Search Publications
Gas Kinematics and Ionization along the Extended Sight Line to HD 116852
Sembach, Kenneth R.; Savage, Blair D.
We present Goddard High-Resolution Spectrograph intermediate observations of the interstellar medium toward HD 116852, a low halo star at a distance of 4.8 kpc (z = -1.3 kpc) in the direction l = 304. deg 9, b = 16.deg 1. The small science aperture observations have signal-to-noise ratios ranging from 30 to 90 and resolutions of 11 to 18 km/s (FWH…
N III Intercombination Lines in the IUE Spectra of Gaseous Nebulae
Feibelman, W. A.; Dufton, P. L.; Keenan, F. P. +3 more
Theoretical N III electron density-sensitive emission-line ratios involving intercombination transitions, derived using recent calculations of electron impact excitation rates and oscillator strengths, are presented for R1 = I(1754.0 Å)/I(1749.7 Å), R2 = I(1752.2 Å)/I(1749.7 Å), R3 = I(1748.6 Å)/I(1749.7 Å), and R<…
The Chromospheric Structure of the Cool Giant Star G Herculis
Johnson, Hollis R.; Luttermoser, Donald G.; Eaton, Joel
Non-Local Thermodynamic Equilibrium (LTE) calculations of semiempirical chromospheric models are presented for 30 g Her (M6 III). This star is one of the coolest (Teff = 3250 K) SRb (semiregular) variable stars and has a mass perhaps as great as 4 solar mass. Chromospheric features we have observed in its spectrum include Mg II h and k;…
A Statistical Equilibrium Analysis of Interstellar CO toward zeta Ophiuchi as Recorded by the Goddard High Resolution Spectrograph
Smith, Andrew M.; Bruhweiler, Frederick C.; Lyu, Cheng-Hsuan
High-resolution and high signal-to-noise ratio echelle observations made by the Goddard High Resolution Spectrograph (GHRS), aboard the Hubble Space Telescope, of molecular (12)C(16)O and (13)C(16)O in the absorbing gas toward zeta Oph are reported. A statistical equilibrium model, incorporating a different way of dealing with the radiation field …
Comparison of New Experimental and Astrophysical f-Values for Some RU II Lines, Observed in HST Spectra of chi LUPI
Wahlgren, Glenn M.; Leckrone, David S.; Johansson, Sveneric G. +6 more
We report an experimental absolute oscillator strengths for 18 UV lines of Ru II, obtained by combining laser-induced flourescence measurements of radiative lifetimes and branching fractions from line intensities in a calibrated Fourier-transform spectrum Hubble Space Telescope/Goddard High Resolution Spectrograph (HST/GHRS) observations of the sp…
Narrowband HST Imagery of the Young Planetary Nebula Henize 1357
Bobrowsky, M.
We present Hubble Space Telescope (HST) Planetary Camera observations showing the first optically resolved images of the planetary nebula Henize 1357 . The small size of this object has heretofore precluded optical investigations of its morphology. In H-beta, He 3-1357 appears to have an equatorial ring of enhanced density tilted approximately 56 …
Low-Velocity Variability in the Stellar Wind of HD 152408 (O8: Iafpe)
Fullerton, A. W.; Prinja, Raman K.
We describe high-quality, spectroscopic time series observations of variability at low velocities in the stellar wind of the extreme O-supergiant HD 152408. These observations were obtained during a monitoring campaign coordinated between Australia and Chile in 1992 July. Systematic variability on hourly time scales is particularly apparent in the…
Intersystem Transitions of Interstellar Carbon Monoxide toward zeta Ophiuchi
Federman, S. R.; Lambert, David L.; Cardelli, Jason A. +2 more
Absorption from seven intersystem (triplet-singlet) transitions of interstellar (12)CO were detected in ultraviolet spectra of zeta Oph. The observed equivalent widths are approximately consistent with the transitions' predicted f-values and the (12) CO column density derived from the weakest of the observed A-X bands. These unsaturated intersyste…
Interstellar Gas and Dust in the Young Cluster IC 348
Snow, Theodore P.; Hanson, Margaret Murray; Seab, Gregory C. +1 more
We have completed a multiband absorption- and emission-line study of a star embedded in the young cluster IC 348, to determine the environmental effect of star formation on the interstellar medium (ISM) local to the region. The hottest and youngest star in IC 348 is BD +31 deg 643, a B5 V star which samples the inner bright nebular region. The nea…
An Ultraviolet and Visible Spectroscopic Study of a Pulsational Cycle of RY Sagittarii
Cottrell, P. L.; Lawson, W. A.; Clayton, Geoffrey C. +3 more
High-dispersion visible and ultraviolet spectra and UBVRI photometry, covering a complete pulsation of the R Coronae Borealis star RY Sgr, have been obtained. The UV spectra were the first high-dispersion data ever obtained for the star. Together these observations comprise the most complete data set covering an RCB star pulsation cycle. The cycle…