Search Publications
A study of a high resolution IUE spectrum of AM Canum Venaticorum.
Sion, E. M.; Solheim, J. -E.
We have obtained the first high resolution IUE spectrum of the helium-rich, cataclysmic variable star AM CVn. The spectrum is greatly underexposed, but we can still detect both wide and narrow line profiles. We report broad, shortward-shifted, P-Cygni-like absorption and in some cases emission lines in the far UV high ionization resonance lines of…
Independent Distance Determinations to Milky Way Cepheids in Open Clusters and Associations. I. The Binary Cepheid DL CAS in NGC 129
Welch, Douglas L.; Matthews, Jaymie M.; Gieren, Wolfgang P. +2 more
As an eight-day Cepheid which is both a component of a spectroscopic binary and a member of the open cluster NGC 129, DL Cas is potentially a very accurate calibrator of the period-luminosity (PL) relation and Cepheid mass. From 160 high-precision (sigma less than 1.5 km/s) radial velocity observations made with the CORAVEL and DAO spectrometers -…
Ultraviolet Spectral Classification and Stellar Winds in a Sample of Be and Standard Stars
Slettebak, Arne
Equivalent widths of 16 lines of C I, C II, C III, C IV, Si II, Si III, Si IV, Al II, Al III, Fe II, and Fe III, plus centriod and edge velocities of the Si IV and C IV lines, were measured in International Ultraviolet Explorer spectra of 39 Ble-B8e and 18 B1-B8 standard non-emission-line stars. These suggest the following: (1) Certain line ratios…
Spectropolarimetric Variability in OB Stars
Bjorkman, K. S.
Data from the Wisconsin spectropolarimetric monitoring program provide information about the polarimetric variability of numerous types of stars. Examining the data that exist thus far, we find, not surprisingly, that many OB stars, especially OB supergiants and Be stars, are polarimetric variables. Be stars show the most extreme variability as a …
Flatfielding and Photometric Accuracy of The First Hubble Space Telescope Wide Field Camera
Illingworth, Garth D.; Forbes, Duncan A.; Bershady, Matthew A. +2 more
Long exposures with the original Hubble Space Telescope (HST) Wide Field Camera (WFC) through the F555W and F785LP filters show gradients in the background following standard pipeline calibration. We show that these gradients also appear in stellar photometry, and thus must be predominantly the result of inaccurate flatfielding at a level of 10 to…
Observations of SN 1987A with the COSTAR-corrected Faint Object Camera
Panagia, N.; Jakobsen, P.; Macchetto, F. +1 more
New near-ultraviolet and visible [O III] observations of SN 1987A obtained 2511 and 2533 days after outburst with the Corrective Optics Space Telescope Axial Replacement (COSTAR) corrected Faint Object Camera on board the Hubble Space Telescope are presented. Even though the supernova is now very faint (m ~ 19), the new data are of dramatically hi…
Shock normal determination for multiple-ion shocks
Coates, A. J.; Neubauer, F. M.; Motschmann, U. +1 more
We have adapted the single-ion Viñas and Scudder (1986) solution to the Rankine-Hugoniot problem to a multiple-ion solution. Using this technique, we can calculate a shock normal direction, shock speed, best estimate of the upstream and downstream magnetic field and plasma asymptotic states, and θBn, the angle between the shock normal a…
An unusual high-redshift object discovered with the Hubble Space Telescope : peculiar starburst galaxy or new gravitational lens?
Glazebrook, K.; Griffiths, R.; Ellis, R. +2 more
We report the discovery of an object with a very peculiar structure, using observations from the refurbished Hubble Space Telescope (HST) as part of the Medium-Deep Survey project. The object includes four compact blue components arranged around an extended red component, with mutual separations of <1 arcsec. Using a ground-based spectrum as an…
Evolution of Solitary Density Waves in Stellar Winds of Early-Type Stars: A Simple Explanation of Discrete Absorption Component Behavior
Waldron, Wayne L.; Altner, Bruce; Klein, Larry
We model the evolution of a density shell propagating through the stellar wind of an early-type star, in order to investigate the effects of such shells on UV P Cygni line profiles. Unlike previous treatments, we solve the mass, momentum, and energy conservation equations, using an explicit time-differencing scheme, and present a parametric study …
3 Puppis : a peculiar object with infrared excess.
Rovero, Adrian C.; Ringuelet, Adela E.
We present a model that accounts for the UV, photographic, and IR observations of 3 Puppis. The model consists of a binary system in which the primary is an A supergiant with a mild chromosphere; the primary fills its Roche lobe. The velocity law in the extended atmosphere, which is responsible for the density distribution of the gas, and a chromo…