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The properties of astrophysical masers are governed by the physical conditions of circumstellar envelopes of evolved stars, implying a connection between maser and mass-loss phenomena. Although similar studies to another type of mass-losing star, Asymptotic Giant Branch (AGB) stars, have been conducted, a quantitative understanding for the case of Red Supergiants (RSGs) is still largely lacking. Recently, more and more galactic massive clusters are discovered and studied, which provide a coeval environment to investigate the evolution of cool massive evolved stars with similar distance and metallicity. Among them, Westerlund 1 (Wd1) is one of the most massive open clusters, classified as Super Star Clusters (SSCs), within the Milky Way harboring 4 RSGs. We have 2 goals in this project. We aim to investigate the relationship between SiO maser detection and mass-loss behavior of RSGs in massive clusters, in order to explore the possibility of developing SiO maser as an evolutionary indicator of RSGs. We also aim to determine the kinematic properties of Wd1 with the aid of SiO maser. We report on observation of 43 GHz SiO (v = 1, J = 1–0) maser towards Wd1 conducted with Australia Telescope Compact Array (ATCA). We also make use of archival 22 GHz H2O maser (616–523) in help of studying kinematic of Wd1. We derive the maser detection information and stellar velocities from maser data. We also compile an extra sample of 36 RSGs, which surveyed in SiO maser before, within massive clusters, e.g. Red Supergiant Cluster 1 (RSGC1), Red Supergiant Cluster 2 (RSGC2), Perseus OB association 1 (Per OB 1) and Mercer et al.’s #8 (Mc8), and organize their photometric data from 2MASS, GLIMPSE, MSX, AKARI and WISE to derive their spectral energy distributions (SEDs). Luminosity, effective temperature and mass-loss rate are derived from fitting the SEDs with DUSTY model in order to search for correlations between mass-loss rate, SiO maser properties and evolution of RSGs. We detected SiO maser emission towards 2 RSGs (W 237 and W 26) in Wd1. These 2 RSGs also emit H2O maser as revealed from archival H2O maser observation data. We noticed that SiO masers tend to be detected towards RSGs with higher luminosity and mass-loss rate. We also determined the kinematic distance of Wd1 to be 3.3 kpc. From that result, we conclude that SiO maser is an effective evolution indicator for RSGs, which traces RSGs with high massloss rate. We also show that the age of RSGs in Wd1 is 10 ± 2 Myr which support the multi-generation star formation scenario in Wd1. / published_or_final_version / Physics / Master / Master of Philosophy

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The underlying theme of this thesis is the application of electronography to the study of stars in globular clusters through the use of both broad and intermediate-band photometric systems. Introductions to both the study of globular clusters and to the use of electronography are given in Chapter 1. In Chapters 2 and 3 observations based upon electronographic exposures are presented for two little-studied clusters, NGC 5053 and NGC 6366. Both are loose, sparsely populated clusters but despite their similarity in appearance, the photometry shows that NGC 5053 is an unreddened, metal-poor globular, while NGC 6366 is found to be a highly reddened metal-rich cluster. One variable star in NGC 6366 is shown to be an a-type RR Lyrae - an unusual occurrence in a cluster of high metallicity. Chapter 4 describes developments in the reduction of stellar electronographs made by the author. An automatic method of fitting Gaussian profiles to the density volumes is shown to produce photometry as accurate and linear as previous manual techniques, but with a much increased efficiency. This work is extended to investigate the use of more flexible profiles which are then shown to be useful for allowing photometry of crowded images. Finally, an application of the Gaussian profile fitting routines to photographic stellar photometry is discussed. Chapter 5 reports the use of this reduction scheme on photographic plates of the globular cluster M 15. Using the David Dunlap Observatory (DDO) intermediate-band photometric system, cluster members are easily distinguished from foreground dwarfs. Chapter 6 describes the results of a programme of DDO electronography of the globular clusters M 5 and M 13. An accuracy of 0.03 is obtained for the DDO colours which, although comparable with some earlier photoelectric work, shows that, with the observational and reduction techniques employed, electronographic stellar photometry has not yet attained its potential as two-dimensional photoelectric photometry.

An examination of a IIIaJ plate taken on the United Kingdom Schmidt Telescope of Survey field 405 revealed a possible supercluster of clusters of galaxies. Three rich clusters could be seen grouped within one degree, and which appeared to be of similar distance. The project described in this thesis has investigated the supercluster hypothesis by determining relative (and less precisely, absolute) distances to the three component clusters. It is described how the photographic material was painstakingly reduced to relative magnitudes and colours, and how these values were calibrated using a stellar sequence photo-electrically observed using the 1m telescope at South African Astronomical Observatory. Radial velocities were determined by a process which maximises the amount of information derived from intrinsically low-precision objective prism material. It is found that the Supercluster has, within the errors, a line-of-sight dimension of twice its projected dimension; this suggests that in fact the clusters of galaxies are in as close proximity spatially as they are apparently. The distance derived to the supercluster is 550 Mpc, giving a projected diameter of 10Mpc, with a recession velocity of 47700 kms−1 which Leads to a determination of Hubble's constant: H0 = 87 ±20kms−1 Mpc−1.

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Typescript. / Thesis (Ph. D.)--University of Hawaii at Manoa, 1990. / Includes bibliographical references. / Microfiche. / xii, 178 leaves, bound ill. 29 cm

Mode of access: World Wide Web. / Thesis (Ph. D.)--University of Hawaii at Manoa, 2005. / Includes bibliographical references. / Electronic reproduction. / Also available by subscription via World Wide Web / xvii, 261 leaves, bound ill. (some col.) 29 cm