Optical and near infrared observations of accretion processes in galactic compact objects
University College Cork
In this thesis, we present optical and near-infrared observations of compact binary systems. The observations are used to refine the binary parameters of several Low Mass X-ray Binaries, and to better understand the accretion processes in these systems. Accretion is essential in the formation of stars, planets and solar systems yet remains poorly understood. In this thesis, we present results that focus on the accretion processes in two important Low Mass X-ray Binary systems. In Chapter 3, optical photometry and spectroscopy are used to study the pulsar system PSR J102341.6+003841. The system has been observed to be accreting material from its companion, while radio pulsations indicate this accretion process is transient in nature. Combining quiescent photometry and spectroscopy allows us to constrain the binary orbital parameters, while photometry obtained when the system was in outburst allows us to investigate the nature of accretion within the system. In Chapter 4, simultaneous optical photometry and spectroscopy is used to present a proof of concept for the black hole system A0620-00. We used spectroscopy to determine the contribution of the light from the accretion disc at each phase of our observation. This contribution was then removed from the optical light curve, leaving the pure ellipsoidal modulation due to the motion of the secondary ii star. Our results suggest that for systems such as A0620, we will require the next generation of telescopes to successfully complete such a study. Finally, Chapter 5, focuses on the black hole system GRS1915+105, one of the most massive stellar mass black holes in the Galaxy. We present infrared spectroscopy in an attempt to constrain the mass of the black hole and determine any orbital period variation. The presence of double peaked emission lines in the spectra allow us to probe the nature of the very large accretion disc in this long period system.
McConnell, O. 2017. Optical and near infrared observations of accretion processes in galactic compact objects. PhD Thesis, University College Cork.