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The Hot White Dwarf Companions of HR 1608, HR 8210, and HD 15638
Bergeron, P.; Simon, Theodore; Landsman, Wayne
We have obtained low-dispersion IUE spectra of the late-type stars HD 15638 (F3 V), HR 1608 (=63 Eri, K0 IV), and HR 8210 (A8m). Each of these stars had been detected as a strong EUV source with the Wide Field Camera (WFC) aboard the ROSAT satellite. The short-wavelength IUE spectrum of each star reveals the presence of a hot white dwarf companion…
The Boron Abundance of Procyon
Lambert, David L.; Edvardsson, Bengt; Lemke, Michael
The B I 2496.8 A resonance line and HST/GHRS echelle spectra are used with model atmospheres and synthetic spectra to derive the B abundance of the F dwarfs Procyon (alpha CMi), Theta UMa, and Iota Peg. The B abundance (log epsilon(B)~/=2.3) of Theta UMa and Iota Peg is similar to that derived by Boesgaard and Heacox from the B II resonance line i…
A General Bayesian Image Reconstruction Algorithm with Entropy Prior. Preliminary Application to HST Data
Nunez, Jorge; Llacer, Jorge
This paper describes a general Bayesian iterative algorithm with entropy prior for image reconstruction. It solves the cases of both pure Poisson data and Poisson data with Gaussian readout noise. The algorithm maintains positivity of the solution; it includes case-specific prior information (default map) and flatfield corrections; it removes back…
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…
Periodic Low Amplitude Variations in the Brightness of Proxima Centauri
Benedict, G. F.; Franz, O. G.; Hemenway, P. D. +10 more
Using data acquired with Fine Guidance Sensor #3 on board the Hubble Space Telescope we find that the brightness of Proxima Centauri varies with an amplitude of 0.01 magnitude and a period P=41.6 +/- 0.6 days. We interpret this variation as rotational modulation of star spots or bright regions in the photosphere of Proxima Centauri. In a total of …
Imaging the Bipolar Nebula around HM Sagittae
Paresce, Francesco; Hack, Warren J.
Hubble Space Telescope Faint Object Camera UV images are presented for HM Sge showing a bipolar optical nebula similar to that in R Aquarii and RX Puppis. The nebula extends to a distance of 0.174" with a P.A. of 135 degrees inside a faint halo extending to a radius of 0.28". A kinematic distance to HM Sge based on positions of features in the neb…
Signal-to-Noise Ratios in IUE Low-Dispersion Spectra. II. Photometrically-Corrected Images
Ayres, Thomas R.
The character of detector noise is explored in photometrically-corrected images from the shortwavelength and longwavelength prime intensified vidicon cameras of the International Ultraviolet Explorer. A protocol is proposed for deriving realistic "noise models"--crucial to the application of Optimal extraction algorithms like that of Kinney, Bohli…
Rapid Mass-Loss Transients in VV Cephei
Stencel, Robert E.; Potter, Daniel E.; Bauer, Wendy H.
Biweekly ultraviolet observations of the red supergiant-hot dwarf binary, VV Cephei during 1991, obtained near third quadrature, have revealed the existence of short-term continuum variations. We infer these are superposed on an underlying emission-line spectrum. The viewing geometry of this long period system suggests we are seeing a process asso…
The Companion of the Classical Cepheid Z Lacertae
Evans, Nancy R.; Welch, Douglas L.
A deep IUE exposure of the Cepheid Z Lac from 1200 to 2000 A has been taken in order to search for light from the radial velocity companion. A faint signal of approximately 1.0 X 10^-14 ergs A^-1 sec^-1 cm^-2 has been detected in the dereddened spectrum. Because this is approximately the flux expected due to "camera artifacts," we consider that at…
Recent Results from the Hubble Space Telescope
Maran, Stephen P.; Kinney, Anne L.
A selection of recent findings from the Hubble Space Telescope (HST) are presented as a supplement to the earlier review by Kinney & Maran (1991). In stellar astrophysics, noteowrthy results include the first ultraviolet science from the High Speed Photometer, as well as spectroscopic studies of black hole and neutron star binaries and a flare…