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Spectroscopic studies of RV TAU and related objects (Record no. 18699)

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003 - CONTROL NUMBER IDENTIFIER
control field IN-BaIIA
005 - DATE AND TIME OF LATEST TRANSACTION
control field 20211112142423.0
008 - FIXED-LENGTH DATA ELEMENTS--GENERAL INFORMATION
fixed length control field 211028s9999 xx 000 0 eng d
040 ## - CATALOGING SOURCE
Transcribing agency IIA Library
080 ## - UNIVERSAL DECIMAL CLASSIFICATION NUMBER
Universal Decimal Classification number 043:524.358
Item number SUM
100 ## - MAIN ENTRY--PERSONAL NAME
Personal name Sumangala Rao, S
9 (RLIN) 35782
Relator term Author
245 #0 - TITLE STATEMENT
Title Spectroscopic studies of RV TAU and related objects
Remainder of title a thesis submitted for the award of the degree of doctor of philosophy in physics, the Mangalore university
Statement of responsibility, etc. S. Sumangala Rao
Medium [Ph.D Thesis]
260 ## - PUBLICATION, DISTRIBUTION, ETC.
Place of publication, distribution, etc. Bangalore
Name of publisher, distributor, etc. Indian Institute of Astrophysics
Date of publication, distribution, etc. 2013
300 ## - PHYSICAL DESCRIPTION
Extent xvi, 245p.
500 ## - GENERAL NOTE
General note Thesis Supervisor Giridhar, Sunetra
502 ## - DISSERTATION NOTE
Degree type Doctor of Philosophy
Name of granting institution Mangalore University, Karnataka
Year degree granted 2012
520 ## - SUMMARY, ETC.
Summary, etc. Post-AGB stars represent a crucial phase in the evolution of low and intermediate mass stars (0.8-8M ) where rapid change in the surface composition of the star and its circumstellar envelope takes place. A very small fraction of the known post-AGB objects show hard core post-AGB abundance pattern i.e. the C/O larger than 1 and enhancement of s-process elements. Many of them show chemical peculiarities not caused by the nucleosynthesis. From the spectroscopic studies of a number of RV Tauri and post-AGB objects it is found that many of these show abundance anomalies due to selective depletion of condensable elements. These abundance anomalies are found to be correlated with their condensation temperatures and this process is known as the Dust-Gas Winnowing. A large fraction of these stars are found to be binaries and this depletion is thought to be occurring in a dusty circumbinary disk. A few RV Tau stars show abundance anomalies correlated with the ionization potential of the neutral atoms. This process is known as the First Ionisation Potential (FIP) effect. In our spectroscopic study of RV Tauri and post-AGB candidates, we try to find the signature of various processes that may affect the stellar composition during the course of its evolution like the initial composition of the Interstellar Medium (ISM), effect of First Dredge Up (FDU), effect of thermal pulses and Third Dredge Up (TDU), effects of dustgas winnowing and FIP effect and also try to refine the boundary conditions (temperature, metallicity, binarity) for these processes to operate. We have undertaken the study of unexplored (as well as the ones lacking comprehensive abundance analysis) RV Tau stars and post-AGB objects to understand the chemical changes taking place during the late stages of stellar evolution of low and intermediate mass stars. We have tried to enlarge the RV Tau and post-AGB sample and also present<br/>a critical compilation of all these objects studied till now to understand the importance of the stellar parameters and of the conditions such as binarity on post-AGB evolution. We have divided our compilations into several sub-groups such as those showing s-process enrichment, dust-gas winnowing, FIP effect and those having normal compositions. This compilation has enabled us to explore the evolutionary link between RV Tau and post-AGB stars; the latter appear to be in a more advanced stage of evolution. This finding has been further supported by their photometric behaviour. We also find that RV Tau stars generally do not exhibit s-process enhancement but they outnumber post-AGBs in dust-gas winnowing and exhibit different families of depletion curves. Starting with the depletion curve of R Sct with an almost precipice like fall at high condensation temper atures, the length and height of low and intermediate condensation temperature plateau show considerable variations. There are another set of RV Tau stars with depletion curve asymptoting at higher condensation temperatures at different [X/H] levels. An attempt has been made to explain the observed depletion curves taking into consideration conditions such as the temperature and composition of the circumstellar environment as well as the efficiency of mixing between the accreted clean gas with the atmosphere/envelope<br/>of the star. In our exploration of post-AGB candidates we also discovered two mildly hydrogendeficient<br/>stars: SAO 40039 and HD 187885 (with strong He I lines). The detections of these stars are very important as they provide an important evolutionary link between hydrogen-normal and hydrogen-deficient stars.<br/>
650 ## - SUBJECT ADDED ENTRY--TOPICAL TERM
Topical term or geographic name entry element RV Tauri stars
9 (RLIN) 35783
650 ## - SUBJECT ADDED ENTRY--TOPICAL TERM
Topical term or geographic name entry element Spectroscopy
9 (RLIN) 1535
700 ## - ADDED ENTRY--PERSONAL NAME
Personal name Sunetra Giridhar
Relator term Supervisor
9 (RLIN) 48932
856 ## - ELECTRONIC LOCATION AND ACCESS
Uniform Resource Identifier <a href="http://prints.iiap.res.in/handle/2248/6058">http://prints.iiap.res.in/handle/2248/6058</a>
Link text Click Here to Access eThesis
942 ## - ADDED ENTRY ELEMENTS (KOHA)
Koha item type Thesis & Dissertations
Source of classification or shelving scheme Universal Decimal Classification
Holdings
Withdrawn status Lost status Source of classification or shelving scheme Damaged status Not for loan Home library Current library Shelving location Date acquired Full call number Barcode Date last seen Price effective from Koha item type
    Universal Decimal Classification     IIA Library-Bangalore IIA Library-Bangalore General Stacks 09/05/2013 043:524.358/ SUM 19621 05/11/2021 09/05/2013 Thesis & Dissertations

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