Search Publications
Lithium Isotope Ratios in Halo Stars. III.
Rebull, L. M.; Hobbs, L. M.; Thorburn, J. A.
New, high-quality echelle spectra of four halo stars with metallicities in the range -2.0<=[Fe/H]<=-0.9 have been obtained in the region of the Li I λ6707 lines. Upper limits on the Li isotopic ratio ranging from 6Li/7Li<=0.02 to 6Li/7Li<=0.08 are found for HD 76932, HD 218502, and HD 284248.…
Detection of the Methyl Radical on Neptune
Encrenaz, T.; Feuchtgruber, H.; Bézard, B. +1 more
We report the first detection of the methyl radical (CH3) in the upper atmosphere of Neptune. Observations with the Short-Wavelength Spectrometer of the Infrared Space Observatory (ISO) satellite at a resolving power of 2200 revealed several emission features from the ν2 Q-branch of CH3 around 16.50 µm. The c…
Interplanetary Lyman α line profiles derived from SWAN/SOHO hydrogen cell measurements: Full-sky Velocity Field
Bertaux, Jean-Loup; Lallement, Rosine; Quémerais, Eric +3 more
We present here an analysis of 1 year of data obtained by the solar wind anisotropies (SWAN) instrument on board the SOHO spacecraft orbiting around the L1 Lagrange point at 1.5×106km sunward from Earth. This instrument is measuring the interplanetary Lyman α background due to solar photons backscattered by hydrogen atoms in the interpl…
HST/FOS Spatially Resolved Spectral Classification of Compact OB Groups in the Large Magellanic Cloud
Walborn, Nolan R.; Parker, Joel Wm.; White, Richard L. +3 more
Blue-violet spectrograms of individual components in four compact OB groups of the Large Magellanic Cloud, obtained with the Hubble Space Telescope (HST) Faint Object Spectrograph (FOS), are presented and discussed. Two of the massive multiple systems are in the 30 Doradus periphery, while the other two represent the core and the peripheral, trigg…
Detection of HD in the Orion molecular outflow
Wright, Christopher M.; Bertoldi, Frank; Timmermann, Ralf +2 more
We report a detection in the interstellar medium of an infrared transition within the electronic ground state of the deuterated hydrogen molecule, HD. Through a deep integration with the Short-Wavelength-Spectrometer (SWS) on board the Infrared Space Observatory (ISO), the pure rotational v=0-0 R(5) line at 19.43 mu m was detected toward the Orion…
Late-Time Optical and Ultraviolet Spectra of SN 1979C and SN 1980K
Filippenko, Alexei V.; Fransson, Claes; Chevalier, Roger A. +8 more
A low-dispersion Keck I spectrum of SN 1980K taken in 1995 August (t=14.8 yr after explosion) and a spectrum taken in 1997 November (t=17.0 yr) at the MDM Observatory show broad 5500 km s^-1 emission lines of Hα, [O I] 6300, 6364 Å, and [O II] 7319, 7330 Å. Weaker but similarly broad lines detected include [Fe II] 7155 Å, [S II] 4068, 4072 Å, and …
The Nuclear Spectral Energy Distribution of NGC 4395, the Least Luminous Type 1 Seyfert Galaxy
Moran, Edward C.; Filippenko, Alexei V.; Ho, Luis C. +5 more
We present X-ray (ROSAT), infrared, and radio observations of NGC 4395, which harbors the optically least luminous type 1 Seyfert nucleus discovered thus far. In combination with published optical and ultraviolet spectra, we have used these data to assemble the broadband spectral energy distribution (SED) of the galaxy's nucleus. Interestingly, th…
Mapping Low-Density Intergalactic Gas: A Third Helium LYalpha Forest
Williams, Benjamin F.; Anderson, Scott F.; Hogan, Craig J. +1 more
We present a new HST/STIS spectrum of the z=3.18 quasar PKS 1935-692 and summarize the spectral features shortward of 304 Å in the rest frame likely to be caused by foreground He II Lyalpha absorption. In accord with the previous results on two other quasars at similar redshifts, we demonstrate a correlation with the H I Lyalpha forest absorption …
Intrinsic Absorption Lines in the Seyfert 1 Galaxy NGC 5548: Ultraviolet Echelle Spectra from the Space Telescope Imaging Spectrograph
Crenshaw, D. Michael; Kraemer, Steven B.
We present the first observations of a Seyfert galaxy with the echelle gratings on the Space Telescope Imaging Spectrograph (STIS), which provide high-resolution (λ/Δλ~ 40,000) coverage of the intrinsic UV absorption lines in NGC 5548. We confirm the presence of five kinematic components of absorption in Lyα, C IV, and N V at radial velocities of …
On the origin of [O iv] emission in Wolf-Rayet galaxies
Schaerer, Daniel; Stasińska, Grażyna
We propose that the emission of the high excitation [O iv] 25.9 mu m line observed with ISO in