dx.doi.org/10.1007/978-3-662-47290-3_14.

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Conference papers on the topic "Pre-main-sequence"

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Gomez de Castro, Ana Ines, and Pablo Marcos-Arenal. "Pre main sequence interacting binaries." In XI Multifrequency Behaviour of High Energy Cosmic Sources Workshop. Trieste, Italy: Sissa Medialab, 2016. http://dx.doi.org/10.22323/1.246.0019.

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Mathieu, Robert D. "Accretion in pre-main-sequence binaries." In The seventh astrophysical conference: Star formation, near and far. AIP, 1997. http://dx.doi.org/10.1063/1.52750.

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Calvet, Nuria. "Disk accretion in pre-main sequence stars." In Accretion processes in astrophysical systems: Some like it hot! - eigth astrophysics conference. AIP, 1998. http://dx.doi.org/10.1063/1.55938.

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Eretnova, O., and A. Dudorov. "The mass function of pre-main sequence stars." In ASTRONOMY AT THE EPOCH OF MULTIMESSENGER STUDIES. Proceedings of the VAK-2021 conference, Aug 23–28, 2021. Crossref, 2022. http://dx.doi.org/10.51194/vak2021.2022.1.1.040.

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The information about 26 pre-man sequence (PMS) binary stars and 34 stars with protoplanetary disks with well determinedmasses from the observations is collected. We constructed the mass distribution of PMS stars and approximated it with apower law dN ∼M −γ dM . The slope is γ = 2.16±0.17 for stars in a mass range of 0.6M ⊙ < M < 6.3M ⊙ , which is close tothe Salpeter mass function. Over the entire mass range, the mass distribution of young stars may be approximated with alognormal law, which the most probable mass M prob = (0.78 ± 0.12)M ⊙ .
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de Castro, Ana I. Gómez, Michael E. Van Steenberg, George Sonneborn, H. Warren Moos, and William P. Blair. "Understanding the Accretion Engine in Pre-main Sequence Stars." In FUTURE DIRECTIONS IN ULTRAVIOLET SPECTROSCOPY: A Conference Inspired by the Accomplishments of the Far Ultraviolet Spectroscopic Explorer Mission. AIP, 2009. http://dx.doi.org/10.1063/1.3154062.

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Prada Moroni, P. G., E. Tognelli, and S. Degl'Innocenti. "Standard pre-main sequence models of low-mass stars." In SEVENTH EUROPEAN SUMMER SCHOOL ON EXPERIMENTAL NUCLEAR ASTROPHYSICS: Proceedings of the 7th European Summer School on Experimental Nuclear Astrophysics. AIP Publishing LLC, 2014. http://dx.doi.org/10.1063/1.4875290.

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Marsden, Stephen C., Ian A. Waite, Bradley D. Carter, and Eric Stempels. "Magnetic fields and differential rotation on the pre-main sequence." 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/10.1063/1.3099217.

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Bally, John. "Observations of outflows and disks in pre-main sequence systems." In Accretion processes in astrophysical systems: Some like it hot! - eigth astrophysics conference. AIP, 1998. http://dx.doi.org/10.1063/1.55941.

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Nakano, Takenori. "Prof. Hayashi’s work on the pre-main sequence evolution and brown dwarfs." In FIRST STARS IV – FROM HAYASHI TO THE FUTURE –. AIP, 2012. http://dx.doi.org/10.1063/1.4754322.

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Cusano, F., E. W. Guenther, M. Esposito, M. Mundt, E. Covino, J. M. Alcalà, and Eric Stempels. "Testing evolutionary tracks of Pre-Main Sequence stars: the case of HD113449." 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/10.1063/1.3099234.

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Reports on the topic "Pre-main-sequence"

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Atkinson, E. A. Regional mapping and qualitative petroleum resource assessment of the Magdalen Basin, Gulf of St. Lawrence, Quebec, Prince Edward Island, New Brunswick, Nova Scotia, and Newfoundland and Labrador. Natural Resources Canada/CMSS/Information Management, 2023. http://dx.doi.org/10.4095/331452.

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The Geological Survey of Canada conducted a broad regional study of the Magdalen Basin in the Gulf of St. Lawrence, as part of the Marine Conservation Targets initiative. MCT is a national initiative to protect more of Canada's offshore areas, and resource assessment and related regional mapping are part of the review process. This study assembled a large seismic and geologic database that allowed new regional mapping of several key horizons in this basin. Digital seismic data was donated by industry, and reprocessing undertaken both in-house and with contractors. Wells were correlated and tops from literature were used to indentify regional reflection packages. Regionally consistent two-way time interpretations add to confidence. Depth conversion used regional time-depth functions from literature, which were developed from refraction data, with a residual correction for the water column. Nine regional depth maps and eight isopach maps were produced, including Pre-Horton Basement, Horton Group Isopach, Base Windsor Group, Top Salt, Top Bradelle Formation, Bradelle / Cumberland Isopach, and Top Cable Head Formation. These maps illustrate that the Pre-Horton basement is about 15 km deep in the centre of the basin. Two main trends are visible in the Horton Grabens, which may relate to basin formation, and no significant reactivation of deeper Appalachian structure is observed. In the basin centre, the more robust Base Windsor Unconformity horizon reaches about 12 km deep, and a key reservoir and source sequence in the Bradelle Formation reaches 7 km. These maps are useful for considering regional stratigraphy. The new mapping also constrained basin models and became the input for our Qualitative Petroleum Potential map. Basin modelling reveals scenarios where oil may be preserved. The petroleum potential of the region is highest north of Îles de la Madeleine and southeast of Îles de la Madeleine and northwest of Cape Breton.
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Sherman, Amir, Rebecca Grumet, Ron Ophir, Nurit Katzir, and Yiqun Weng. Whole genome approach for genetic analysis in cucumber: Fruit size as a test case. United States Department of Agriculture, December 2013. http://dx.doi.org/10.32747/2013.7594399.bard.

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The Cucurbitaceae family includes a broad array of economically and nutritionally important crop species that are consumed as vegetables, staple starches and desserts. Fruit of these species, and types within species, exhibit extensive diversity as evidenced by variation in size, shape, color, flavor, and others. Fruit size and shape are critical quality determinants that delineate uses and market classes and are key traits under selection in breeding programs. However, the underlying genetic bases for variation in fruit size remain to be determined. A few species the Cucurbitaceae family were sequenced during the time of this project (cucumber was already sequenced when the project started watermelon and melon sequence became available during the project) but functional genomic tools are still missing. This research program had three major goals: 1. Develop whole genome cucumber and melon SNP arrays. 2. Develop and characterize cucumber populations segregating for fruit size. 3. Combine genomic tools, segregating populations, and phenotypic characterization to identify loci associated with fruit size. As suggested by the reviewers the work concentrated mostly in cucumber and not both in cucumber and melon. In order to develop a SNP (single nucleotide polymorphism) array for cucumber, available and newly generated sequence from two cucumber cultivars with extreme differences in shape and size, pickling GY14 and Chinese long 9930, were analyzed for variation (SNPs). A large set of high quality SNPs was discovered between the two parents of the RILs population (GY14 and 9930) and used to design a custom SNP array with 35000 SNPs using Agilent technology. The array was validated using 9930, Gy14 and F1 progeny of the two parents. Several mapping populations were developed for linkage mapping of quantitative trait loci (QTL) for fruit size These includes 145 F3 families and 150 recombinant inbred line (RILs F7 or F8 (Gy14 X 9930) and third population contained 450 F2 plants from a cross between Gy14 and a wild plant from India. The main population that was used in this study is the RILs population of Gy14 X 9930. Phenotypic and morphological analyses of 9930, Gy14, and their segregating F2 and RIL progeny indicated that several, likely independent, factors influence cucumber fruit size and shape, including factors that act both pre-anthesis and post-pollination. These include: amount, rate, duration, and plane of cell division pre- and post-anthesis and orientation of cell expansion. Analysis of F2 and RIL progeny indicated that factors influencing fruit length were largely determined pre-anthesis, while fruit diameter was more strongly influenced by environment and growth factors post-anthesis. These results suggest involvement of multiple genetically segregating factors expected to map independently onto the cucumber genome. Using the SNP array and the phenotypic data two major QTLs for fruit size of cucumber were mapped in very high accuracy (around 300 Kb) with large set of markers that should facilitate identification and cloning of major genes that contribute to fruit size in cucumber. In addition, a highly accurate haplotype map of all RILS was created to allow fine mapping of other traits segregating in this population. A detailed cucumber genetic map with 6000 markers was also established (currently the most detailed genetic map of cucumber). The integration of genetics physiology and genomic approaches in this project yielded new major infrastructure tools that can be used for understanding fruit size and many other traits of importance in cucumber. The SNP array and genetic population with an ultra-fine map can be used for future breeding efforts, high resolution mapping and cloning of traits of interest that segregate in this population. The genetic map that was developed can be used for other breeding efforts in other populations. The study of fruit development that was done during this project will be important in dissecting function of genes that that contribute to the fruit size QTLs. The SNP array can be used as tool for mapping different traits in cucumber. The development of the tools and knowledge will thus promote genetic improvement of cucumber and related cucurbits.
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Boily-Auclair, É., P. Mercier-Langevin, P. S. Ross, and D. Pitre. Alteration and ore assemblages of the LaRonde Zone 5 (LZ5) deposit and Ellison mineralized zones, Doyon-Bousquet-LaRonde mining camp, Abitibi, Quebec. Natural Resources Canada/CMSS/Information Management, 2022. http://dx.doi.org/10.4095/329637.

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The LaRonde Zone 5 (LZ5) mine is part of the Doyon-Bousquet-LaRonde mining camp and is located in the southern part of the Abitibi greenstone belt in northwestern Quebec. The LZ5 deposit consists of three stacked mineralized corridors: Zone 4, Zone 4.1, and Zone 5. Zones 4 and 4.1 are discontinuous satellite mineralized corridors, whereas Zone 5 represents the main mineralized body. The mineralized zones of the LZ5 deposit and adjacent Ellison property (Ellison A and B zones) are hosted in the strongly-deformed, 2699-2695 Ma transitional to calcalkaline, intermediate to felsic, volcanic and volcaniclastic rocks of the Bousquet Formation upper member, which is part of the Blake River Group (2704-2695 Ma). Zones 4, 4.1, and 5 at the LZ5 mine are hosted in intermediate volcanic and volcaniclastic rocks of the Westwood andesitic to rhyodacitic unit (unit 5.1a), which forms the base of the upper member of the Bousquet Formation. The Ellison Zone A is hosted higher up in the stratigraphic sequence within a newly described intermediate volcanic unit. The Ellison Zone B is hosted in felsic volcanic and volcaniclastic rocks of the Westwood feldsparphyric rhyolite dome (subunit 5.3a-(b)). Mineralization in all three zones of the LZ5 deposit consists of discordant networks of millimeter- to centimeter-thick pyrite ±chalcopyrite ±sphalerite ±pyrrhotite veins and veinlets (10-20 % of the volume of the rock) and, to a lesser extent, very finely disseminated pyrite and boudinaged veins (less than or equal to 5 vol. % each) in strongly altered host rocks. Gold commonly occurs as microscopic inclusions in granoblastic pyrite and at the triple junction between recrystallized grains. The veins, stockworks, and disseminations were intensely folded and transposed in the steeply south-dipping, east-west trending S2 foliation. The vein network is at least partly discordant to the stratigraphy. A distal alteration halo envelops the LZ5 mineralized corridors and consists of a sericite-carbonate-chlorite- feldspar ±biotite assemblage. A proximal sericite-carbonate-chlorite-pyrite-quartz- feldspar-biotite ±epidote alteration assemblage is present within the LZ5 mineralized zones. A local proximal alteration assemblage of sericite-quartz-pyrite is also locally developed within Zone 4 and Zone 5 of the LZ5 deposit. Mass gains in Fe2O3 (t) and K2O, and mass losses in CaO, MgO, Na2O, and locally SiO2, are characteristic of the LZ5 alteration zones. The Ellison zone A and B are similar to LZ5 in terms of style of mineralization, but thin (10-20 cm) veins or bands of semi-massive to massive, finely recrystallized disseminated pyrite (0.1-1 mm) are distinctive. Chalcopyrite and sphalerite are also slightly more abundant in the mineralized corridors of the Ellison property and are usually associated with elevated gold grades. The zones are also slightly richer than at LZ5 in terms of gold and silver content, but narrower and less continuous in general. The Ellison Zone A is characterized by gains in Fe2O3 (t) and K2O and losses in CaO, MgO, Na2O, and SiO2. Gains in Fe2O3 (t) and local gains in K2O, MgO, and MnO, and losses in CO2, Na2O, P2O5, and SiO2, characterize the felsic host rocks of the Zone B corridor. The style of mineralization at LZ5 (pyrite ±chalcopyrite veins and veinlets, ±disseminated pyrite with low base metal content), its setting (i.e. in rocks of intermediate composition at the base of the upper member of the Bousquet Formation), and the geometry of its ore zones (stacked lenses of sulfide veins and veinlets, without massive sulfide lenses) differ from the other major deposits of the Doyon-Bousquet-LaRonde mining camp. Despite these differences, this study indicates that the LZ5 and Ellison mineralized corridors are of synvolcanic hydrothermal origin and have most likely been formed by convective circulation of seawater below the seafloor. An influx of magmatic fluids from the Mooshla synvolcanic intrusive complex or its parent magma chamber could explain the Au enrichment at LZ5, as has been suggested for other deposits of the camp. Evidence for a pre-deformation synvolcanic mineralization at LZ5 includes ductile deformation and recrystallization of the sulfides, the stacked nature of its ore zones, subconcordant alteration halos that envelop the mineralized corridors, evidence that the mineralized system was already active when the LZ5 lenses were deposited and control on mineralization by primary volcanic features such as the permeability and porosity of the volcanic rocks.
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