MARC details
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07849nam a2200253Ia 4500 |
| 003 - CONTROL NUMBER IDENTIFIER |
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IN-BaIIA |
| 005 - DATE AND TIME OF LATEST TRANSACTION |
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20211108142407.0 |
| 008 - FIXED-LENGTH DATA ELEMENTS--GENERAL INFORMATION |
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211028s9999 xx 000 0 eng d |
| 040 ## - CATALOGING SOURCE |
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| Transcribing agency |
IIA Library |
| 080 ## - UNIVERSAL DECIMAL CLASSIFICATION NUMBER |
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| Universal Decimal Classification number |
043:52 |
| Item number |
ANU |
| 100 ## - MAIN ENTRY--PERSONAL NAME |
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| Personal name |
Anupama, G. C. |
| 9 (RLIN) |
17056 |
| Relator term |
Author |
| 245 #0 - TITLE STATEMENT |
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| Title |
Studies of classical and recurrent novae |
| Statement of responsibility, etc. |
G. C. Anupama |
| Medium |
[Ph.D Thesis] |
| 260 ## - PUBLICATION, DISTRIBUTION, ETC. |
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| Place of publication, distribution, etc. |
Bangalore |
| Name of publisher, distributor, etc. |
Indian Institute of Astrophysics |
| Date of publication, distribution, etc. |
1990 |
| 300 ## - PHYSICAL DESCRIPTION |
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| Extent |
x,173p. |
| 502 ## - DISSERTATION NOTE |
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| Degree type |
Doctor of Philosophy |
| Name of granting institution |
Indian Institute of Astrophysics, Bangalore |
| Year degree granted |
1990 |
| 520 ## - SUMMARY, ETC. |
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| Summary, etc. |
Novae belong to the cataclysmic variable class of objects, which includes dwarf<br/>novae, recurrent novae and classical novae. These systems undergo out bursts ranging<br/>from Δm ∼ 2-5 mag for dwarf novae, Δm ∼ 7-9 mag for recurrent novae, to<br/>Δm ∼ 9-> 14 mag for classical novae, with the inter-outburst periods being ∼<br/>weeks to years for dwarf novae, ∼ decades for recurrent novae and ∼ 104 years for<br/>classical novae. Cataclysmic variables are interacting binary star systems consisting<br/>of a Roche-lobe filling secondary, on or near main sequence, losing hydrogen-rich<br/>material through the inner Lagrangian point onto an accretion disc that surrounds<br/>the primary, which is a white dwarf in most cases. A classical nova outburst is<br/>caused by a thermonuclear runaway on the surface of the white dwarf primary,<br/>whereas in dwarf novae the outburst is due to accretion disc instabilities, caused by<br/>factors such as enhanced mass transfer.<br/>Novae serve as valuable astrophysical laboratories. The physics of accretion<br/>onto compact, evolved objects, thermonuclear runaways on semi-degenerate surfaces,<br/>line formation and transfer processes in moving atmospheres, and formation<br/>of dust in the ejected matter are some of the astrophysical problems that can be<br/>understood better by detailed studies of novae. Such problems are also encountered<br/>in other instances of ejection of matter such as supernovae and planetary nebulae.<br/>In this study we present optical spectroscopic data of the classical novae LW<br/>Serpentis 1978, Nova Scuti 1989 and of the recurrent nova RS Ophiuchi 1985,<br/>obtained during outbursts. Spectroscopic data of the recurrent novae T Coronae<br/>Borealis, RS Ophiuchi and T Pyxidis and the classical nova GK Persei 1901 obtained<br/>during quiescence are also presented. Also, CCD images of the shells of GK Persei,<br/>and T Pyxidis are presented. Most of the data used in the study were obtained with<br/>the 102 cm reflector at the Vainu Bappu Observatory (VBO). In addition, some<br/>data obtained at the European Southern Observatory (ESO), kindly made available<br/>by H.W. Duerbeck and also some archival data from the International Ultraviolet<br/>Explorer (IUE), kindly made available by A. Cassatella are made use of. All data<br/>were reduced at VBO using the locally developed RESPECT software package, as<br/>also the STARLINK package with locally developed application routines. These<br/>data have been used to study the physical conditions in the nova envelopes, and<br/>the components of the binary system.<br/>Chapter I contains a general introduction to the field, and the outline of the dissertation. Chapter II describes the procedure of data reduction.<br/>Results on three classical novae are presented in Chapter III. The outburst<br/>spectrum of the moderately slow nova LW Serpent is 1978 compares well with that<br/>of a typical nova. Based on moderate-resolution Ha-line profile, a kinematical<br/>model for the shell of LW Serpentis is proposed. The spectrum of Nova Scuti 1989,<br/>also a moderately slow nova, compares well with LW Serpent is at similar epochs.<br/>The fluxes in emission lines have been used in determining the physical conditions<br/>in the ejected material. Spectra observed during oscillations in the light curve<br/>show that the variations are mostly in the continuum, and hence imply a change in<br/>photospheric radius.<br/>CCD images of the shell of nova GK Persei obtained in the lines of [N II] and<br/>[0 III] are used to determine the expansion of the shell by comparison with data<br/>available in literature. The shell is asymmetric with bulk of the emission arising in<br/>the southwest quadrant in the [N II] image. There is a difference in the distribution<br/>of [0 III] and [N II] emission indicating chemical. inhomogeneities. The spectrum<br/>at quiescence is decomposed into those of KO-2 IV secondary and the hot accretion<br/>disc. The mass transfer rate is estimated to be ∼ 10-10 С yr-1 . The He/H<br/>abundance in the accretion disc is ≤ 0.24.<br/>Results on three recurrent novae are presented in Chapter IV. Although the<br/>outburst characteristics of recurrent novae are similar to those of classical novae, the<br/>cause of the outburst in these systems is rather uncertain. Outburst in most cases<br/>appears to be due to thermonuclear runaways on massive white dwarfs. However,<br/>in the case of recurrent novae RS Ophiuchi and T Coronae Borealis, alternative<br/>explanations also exist, according to which the primary in these systems is a main<br/>sequence star, with outbursts attributed to instabilities in the disc.<br/>The fluxes in the Ha, He I and He II emission lines during the out burst of RS<br/>Ophiuchi have been used to determine the electron density and helium abundance<br/>(He/H= 0.16) in the envelope. Based on an estimate of the number of hydrogen<br/>and helium ionizing photons, the temperature and radius of the ionizing source<br/>have been determined. The results obtained during the late stages of outburst<br/>are consistent with the primary being a white dwarf rather than a main sequence<br/>star. The coronal line :B.uxes have been used to determine the temperature in the<br/>shocked ejecta. Spectra obtained during quiescence indicate that the secondary is<br/>an Mʘ ± 1 giant. The presence of strong 0 18446 Å emission line implies presence<br/>of Ly(3 fluorescence and a high temperature for the ionizing source. The presence<br/>of 0 I 7774 Å. line in absorption indicates that the accretion disc is optically thick.<br/>The quiescence spectrum is decomposed into the spectra of cool secondary and<br/>hot accretion disc. The mass transfer rate is estimated to be '" 10-6 Mʘ yr-1 .<br/>Spectra of the recurrent nova T Coronae Borealis obtained during its quiescence<br/>phase (1985-1990) show that the secondary is an M4 ± 1 giant. The emission lines<br/>in the spectra are variable in strength. The Ha flux shows a long term variation<br/>with a period ∼ 2400 days. Superposed over this is an orbital phase dependent<br/>variation with maxima at '" 0.5 and rv 0.9 phase. The estimated mass transfer rate<br/>is '" 10-7 Mʘ yr-1 .<br/>Images of T Pyxidis in [N II] and [0 III] reveal a bright shell ejected in the<br/>1944 outburst and a faint extension due to the 1920 outburst. Comparison of<br/>VBO and ESO images shows that the bright shell expanded by 0.2 ± 0.1 arcsec<br/>in 3 years. The differences in [0 III] and [N II] images suggest the presence of<br/>chemical inhomogeneities as in the case of GK Persei. The spectrum at quiescence is<br/>dominated by the accretion disc, and has a high degree of excitation. The estimated<br/>mass transfer rate is ('V 10-8 Mʘ yr-1 , and HelH abundance is ≤0.24.<br/>The results of the study are summarized in Chapter V. A mention is also made of<br/>the problems that require further investigation using medium and large telescopes,<br/>and multiwavelength long~term monitoring.<br/>The tables, figures and equations are numbered sequentially in each section,<br/>with the chapter and section numbers indicated by suffixes. |
| 650 ## - SUBJECT ADDED ENTRY--TOPICAL TERM |
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| Topical term or geographic name entry element |
Astronomy and Astrophysics Thesaurus |
| 650 ## - SUBJECT ADDED ENTRY--TOPICAL TERM |
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| Topical term or geographic name entry element |
Novae |
| 9 (RLIN) |
1356 |
| 650 ## - SUBJECT ADDED ENTRY--TOPICAL TERM |
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| Topical term or geographic name entry element |
Ph.D. Thesis |
| 9 (RLIN) |
1344 |
| 650 ## - SUBJECT ADDED ENTRY--TOPICAL TERM |
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| Topical term or geographic name entry element |
Recurrent Novae |
| 9 (RLIN) |
1282 |
| 700 ## - ADDED ENTRY--PERSONAL NAME |
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| Personal name |
T. P. Prabhu |
| Relator term |
Supervisor |
| 9 (RLIN) |
48848 |
| 856 ## - ELECTRONIC LOCATION AND ACCESS |
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| Uniform Resource Identifier |
<a href="http://prints.iiap.res.in/handle/2248/137">http://prints.iiap.res.in/handle/2248/137</a> |
| Link text |
Click Here to Access eThesis |
| 942 ## - ADDED ENTRY ELEMENTS (KOHA) |
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| Koha item type |
Thesis & Dissertations |
| Source of classification or shelving scheme |
Universal Decimal Classification |
