Simultaneous X-ray, ultraviolet, and optical observations of the BL Lacertae object PKS 2155-304

view Abstract Citations (62) References (38) Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS Simultaneous X-Ray, Ultraviolet, and Optical Observations of the BL Lacertae Object PKS 2155-304 Treves, A. ; Morini, M. ; Chiappetti, L. ; Fabian, A. ; Falomo, R. ; Maccagni, D. ; Maraschi, L. ; Tanzi, E. G. ; Tagliaferri, G. Abstract X-ray observations of PKS 2155-304, performed at nine epochs in 1983-1985 with the EXOSAT satellite, are reported. The source was observed quasi-simultaneously in the far-UV with IUE, and in the optical and infrared with ESO telescopes. X-ray light curves with 400 s time resolution are derived. On two occasions the flux showed a rapid regular rising with a doubling time ~ 1 hr. Spectral fits performed on X-ray data averaged over each observation yield the following results. The medium energy data (1-10 keV) are well fitted by single power laws plus absorption, with energy index between 1.5 and 2. Marginal evidence for an absorption edge at ~ 7 keV is found in the best exposed spectrum. If we combine the ME data with those obtained with the low energy telescope (0.1-2 keV), evidence for some spectral depression at ~ 1 keV is found. This may be modeled with an edge at 660+/-26 eV with optical depth Ï„ = 1.8 +/- 0.2. The quasi-simultaneous ultraviolet and optical data allow the reconstruction of the energy distribution on several occasions. In all cases but one, the optical, UV, and X-ray intensities are correlated. However, the variability amplitudes decrease, and the time scales increase, with decreasing frequency. These results are indicative of a synchrotron origin for the X-rays and of distinct, but connected, emission regions for the X-ray, ultraviolet, and optical bands. Publication: The Astrophysical Journal Pub Date: June 1989 DOI: 10.1086/167532 Bibcode: 1989ApJ...341..733T Keywords: Bl Lacertae Objects; Light Curve; Ultraviolet Spectra; X Ray Sources; Exosat Satellite; Iue; Spectrum Analysis; Synchrotron Radiation; Temporal Resolution; Astrophysics; BL LACERTAE OBJECTS; GALAXIES: INDIVIDUAL ALPHANUMERIC: PKS 2155-304; X-RAYS: SOURCES; ULTRAVIOLET: SPECTRA full text sources ADS | data products SIMBAD (2) NED (2) MAST (1) INES (1)