Notes on some changing light curves.
BB Cep and KU Cyg
Observations of BB Cep and KU Cyg have generated light curves which appear to show that the shape of the light curves have changed over time. In order to try to eliminate at least some sources of possible error the following checks were carried out.
Images of the two stars before and after the changes to their light curves were examined.
The changes to the light curve of BB Cep do not coincide with the changes to the light curve of KU Cyg. That of BB Cep occurs between JD 2458024.7 (2017 September 28) and JD 2458029.4 (2017 October 2), while that of KU Cyg occurs between JD 2458352.7 (2018 Aug 22) and JD 2458479.3 (2018 December 26).
The changes do not correspond to changes to the COAST camera, focus and seeing, binning (1x1 with the ‘old’ camera, 2x2 binning with the ‘new’ camera), calibration or exposure times, and are independent of photometry apertures and comparison stars used. Also, such changes as there have been to the telescope system do not correspond to any equivalent changes to the deduced light curves.
Other variables observed using the same telescope when these changes occur do not show a similar effect.
For now, I will assume that the changes in the light curves are due to real changes in the magnitudes of the stars, but more observations of both stars will be made in order to investigate this further.
The changes to the light curve of BB Cep do not coincide with the changes to the light curve of KU Cyg. That of BB Cep occurs between JD 2458024.7 (2017 September 28) and JD 2458029.4 (2017 October 2), while that of KU Cyg occurs between JD 2458352.7 (2018 Aug 22) and JD 2458479.3 (2018 December 26).
The changes do not correspond to changes to the COAST camera, focus and seeing, binning (1x1 with the ‘old’ camera, 2x2 binning with the ‘new’ camera), calibration or exposure times, and are independent of photometry apertures and comparison stars used. Also, such changes as there have been to the telescope system do not correspond to any equivalent changes to the deduced light curves.
Other variables observed using the same telescope when these changes occur do not show a similar effect.
For now, I will assume that the changes in the light curves are due to real changes in the magnitudes of the stars, but more observations of both stars will be made in order to investigate this further.
[This page updated 2020 January 17]