Brief Vitae

Degrees

Research Interests

My current research has been primarily in the area of creating images of the surface features of stars using the indirect techniques of reconstruction of an image through a process that has come to be known as Doppler imaging. This technique is more complicated than the medical imaging called CAT scanning but uses the same fundamental idea. One outgrowth of this technology has been an increasing awareness of the second “high resolution frontier” in astronomy. While non-stellar astronomers have focussed on the remarkable increase in knowledge that comes from the improved resolution in direct images obtained either from the Hubble telescope or from the improvement in ground based images obtained at excellent sites with active optics, stellar astronomers have been accomplishing imaging that in angular terms goes far beyond what can be obtained using the Hubble telescope or active optics.

The Doppler imaging code I have developed has been applied to numerous stars. Generally there are two classes of stars that exhibit line profile variations in their high resolution spectra. One class is the hot stars at the high mass or upper end of the main sequence of the traditional HR diagram. Among these hot stars are those where the abundance of elements present in the photospheres of these stars is distributed non-uniformly over the surface of the star and this non-uniform distribution causes the line profile variations as the star rotates. These stars are referred to as Chemically Peculiar stars and many of them exhibit stronger magnetic surface fields than their more normal cousins. The Doppler imaging code has been used to map the distribution of these elements over the star’s surface by inverting the information in the variable line profiles. We then try to relate the abundance distribution to the magnetic field pattern.

The second class of stars where Doppler Imaging can be applied is the cooler stars where large versions of what we see on the Sun as sunspots occur. These spots are so large that as the star rotates the variation in contribution to the light output from various parts of the stellar surface causes the line profiles to distort in phase with the rotation. Doppler imaging can be used to reconstruct the spot pattern on the stellar surface. By studying the spot patterns we have been able to identify polar spots (originally seen as being hard to believe given that the Sun’s spots never go to the poles), differential rotation, a flip flop phenomenon in spot longitudes seen over time and the effects of close binary star companions on the surface spot structure. Other more subtle effects have been discussed in our papers over the last two decades.

Courses Taught

• Introductory Astronomy for liberal arts students
• Electricity and Magnetism for second year physics students
• Electronics for third year physics students
• Electromagnetic Fields and Waves for third/fourth year physics students
• Basic Quantum Mechanics & Intermediate Quantum Mechanics – two courses for third and fourth year physics students
• Digital Computer Fundamentals primarily for computer science and physics students
• Microprocessors primarily for computer science students
• Optics for second year physics students
• Acoustics a general course for music students