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UV and optical observations of nova Sagittarii 1982.
Mazeh, T.; Netzer, H.; Cacciari, C. +6 more
Ultraviolet and optical observations of Nova Sagittarii 1982, are presented and discussed. The light curve and continuum energy distribution give a distance estimate of 4.7 kpc, visual extinction of 1±0.3 mag and Mv(max) = -6.35±0.5 mag. Simultaneous ultraviolet and optical data obtained 4 d after visual maximum, enable to study in deta…
UV fluxes of population II stars.
Cacciari, C.
A catalogue of IUE ultraviolet fluxes and calibrated plots for 36 metal-poor field halo stars is presented. The fluxes at 5 Å intervals cover the wavelength range λλ1155 - 3195, or λλ1955 - 3195 for cool stars. For all these stars absolute energy distributions in the visual are available in the literature. The purpose of the present collection of …
UV and optical observations of PG 1351+64, a bright Seyfert galaxy ORA low-luminosity QSO.
Tanzi, E. G.; Falomo, R.; Treves, A. +3 more
PG 1351+64 was repeatedly observed in 1979 - 83 with IUE. Variations of a factor of 2 in both line and continuum intensity were observed with a time-scale of ≡1 month. Coordinated optical observations suggest that the ultraviolet variability is not accompanied by optical variability, so that the overall energy distribution changes shape. The prope…
He 2-36 : a planetary nebula with a high-velocity jet ?
Feibelman, W. A.
The ultraviolet spectrum of the planetary nebula He2-36 was observed in the low-dispersion mode of the IUE. Strong emission lines of C III], He II, and C IV are observed, as well as some weak lines and a moderately strong stellar continuum, suggesting a hot companion to the visual A2 III central star. The extinction to He2-36 was determined from t…
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…