2002/12/20 by F. Vagnetti, Vagnetti, F., D. Trèvese +2
Engineering · Physics and Astronomy · #Astronomical Observations and Instrumentation #Astronomy and Astrophysical Research #Astrophysics (astro-ph) #FOS: Physical sciences #Stellar, planetary, and galactic studies #astro-ph
paper · pdf · doi:10.48550/arxiv.astro-ph/0212474
4 pages, 1 figure, Mem. SAIt LaTeX class mem.cls, to appear in "Workshop on Variability with Wide Field Imagers", Lampedusa, Italy, September 2002
arxiv created 2002/12/20 · openalex publication_date 2002/12/20 · arxiv updated 2009/12/01 · openalex created_date 2025/10/10 · openalex updated_date 2026/07/28
Optical spectral variability of quasars and BL Lac Objects is compared by means of the spectral variability parameter beta (Trevese & Vagnetti 2002). Both kinds of objects change their spectral slopes alpha, becoming bluer when brighter, but BL Lac Objects have smaller beta values and are clearly separated from quasars in the alpha-beta plane. Models accounting for the origin of the variability are discussed for both classes of objects.