Search Publications
Multi-line analysis of the spectra of Herbig Ae/Be stars
Bouret, J. -C.; Catala, C.
We present the results of the study of four Herbig Ae/Be stars (AB Aur, BD+46(deg) 3471, HD250550, BD+61(deg) 154). For each of them, semi-empirical models of the structure of their winds have been constructed; we then calculated the Hα line, the Balmer discontinuity, as well as the C IV 1548 Angstroms and Mg II h or k resonance lines. Thanks to c…
Hubble Space Telescope Eclipse Observations of the Nova-like Cataclysmic Variable UX Ursae Majoris
Horne, Keith; Hubeny, Ivan; Long, Knox S. +4 more
We present and analyze Hubble Space Telescope observations of the eclipsing nova-like cataclysmic variable UX UMa obtained with the Faint Object Spectrograph. Two eclipses each were observed with the G160L grating (covering the ultraviolet waveband) in 1994 August and with the PRISM (covering the near-ultraviolet to near-infrared) in November of t…
HIPPARCOS parallaxes and period-luminosity relations of high-amplitude delta Scuti stars
Hog, E.; Petersen, J. O.
Hipparcos parallaxes of high-amplitude delta Scuti stars are used to derive a period-luminosity relation with a scatter of about +/-0.1 mag, which is independent from photometric calibrations to absolute luminosities. Comparisons with several P-L relations from the literature show satisfactory agreement, and all deviations from the Hipparcos mean …
Saturn's hydrogen aurora: Wide field and planetary camera 2 imaging from the Hubble Space Telescope
Krist, John E.; Holtzman, Jon A.; Trauger, John T. +8 more
Wide field and planetary camera 2/Hubble Space Telescope (WFPC2/HST) images of Saturn's far ultraviolet aurora reveal emissions confined to a narrow band of latitudes near Saturn's north and south poles. The aurorae are most prominent in the morning sector with patterns that appear fixed in local time. The geographic distribution and vertical exte…
Evidence in Support of the ``Nanoflare'' Picture of Coronal Heating from SUMER Data
Judge, P. G.; Wilhelm, K.; Schühle, U. +3 more
We study high signal-to-noise profiles of O IV emission lines obtained using the SUMER instrument on SOHO. Data for the quiet Sun obtained close to the disk center and at the solar limb were acquired. After careful data processing in which disk data were analyzed differentially against limb data, we find a systematic correlation between a density-…
Inclined Gas Disks in the Lenticular Seyfert Galaxy NGC 5252
Wilson, Andrew S.; Morse, Jon A.; Tsvetanov, Zlatan I. +1 more
We discuss the morphology and kinematics of the extended gas in the type 2 Seyfert galaxy NGC 5252 based on Hubble Space Telescope (HST) WFPC2 continuum and emission-line images (including a new [O III] λ5007 image) and a ground-based Fabry-Perot (F-P) velocity map of the ionized gas. The fine-scale morphology of the ionized gas in this galaxy's v…
Young star clusters in the Antennae: a clue to their nature from evolutionary synthesis
Fritze-v. Alvensleben, Uta
We analyse the population of bright star clusters in the interacting galaxy pair NGC 4038/39 detected with HST WFPC1 by Whitmore & Schweizer (1995). Making use of our spectrophotometric evolutionary synthesis models for various initial metallicities we derive the ages of these star clusters and calculate their future luminosity evolution. This…
On the Latitude Variation of Ammonia, Acetylene, and Phosphine Altitude Profiles on Jupiter from HST Faint Object Spectrograph Observations
Simon, A. A.; Edgington, S. G.; Atreya, S. K. +5 more
Ultraviolet spectra in the spectral region from 160 to 230 nm were taken with the Hubble Space Telescope Faint Object Spectrograph in May 1992. We analyze these data to obtain the altitude distribution of ammonia and its variation with latitude from 6°N to 25°N. Ammonia condenses below the 150-mbar level, above which it departs from saturation due…
Multiwavelength properties of blazars
Urry, C. Megan
The multiwavelength spectra of blazars appear to be dominated by nonthermal emission from a relativistic jet oriented close to the line of sight. The recent detection of many blazars at gamma-ray energies strongly supports this scenario. High quality multiwavelength monitoring data for the brightest one or two blazars suggest the optical through X…
Waves in the solar transition region
Doyle, J. G.; Banerjee, D.; O'Shea, E. +1 more
The power spectra for line intensities of several lines formed in the upper transition region around 100000 to 250000 K are presented. A period of ∼5 min is clearly present in lines due to Oiii, Oiv, and Ov. In one dataset a period approaching 10 min is present for ∼40 min. The size of the emitting features is limited to ∼7 arc sec squared. In all…