Search Publications
Modulation effects of anisotropic perpendicular diffusion on cosmic ray electron intensities in the heliosphere
Ferreira, S. E. S.; Potgieter, M. S.; Heber, B. +1 more
The modulation of cosmic ray electrons provides a useful tool to study the diffusion tensor applicable to heliospheric modulation. Electron modulation responds directly to the assumed energy dependence of the diffusion coefficients below ~500 MeV in contrast to protons which experience large adiabatic energy losses below this energy. As a result o…
Young Red Spheroidal Galaxies in the Hubble Deep Fields: Evidence for a Truncated Initial Mass Function at ~2 Msolar and a Constant Space Density to Z ~ 2
Broadhurst, Tom; Bouwens, Rychard J.
The optical-IR images of the northern and southern Hubble Deep Fields are used to measure the spectral and density evolution of early-type galaxies. The mean spectral energy distribution is found to evolve passively toward a mid-F star-dominated spectrum by z~2, becoming more sharply peaked around the 4000 Å break. We demonstrate with realistic si…
The effective temperature scale of giant stars (F0-K5). III. Stellar radii and the calibration of convection
Salaris, M.; Arribas, S.; Asensio Ramos, A. +2 more
We present an analysis of radii of giant stars with 6200 K>= T_eff >= 3800 K based on angular diameters obtained by means of the IRFM and distances computed from Hipparcos parallaxes. In order to asses the reliability of IRFM diameters we have considered a selected sample of stars whose diameters have been directly measured by interferometri…
Saturn's Ring-Plane Crossings of August and November 1995: A Model for the New F-Ring Objects
Nicholson, Philip D.; Sicardy, Bruno; Karkoschka, Erich +2 more
We analyze observations made in August and November 1995 during the Earth and Sun crossings of Saturn's ring plane, respectively. The August 1995 observations combine data taken with the Adonis adaptive optics system at the European Southern Observatory (ESO) and images from the Hubble Space Telescope (HST). The November 1995 data are based on HST…
Hubble Space Telescope NICMOS Color Transformations and Photometric Calibrations
Rich, R. Michael; Jablonka, Pascale; Frogel, Jay A. +4 more
This paper presents color transformations for Hubble Space Telescope Near Infrared Camera and Multi-Object Spectrometer (NICMOS) camera 2 observations to the ground-based Carnegie image tube photometric system at Cerro Tololo Inter-American Observatory (CIT/CTIO), using observations of 19 moderately bright, red stars in Baade's window in the color…
The Globular Cluster Systems in the Coma Ellipticals. III. The Unique Case of IC 4051
Harris, William E.; Woodworth, Sean C.
IC 4051 is a giant E galaxy on the outskirts of the Coma Cluster core. Using archival HST WFPC2 data, we derive the metallicity distribution, luminosity function, and spatial structure of its globular cluster system (GCS). The metallicity distribution derived from the V-I colors has a mean <Fe/H>~=-0.3, a near-complete lack of metal-poor clu…
ISO-LWS observations of rotational CO lines from C-rich objects: AFGL 2688, AFGL 618 and NGC 7027
Justtanont, K.; Barlow, M. J.; Tielens, A. G. G. M. +6 more
We present ISO-LWS full scan observations of CO rotational emission lines (J=14-13 up to J=37- 36) from two C-rich post-AGB objects, AFGL 2688; AFGL 618, and one C-rich PN, NGC 7027. The presence of high rotational lines cannot be explained by a spherical, constant velocity wind during the previous AGB phase, but indicates a layer of warm, dense g…
Looking at the photon-dominated region in NGC 2024 through FIR line emission
White, G. J.; Benedettini, M.; Spinoglio, L. +6 more
We present the ISO-LWS spectra (45-200 mu m) of both the molecular cloud NGC 2024 and its associated HII region. We observed the two Class 0 objects FIR3 and FIR5 and the infrared source IRS2. All the spectra appear quite similar, with approximately the same strength high-J CO rotational lines (from Jup=17 to Jup=14), and ato…
The Role of Velocity Redistribution in Enhancing the Intensity of the HE II 304 Å Line in the Quiet-Sun Spectrum
Andretta, Vincenzo; Brosius, Jeffrey W.; Thompson, William T. +5 more
We present observational evidence of the effect of small-scale (``microturbulent'') velocities in enhancing the intensity of the He II λ304 line with respect to other transition region emission lines, a process we call ``velocity redistribution,''. We first show results from the 1991 and 1993 flights of SERTS (Solar EUV Rocket Telescope and Spectr…
Theoretical Oscillator Strengths inPr III and Application to Some CP Stars
Quinet, P.; Frémat, Y.; Palmeri, P. +2 more
A set of transition probabilities is obtained for the first time for many transitions of Pr III of astrophysical interest. A relativistic Hartree-Fock method, combined with a least-squares fitting of the available experimental levels, including a large number of newly determined values, has been used for the calculations in which configuration int…