Search Publications
Hubble Space Telescope Spectroscopy of the Dwarf Nova RX Andromedae. I. The Underlying White Dwarf
Szkody, Paula; Sion, Edward M.; Cheng, F. H. +3 more
We obtained Hubble Space Telescope Goddard High Resolution Spectrograph phase-resolved spectroscopic observations of the dwarf nova RX Andromedae at three times in its outburst cycle: (1) near the end of an extraordinarily deep and long dwarf nova quiescence, 3 months after the last outburst; (2) during the rise to outburst; and (3) near the end o…
Modeling Mid-Ultraviolet Spectra. I. Temperatures of Metal-poor Stars
Dorman, Ben; Rood, Robert T.; Peterson, Ruth C.
Determining the properties of remote globular clusters and elliptical galaxies using evolutionary population synthesis requires a library of reliable model stellar fluxes. Empirical libraries are limited to spectra of stars in the solar neighborhood, with nearly solar abundances and abundance ratios. We report here a first step toward providing a …
Time-resolved Hubble Space Telescope Spectroscopy of Four Eclipsing Magnetic Cataclysmic Variables
Schmidt, Gary D.; Stockman, H. S.
Time-resolved, multiepoch, Hubble Space Telescope ultraviolet eclipse spectrophotometry is presented for the magnetic cataclysmic variables (MCVs) V1309 Ori, MN Hya, V2301 Oph, and V1432 Aql. Separation of the eclipse light curves into specific wavebands allows the multiple emission components to be distinguished. Accretion-heated photospheric spo…
Differences in the Sun's Radiative Output in Cycles 22 and 23
de Toma, Giuliana; White, Oran R.; Chapman, Gary A. +4 more
Analysis of the current solar cycle 23 shows a greater increase in total solar irradiance (TSI) for the early phase of this cycle than expected from measurements of the total magnetic flux and traditional solar activity indices, which indicate that cycle 23 is weaker than cycle 22. In contrast, space observations of TSI from the Solar and Heliosph…
Near-Infrared Coronagraphic Imaging of the Circumstellar Disk around TW Hydrae
Barnes, J. W.; Brown, R. H.; Koerner, D. W. +2 more
We present ground-based near-infrared (H-band) imaging of the circumstellar disk around the nearby classical T Tauri star TW Hydrae. The scattered-light image shows a face-on disk with a radius of 4" (corresponding to 225 AU) and a morphology that agrees with recent images from the Hubble Space Telescope and the Very Large Array. The best-fit powe…
A Search for High-Velocity Be Stars
Gies, D. R.; Berger, D. H.
We present an analysis of the kinematics of Be stars based upon Hipparcos proper motions and published radial velocities. We find approximately 23 of the 344 stars in our sample have peculiar space motions greater than 40 km s-1 and up to 102 km s-1. We argue that these high-velocity stars are the result of either a supernova…
Differential Flow Speeds of Ions of the Same Element: Effects on Solar Wind Ionization Fractions
Esser, Ruth; Edgar, Richard J.
In previous studies of solar wind ion fractions it has always been assumed that ions of the same element flow with the same flow speed. In the present paper, we investigate the effects of differential flow speeds between different ionization states of the same element on the formation of O, C, Mg, Si, and Fe ions. We show that if the difference in…
Keck LWS Images of the Compact Nebula around RY Scuti in the Thermal Infrared
Smith, Nathan; Gehrz, Robert D.; Yahil, Amos +2 more
We report new 3 to 20 µm Keck Telescope images of the massive eclipsing binary RY Scuti with ~0.25" spatial resolution. These images show complex structure near the diffraction limit of the 10 m telescope in a nebula less than 2" across. The limb-brightened structure is consistent with optically thin emission from a circumstellar torus. At 3…
Optical Spectrum of the Compact Planetary Nebula IC 5117
Feibelman, Walter A.; Hyung, Siek; Aller, Lawrence H. +1 more
High-resolution spectroscopic data of the very compact planetary nebula IC 5117 were obtained in optical wavelengths of 3700-10050 Å with the Hamilton Echelle Spectrograph at the Lick Observatory and have been analyzed along with the International Ultraviolet Explorer UV archive data. Although a diagnostic diagram shows significant density and tem…
RR Lyrae Variables in the Globular Clusters of M31: A First Detection of Likely Candidates
Clementini, G.; Cacciari, C.; Bellazzini, M. +3 more
The purpose of this Letter is to show that RR Lyrae variables exist and can be detected in M31 globular clusters. We report on the first tentative identification of RR Lyrae candidates in four globular clusters of the Andromeda galaxy, i.e., G11, G33, G64, and G322. Based on Hubble Space Telescope Wide Field Planetary Camera 2 archive observations…