Stellar CCD Photometry in the Auroral Zone

Abstract

Observing pulsating stars in the auroral zone, seemed for many years to be an impossible task. Due to the aurora, the sky is bright and rapidly changing. Precise photometry could only be performed on stars down to 7 th. magnitude.<p>

<p>A new instrument for continuous photometry, with the use of CCD technology, and windowed readout, is developed by the Astrophysics group at the University of Tromsø. The Tromsø CCD Photometer (TCP), has been tested for stellar photometry in the auroral zone during the winter 1999/2000.<p>

<p>The windowed readout makes it possible to have sampling time down to 5 seconds, and this open the possibility to use CCD's for fast photometry. The data reduction package developed for the system has proven to work perfectly for reducing the photometric data obtained under aurora conditions. Using individual sky background close to each star observed, for correcting the sky level in front of the star, was specially useful.<p>

<p>The observations was done at the Skibotn Observatory with the 50 cm telescope. In the thesis we present the observations and reductions of the white d warf GD 358, and the catalysmic variable star AM CV_n.<p>

<p>The performance of the instrument was excellent, and we obtained good photometric data on variable stars down to magnitude 14.5, under aurora conditions. This opens the possibility to use the long arctic and antarctic nights to obtain long continuous light curves.