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Asymmetries in the HD 141569 circumstellar disk
Ménard, F.; Mouillet, D.; Augereau, J. C. +1 more
We present HST/STIS coronagraphic observations of the disk around HD 141569. The data, with a spatial resolution and signal to noise higher than those previously obtained with HST/NICMOS2 allow a more detailed insight in the system. They reveal a very structured system, in which two ring-like structures at distances =~ 200 and 325 AU from the star…
Kinematics of young stars. II. Galactic spiral structure
Figueras, F.; Torra, J.; Fernández, D.
The young star velocity field is analysed by means of a galactic model which takes into account solar motion, differential galactic rotation and spiral arm kinematics. We use two samples of Hipparcos data, one containing O- and B-type stars and another one composed of Cepheid variable stars. The robustness of our method is tested through careful k…
A Strategy for Identifying the Grid Stars for the Space Interferometry Mission
Quirrenbach, Andreas; Röser, Siegfried; Schilbach, Elena +2 more
We present a strategy to identify several thousand stars that are astrometrically stable at the microarcsecond level for use in the Space Interferometry Mission (SIM) astrometric grid. The requirements on the grid stars make this a rather challenging task. Taking a variety of considerations into account, we argue for K giants as the best type of s…
Crystallinity versus mass-loss rate in asymptotic giant branch stars
Waters, L. B. F. M.; de Koter, A.; Tielens, A. G. G. M. +1 more
Infrared Space Observatory (ISO) observations have shown that O-rich Asymptotic Giant Branch (AGB) stars exhibit crystalline silicate features in their spectra only if their mass-loss rate is higher than a certain threshold value. Usually, this is interpreted as evidence that crystalline silicates are not present in the dust shells of low mass-los…
Direct measurement of winds on Titan
Fast, Kelly E.; Hewagama, Tilak; Kostiuk, Theodor +4 more
We report the first direct measurement of wind velocity in the atmosphere of Titan, one of only two examples in our solar system of a slowly-rotating body with a dense atmosphere and a prime target of the Cassini mission. Zonal wind velocity was determined from Doppler shift of ethane lines emitted from Titan's stratosphere (∼0.1-7 mbar) measured …
Hubble Space Telescope WFPC2 Imaging of Cassiopeia A
Chevalier, Roger A.; Borkowski, Kazimierz J.; van den Bergh, Sidney +4 more
The young galactic supernova remnant Cassiopeia A was imaged with Wide Field Planetary Camera 2 (WFPC2) aboard the Hubble Space Telescope through filters selected to capture the complete velocity range of the remnant's main shell in several emission lines. The primary lines detected, along with the specific WFPC2 filters used, were [O III] λλ4959,…
The Galaxy Population of Cluster RX J0848+4453 at Z=1.27
Dickinson, M.; van Dokkum, P. G.; Stanford, S. A. +3 more
We present a study of the galaxy population in the IR-selected cluster RX J0848+4453 at z=1.27, using deep Hubble Space Telescope (HST) NICMOS HF160W and WFPC2 IF814W images of the cluster core. We morphologically classify all galaxies to Ks=20.6 that are covered by the HST imaging and determine photometric redshif…
Quiescent Giant Molecular Cloud Cores in the Galactic Center
Li, Y.; Lis, D. C.; Zylka, R. +1 more
We have used the Long Wavelength Spectrometer aboard the Infrared Space Observatory to map the far-infrared continuum emission (45-175 µm) toward several massive giant molecular cloud (GMC) cores located near the Galactic center. The observed far-infrared and submillimeter spectral energy distributions imply low temperatures (~15-22 K) for t…
Chandra, EUVE, HST, and VLA Multiwavelength Campaign on HR 1099: Instrumental Capabilities, Data Reduction, and Initial Results
Ayres, Thomas R.; Brown, Alexander; Drake, Jeremy J. +4 more
In mid-September of 1999, a multiwavelength campaign was carried out on the coronally active RS Canum Venaticorum binary HR 1099 (K1 IV+G5 V P=2.84 days), during commissioning of the High Energy Transmission Grating Spectrometer (HETGS) of the Chandra X-ray Observatory (CXO). The coordinated program involved the Extreme Ultraviolet Explorer (EUVE)…
Dust in the Tycho, Kepler and Crab supernova remnants
Dwek, E.; Lagage, P. O.; Cesarsky, C. J. +1 more
SuperNova Remnants (SNR) have been extensively studied in radio, X-rays and optical, but barely in the InfraRed (IR). From IRAS observations, SNR are known to be IR emitters, but the origin of the emission is difficult to assess because of the limited angular and spectral resolution of IRAS observations. ISO follow-up observations of the Cassiopei…