Download or read book Multiwavelength Observations of Young Stars and Their Circumstellar Disks written by David A. Principe and published by . This book was released on with total page 294 pages. Available in PDF, EPUB and Kindle. Book excerpt: "Observational studies of star and planet formation represent a fundamental means to understand the origins of exoplanetary systems and our own solar system. In this dissertation I present a multiwavelength approach to study a wide range of stages of the evolution of protostars and pre-main sequence (pre-MS) stars. I have investigated, via an infrared and multi-epoch X-ray study of the L1630 dark cloud, whether and how X-ray variability in young stellar objects is related to protostellar evolutionary state. Among a subsample of 52 X-ray-emitting young stars in L1630, I find that the earliest stages of young stellar evolution show the highest levels of X-ray variability, indicative of high levels of magnetic activity during star formation. I also find evidence of active magnetospheric accretion in three L1630 stars with circumstellar disks. I also present multiwavelength analyses of several phenomenologically interesting young stars at different stages of pre-MS stellar evolution. I investigate, via contemporaneous X-ray and optical/IR observations, the nearby, pre-main sequence star/disk systems T Chamaeleontis (T Cha) and TWA 30A and 30B. I analyze X-ray and optical emission signatures of accretion and magnetic activity in T Cha, and infer the X-ray absorbing properties of its circumstellar disk. Like T Cha, each component of the wide binary TWA 30A and 30B is viewed through a highly inclined circumstellar disk. Both TWA 30A and 30B display large near-IR variability, suggestive of (respectively) variable obscuration of the stellar photosphere and a possible disk-rim warp. In the case of T Cha and TWA 30A, I find a correlation of optical/near-IR and X-ray extinction consistent with that of photospheric obscuration from an intervening disk clump."--Abstract.

Download or read book Physical Processes in Circumstellar Disks around Young Stars written by Paulo J. V. Garcia and published by University of Chicago Press. This book was released on 2011-04-15 with total page 437 pages. Available in PDF, EPUB and Kindle. Book excerpt: Circumstellar disks are vast expanses of dust that form around new stars in the earliest stages of their birth. Predicted by astronomers as early as the eighteenth century, they weren’t observed until the late twentieth century, when interstellar imaging technology enabled us to see nascent stars hundreds of light years away. Since then, circumstellar disks have become an area of intense study among astrophysicists, largely because they are thought to be the forerunners of planetary systems like our own—the possible birthplaces of planets. This volume brings together a team of leading experts to distill the most up-to-date knowledge of circumstellar disks into a clear introductory volume. Understanding circumstellar disks requires a broad range of scientific knowledge, including chemical processes, the properties of dust and gases, hydrodynamics and magnetohydrodynamics, radiation transfer, and stellar evolution—all of which are covered in this comprehensive work, which will be indispensable for graduate students, seasoned researchers, or even advanced undergrads setting out on the study of planetary evolution.

Download or read book ISO Surveys of a Dusty Universe written by D. Lemke and published by Springer. This book was released on 2008-01-11 with total page 429 pages. Available in PDF, EPUB and Kindle. Book excerpt: Many of the ISO observers who assembled for this workshop at Ringberg c- tle met for the third time in the Bavarian Alps. At two previous meetings in 1989 and 1990 surveys were only a minor topic. At that time we were excited by the discoveries of the IRAS survey mission and wanted to follow it up with pointed observations using an observatory telescope equipped with versatile instruments. With the rapid development of detector arrays and stimulated by ISO’s Observing Time Allocation Committee, however, surveys eventually became an issue for the upcoming mission. In a review paper on “Infrared S- veys - the Golden Age of Exploration” given at an IAU meeting in 1996, Chas Beichman already mentioned that there are ISO surveys. They were at the bottom of his hit list, while the winners were future space missions (Planck, SIRTF, etc. ) and ground-based surveys in preparation (Sloan, 2MASS, DE- NIS, etc. ). He organized his table according to the relative explorable volume, calculated from the solid angle covered on the sky and the maximum distance derived from the detection sensitivity. Clearly, with this ?gure of merit, ISO, as a pointed observatory, is rated low. Applying the classical de?nition of a survey, i. e. to search in as large a volume as possible for new or rare objects and/or study large numbers of objects of various classes in order to obtain statistical properties, ISO was indeed limited.

Download or read book Young Low mass Stars written by Kristina Marie Punzi and published by . This book was released on 2018 with total page 225 pages. Available in PDF, EPUB and Kindle. Book excerpt: "Nearby, young stars are the ideal targets for investigations of stellar and protoplanetary disk evolution, so as to understand the processes involved in planet formation and evolution, as well as the origins of our Solar System. High energy radiation (X-ray and FUV) from the central star significantly alters the structure, chemistry, and ionization of planet-forming circumstellar disks. In this dissertation, I present observations of young stars and star-disk systems to better understand the connection between stellar high energy radiation and the evolution of circumstellar environments, and to further develop methods to exploit the signatures of youth, as well as methods to identify nearby, young stars. Our unbiased radio spectroscopic survey with the Institute de Radioastronomie Millimétrique (IRAM) 30 meter telescope reveals the chemical richness of the circumstellar disk orbiting the ~2-5 Myr-old, actively accreting solar analog LkCa 15. We find that high-energy (FUV and/or X-ray) radiation from the central star, a known X-ray-luminous source, may be enhancing the abundances of CN and C 2 H within the disk. To ascertain the evolutionary status of the erratically variable star RZ Piscium (RZ Psc), we obtained observations of RZ Psc with the European Space Agency’s X-ray Multi-Mirror Mission (XMM-Newton), as well as high-resolution optical spectroscopy with the Hamilton Echelle on the Lick Shane 3 m telescope and with HIRES on the Keck I 10 m telescope. These data provide strong support for the young-star status of RZ Psc, as well as evidence for the presence of a significant mass of circumstellar gas, suggesting the recent destruction of one or more young exoplanets within 1 au of the star. It is evident from our Chandra X-ray Observatory survey of very cool members of the ~8 Myr-old TW Hydra Association (TWA) that X-ray luminosity relative to bolometric luminosity (L X /L bol ) decreases with decreasing effective temperature (T ef f ). The fraction of TWA stars that display evidence for residual primordial disk material sharply increases in this same (mid-M) spectral type regime, suggesting that disk survival times may be longer for ultra-low mass stars and brown dwarfs than for higher-mass M stars. Finally, we use parallax data available in Gaia Data Release 1 (DR1) to estimate the distances and ages of a sample of candidate young stars identified by the Galex Nearby Young Star Survey (GALNYSS). The youth of these stars is confirmed by their relative positions, compared to main sequence stars and giant stars, in Gaia-based color-magnitude and color-color diagrams produced for all Galex and WISE-detected stars with parallax measurements available in Gaia DR1."--Abstract.

Download or read book Circumstellar Disks Outflows and Star Formation written by and published by . This book was released on 1995 with total page 416 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Catalog of Infrared Observations written by Daniel Y. Gezari and published by . This book was released on 1993 with total page 884 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book JET Simulations Experiments and Theory written by Christophe Sauty and published by Springer. This book was released on 2019-08-02 with total page 154 pages. Available in PDF, EPUB and Kindle. Book excerpt: In 2008, the European FP6 JETSET project ended. JETSET, for Jet, Simulations, Experiments, and Theory, was a joint research network of European expert teams on protostellar jets. The present proceedings are a collection of contributions presenting new results obtained by those groups since the end of the JETSET program. This is also the occasion to celebrate Kanaris Tsinganos’ important contributions to this network and for his enlightening insight in the subject that inspired us all. Some of the former JETSET students are now in the academic world and the subject has never been so alive. So we present here a collection of results of what has been done in the field of protostellar jets in the past ten years from the theoretical, numerical, observational and experimental point of view. We also present new challenges in the field of protostellar jets and what we should expect from the development of new instruments and new numerical codes in the near future. We also gather results on the impact of the study of protostellar jets on other jet studies in particular on relativistic jets. As a matter of fact, it is time for a new network.

Download or read book Protoplanetary Dust written by Dániel Apai and published by Cambridge University Press. This book was released on 2010-01-21 with total page 397 pages. Available in PDF, EPUB and Kindle. Book excerpt: The first comprehensive overview of planet formation for students and researchers in astronomy, cosmochemistry, laboratory astrophysics and planetary sciences.

Download or read book Star Formation in the Auriga California Giant Molecular Cloud and Its Circumstellar Disk Population written by Hannah Broekhoven-Fiene and published by . This book was released on 2016 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: This thesis presents a multiwavelength analysis, from the infrared to the microwave, of the young, forming stars in the Auriga-California Molecular Cloud and a first look at the disks they host and their potential for forming planetary systems. At the beginning of this thesis, Auriga-Cal had only recently been identified as one contiguous cloud with its distance placing it within the Gould Belt of nearby star-forming regions (Lada et al. 2009). This thesis presents the largest body of work to date on Auriga-Cal's star formation and disk population. Auriga-Cal is one of two nearby giant molecular clouds (GMCs) in the Gould Belt, the other being the Orion A molecular cloud. These two GMCs have similar mass (~10^5 Msolar), spatial scale (~80 pc), distance (~450 pc), and filamentary morphology, yet the two clouds present very different star formation qualities and quantities. Namely, Auriga-Cal is forming far fewer stars and does not exhibit the high-mass star formation seen in Orion A. In this thesis, I present a census of the star forming objects in the infrared with the Spitzer Space Telescope showing that Auriga-Cal contains at least 166 young stellar objects (YSOs), 15-20x fewer stars than Orion A, the majority of which are located in the cluster around LkHalpha 101, NGC 1529, and the filament extending from it. I find the submillimetre census with the James Clerk Maxwell Telescope, sensitive to the youngest objects, arrives at a similar result showing the disparity between the two clouds observed in the infrared continues to the submillimetre. Therefore the relative star formation rate between the two clouds has remained constant in recent times. The final chapter introduces the first study targeted at the disk population to measure the formation potential of planetary systems around the young stars in Auriga-Cal. The dust thermal emission at cm wavelengths is observed to measure the relative amounts of cm-sized grains, indicative of the grain growth processes that take place in disks and are necessary for planet formation. For a subsample of our targets, we are able to measure the spectral slope in the cm to confirm the thermal nature of the observed emission that we detect and characterize the signature of grain growth. The sensitivity of our observations probes masses greater than the minimum mass solar nebula (MMSN), the disk mass required to form the Solar System. We detect 19 disks, representing almost a third of our sample, comparable to the numbers of disks in other nearby star-forming regions with disks masses exceeding the MMSN, suggesting that the disk population in Auriga-Cal possesses similar planet formation potential as populations in other clouds. Confirmation of this result requires future observations with mm interferometry, the wavelength regime where the majority of statistics of disks has been measured.

Download or read book High Angular Resolution Studies of the Structure and Evolution of Protoplanetary Disks written by Joshua Eisner and published by Universal-Publishers. This book was released on 2005 with total page 240 pages. Available in PDF, EPUB and Kindle. Book excerpt: Young stars are surrounded by massive, rotating disks of dust and gas, which supply a reservoir of material that may be incorporated into planets or accreted onto the central star. In this dissertation, I use high angular resolution observations at a range of wavelengths to understand the structure, ubiquity, and evolutionary timescales of protoplanetary disks. First, I describe a study of Class I protostars, objects believed to be at an evolutionary stage between collapsing spherical clouds and fully-assembled young stars surrounded by protoplanetary disks. I use a Monte Carlo radiative transfer code to model new 0.9 micron scattered light images, 1.3 mm continuum images, and broadband spectral energy distributions. This modeling shows that Class I sources are probably surrounded by massive protoplanetary disks embedded in massive infalling envelopes. For the best-fitting models of the circumstellar dust distributions, I determine several important properties, including envelope and disk masses, mass infall rates, and system inclinations, and I use these results to constrain the evolutionary stage of these objects. Second, I discuss observations of the innermost regions of more evolved disks around T Tauri and Herbig Ae/Be stars, obtained with the Palomar Testbed and Keck Interferometers. I constrain the spatial and temperature structure of the circumstellar material at sub-AU radii, and demonstrate that lower-mass stars are surrounded by inclined disks with puffed-up inner edges 0.1-1 AU from the star. In contrast, the truncated inner disks around more massive stars may not puff-up, indicating that disk structure depends on stellar properties. I discuss the implications of these results for disk accretion, terrestrial planet formation and giant planet migration. Finally, I put these detailed studies of disk structure into a broader context by constraining the mass distribution and evolutionary timescales of circumstellar disks. Using the Owens Valley Millimeter Array, I mapped the millimeter continuum emission toward >300 low-mass stars in the NGC 2024 and Orion Nebula clusters. These observations demonstrate that the average disk mass in each cluster is comparable to the "minimum-mass protosolar nebula," and that there may be disk evolution on one million year timescales.

Download or read book The Role of Disks in the Angular Momentum Evolution of Young Low mass Stars written by Thompson S. Le Blanc and published by . This book was released on 2012 with total page 192 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Issues in Astronomy and Astrophysics 2011 Edition written by and published by ScholarlyEditions. This book was released on 2012-01-09 with total page 2981 pages. Available in PDF, EPUB and Kindle. Book excerpt: Issues in Astronomy and Astrophysics / 2011 Edition is a ScholarlyEditions™ eBook that delivers timely, authoritative, and comprehensive information about Astronomy and Astrophysics. The editors have built Issues in Astronomy and Astrophysics: 2011 Edition on the vast information databases of ScholarlyNews.™ You can expect the information about Astronomy and Astrophysics in this eBook to be deeper than what you can access anywhere else, as well as consistently reliable, authoritative, informed, and relevant. The content of Issues in Astronomy and Astrophysics: 2011 Edition has been produced by the world’s leading scientists, engineers, analysts, research institutions, and companies. All of the content is from peer-reviewed sources, and all of it is written, assembled, and edited by the editors at ScholarlyEditions™ and available exclusively from us. You now have a source you can cite with authority, confidence, and credibility. More information is available at http://www.ScholarlyEditions.com/.

Download or read book Circumstellar disks deduced from sub arcsecond polarization observations of two young stars written by Vilppu Piirola and published by . This book was released on 1992 with total page 3 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Young Stars Near Earth written by Ray Jayawardhana and published by . This book was released on 2001 with total page 432 pages. Available in PDF, EPUB and Kindle. Book excerpt: Annotation From the March 2001 workshop come 67 papers dedicated to the study of the young stellar groups and young isolated stars identified within 100 parsecs of the sun. It is the feeling of Jayawardhana (University of California at Berkeley) and Greene (NASA Ames Research Center) that these bodies constitute laboratories for testing ideas about star and planet formation as they may give the best chance of directly imaging a young extrasolar planet. The papers are organized into sections on stellar groups, origins, stars, disks, companions, and missions and facilities. Annotation c. Book News, Inc., Portland, OR (booknews.com)

Download or read book The Very Large Telescope Interferometer Challenges for the Future written by Paulo J.V. Garcia and published by Springer Science & Business Media. This book was released on 2013-11-11 with total page 313 pages. Available in PDF, EPUB and Kindle. Book excerpt: A JENAM 2002 Workshop, Porto, Portugal, 3-5 September 2002

Download or read book Panel Reports New Worlds New Horizons in Astronomy and Astrophysics written by National Research Council and published by National Academies Press. This book was released on 2011-05-18 with total page 578 pages. Available in PDF, EPUB and Kindle. Book excerpt: Every 10 years the National Research Council releases a survey of astronomy and astrophysics outlining priorities for the coming decade. The most recent survey, titled New Worlds, New Horizons in Astronomy and Astrophysics, provides overall priorities and recommendations for the field as a whole based on a broad and comprehensive examination of scientific opportunities, infrastructure, and organization in a national and international context. Panel Reportsâ€"New Worlds, New Horizons in Astronomy and Astrophysics is a collection of reports, each of which addresses a key sub-area of the field, prepared by specialists in that subarea, and each of which played an important role in setting overall priorities for the field. The collection, published in a single volume, includes the reports of the following panels: Cosmology and Fundamental Physics Galaxies Across Cosmic Time The Galactic Neighborhood Stars and Stellar Evolution Planetary Systems and Star Formation Electromagnetic Observations from Space Optical and Infrared Astronomy from the Ground Particle Astrophysics and Gravitation Radio, Millimeter, and Submillimeter Astronomy from the Ground The Committee for a Decadal Survey of Astronomy and Astrophysics synthesized these reports in the preparation of its prioritized recommendations for the field as a whole. These reports provide additional depth and detail in each of their respective areas. Taken together, they form an essential companion volume to New Worlds, New Horizons: A Decadal Survey of Astronomy and Astrophysics. The book of panel reports will be useful to managers of programs of research in the field of astronomy and astrophysics, the Congressional committees with jurisdiction over the agencies supporting this research, the scientific community, and the public.

Download or read book Structure Formation in Astrophysics written by Gilles Chabrier and published by Cambridge University Press. This book was released on 2009-01-15 with total page 455 pages. Available in PDF, EPUB and Kindle. Book excerpt: A unique reference for graduate students and researchers addressing common problems and methods in studying galaxy, star and planet formation.