Mapping Stellar Surface Features

Paul V. Noah
1988 Publications of the Astronomical Society of the Pacific  
New photometric and spectroscopic observations of the RS Canum Venaticorum binaries a Geminorum and UX Arietis are reported along with details of the Doppler imaging program SPOTPROF. The observations suggest that the starspot activity on a Gem has decreased to 0.05 mag in two years. A photometric spot model for September 1984 to January 1985 found that a single spot covering 2% of the surface and 1000 K cooler than the surrounding photosphere could model the light variations. Equivalent-width
more » ... bservations contemporaneous with the photometric observations did not show any significant variations. Line-profile models from SPOTPROF predict that the variation of the equivalent width of the 6393 A Fe I line should be ~ 1 mÀ. Photometric observations of UX Ari from January 1984 to March 1985 show an 0.3-mag variation indicating a large spot group must cover the surface. Contemporaneous spectroscopic observations show asymmetric line profiles. The Doppler imaging and the photometric light-curve models were used in an iterative method to describe the stellar-surface spot distribution and successfully model both the photometric and the spectroscopic variations. A number of spots covering 12% of the surface and 1000 K cooler than the surrounding photosphere are necessary to account for the observations. Estimates of the vertical component of the magnetic field yield a field strength of 2.5 kgauss. In addition, the construction of a Reticon solid-state detector system at Ritter Observatory is described. The system is capable of producing a signal-to-noise ratio of 200:1 with an image intensifier and over 400:1 without the image intensifier. 1024
doi:10.1086/132266 fatcat:5wyqpno57jffhbypb5zn3sx3ce