Search Publications
Direct observational evidence for a heliospheric magnetic field with large excursions in latitude
Schwadron, N. A.; Zurbuchen, T. H.; Fisk, L. A.
Fisk has pointed out that the heliospheric magnetic field in fast solar wind, that is, at the higher heliographic latitudes, may undergo large excursions in heliographic latitudes, and thus that the field will deviate from the expected Archimedes spiral pattern. These excursions result from the interplay between the nonradial expansion of the sola…
O Stars in Transition. II. Fundamental Properties and Evolutionary Status of Ofpe/WN9 Stars from HST Ultraviolet Observations
Moffat, Anthony F. J.; Leitherer, Claus; Schmutz, Werner +4 more
We present new HST/FOS ultraviolet spectroscopic observations of seven LMC Ofpe/WN9 stars. We find that Ofpe/WN9 stars have slow winds with terminal velocities of about 400 km s-1 and high mass-loss rates of the order of 2-5 × 10-5 M⊙ yr-1. Ofpe/WN9 stellar temperatures and radii are in the range 30,000-…
The Green Line Corona and Its Relation to the Photospheric Magnetic Field
Michels, D. J.; Schwenn, R.; Howard, R. A. +8 more
Images of the green line corona made with the LASCO C1 coronagraph on SOHO are analyzed by applying current-free extrapolations to the observed photospheric field. The Fe XIV λ5303 emission is shown to be closely related to the underlying photospheric field strength. By modeling the observed intensity patterns as a function of latitude and height …
An ISO Long Wavelength Spectrometer detection of CH in NGC 7027 and an HeH^+ upper limit
Barlow, M. J.; Cernicharo, J.; Liu, X. -W. +10 more
We have detected an emission line at 149.18+/-0.06 µm in the ISO Long Wavelength Spectrometer (LWS) grating spectrum of the planetary nebula NGC 7027. This line coincides in wavelength with both the HeH^+ J=1-0 fundamental pure rotational line at 149.14 µm and the CH ^2Pi_3/2 (F_2) J=3/2-^2Pi_1/2 (F_2) J=1/2 fundamental pure rotational…
White dwarfs observed by the HIPPARCOS satellite.
Koester, D.; Vauclair, G.; Schmidt, H. +1 more
The HIPPARCOS satellite has measured trigonometric parallaxes for 20 white dwarfs. With the exception of one each of the spectral types DZ, DC, DB, DQ, the majority are of spectral type DA. We compare the parallaxes with the most recent ground-based determinations. From a spectroscopic analysis of new optical observations we determine atmospheric …
Elemental abundances in normal late-B and HgMn stars from co-added IUE spectra V. Mercury.
Smith, K. C.
Atmospheric mercury abundances are derived for a sample of 40 main-sequence, late-B stars, of which 14 are classified normal, and 26 are known chemically peculiar stars of HgMn or related He-weak types. The observational material for this study comprises co-added, short-wavelength IUE spectra encompassing the HgII λ1942 resonance line, coupled wit…
ISO Observations of Interstellar Ices and Implications for Comets
Ehrenfreund, P.; Dartois, E.; Habing, H. J. +4 more
We report on first ISO observations of interstellar ices in the direction of the protostellar object RAFGL 7009S. Due to its extreme extinction this source represents a unique target for the detection of interstellar ices. Identified molecules include H2O, CO, and CO2together with13CO2, CH4, O…
Hot Interstellar Gas in the Irregular Galaxy NGC 4449
Chu, You-Hua; Bomans, Dominik J.; Hopp, Ulrich
NGC 4449 is an irregular galaxy with a moderately high star formation activity. The massive stars in NGC 4449 have given rise to many bright HII regions, superbubbles, supergiant shells, and ``chimney-like'' radial filaments. ROSAT X-ray observations of NGC4449 have revealed four point-like sources and a wide-spread diffuse emission. The spectral …
Widespread water vapour absorption in SGR B2.
Clegg, P.; Caux, E.; Cernicharo, J. +6 more
We report the discovery of widespread water vapour absorption in the 2_12_-1_01_ 179.5µm transition toward the SgrB2 molecular cloud. The data were obtained with the Long Wavelength Spectrometer (LWS) on board the ISO satellite. A raster map centered on SgrB2 made with the LWS grating clearly shows the 179.5µm H_2_O line in absorption …
Hubble Space Telescope Observations of the Dwarf Nova WZ Sagittae: A Very Rapidly Rotating White Dwarf
Szkody, Paula; Sion, Edward M.; Cheng, F. H. +1 more
We present Hubble Space Telescope Goddard High-Resolution Spectrograph G140L spectra of the white dwarf in WZ Sge, exposed during quiescence. Our best-fitting synthetic spectra yield a rapidly rotating white dwarf with velocity Vrot sin i = 1200+300-400 km s-1, white dwarf effective temperature Twd<…