Search Publications
Direct Analysis of Spectra of the Type IC Supernova SN 1994I
Filippenko, Alexei V.; Kirshner, R. P.; Suntzeff, N. B. +12 more
Synthetic spectra generated with the parameterized supernova synthetic-spectrum code SYNOW are compared to observed photospheric-phase spectra of the Type Ic supernova SN 1994I. The observed optical spectra can be well matched by synthetic spectra that are based on the assumption of spherical symmetry. We consider the identification of the infrare…
The Age and Metallicity Range of Early-Type Galaxies in Clusters
Charlot, Stéphane; Ferreras, Ignacio; Silk, Joseph
We present an unbiased method for evaluating the ranges of ages and metallicities that are allowed by the photometric properties of the stellar populations that dominate the light of early-type galaxies in clusters. The method is based on the analysis of morphologically classified early-type galaxies in 17 clusters at redshifts 0.3<~z<~0.9 a…
The Detection and Photometric Redshift Determination of Distant Galaxies Using SIRTF's Infrared Array Camera
Simpson, Chris; Eisenhardt, Peter
We investigate the ability of the Space Infrared Telescope Facility's Infrared Array Camera to detect distant (z~3) galaxies and measure their photometric redshifts. Our analysis shows that changing the original long-wavelength filter specifications provides significant improvements in performance in this and other areas.
Electron density and temperature of the lower solar corona
Del Zanna, G.; Fludra, A.; Bromage, B. J. I. +1 more
Off limb observations of the quiet Sun corona were made with the Coronal Diagnostic Spectrometer (CDS) on SOHO during the Whole Sun Month campaign in August 1996. Selected spectral lines in the Normal Incidence range were recorded up to 1.2 solar radii above the east and west limb and above the polar coronal holes. Intensities of the coronal lines…
Lithium in population I subgiants
Pasquini, L.; Pallavicini, R.; Randich, S. +2 more
We present a lithium survey for a sample of 91 Pop. I stars. JHKL photometry was also obtained for 61 stars in the sample. Besides Li abundances, [Fe/H] values were derived. Thanks to Hipparcos parallaxes, we could infer absolute V magnitudes for our sample stars and were able to place them on the color-magnitude diagram, which allowed us to const…
Hubble Space Telescope Measurements of the Expansion of NGC 6543: Parallax Distance and Nebular Evolution
Casertano, Stefano; Panagia, Nino; Balick, Bruce +5 more
The optical expansion parallax of NGC 6543 has been detected and measured using two epochs of Hubble Space Telescope images separated by a time baseline of only 3 years. We have utilized three separate methods of deriving the angular expansion of bright fiducials, with excellent agreement in the results. We combine our angular expansion estimates …
The Elephant's Trunk: Spectroscopic diagnostics applied to SOHO/CDS observations of the August 1996 equatorial coronal hole
Del Zanna, G.; Bromage, B. J. I.
A large equatorial coronal hole, named the ``Elephant's Trunk,'' was observed by the coronal diagnostic spectrometer (CDS) on board the Solar and Heliospheric Observatory (SOHO) during the last week of August 1996. Spatially averaged spectra within the hole and in neighboring quiet sun regions are analyzed and calibrated in intensity. Spectroscopi…
Detection of HD in the atmospheres of Uranus and Neptune: a new determination of the D/H ratio
de Graauw, Th.; Lellouch, E.; Feuchtgruber, H. +3 more
Observations with the Short Wavelength Spectrometer (SWS) onboard the Infrared Space Observatory (ISO) have led to the first unambiguous detection of HD in the atmospheres of Uranus and Neptune, from its R(2) rotational line at 37.7 mu m. Using S(0) and S(1) quadrupolar lines of H_2 at 28.2 and 17.0 mu m as atmospheric thermometers, we derive D/H …
Disappearance of stellar debris disks around main-sequence stars after 400 million years
Kessler, M. F.; Siebenmorgen, R.; Metcalfe, L. +7 more
Almost 5 billion years ago, the Sun formed in a local contraction of a cloud of molecular gas. A rotating disk of gas and dust is believed to have fed material onto the proto-Sun for the first few million years of its life, and to have formed the planets, comets and other Solar System objects. Similar disks, but with less mass, have been observed …
Selection of a sample of bright southern Slowly Pulsating B Stars for long-term photometric and spectroscopic monitoring
De Ridder, J.; Aerts, C.; Cuypers, J. +7 more
The photometric experiment on Hipparcos has led to the discovery of, among other types of variables, a large amount of new Slowly Pulsating B Stars. We have selected twelve bright southern stars of this sample, together with five previously known Slowly Pulsating B Stars, for spectroscopic and photometric monitoring. These seventeen stars have spe…