Prospects of Plate Archive Photometric Calibration by GAIA SED fluxes
M. Raouph1, A. Schrimpf1, P. Kroll2
1 Philipps Universität Marburg, Germany, 2 Sonneberg Observatory, Sonneberg, Germany
In this study, we are working on improving the photometric calibration of astronomical photo plates. We selected the sky patrol of the largest German digitized photographic plates archive located at Sonneberg Observatory, Thuringia which comprises about 300,000 plates. Carrying out tasks in the digitization workflow of photo plates which contain the extraction of sources on direct images, astrometric calibration, and photometric calibration is implemented using an open-source Python package (PyPlate). Due to the difference in terms of color sensitivity in the photo plates’ emulsion response, there are offsets in zero points, which are very hard to determine and to remove from light curves, especially when combing data from different photo plate series. The newly released Gaia DR3 dataset contains the mean low-resolution spectra (SED) with full sky coverage complete down to magnitudes of G < 17.6 mag covering the optical to near-infrared wavelength range [330, 1050] nm. By applying the GaiaXPy tool we are able to calculate the Gaia determined brightness of stars in the photo plates’ color systems for use in the photometric calibration. The result of the study is to obtain a consistent astrometric and, for the first time, photometric calibration of the Sonneberg plates and those of other archives such as APPLAUSE.