Bernard Bopp (Stellar Surface Phenomena)

Distinguished University Professor of Astronomy
Ph.D., 1973, University of Texas

With the single exception of the sun, all the stars are sufficiently distant that when viewed even with large telescopes they appear as point sources. Yet the behavior seen on the resolved disc of our sun is remarkably complex. Many forms of activity (e.g., flares, prominences) are present. It is natural to ask if these same phenomena occur on the surfaces of other stars. Although stars cannot be resolve into discs, nevertheless evidence of stellar surface activity can be detected. For example, many faint red stars are known to exhibit rapid, intense increases in brightness; this is a stellar flare, analogous to a solar flare but perhaps 100 times more energetic. Other stars may show slow variations in brightness, with periods of several days and amplitudes 10-20%. These variations as due to the presence of a cooler, darker starspot on the surface of a rotating star. With suitable photometry and spectroscopic data from the Ritter telescope, it is possible to determine starspot sizes, temperatures and locations in stellar longitude and latitude. The observational facilities at Ritter, available on a nearly continuous basis, lend themselves very well to synoptic observations of these manifestations of stellar surface activity, which can vary on timescales ranging from minutes to years.

Bopp, B.W., Fekel, F.C., Aufdenberg, J., Dempsey, R., and Dadonas, V. 1993. The extremely active long-period RS CVn binary HD 12545. Astron. J 106:2502-2509.

Dempsey, R., Bopp, B.W., Henry, G., and Hall, D. 1993. Observations of the Ca II infrared triplet in chromospherically active single and binary stars. Astrophys. J. Suppl 86:293-306.

Fekel, F.C., and Bopp, B.W. 1993. Optical spectroscopy of the dusty K5 V star HD 98800. Astrophys. J. (Letters) 419:L89-92.