Gordon A.H. Walker
I took early retirement in 1998 but continue to be active in resesrch and, since retirement I have supervised one successful PhD student, Evgena Shkolnik. Currently, my principal research involves data returned by the MOST (Microvariability & Oscillations of STars) photometric satellite for which I contributed the experimental design [The MOST Asteroseismology Mission: Ultraprecise Photometry From Space]. The satellite was launched in 2003 and continues to produce photometry of very high fidelity. Continuous monitoring for weeks at a time lets one detect and resolve the frequencies of natural oscillation and their harmonics for a variety of stars leading to plausible models of internal structure. My first interest was in the hottest emission line stars where models have now been fitted convincingly in terms of the kappa-mechanism associated with the Fe-opacity-bump [eg. Pulsations of the Oe Star Zeta Ophiuchi from MOST Satellite Photometry and Ground-based Spectroscopy, MOST detects g-modes in the Be Star HD 163868].
I am now particularly interested in the differential rotation of solar-type stars which is a basis for dynamo action and which has implications for magnetic interaction of parent stars with planets in those cases where the planet is very close to the star [Hot Jupiters and Hot Spots: The Short- and Long-Term Chromospheric Activity on Stars with Giant Planets ]. MOST photometry has allowed us for the first time to track pairs, and sometimes triple, star spots simultaneously as they rotate at different periods which depend on their stellar latitude and also detect weak signals from interaction of close planets with the magnetospheres of thier parent stars [see Differential rotation of Epsilon Eridani detected by MOST, The differential rotation of Kappa-1 Ceti as observed by MOST].
Three stars, whose radial velocities my group began to monitor more than twenty-five years ago for perturbation by companion planets, have proved to indeed have long-period planets based on subsequent observations [The First High-Precision Radial Velocity Search for Extra-Solar Planets]. I have a continuing interest in extra-solar planet detection and collaborate with more than one group.Large carbon-based, probably cyclical, molecules are the most likely candidates producing the profusion of (diffuse interstellar) absorption bands in the spectra of stars seen through clouds of interstellar dust. A Swiss colleague is taking laboratory spectra of increasingly complex molecules at very low temperatures in his lab and together with a colleague at the HIA I search for them in the stellar spectra, so far without success except for C3 [Detection of C3 in Diffuse Interstellar Clouds]. This remains one of the longest unsolved problems in science.
I have a continuing strong interest in astronomical instrumentation, spectrographs in particular, and regulary act in an advisory role.Current CV