Instrument development for high-speed infrared and optical photometry and observational studies of pulsars
Abstract
This thesis consists of two parts. In the first hart, we present the development of instruments for high-speed infrared and optical photometry optimized for pulsar observations. In the second part, we present observational studies of pulsars, mainly on accretion- powered pulsars but also on rotation-powered pulsars. For the instrument development, we first built the Cornell High-Speed Data Acquisition System (CHISDAS) for multi-channel infrared and optical photometry based on the technologies of Field Programmable Gate Array, Global Positioning System, and Peripheral Component Interconnect. CHISDAS is capable of recording photon arrival times with ∼1 microsecond accuracy. It also has the capacity of direct decoding of the GPS time- format signal and of real-tune monitoring of the observed data, which were not available with previous instruments. Next, we built a new infrared photon-counting photometer based on the Edge-illuminated Solid-state Photomultiplier. This new photometer is expected to be at least a few times more sensitive than any previously- built instrument of microsecond resolution. It is equipped with JHK filters, and is optimized for the 5-m Hale telescope of the Palomar Observatory, though its flexible optical design allows it to be used on other telescopes easily. For observational studies of pulsars, we discovered the first clear evidence for coupling between periodic and aperiodic variabilities from the accretion-powered pulsars LMC X-4 and Her X-1. The phenomena were predicted some time ago, but never confirmed observationally until our results. From these sources, we also discovered milli-hertz quasi-periodic oscillations, and investigated the details of their accretion disks. In addition, we discovered active flares from SMC X-1 which are most likely caused by viscous instability in the accretion disk. This discovery led us to suggest that SMC X-1 may in fact be an intermediate-stage source (like the bursting pulsar GRO J1744-28) due to its relatively weak magnetic field. We also found that the super-Eddington radiation of the large LMC X-4 flares is owing to inhomogeneous polar cap accretion flows, which may be the first evidence that inhomogeneous atmospheres may really be responsible for super-Eddington radiation. We finally present our results on the pulsar wind nebula of PSR, B1951+32. Using our optical data and X-ray data obtained with Chandra, we find in this source the long-sought double shock structure of pulsar wind nebula.
- Publication:
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Ph.D. Thesis
- Pub Date:
- June 2004
- Bibcode:
- 2004PhDT........16M
- Keywords:
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- Physics: Astronomy and Astrophysics