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71 Tauri: Hyades Enigma Resolved?
Ayres, Thomas R.; Simon, Theodore
71 Tauri (HD 28052; F0 IV-V) is an enigmatic object for two reasons: (1) it is the second brightest X-ray source in the Hyades, yet early F stars as a rule are not strong coronal emitters; and (2) it lies a magnitude above the cluster main sequence, but radial velocity studies and speckle imaging suggest that it is single. Recently, long-slit ultr…
ISO far-infrared observations of rich galaxy clusters. III. Abell 2029, Abell 2052, Abell 2142
Nørgaard-Nielsen, H. U.; Pedersen, K.; Hansen, L. +3 more
A sample of five rich galaxy clusters has been mapped by ISO at 60 mu m, 100 mu m, 135 mu m, and 200 mu m using the PHT-C camera. In previous papers Abell 2670 and Sérsic 159-03 were discussed. Here we present the results for Abell 2029, Abell 2052, and Abell 2142. The conclusion of the survey is that the relatively small fields (~60 square arc mi…
On the Correlation between CO Absorption and Far-Ultraviolet Nonlinear Extinction toward Galactic OB Stars
Feldman, Paul D.; Andersson, B. -G.; Burgh, Eric B. +1 more
A sample of 59 sight lines to reddened Galactic OB stars was examined for correlations of the strength of the CO Fourth Positive (A1Π-X1Σ+) absorption band system with the ultraviolet interstellar extinction curve parameters. We used archival high-dispersion NEWSIPS IUE spectra to measure the CO absorption for comp…
Mode Identification in Pulsating White Dwarfs Using the HST
Kepler, S. O.; Clemens, J. C.; Jiang, X. J. +3 more
We obtained time-resolved ultraviolet spectroscopy for the pulsating DA stars G 226-29 and G 185-32 and for the pulsating DBV star PG 1351+489 with the Hubble Space Telescope Faint Object Spectrograph, to compare the ultraviolet to the optical pulsation amplitudes. We find that for essentially all observed pulsation modes the amplitude rises to th…
The spectral variations of the O-type runaway supergiant HD 188209
Galeev, A.; Herrero, A.; Kaufer, A. +4 more
We report spectral time series of the late O-type runaway supergiant HD 188209. Radial velocity variations of photospheric absorption lines with a possible quasi-period of ~6.4d have been detected in high-resolution echelle spectra. Night-to-night variations in the position and strength of the central emission reversal of the Hα profile occurring …
Emission lines of O bt III in the optical and ultraviolet spectra { } of planetary nebulae
Feibelman, W. A.; Keenan, F. P.; Aller, L. H. +3 more
Recent R-matrix calculations of electron impact excitation rates in O Iii are used to calculate electron temperature and density-dependent emission line ratios R1 = I(4363 Å) / I(4960 Å+ 5007 Å), R2 = I(1661 Å+ 1667 Å) / I(4960 Å+ 5007 Å) and R3 = I(2322 Å) / I(1661 Å+ 1667 Å), for a range of electron temperatures …
Chemical enrichment by massive stars
Thuan, T. X.; Izotov, Y. I.
Heavy element abundances derived from high-quality ground-based and Hubble Space Telescope (HST) spectroscopic observations of low-metallicity blue compact galaxies (BCGs) with oxygen abundances 12+log O/H between 7.1 and 8.3 are discussed. None of the heavy element-to-oxygen abundance ratios studied here (C/O, N/O, Ne/O, Si/O, S/O, Ar/O, Fe/O) de…
Far-infrared [C Ii]/continuum ratio toward the central kiloparsecs of M31. Comparison with that of our Galaxy
Mochizuki, K.
We observed the nearby spiral galaxy M31 with the Long-Wavelength Spectrometer on board the Infrared Space Observatory. Far-infrared line-to-continuum ratios of [C II] / 100 µ m =~ 6 x 10-3 were obtained for the central kiloparsec region along the major axis of the galaxy. These ratios are 2-3 times higher than those in the Galact…
Astrophysics in 1999
Aschwanden, Markus J.; Trimble, Virginia
The year 1999 saw the arrival of a star with three planets, a universe with three parameters, and a solar corona that could be heated at least three ways. In addition, there were at least three papers on every question that has ever been asked in astrophysics, from ``Will the Universe expand forever?'' to ``Does mantle convection occur in one or t…
Single Be stars as binary ejecta?
Rinehart, S. A.
Among the mechanisms suggested for the creation of discs around Be stars is interaction with binary companions. This idea has largely been dismissed, because the majority of Be stars have no observed companion. This difficulty can be circumvented if single Be stars are actually ejected from binary systems (owing, for instance, to the supernova of …