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EXOSAT / Optical Observations of the Am-Herculis Star H0139-68
Motch, C.; Beuermann, K.; Schwope, A. +1 more
We report preliminary results of X-ray and optical observations of the AM Her star HO139-68 during its low state at V ∼ 17 to 18. X-rays were detected only during ∼ 45 % of the orbital period when the system was optically bright and the radial velocity of the Balmer lines was positive. Our data show no evidence for accretion onto two active poles …
The exosat mission
Taff, L. G.; Beatty, D. E.; Yakutis, A. J. +1 more
Exosat, the European X-ray Observatory, was placed in orbit on 26 May 1983. The spacecraft, stabilized axes in three to a few arc second, carries four instruments, two one-metre focal length imaging telescopes, a large area proportional counter array and a gas scintillation proportional counter spectrometer. The salient features of the instrumenta…
The 1984 eclipse of the symbiotic binary SY Muscae.
Lutz, J. H.; Kafatos, M.; Michalitsianos, A. G. +1 more
The authors present ultraviolet and optical observations of the 1984 eclipse of the symbiotic binary star SY Mus. The optical light curve shows a 627-day variation which is reflected in the intensity of the far-UV continuum (λ < 2000 Å) and in the intensities of all strong, permitted UV emission lines. This contrasts sharply with other eclipsin…
Chromospheric activity and TiO bands in M giants.
Johnson, H. R.; Steiman-Cameron, T. Y.; Honeycutt, R. K.
Low-resolution IUE spectra of 23 cool giant stars ranging from K3 through M6 have been used to examine chromospheric activity in late-type giants. Previous studies have suggested a decrease in the fractional flux, normalized to bolometric flux, of the Mg II resonance lines (an indicator of chromospheric activity) with effective temperature. Using …
EXOSAT and EINSTEIN High Resolution Images of the Small Magellanic Cloud
McHardy, I. M.; Jones, L. R.; Pye, J. P. +1 more
In order to obtain optical identifications and further information about the X-ray emission of sources discovered in the EINSTEIN IPC survey of the Small Magellanic Cloud (SMC), we have used the EXOSAT CMA and EINSTEIN HRI at selected positions. These observations have so far resulted in several identifications (including 4 stellar objects with m<…
Variability of Bl-Lacertae Objects at X-Ray and Other Frequencies
Pollock, A. M. T.; Robson, E. I.; Brand, P. W. J. L. +1 more
EXOSAT observations reveal that daily X-ray variability appears to be a common property of high luminosity BL Lac objects. Results are reported for PKS0735+178, OM280(=1147+245), OQ530(=1418+546), OV-236 (=1921-293) and OJ287(=0851+202). In OJ287, for which we have the most extensive coverage, the amplitude of variability at X-ray frequencies appe…
IUE observations of comet P/Crommelin (1983 n)
Keller, H. U.; Evans, A.; Wallis, M. K. +2 more
Comet P/Crommelin has always been a difficult object to observe because of both its intrinsic faintness and its poor location in northern skies at the time of maximum activity. Observations were attempted with the International Ultraviolet Explorer (IUE) over a seven week period starting five days after the comet had reached perihelion. The nature…
Remote Sensing of the Magnetic Moment of Uranus: Predictions for Voyager
Hill, T. W.; Dessler, A. J.
Power is supplied to a planet's magnetosphere from the kinetic energy of planetary spin and the energy flux of the impinging solar wind. A fraction of this power is available to drive numerous observable phenomena, such as polar auroras and planetary radio emissions. In this report our present understanding of these power transfer mechanisms is ap…
Images in the rocket ultraviolet : the initial helium abundance and distance modulus of the globular cluster M5 from photometry of horizontal-branch stars.
Bohlin, R. C.; Stecher, T. P.; Cornett, R. H. +2 more
A natural laboratory for the study of postmain-sequence evolution of low-mass (less than one solar mass) metal-poor stars is provided by globular clusters. These clusters are, therefore, a critical aid for developing an understanding of advanced stages of stellar evolution and of the chemical evolution of the Galaxy. Bohlin et al. (1983) have desc…
EXOSAT Observations of the Bright X-Ray Source GX9+1
Hasinger, G.; Sztajno, M.; Truemper, J. +1 more
We present the results of the spectral and timing analysis of an observation of GX9+1/4U1758-205 performed with the Medium Energy Experiment aboard EXOSAT. During our observation the source flux varied irregularly in time scales from minutes to hours. No periodic emission in the period range from 16 msec to 2000 sec was found with an upper limit o…