Search Publications
Planetary Camera Observations of the Central Parsec of M32
Lauer, Tod R.; Faber, S. M.; Currie, Douglas G. +8 more
Analysis of V band HST Planetary Camera images of the elliptical galaxy M32 shows that its nucleus is extremely dense and remains unresolved at even the HST diffraction limit. A combined approach of image deconvolution and model fitting is used to investigate the starlight distribution into limiting radii of 0.04" (0.14 pc at 700 kpc). The logarit…
Combined Infrared and Analytical Electron Microscope Studies of Interplanetary Dust Particles
Bradley, J. P.; Humecki, H. J.; Germani, M. S.
Ultramicrotomed thin sections (less than 100 nm thick) of eight chondritic interplanetary dust particles (IDPs) were studied by analytical electron microscopy and IR microspectroscopy with the objective of identifying IDPs or their specific components with IR spectral transmission characteristics at 10 microns similar to those of comets. Two IDPs …
Near-infrared spectroscopy of galactic Wolf-Rayet stars.
Schmutz, Werner; Howarth, Ian D.
We present high-quality near-IR spectra of 24 Galactic WR stars, of a broad range of subtypes, selected as having known distances. The data cover the region 0.97-1.12 micron and include the 10830-A He I triplet. Measurements of He I and He II lines, together with the absolute magnitudes, yield temperatures, luminosities, mass-loss rates, and termi…
Low-energy solar electrons and ions observed at Ulysses February-April, 1991: The inner heliosphere as a particle reservoir
Simnett, G. M.; Tappin, S. J.; Lanzerotti, L. J. +3 more
Ulysses observations at 2.5 AU of 38-315 keV electrons and 61-4752 keV ions during February-April 1991 suggest in several ways that, during periods of sustained high solar activity, the inner heliosphere serves as a “reservoir” for low-energy solar particles. Particle increases were not associated one-to-one with large X-ray flares because of thei…
The Cepheid Distance to IC 4182: Calibration of M V(max) for SN IA 1937C and the Value of H 0
Saha, A.; Panagia, Nino; Sandage, Allan +2 more
Cepheid variables with periods from 2 to more than 50 days have been found in IC 4182 from observations with the Hubble Space Telescope over a time interval of 47 days, comprised of 20 epochs. The period-luminosity relation from photometry of 27 Cepheids in the F555W HST magnitude system gives an apparent V distance modulus of (m - M)_AV_ = 28.47 …
Hubble Space Telescope Planetary Camera Images of R136
Lauer, Tod R.; Faber, S. M.; Holtzman, Jon A. +9 more
The Planetary Camera of the Hubble Space Telescope has been used to obtain broad and narrowband images of R136, the core of the massive star cluster 30 Doradus in the Large Magellanic Cloud. R136a, the brightest component of R136, is shown to have at least 12 separate components, including the eight originally identified by speckle interferometry.…
Improved Calculations for the C III lambda lambda 1907,1909 and SI III lambda lambda 1883,1892 Electron Density Sensitive Emission-Line Ratios, and a Comparison with IUE Observations
Feibelman, W. A.; Keenan, F. P.; Berrington, K. A.
Atomic data are used in conjunction with the statistical equilibrium code of Dufton (1977) to calculate relative C III and Si III level populations, and hence emission-line strengths for a range of electron temperatures and densities. It is assumed that photoexcitation and deexcitaton rates are negligible in comparison with the corresponding colli…
EXOSAT X-Ray Spectra of Quasars
Comastri, Andrea; Setti, Giancarlo; Zamorani, Giovanni +4 more
We have measured the X-ray spectra in the 0.1-10 keV energy range for 17 AGNs (mostly PG quasars) using the EXOSAT Low and Medium Energy arrays. The sample has been selected on the basis of soft X-ray flux and includes all the AGNs in the 1981 Zamorani et al. and 1986 Tananbaum et al. publications with an Einstein flux greater than 6x10^-12^ ergs …
Globular Cluster Photometry With the Hubble Space Telescope. I. Description of the Method and Analysis of the Core of 47 TUC
Schneider, Donald P.; Yanny, Brian; Bahcall, John N. +1 more
Accurate photometry for individual post-main-sequence stars in the core of the Galactic globular cluster 47 Tuc is presented and analyzed using an empirical point spread function model and Monte Carlo simulations. A V vs. V-I color-magnitude diagrams is constructed which shows several distinct stellar types, including RGB and HB stars. Twenty-four…
Jupiter's Magnetosphere: Plasma Description from the Ulysses Flyby
Goldstein, Bruce E.; Neugebauer, Marcia; Thomsen, Michelle F. +7 more
Plasma observations at Jupiter show that the outer regions of the Jovian magnetosphere are remarkably similar to those of Earth. Bow-shock precursor electrons and ions were detected in the upstream solar wind, as at Earth. Plasma changes across the bow shock and properties of the magnetosheath electrons were much like those at Earth, indicating th…