Testing the Photometric Stability of BRITE-Constellation

Thomas Kallinger, Werner W. Weiss and the BRITE Team

To characterise the long-term stability and true photometric sensitivity of a space-based instrument is a difficult task and can be done best with independent measurements of a relatively quiet star. A rare occasion for such a test are the complementary observations of some bright Pleiades stars with the Kepler /K2 telescope and the BRITE-Austria (BAb) and UniBRITE (UBr) satellites. While most of them show a complex oscillatory behaviour, the frequency spectrum of the bright B-type star Atlas is relatively simple. From the 71-day K2 observations we extract the three dominant frequencies and show that the residuals have a noise level of less than 10 ppm. While the BAb observations are not sensitive enough, we find the same periodicities in the 167-day UBr data set, which shows no additional significant signal down to a noise level of about 100 ppm. This impressively demonstrates the stability of the BRITE instruments in the low-frequency regime and their capability to detect sub-mmag variability, even for stars close to the faint end of the nominal dynamic range.

Proceedings of the Polish Astronomical Society, vol. 8, 170-174 (2018)

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