galaxies: active, methods: data analysis, techniques: photometry, Astrophysics - Instrumentation and Methods for Astrophysics, Astrophysics - Astrophysics of Galaxies
Beschreibung:
Background:At the Hamburger Sternwarte, an effort was started in 2010 with theaim of digitizing its more than 45,000 photographic plates and films stored in itsplate archives. At the time of writing, more than 31,000 plates have already beenmade available on the Internet for researchers, historians, and the interested public.Materials and Methods:The digitization process and the Internet presentationof the plates and accompanying handwritten material (plate envelopes, logbooks,observer notes) are presented here. To fully exploit the unique photometric and astro-metric data, stored on the plates, further processing steps are required includingregistering the plate to celestial coordinates, masking of the plates, and a calibra-tion of the photoemulsion darkening curve. To demonstrate the correct functioningof these procedures, historical light curves of two bright BL Lac-type active galacticnuclei are extracted.Results:The resulting light curve of the blazar 1ES 1215+303 exhibits a largedecrease in the magnitude from 14.25+0.07−0.12 to 15.94+0.09−0.13in about 300 days, whichproves the variability in the optical region. Furthermore, we compare the measuredmagnitudes for the quasar 3C 273 with contemporaneous measurements and findgood agreement.