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The accreting circumstellar gas envelope of HD 176386 a young star inthe R Coronae Austrinae star formation region.
Grady, C. A.; Perez, M. R.; The, P. S.
We report recent and archival IUE observations of the Herbig Be star HD 176386. We find accreting gas toward the star with velocities up to +300 km s-1 in C IV and Si IV. Detection of these species in a B9.5 star is consistent with collisional ionization of the accreting gas to temperatures in excess of the stellar Teff. The …
R 40 : the first luminous blue variable in the Small Magellanic Cloud.
Stahl, O.; Bouchet, P.; Zickgraf, F. -J. +3 more
During the past decade R 40 in the SMC has brightened in the visual range by about 0.5 magnitudes. Correlated with the brightening the spectral type has changed from B8Ia to A3Ia-O. This behaviour shows R 40 to be an LBV, the first one discovered in the SMC. During the past eight years we obtained extensive Stromgren photometry. R 40 was also obse…
Compact subarcsec structures of the double nucleus of NGC 6240 revealed with HST.
Boksenberg, A.; Barbieri, C.; Weigelt, G. +18 more
We have used the Faint Object Camera on board of the Hubble Space Telescope to obtain a high spatial resolution ultraviolet image of the central region of NGC 6240. This image resolves the well known double nucleus of the galaxy into several compact knots with sizes 0.1"-0.2" (about 45-90 pc for H_0_ = 75 km s^-1^Mpc^-1^) and extended low surface …
The Distant Future of Solar Activity: A Case Study of beta Hydri. II. Chromospheric Activity and Variability
Gahm, G. F.; Fredga, K.; Linde, P. +1 more
A detailed comparison of the present sun with the very old star Beta Hyi (G2 IV) is presented in order to study the secular evolution of solar-type chromospheres, with emphasis placed on chromospheric features and their time variability. High-resolution Ca II H and K profiles show the emission to be about half that for the sun, but with the same s…
The Abundances of the Elements in Sharp-lined Early-Type Stars from IUE High-Dispersion Spectrograms. I. Cr, Mn, Fe, Ni, and CO
Adelman, Saul J.; Wahlgren, Glenn M.; Leckrone, David S. +2 more
The current study was undertaken to test the viability of lUE archives as a source of information on elemental species unavailable from (ground-based) coudé spectra. The first step in this endeavor is to check the consistency of abundances obtained from lUE material and those derived from the ground especially as reported in a series of papers by …
The Spectrum of the Planetary Nebula NGC 6567
Feibelman, Walter A.; Hyung, Siek; Aller, Lawrence H.
Because of the similarity of its spectrum to that of NGC 6572 particularly in the UV we have made a detailed study of NGC 6567 using both the IUE for the UV region and the Hamilton Echelle at Lick Observatory for the optical region. Plasma diagnostics suggest an electron temperature of about 11,500K and an electron density near 9000 cm^-3. The che…
Magnetic fields throughout the heliosphere
Smith, Edward J.
Measurements of the heliospheric magnetic field made over the last several years are surveyed with emphasis on Pioneer 11 observations near 35 AU and Ulysses observations between 1 and 5 AU. The increase in field magnitude at 1 AU near the recent sunspot maximum is also seen at Pioneer 11. Extrapolation of the magnitude and azimuthal component of …
Propagation of jovian electrons in and out of the ecliptic
Sierks, H.; Kunow, H.; Wibberenz, G. +5 more
Since its switch-on in Oct. 90, the Kiel Electron Telescope onboard Ulysses has detected many quiet time increases of the flux of 3-30 MeV electrons, known to originate from Jupiter. We report on the long term variations of this flux for the Ulysses ecliptic journey, and at the beginning of the out of ecliptic phase. They are well accounted for by…
Improved effective temperatures for hydrogen-deficient binary stars.
Jeffery, C. S.; Dudley, R. E.
Effective temperatures are obtained for all four known hydrogen-deficient binary stars, using published and archival photometry and new line-blanketed model atmospheres. These model atmospheres largely resolve the well-known mismatch between the theoretical and observed flux distribution for Upsilon Sgr, although a discrepancy persists at short wa…
Compton modelling of spectral variations observed in Z sources.
Wijers, R. A. M. J.; Schulz, N. S.
We present a simple model to fit the spectra of Z sources: a neutron star radiating at the centre of a hot scattering cloud. It is shown that the EXOSAT data of GX 17+2, GX 5-1, GX 340+0, and Sco X-2 (GX 349+2) in all branches of their Z profiles are represented well by this model. The neutron star temperature increases from the Horizontal Branch …