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Hubble Space Telescope Observations of the Nucleus of Comet 9P/Tempel 1
Lamy, P. L.; A'Hearn, M. F.; Toth, I. +2 more
The nucleus of Comet 9P/Tempel 1, the target of the Deep Impact mission, was detected during Hubble Space Telescope observations taken with the wide-field planetary camera 2 (WFPC2) on 31 December 1997 when the comet's solar phase angle was 3.°8, its heliocentric distance was 4.48 AU, and its geocentric distance was 3.53 AU. Sixteen images were ta…
Research Note Hipparcos photometry: The least variable stars
Adelman, S. J.
The data known as the Hipparcos Photometry obtained with the Hipparcos satellite have been investigated to find those stars which are least variable. Such stars are excellent candidates to serve as standards for photometric systems. Their spectral types suggest in which parts of the HR diagrams stars are most constant. In some cases these values s…
Oscillations in an active region filament: Observations and comparison with MHD waves
Régnier, S.; Solomon, J.; Vial, J. C.
During the MEDOC Campaign 4, on October 1999, observations of a solar active region filament were carried out by the SUMER/SoHO spectrometer. A time sequence of this filament has been obtained with a duration of 7 h 30 min and with a temporal resolution of 30 s. The Fourier analysis of the line-of-sight Doppler velocities measured in the 584.33 Å …
Horizontal-Branch Morphology and Dense Environments: Hubble Space Telescope Observations of Globular Clusters NGC 2298, 5897, 6535, and 6626
Testa, Vincenzo; Iannicola, Giacinto; Buonanno, Roberto +4 more
HST observations of the core of four galactic globular clusters allowed us to obtain interesting clues about the influence of the environment on the star distribution along the horizontal branch. The chemical composition and the age of the target clusters have been derived through a detailed analysis of the (V,V-I) color-magnitude diagrams. The ph…
Analysis of Type IIn SN 1998S: Effects of Circumstellar Interaction on Observed Spectra
Filippenko, Alexei V.; Kirshner, R. P.; McCray, R. +20 more
We present spectral analysis of early observations of the Type IIn supernova 1998S using the general non-local thermodynamic equilibrium atmosphere code PHOENIX. We model both the underlying supernova spectrum and the overlying circumstellar interaction region and produce spectra in good agreement with observations. The early spectra are well fitt…
Low-excitation atomic gas around evolved stars. I. ISO observations of C-rich nebulae
Bujarrabal, V.; Tielens, A. G. G. M.; Meixner, M. +5 more
We present ISO LWS and SWS spectra of far-infrared (FIR) atomic fine structure lines in 12 carbon-rich evolved stars including asymptotic giant branch (AGB) stars, proto-planetary nebulae (PPNe) and planetary nebulae (PNe). The spectra include grating and Fabry-Perot measurements of the line emission of [O I], [C Ii], [Si I], [Si Ii], [S I], [Fe I…
Modelling the spin pulse profile of the isolated neutron star RX J0720.4-3125 observed with XMM-Newton
Haberl, F.; Motch, C.; Cropper, M. +2 more
We model the spin pulse intensity and hardness ratio profiles of the isolated neutron star RX J0720.4-3125 using XMM-Newton data. The observed variation is approximately sinusoidal with a peak-to-peak amplitude of 15%, and the hardness ratio is softest slightly before flux maximum. By using polar cap models we are able to derive maximum polar cap …
Kinematics of 1200 Kilometer per Second Jets in HE 3-1475
Borkowski, Kazimierz J.; Harrington, J. Patrick
Spectroscopic observations of a proto-planetary nebula He 3-1475 with the Space Telescope Imaging Spectrograph reveal the kinematics of its high-velocity (1200 km s-1) jets. The jets are formed at a large (0.15 pc) distance from its central star by collimation of an asymmetric stellar wind in a pair of conical shocks seen in Wide Field …
CCD Speckle Observations of Binary Stars from the Southern Hemisphere. III. Differential Photometry
Franz, Otto G.; Horch, Elliott; Ninkov, Zoran
Two hundred seventy-two magnitude difference measures of 135 double star systems are presented. The results are derived from speckle observations using the Bessel V and R passbands and a fast readout CCD camera. Observations were taken at two 60 cm telescopes, namely the Helen Sawyer Hogg Telescope, formerly at Las Campanas, Chile, and the Lowell-…
An Astrometric Study of the Triple Star ADS 48
Kiselev, A. A.; Kiyaeva, O. V.; Polyakov, E. V. +1 more
We analyze the series of relative positions of the hierarchical triple system ADS 48 ABF (AB = 6 arcsec, AF = 327 arcsec) obtained with the 26-inch Pulkovo refractor during 1961-1995 and measured with the Fantazia automated measuring system. A new relative orbit of pair AB is determined by the method of apparent-motion parameters using new observa…