Very old and very young compact objects : X-ray studies of galactic globular clusters and recent core-collapse supernovae
Author(s)Pooley, David Aaron, 1976-
Massachusetts Institute of Technology. Dept. of Physics.
Walter H.G. Lewin.
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This thesis comprises the results of two distinct areas of research, namely, X-ray studies of Galactic globular clusters and X-ray studies of recent core collapse supernovae. My analyses of the Chandra X-ray Observatory observations of the globular clusters NGC 6752 and NGC 6440 revealed as many low-luminosity X-ray sources as was in the entire census of globular cluster sources with the previous best X-ray imaging instrument, Rontgensatellit. In the observation of NGC 6752, I detect 6 X-ray sources within the 10':5 core radius and 13 more within the 115" half-mass radius down to a limiting luminosity of Lx = 1030 ergs s-l for cluster sources. Based on a reanalysis of archival data from the Hubble Space Telescope and the Australia Telescope Compact Array, I make 12 optical identifications and one radio identification. Based on X-ray and optical properties of the identifications, I find 10 likely cataclysmic variables (CVs), 1-3 likely RS CVn or BY Dra systems, and 1 or 2 possible background objects. Of the 7 sources for which no optical identifications were made, one was detected in the archival radio data, and another was found to be a millisecond pulsar. Of the remaining sources, I expect that 2-4 are background objects and that the rest are either CVs or millisecond pulsars whose radio emission has not been detected. These and other Chandra results on globular clusters indicate that the dozens of CVs per cluster expected by theoretical arguments are being found. The findings to date also suggest that the ratio of CVs to other types of X-ray sources is remarkably similar in clusters of very different structural parameters.(cont.) In the observation of NGC 6440, I detect 24 sources to a limiting luminosity of 2 x 1031 ergs s-1 (0.5-2.5 keV) inside the cluster's half-mass radius, all of which lie within 2 core radii of the cluster center. I also find excess emission in and around the core which could be due to unresolved point sources. Based upon X-ray luminosities and colors, I conclude that there are 4-5 likely quiescent low-mass X-ray binaries and that most of the other sources are cataclysmic variables. I compare these results to Chandra results from other globular clusters and find the X-ray luminosity functions differ among the clusters. Observations of the Type II-P (plateau) Supernova (SN) 1999em and Type IIn (narrow emission line) SN 1998S have enabled estimation of the profile of the SN ejecta, the structure of the circumstellar medium (CSM) established by the pre-SN stellar wind, and the nature of the shock interaction. SN 1999em is the first Type II-P detected at both X-ray and radio wavelengths. It is the least radio luminous and one of the least X-ray luminous SNe ever detected (except for the unusual and very close SN 1987A). My analysis of the Chandra X-ray data indicate non-radiative interaction of SN ejecta with a power-law density profile ... for a pre-SN wind with a low mass-loss rate of ... for a wind velocity of 10 km s-1, in agreement with radio mass-loss rate estimates. The Chandra data show an unexpected, temporary rise in the 0.4-2.0 keV X-ray flux at 100 days after explosion. My analysis of SN 1998S yielded the first X-ray spectrum of a supernova in which numerous heavy element emission features (Ne, Al, Si, S, Ar, Fe) were present ...
Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Physics, 2003.Includes bibliographical references.
DepartmentMassachusetts Institute of Technology. Dept. of Physics.
Massachusetts Institute of Technology