Search Publications
Spectroscopic Observation of the Planetary Nebula IC 4846
Hyung, Siek; Aller, Lawrence H.; Lee, Woo-baik
A high-dispersion optical (3700-10100 Å) spectrum was secured with the Hamilton echelle spectrograph at the coudé focus of the 120 inch (3 m) Shane telescope at Lick Observatory, with the goal of deriving chemical abundances for the compact planetary nebula IC 4846. We also remeasured the UV spectra from the IUE archive. Diagnostics indicate that …
A Cepheid is No More: Hubble's Variable 19 in M33
Stanek, K. Z.; Macri, L. M.; Sasselov, D. D.
We report on the remarkable evolution in the light curve of a variable star discovered by Hubble in M33 and classified by him as a Cepheid. Early in the 20th century, the variable, designated as V19, exhibited a 54.7 day period, an intensity-weighted mean B magnitude of 19.59+/-0.23 mag, and a B amplitude of 1.1 mag. Its position in the period-lum…
Modulation of galactic and anomalous cosmic rays in the inner heliosphere
Heber, B.
Our knowledge on how galactic and anomalous cosmic rays are modulated in the inner heliosphere has been dramatically enlarged due to measurements provided by several missions launched in the past ten years. The current paradigma of singly charged anomalous cosmic rays has been confirmed by recent measurements from the SAMPEX and ACE satelite. Ulys…
Evolution of globular cluster systems in three galaxies of the Fornax cluster
Donnarumma, I.; Capuzzo-Dolcetta, R.
We studied and compared the radial profiles of globular clusters and of the stellar bulge component in three galaxies of the Fornax cluster observed with the WFPC2 of the Hubble Space Telescope (HST). The stars are more concentrated toward the galactic centres than globular clusters, in agreement with what has already been observed in many other g…
Measurement of coronal magnetic twists during loop emergence of NOAA 8069
Delaboudinière, J. -P.; Démoulin, P.; Portier-Fozzani, F. +3 more
Emerging coronal loops were studied with extreme ultraviolet observations performed by SOHO/EIT on 5 and 6 August 1997 for NOAA 8069. Physical parameters (size and twist) were determined by a new stereoscopic method. The flux tubes were measured twisted when first observed by EIT. After emerging, they de-twisted as they expanded, which corresponds…
A multi-wavelength study of solar coronal-hole regions showing radio enhancements
Wilhelm, K.; Gopalswamy, N.; Dammasch, I. E. +1 more
We observed 17 GHz microwave-enhanced regions in equatorial coronal holes (ECH) together with extreme-ultraviolet (EUV), far-ultraviolet (FUV) and visible emissions in a search for temperature increases which might explain the bright spots in radio wavelengths. The ultraviolet (UV) observations span a wide range of formation temperatures (8000 K t…
Capability of the Cassini/Huygens PWA-HASI to measure electrical conductivity in Titan
Rodrigo, R.; López-Moreno, J. J.; Molina-Cuberos, G. J. +1 more
The penetration of the Huygens probe through the atmosphere of Titan in 2004 will provide a unique opportunity to measure the electrical properties of its lower atmosphere. Many studies have been carried out to predict the density of electrons and the distribution of the major positive ions, but there is no recent analysis concerning the electrica…
Joint Ulysses and ACE observations of a magnetic cloud and the associated solar energetic particle event
Lario, D.; Forsyth, R. J.; Tappin, S. J. +3 more
On day 49 of 1999 a strong interplanetary shock was observed by the ACE spacecraft located at 1 AU from the Sun. This shock was followed 10 hours later by a magnetic cloud (MC). A large solar energetic particle (SEP) event was observed in association with the arrival of the shock and the MC at ACE. The Ulysses spacecraft, located at 22° S heliolat…
Terminal Speeds and Ion Fractions from [Ca IV] 3.207 µm in Three Single WN Stars
Ignace, R.; Cassinelli, J. P.; Babler, B. +1 more
We report on the forbidden emission lines of [Ca IV] at 3.207 µm and [Ne III] at 15.56 µm based on Infrared Space Observatory observations. The data set consists of three single Wolf-Rayet stars (WR 1, WR 134, and WR 136) and three binary systems (WR 11, WR 146, and WR 147). For the single stars, only the [Ca IV] line was observed. Our…
Detection of X-ray line emission from the shell of SNR B0540-69.3 with XMM-Newton RGS
Kaastra, J. S.; Branduardi-Raymont, G.; Paerels, F. +2 more
We present X-ray observations of PSR 0540-69.3 with the XMM-Newton observatory. The spectra obtained with the Reflection Grating Spectrometer reveal, for the first time, emission from ionized species of O, Ne and Fe originating from the SNR shell. Analysis of the emission line spectrum allows us to derive estimates of the temperature, ionization t…