Search Publications
The C-C-C bending modes of PAHs: a new emission plateau from 15 to 20 µm
Waters, L. B. F. M.; Hony, S.; Tielens, A. G. G. M. +9 more
We have obtained 2.5-45 mu m spectra of a sample of compact H ii regions, YSOs and evolved stars in order to study the origin and evolution of interstellar Polycyclic Aromatic Hydrocarbon molecules (PAHs). Besides the well-known, strong PAH bands at 3.3, 6.2, 7.7, 8.6, and 11.2 mu m, these spectra reveal for the first time, a ubiquitous emission p…
STIS Observations of HE II Gunn-Peterson Absorption toward Q0302-003
Tripp, Todd M.; Jenkins, Edward B.; Hubeny, Ivan +5 more
The ultraviolet spectrum (1145-1720 Å) of the distant quasar Q0302-003 (z=3.286) was observed at 1.8 Å resolution with the Space Telescope Imaging Spectrograph aboard the Hubble Space Telescope. A total integration time of 23,280 s was obtained. The spectrum clearly delineates the Gunn-Peterson He II absorption trough, produced by He II Lyα along …
Variations of Saturn's radio rotation period measured at kilometer wavelengths
Lecacheux, Alain; Galopeau, Patrick H. M.
The Unified Radio and Plasma Wave (URAP) experiment on the interplanetary spacecraft Ulysses is able to detect the Saturnian kilometric radiation (SKR) thanks to the high sensitivity of the receiver and in spite of the remoteness of the planet (8-13 AU). Our knowledge about Saturn comes essentially from the observations by the two Voyager spacecra…
The Local Lyα Forest. II. Distribution of H I Absorbers,Doppler Widths, and Baryon Content
Shull, J. Michael; Stocke, John T.; Penton, Steven V.
In Paper I of this series we described observations of 15 extragalactic targets taken with the Hubble Space Telescope+GHRS+G160M grating for studies of the low-z Lyα forest. We reported the detection of 111 Lyα absorbers at significance level (SL) >=3 σ, 81 with SL>=4 σ, in the redshift range 0.002<z<0.069, over a total path length cΔz…
The Origin of Runaway Stars
de Bruijne, J. H. J.; de Zeeuw, P. T.; Hoogerwerf, R.
Milliarcsecond astrometry provided by Hipparcos and by radio observations makes it possible to retrace the orbits of some of the nearest runaway stars and pulsars to determine their site of origin. The orbits of the runaways AE Aurigae and µ Columbae and of the eccentric binary ι Orionis intersected each other ~2.5 Myr ago in the nascent Tra…
An IUE Atlas of Pre-Main-Sequence Stars. II. Far-Ultraviolet Accretion Diagnostics in T Tauri Stars
Valenti, Jeff A.; Johns-Krull, Christopher M.; Linsky, Jeffrey L.
We use our ultraviolet (UV) atlas of pre-main-sequence stars constructed from all useful, short-wavelength, low-resolution spectra in the International Ultraviolet Explorer (IUE) satellite Final Archive to analyze the short-wavelength UV properties of 49 T Tauri stars (TTSs). We compare the line and continuum fluxes in these TTSs with each other a…
The Three-dimensional Structure of the Warm Local Interstellar Medium. II. The Colorado Model of the Local Interstellar Cloud
Redfield, Seth; Linsky, Jeffrey L.
In this second paper in a series on the structure of the local interstellar medium (LISM), we construct a three-dimensional model of the local interstellar cloud (LIC) based on Hubble Space Telescope (HST), Extreme Ultraviolet Explorer (EUVE), and ground-based Ca II spectra. Starting with hydrogen column densities derived from deuterium column den…
Time-Distance Helioseismology with f Modes as a Method for Measurement of Near-Surface Flows
Duvall, T. L., Jr.; Gizon, L.
Travel times measured for the f mode have been used to study flows near the solar surface in conjunction with simultaneous measurements of the magnetic field. Previous flow measurements of Doppler surface rotation, small magnetic feature rotation, supergranular pattern rotation, and surface meridional circulation have been confirmed. In addition, …
Observations of Irradiance Variations
Fröhlich, Claus
Since November 1978 a complete set of total solar irradiance (TSI) measurements from space is available, yielding a time series of 21 years. From measurements made by different space radiometers (HF on NIMBUS-7, ACRIM I on SMM, ACRIM II on UARS and VIRGO on SOHO) a composite record of TSI can be compiled. The corrections which are needed for each …
Supra-arcade Downflows in Long-Duration Solar Flare Events
McKenzie, D. E.
This report seeks to introduce the reader to a set of observations made during the decay phase of long-duration event (LDE) flares on the Sun. In a number of events, the soft X-ray images from Yohkoh SXT indicate a downward-directed flow field in the region immediately above the flare arcade. The prototypical event is the M5 flare of 20 January 19…