Hard X-Ray Observations of the Extragalactic Sky: The High Energy Focusing Telescope and the Serendipitous Extragalactic X-ray Source Identification Survey

Author: Mao, Peter Hsih-Jen

Year: 2002

Degree: Dissertation (Ph.D.)

Advisor: Harrison, Fiona A.

Committee Members: Harrison, Fiona A.; Readhead, Anthony C. S.; Blandford, Roger D.; Tombrello, Thomas A.

Option: Physics

DOI: 10.7907/R5E3-RQ86

Abstract

Extending the energy range of high sensitivity astronomical x-ray observations to the hard x-ray band (10-100 keV) is important for the study of nonthermal emission mechanisms and heavily obscured sources. This thesis, in two parts, describes the development of the High Energy Focusing Telescope (HEFT), a focusing telescope for the hard x-ray band, and the Serendipitous Extragalactic X-ray Source Identification (SEXSI) survey, a degree-scale x-ray/optical survey of sources detected in the Chandra hard band (2-7 keV).

HEFT is a balloon-borne x-ray telescope that is expected to have its first flight in the fall of 2003. The telescope will be among the first to focus x-rays at energies greater than 20 keV. HEFT's mirrors use graded multilayers -- thin film coatings (~1 µm) that enhance high energy reflectance via constructive interference. In the first half of the thesis, I describe the optimization algorithm that I developed for x-ray optics and how I applied this algorithm to the design of the HEFT optics. In addition, I present x-ray measurements that verify the HEFT multilayer coating designs at energies where the telescope will operate.

The SEXSI survey complements Chandra deep-field surveys by covering a much larger area of the sky, but to a shallower x-ray flux limit. For the SEXSI survey, we use public data from the Chandra archive to compile a catalog of extragalactic sources detected in the 2-7 keV band. We identify the optical counterparts to the x-ray sources and obtain their optical spectra (400-1000 nm). Presently SEXSI includes 30 Chandra fields, covering roughly 2 square degrees and yielding over 1200 x-ray sources to a flux limit of 10⁻¹⁵-10⁻¹³ erg cm⁻² s⁻¹. In the second part of the thesis, I present results from 10 fields for which we have substantial spectroscopic coverage.

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