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  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
1

Molecular gas around the binary star R Aquarii

Olander, Terese January 2017 (has links)
At the end of the lives of low- to intermediate mass stars they can be found on the asymptotic giant branch (AGB). The AGB phase ends when the entire circumstellar envelope (CSE) is blown away in a superwindphase, in the end creating a planetary nebula. It is unknown what shapes the CSE and the planetary nebula. Binarity is a favored theory. In order to test this theory the CSE around the star R Aquarii has been studied using the emission from different molecules observed with ALMA. R Aquarii is a nearby binary system and therefore easy to study. The system consists of a Mira variable on the AGB and a hot white dwarf. It was found that only in the emission from the 12CO J=3–2 transition were the CSE resolved enough for any structure to be seen. The morphology was irregular and no clear symmetry was seen. A spot in the same molecular line was detected at high velocities (v = -23 km/s) relative to the star at a projected distance of 7 arcsec south of R Aqr. Line profiles for 12CO and 13CO follow the same shape but differs in magnitude, indicating that they can be found in the same structure. A mass loss rate of 6.5·10-7 solar masses per year was calculated for R Aquarii using line intensities obtained from the line profile of 12CO. The morphology and kinematics of the CO CSE of R Aquarii are discussed within the limitations of the current data set. More observations with better resolution are needed to better understand the morphology of the CSE of R Aquarii and draw firm conclusions.

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