Search Publications
On the Nature of Intrinsic Absorption in Reddened Seyfert 1 Galaxies
Kraemer, S. B.; Crenshaw, D. M.
We discuss the origin of the ``dusty lukewarm absorber,'' which we previously identified in the reddened Seyfert 1 galaxies NGC 3227 and Akn 564. This absorber is characterized by saturated UV absorption lines (C IV, N V) near the systemic velocity of the host galaxy and is likely responsible for reddening both the continuum and emission lines (in…
Atomic Oxygen Abundance in Molecular Clouds: Absorption toward Sagittarius B2
Schilke, P.; Lis, D. C.; Phillips, T. G. +3 more
We have obtained high-resolution (~35 km s-1) spectra toward the molecular cloud Sgr B2 at 63 µm, the wavelength of the ground-state fine-structure line of atomic oxygen (O I), using the ISO-LWS instrument. Four separate velocity components are seen in the deconvolved spectrum, in absorption against the dust continuum emission of …
The Type IC SN 1990B in NGC 4568
Dickinson, Mark; Filippenko, Alexei V.; Shields, Joseph C. +25 more
We present a study of the Type Ic supernova (SN) 1990B that includes most of the observations obtained from around the world. The combined data set comprises 84 BV(RI)c photometric points spanning approximately 360 days after maximum light and 14 spectra from 5 up to ~150 days after maximum light. In contrast to other Type Ic SNe, SN 19…
Phase-resolved Hubble Space Telescope/STIS Spectroscopy of the Exposed White Dwarf in the High-Field Polar AR Ursae Majoris
Szkody, Paula; Gänsicke, Boris T.; Jordan, Stefan +1 more
Phase-resolved Hubble Space Telescope (HST)/Space Telescope Imaging Spectrograph (STIS) ultraviolet spectroscopy of the high-field polar AR UMa confirms that the white dwarf photospheric Lyα Zeeman features are formed in a magnetic field of ~200 MG. In addition to the Lyα π and σ+ components, we detect the forbidden hydrogen 1s0
Infrared and Millimetric Study of the Young Outflow Cepheus E
Cernicharo, José; Testi, Leonardo; Molinari, Sergio +3 more
The Cepheus E outflow has been studied in the mid- and far-IR using the ISOCAM and Long Wavelength Spectrometer (LWS) instruments and at millimetric wavelengths using the Owens Valley Radio Observatory (OVRO). In the near- and mid-IR, its morphology is similar to that expected for a jet-driven outflow, where the leading bow shocks entrain and acce…
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…