Quasi-simultaneous Ultraviolet Optical and Infrared Observations of the BL Lacertae Object PKS 0048-09
Maraschi, L.; Tanzi, E. G.; Bouchet, P.; Falomo, R.; Treves, A.
Italy, Chile
Abstract
The first International Ultraviolet Explorer (IUE) observations of the BL Lacertae object PKS 0048-09 were obtained on 1987 January 7 and 8, when the object was in a moderately high optical state (m_v_ ~ 15.5 mag). Quasi-simultaneous optical-IR spectrophotometry allows deriving the detailed energy distribution from ~10^14^ to ~2.5 x 10^15^ Hz. Comparison with previous published data, pertaining to a lower state of the source, indicates spectral hardening with increasing intensity on time scales of months.