The general theme of my research has been the study of how light (photons) carry energy, momentum, and diagnostic information out of the region in which they were created, and diffuse from the depths of optically thick gas. This combines the areas called radiative transfer and radiation hydrodynamics. Since light is our primary (indeed, usually our sole) probe of astrophysical plasmas, the diagnostic potential of radiative transfer theory is very important for the study of astronomy. Also, the ability for photons to carry energy is of extreme importance almost everywhere, not the least important example being the transport of life-giving sunlight to Earth. But light also carries momentum, albeit rather inefficiently, and this becomes important for the very brightest of light sources such as extremely hot stars, which can be a million times more luminous than our Sun.
It is perhaps this final aspect of radiation, its ability to drive matter (termed a "wind") from the surface of a bright source, that is its most subtle attribute, and holds particular interest for me. Thus I do work in the area of hot-star winds. However, I am also intrigued by the ability of radiation to provide information about different depths within an emitting region, by looking at different wavelengths. Different "colors" of light, whether visible to us or not, are characterized by their different frequencies, which is related to their wavelengths. This is called a "spectrum". Atomic processes interact with light at special frequencies, and leave particular signatures in the spectrum. Thus I also do work extracting the diagnostic potential of the wavelength-dependent interactions of light and atoms. In particular, I look at narrow and highly opaque wavelength regions, called "resonance lines", and consider how small changes in frequency accrue over the course of many scatterings.
Gayley, K. G. \& Owocki, S. P., 2000, Ap. J., 537, 461: "Radiative Torque and Partial Spindown of Winds from Rotating Hot Stars"
Gayley, K. G. 2000, Ap. J., 529, 1019: "The Surprisingly Weak Effect of Gravity in Retarding Hot-Star Wind Acceleration"
Gayley, K. G., Zank, G. P., Pauls, H. L.,,Frisch, P. C., & Welty, D. E. 1997, Ap. J., 487, 259: "One- vs. 2-Shock Heliosphere: Constraining Models with GHRS Lyman alpha Spectra toward alpha Cen"
Gayley, K. G., Owocki, S. P., & Cranmer, S. R. 1996, Ap. J., 475, 786: "Sudden Radiative Braking in Colliding Hot-Star Winds"
Gayley, K. G. 1994, Ap. J., 431, 806: "Analytic Lyman alpha Wing Diagnostics and the Chromospheric Excitation Balance in Cool Dwarfs"
Gayley, K. G. 1992, Ap. J., 392, 353: "A Modified Eddington-Barbier Approximation for Highly Coherent Resonance Lines"