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3C273 - a Review of Recent Results
Ulrich, M. -H.
3C 273 is the most extensively studied quasar both from the ground and from space. Recent satellite observations have given important information on the overall electromagnetic spectrum of 3C 273 in the γ-ray, X-ray, and UV ranges. The most salient results are: (i) the energy per decade of frequency emitted by 3C 273 is nearly constant between 600…
Ultraviolet and Optical Observations of HDE245770 / A:0535+26 System during an X-Ray Flare
Giovannelli, F.; Persi, P.; Bartolini, C. +4 more
We present high and low dispersion UV spectra of HDE 245770, which is the optical counterpart of the recurrent transient X-ray pulsar A 0535+26,during a decay of an X-ray flare. UBV photometric measurements and medium dispersion optical spectra were simultaneously obtained. The energy distribution of the star in the 12 10 micron range is compared …
Ultraviolet Observations of the X-Ray Sources in the Eta-Carinae Nebula
Macchetto, F.; Viotti, R.; Cassatella, A. +1 more
η Car is surrounded by a dense nebula ejected during the last 150 years. The Einstein satellite recently detected intense X-ray emission from η Car and its nebula indicating the existence of efficient gas heating processes. Ultraviolet observations with IUE confirmed the presence of hot gas in the condensation S of the nebula and in η Car. Possibl…
An Optical Outburst from the Periodic Recurrent X-Ray Transient A0538-66
Charles, P. A.; Willis, A. J.; Thorstensen, J. R. +2 more
We present optical spectroscopy and photometry and IUE spectroscopy of the counterpart of the LMC recurrent X-ray transient A0538-66 during an outburst at the end of December 1980 which was consistent with the 16.6 day X-ray period (Skinner, 1980). The optical spectra show steadily increasing Balmer and HeI emission (indicative of a shell phase) s…
Ultraviolet Study of U1341-CYGNI = CYGNUS-X-2 - Observations of an Accretion Disk
Maraschi, L.; Tanzi, E. G.; Chiappetti, L. +1 more
Observations of Cyg X-2 with the International Ultraviolet Explorer in the range 1200-3000 A are discussed with particular reference to the continuum. The dereddened UV spectrum indicates the presence of a contribution from a hot region of small area which is naturally interpreted as an X-ray heated accretion disk. Assuming an average X-ray lumino…
Is PKS 2155 an extragalactic source?
Maraschi, L.; Tanzi, E. G.; Tarenghi, M. +1 more
The X-ray source H2155-304, identified with the radio source PKS 2155 and with a 14 mag star-like object, is commonly believed to be a BL Lac object on the basis of the blue featureless continuum, the presence of optical polarization, and the violent variability (mB varies from 12.8 to 14.2 on a time scale of months). This paper present…
First Ultraviolet Observations of the Optical Couterpart of the X-Ray Source 2S0114+650
Bianchi, L.
The X-Ray Source 2S0114+650 discovered by SAS-3 in 1978 has been associated with a highly reddened star showing broad Hα emission. We observed this star with the LWR spectrograph on board the I.U.E. Satellite on Sep. 1980 and Feb. 1981. An Ultraviolet flux was detected longward of the 2200 Å bump, consistent with the B0.5 spectral class…
Cos-B X-Ray Observations of CYGNUS-X-3 - an Indications for Apsidal Motion
van der Klis, M.; Bonnet-Bidaud, J. M.
Results are presented of three ∼40 d COS-B X-ray observations of Cyg X-3. The shape of the 4.8 h light curve showed variations on all observational time scales. An ∼20 d periodicity was found in the arrival time of the minimum of the light curve, interpreted as apsidal motion of an orbit with an eccentricity of ∼0.03.
Ultraviolet Observations of Mv-Lyrae
Maraschi, L.; Tanzi, E. G.; Chiappetti, L. +1 more