Simultaneous observations of the BL Lacertae object I ZW 187.
Pollock, J. T.; Huggins, P. J.; Bregman, J. N.; Glassgold, A. E.; Aller, H. D.; Aller, M. F.; Hodge, P. E.; Pica, A. J.; Smith, A. G.; Balonek, T. J.; Dent, W. A.; Rudy, R. J.; Levan, P. D.; Williams, P. M.; Neugebauer, G.; Webb, J. R.; Brand, P. W. J. L.; Ku, W. H. M.
United States
Abstract
Two sets of simultaneous spectra consisting of data obtained with radio, IR, optical, UV and X-ray telescopes were obtained 10 months apart for the X-ray bright BL Lac object IZw 187. In addition, nonsimultaneous observations were made in several of the aforementioned observing bands in order to detect flux variations and galactic light contamination was removed from all observations. The BL Lac component is found to have a weak 3000 A bump superposed on an IR-optical-UV spectrum of slope 0.9. Consistent with the arising of the IR-through-X-ray continuum from a single synchrotron source, the X-ray data fall on or near an extrapolation of this power law. No flux variations have been detected in the flat radio spectrum. Optical and X-ray fluxes are observed to vary by a factor not greater than three, and the shortest variability time scales in these bands are comparable at about one week.