Search Publications
A study of lambda Bootis type stars in the wavelength region beyond 7000 Å
Kamp, I.; Paunzen, E.; Wiesemeyer, H. +1 more
The group of lambda Bootis type stars comprises late B- to early F-type, Population I objects which are basically metal weak, in particular the Fe group elements, but with the clear exception of C, N, O and S. One of the theories to explain the abundance pattern of these stars involves circumstellar or interstellar matter around the objects. Hence…
Iterative Techniques for the Decomposition of Long-Slit Spectra
Walsh, J. R.; Lucy, L. B.
Two iterative techniques are described for decomposing a long-slit spectrum into the individual spectra of the point sources along the slit and the spectrum of the underlying background. One technique imposes the strong constraint that the spectrum of the background be spatially invariant; the other relaxes this constraint. Both techniques are app…
Submillimetre and near-infrared observations of galaxies selected at 170 µm
Dole, H.; Lagache, G.; Puget, J. -L. +5 more
We present results from James Clerk Maxwell Telescope (JCMT) submillimetre (submm) observations of sources selected from the Infrared Space Observatory (ISO) FIRBACK (Far-infrared Background) survey, along with United Kingdom Infrared Telescope (UKIRT) near-infrared imaging of a subsample. This gives valuable insight into the brightest ~10 per cen…
Hubble Space Telescope/NICMOS Near-Infrared Imaging of the Proto-Planetary Nebula OH 231.8+4.2
Hora, J. L.; Tielens, A. G. G. M.; Latter, W. B. +2 more
We present observations of the bipolar nebula OH 231.8+4.2, made with the Hubble Space Telescope (HST) NICMOS camera, in three wide filter bands (F205W, F160W, and F110W). The images have excellent dynamic range after removal of low-level instrumental artifacts. In the F205W filter (λ~2.04 µm), we achieve a peak/rms of greater than 8000 with…
The 2001 April Burst Activation of SGR 1900+14: Pulse Properties and Torque
Frontera, F.; Hurley, K.; Mereghetti, S. +10 more
We report on observations of SGR 1900+14 made with the Rossi X-Ray Timing Explorer (RXTE) and BeppoSAX during the 2001 April burst activation of the source. Using these data, we measure the spin-down torque on the star and confirm earlier findings that the torque and burst activity are not directly correlated. We compare the X-ray pulse profile to…
The Wilson-Bappu effect: A tool to determine stellar distances
Pasquini, L.; Ortolani, S.; Pace, G.
Wilson & Bappu (\cite{orig}) have shown the existence of a remarkable correlation between the width of the emission in the core of the K line of Ca II and the absolute visual magnitude of late-type stars.
Here we present a new calibration of the Wilson-Bappu effect based on a sample of 119 nearby stars. We use, for the first time, width m…Common overabundance of 3He in high-energy solar particles
Torsti, J.; Kocharov, L.; Laivola, J.
Solar energetic particle (SEP) observations of the ERNE instrument (the Energetic and Relativistic Nuclei and Electron experiment) onboard the Solar and Heliospheric Observatory enable measurements of the 3He intensity in the high-energy range, >15 MeV nucleon-1, with a good statistical resolution. We report an overview of…
A 2.5-dimensional MHD Alfvén-wave-driven solar wind model
Habbal, S. R.; Li, X.; Hu, Y. Q.
A 2.5-dimensional MHD analysis of Alfvén-wave-driven solar wind in the heliospheric meridional plane is presented in order to extend the one-dimensional model proposed by [1967] to the two-dimensional case. In our model, no energy input is applied to the helmet streamer, while the solar wind along open field lines is assumed to be driven by Alfvén…
Star Formation and X-Ray Emission in Distant Star-Forming Galaxies
Cohen, Judith G.
About 45% of the point sources detected in the 2 Ms Chandra exposure of the Hubble Deep Field-North (HDF-N) can be matched with moderately bright galaxies with z<1.4 that have been studied by the Caltech Faint Galaxy Redshift Survey. Although the optical spectra of these galaxies appear normal, based on their X-ray properties ~20% of them appea…
Model for vortex turbulence with discontinuities in the solar wind
Tsurutani, B. T.; Verkhoglyadova, O. P.; Dasgupta, B.
A model of vortex with embedded discontinuities in plasma flow is developed in the framework of ideal MHD in a low b plasma. Vortex structures are considered as a result of 2-D evolution of nonlinear shear Alfvén waves in the heliosphere. Physical properties of the solutions and vector fields are analyzed and the observational aspects of the model…