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GHRS and ORFEUS II Observations of the Highly Ionized Interstellar Medium toward ESO 141-055
Sembach, Kenneth R.; Savage, Blair D.; Hurwitz, Mark
We present Goddard High Resolution Spectrograph (GHRS) and ORFEUS II measurements of Si IV, C IV, N V, and O VI absorption in the interstellar medium of the Galactic disk and halo toward the nucleus of the Seyfert galaxy ESO 141-055. The high-ionization absorption is strong, with line strengths consistent with the spectral signature expected for h…
Analysis of Extreme-Ultraviolet Off-Limb Spectra Obtained with SUMER/SOHO: Ne VI-Mg VI Emission Lines
Wilhelm, Klaus; Dwivedi, Bhola N.; Curdt, Werner
We present results from a study of extreme-ultraviolet (EUV) off-limb spectra. These were obtained on 1996 June 20 with the Solar Ultraviolet Measurements of Emitted Radiation (SUMER) instrument on the Solar and Heliospheric Observatory (SOHO). With the capabilities of SUMER, we rastered the emitting source from 40" off the limb outward, and secur…
Imprint of the Sun on the Solar Wind
Habbal, Shadia Rifai; Woo, Richard
Observations of the inner corona in polarized brightness by the Mauna Loa Mk III K-coronameter at 1.15 Rsolar and soft X-rays by Yohkoh at 1.03 Rsolar are combined with 1995 Ulysses radio occultation measurements of the solar wind to demonstrate that the signatures of the coronal hole boundary, active regions, and bright poin…
Infrared Space Observatory Photometric Search of Main-Sequence Stars for Vega-Type Systems
Stencel, R. E.; Backman, D. E.; Fajardo-Acosta, S. B. +1 more
We obtained 3.6-20 µm photometry of 38 bright [IRAS Fν(12 µm)>0.7 Jy] main-sequence stars with the Infrared Space Observatory (ISO). Observations were conducted with the ISOPHOT instrument, in the single-pointing photometry mode, through filters at 3.6, 11.5, and 20.0 µm. We searched for excess (Vega-type) emission …
The Perseus B5 Molecular Cloud Halo: Measurements of Pressure, Temperature, and Composition
Andersson, B. -G.; Federman, S. R.; Wannier, Peter +1 more
We present GHRS observations of interstellar C I and CO toward three stars located in the direction of the Perseus region near the B5 molecular cloud and discuss these together with published results from a fourth sight line. The column densities of the three fine-structure levels of C I are used together with ground-based optical data and publish…
A Study of Microwave-selected Coronal Transient Brightenings
Nindos, A.; Kundu, M. R.; White, S. M.
We present the results of a search for radio-selected transient brightenings (TBs) in the solar atmosphere as a complement to the more common X-ray-selected surveys. The Sun was generally quiet during the observations, making these data sensitive to weak TBs both in and outside active regions. Five small impulsive events were identified in a set o…
Infrared Spectroscopy of NGC 4151: Infrared Space Observatory Observations and Narrow Emission Line Region Line Profiles
Lutz, D.; Genzel, R.; Sturm, E. +3 more
We present Infrared Space Observatory (ISO) Short-Wavelength Spectrometer (SWS) and ISOPHOT-S spectroscopy4 of the Seyfert galaxy NGC 4151. We detect a total of 17 fine-structure emission lines emitted by a wide range of low- and high-excitation ions, two rotational lines of molecular hydrogen, and the Brβ H I line. We find that the mid-IR fine-st…
The Kinematics of Stars Emerging from Expanding Shells: An Analysis of the Gould Belt
Moreno, Edmundo; Alfaro, Emilio J.; Franco, José
Using the available data for nearby stars from the Hipparcos catalog, we derive the velocity ellipsoid of dwarf O-B5.5 stars belonging to the Gould Belt (GB). The resulting vertex deviation for the whole sample of 252 stars is lv~-64deg+/-20deg, and this value is modified to lv=22deg+/-8d…
High-Frequency and High-Wavenumber Solar Oscillations
Basu, Sarbani; Antia, H. M.
We determine the frequencies of solar oscillations covering a wide range of degree (100<l<4000) and frequency (1.5<ν<10 mHz) using the ring diagram technique applied to power spectra obtained from Michelson Doppler Imager (MDI) data. The f-mode ridge extends up to l~3000, where the line width becomes very large, which implies a damping…
The Hubble Space Telescope Key Project on the Extragalactic Distance Scale. XVII. The Cepheid Distance to NGC 4725
Kelson, Daniel D.; Illingworth, Garth D.; Huchra, John P. +22 more
The distance to NGC 4725 has been derived from Cepheid variables as part of the Hubble Space Telescope Key Project on the Extragalactic Distance Scale. Thirteen F555W (V) and four F814W (I) epochs of cosmic-ray-split Wide Field and Planetary Camera 2 observations were obtained. Twenty Cepheids were discovered, with periods ranging from 12 to 49 da…