Download or read book Investigations of Hydrogen Deficient Stars and Related Objects written by Gajendra Pandey and published by . This book was released on 1999 with total page 338 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Hydrogen Deficient Stars and Related Objects written by K. Hunger and published by Springer Science & Business Media. This book was released on 2012-12-06 with total page 472 pages. Available in PDF, EPUB and Kindle. Book excerpt: The first helium star was discovered in 1942, the first scientific meeting on the subject, however, took place in 1985. The meeting was hence long overdue for, in the meantime, a substantial amount of material had been accumulated by a rather small, but active scientific community. Hence, it appeared necessary to review the field in order to define the subject, assess its present status and discuss future developments. Hydrogen deficiency is a widespread phenomenon, occurring in a large variety of stellar and nonstellar objects. It can be readily detected in B stars as these exhibit both hydrogen and helium lines, if the elements are present in appreciable amounts. It becomes less manifest in cool stars, where the temperature is too low to excite helium and where one has to devise indirect methods for proving hydrogen deficiency. Clearly, it was not possible to discuss the whole complex of hydrogen deficiency, i.e. in both stars and diffuse matter, but rather to concentrate on the issue of helium stars.

Download or read book Hydrogen Deficient Stars and Related Ob written by and published by . This book was released on 1986 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Scientific and Technical Aerospace Reports written by and published by . This book was released on 1990 with total page 252 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book On the Origin and Evolution of Wolf Rayet Central Stars of Planetary Nebulae written by Kyle David DePew and published by . This book was released on 2011 with total page 227 pages. Available in PDF, EPUB and Kindle. Book excerpt: The origin of hydrogen-deficiency in the central stars of planetary nebulae (CSPNe) is currently a topic of heated debate. This class of objects is comprised of Wolf-Rayet ([WR]) stars, weak emission-line stars (WELS), and PG 1159 stars, each differentiated by a set of unique spectral characteristics. For some time, there have been questions surrounding the evolutionary status of these rare stars: what environmental conditions, such as chemical abundances, are necessary for their emergence, whether any of them represent different stages of development in the same class of stars, and what the characteristics of their progenitors may be. However, such investigations have been hampered by a lack of a sufficient number of these stars and their various sub-classes until recently. This thesis presents the significant discovery of 22 new [WR] stars and 10 new WELS, many uncovered specifically during this thesis in the course of the MASH survey and through serendipitous fibre placement during follow-up of MASH objects. All examples have been carefully classified as accurately as possible using the best current available data though for many this remains a preliminary assignment pending deeper spectra. This work expands the known sample of H-deficient stars by 30%, allowing a more detailed study of their properties than previously possible and moving us closer to a more complete census of local H-deficient CSPNe. In the course of our classifications, Abell 48 was found to be a particularly interesting object. Further analysis of nebular chemical abundances, modeled temperature, and ionization state as indicated by the chemical species present suggests that the CSPN of Abell 48 may be very similar to the CSPN of PB 8, which has recently been redesignated as the founding member of a new and rare [WN/WC] class (Todt et al. 2010). Its similarity to and differences with other oxygen-rich [WO] and carbon-rich [WC] stars as well as previously identified [WN] stars are examined. All these stars have also been studied in the context of a new subclass-dynamical age relationship that we have also discovered. This major finding is the first to show evidence of an evolutionary trend amongst the [WR] population and was made possible by use of the powerful new surface brightness-radius (SB-r) relation of Frew (2008) that can, at last, provide accurate distances to PN (and hence also their central stars). Key data acquired here as well as modeled effective temperatures and excitation classes of other [WR]s, WELS and PG 1159 central stars found in the literature were also utilized in generating this relationship. Finally, continuing with the SB-r relation, the scale heights of the most complete available sample of [WR], WELS and PG 1159 CS populations are determined and compared. These data show that both WELS and PG 1159 stars are found to possess significantly higher Galactic heights than the members of the [WR] class, implying that PG 1159s do not all descend from [WR]s, and that WELS are not evolutionarily related to [WR]s. This is another major finding of this work. It is possible, however, that the WELS class, and perhaps the PG 1159 class as well, are heterogeneous groups.

Download or read book Observational Tests of the Stellar Evolution Theory written by International Astronomical Union and published by Springer. This book was released on 1984-06-30 with total page 626 pages. Available in PDF, EPUB and Kindle. Book excerpt: Proceedings of IAU Symposium No. 105 held in Geneva, Switzerland, September 12-16, 1983

Download or read book Literature 1975 Part 2 written by Siegfried Böhme and published by Springer Science & Business Media. This book was released on 2013-03-14 with total page 757 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book International Ultraviolet Explorer IUE NASA Newsletter written by and published by . This book was released on 1978 with total page 198 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Nuclear Science Abstracts written by and published by . This book was released on 1976 with total page 934 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Literature 1988 Part 2 written by Astronomisches Rechen-Institut and published by Springer Science & Business Media. This book was released on 2013-06-29 with total page 1308 pages. Available in PDF, EPUB and Kindle. Book excerpt: From the reviews: "Astronomy and Astrophysics Abstracts has appeared in semi-annual volumes since 1969 and it has already become one of the fundamental publications in the fields of astronomy, astrophysics and neighbouring sciences. It is the most important English-language abstracting journal in the mentioned branches. ...The abstracts are classified under more than a hundred subject categories, thus permitting a quick survey of the whole extended material. The AAA is a valuable and important publication for all students and scientists working in the fields of astronomy and related sciences. As such it represents a necessary ingredient of any astronomical library all over the world." Space Science Reviews#1 "Dividing the whole field plus related subjects into 108 categories, each work is numbered and most are accompanied by brief abstracts. Fairly comprehensive cross-referencing links relevant papers to more than one category, and exhaustive author and subject indices are to be found at the back, making the catalogues easy to use. The series appears to be so complete in its coverage and always less than a year out of date that I shall certainly have to make a little more space on those shelves for future volumes." The Observatory Magazine#2

Download or read book International Aerospace Abstracts written by and published by . This book was released on 1991 with total page 832 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Transactions of the International Astronomical Union written by and published by CUP Archive. This book was released on with total page 824 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book The Province of the Law of Tort written by Percy Henry Winfield and published by CUP Archive. This book was released on 1931 with total page 1108 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Bulletin of the Astronomical Society of India written by Bharatiya Jyotir Vijyan Parishad and published by . This book was released on 1995 with total page 650 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Literature 1980 Part 1 written by Siegfried Böhme and published by Springer Science & Business Media. This book was released on 2013-11-11 with total page 949 pages. Available in PDF, EPUB and Kindle. Book excerpt: Astronomy and Astrophysics Abstracts, which has appeared in semi-annual volumes since 1969, is de voted to the recording, summarizing and indexing of astronomical publications throughout the world. It is prepared under the auspices of the International Astronomical Union (according to a resolution adopted at the 14th General Assembly in 1970). Astronomy and Astrophysics Abstracts aims to present a comprehensive documentation of literature in all fields of astronomy and astrophysics. Every effort will be made to ensure that the average time interval between the date of receipt of the original literature and publication of the abstracts will not exceed eight months: This time interval is near to that achieved by monthly abstracting journals, com pared to which our system of accumulating abstracts for about six months offers the advantage of greater convenience for the user. I, 1980; some older Volume 27 contains literature published in 1980 and received before August literature which was received late and which is not recorded in earlier volumes is also included. We acknowledge with thanks contributions to this volume by Dr. J. Bouska, Prague, who surveyed journals and publications in Czech and supplied us with abstracts in English.

Download or read book Bulletin written by Astronomical Society of India and published by . This book was released on 1995 with total page 656 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Astronomy and Astrophysics Abstracts written by S. Böhme and published by Springer Science & Business Media. This book was released on 2013-12-14 with total page 1180 pages. Available in PDF, EPUB and Kindle. Book excerpt: From the reviews: Astronomy and Astrophysics Abstracts has appeared in semi-annual volumes since 1969 and it has already become one of the fundamental publications in the fields of astronomy, astrophysics and neighbouring sciences. It is the most important English-language abstracting journal in the mentioned branches. ... The abstracts are classified under more than hundred subject categories, thus permitting a quick survey of the whole extended material. The AAA is a valuable and important publication for all students and scientists working in the fields of astronomy and related sciences. As such it represents a necessary ingredient of any astronomical library all over the world." Space Science Reviews #1 "Dividing the whole field plus related subjects into 108 categories, each work is numbered and most are accompanied by brief abstracts. Fairly comprehensive cross-referencing links relevant papers to more than one category, and exhaustive author and subject indices are to be found at the back, making the catalogues easy to use. The series appears to be so complete in its coverage and always less than a year out of date that I shall certainly have to make a little more space on those shelves for future volumes." The Observatory Magazine #1