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Active Region Loops Observed with SUMER on Board the SOHO
Wilhelm, Klaus; Qiu, Jiong; Wang, Haimin +2 more
We study the emission and dynamical characteristics of transition region temperature plasmas in magnetic loops by analyzing a high-resolution, limb observation of the active region NOAA 7962. The observations were performed by the Solar Ultraviolet Measurements of Emitted Radiation (SUMER) instrument on board the Solar and Heliospheric Observatory…
The Vega phenomenon around G dwarfs
Dominik, C.; Mayor, M.; Waelkens, C. +2 more
In this paper, we present and discuss photometric infrared measurements taken with ISOPHOT at 60 mu m for a sample of 30 G dwarfs, using C100 3X3 minimaps. This sample was selected from the set of more than 1600 G dwarfs which will be scrutinized for radial-velocity variations by the Geneva group, aiming at the detection of extra-solar planets. In…
Silicate emission in Orion
Lequeux, J.; Cesarsky, D.; Jones, A. P. +1 more
We present mid-infrared spectro-imagery and high-resolution spectroscopy of the Orion bar and of a region in the Orion nebula. These observations have been obtained in the Guaranteed Time with the Circular Variable Filters of the ISO camera (CAM-CVF) and with the Short Wavelength Spectrometer (SWS), on board the European Infrared Space Observatory…
An excess of mid-IR luminous galaxies in Abell 1689?
Elbaz, D.; Duc, P. -A.; Franceschini, A. +4 more
We present the results of infrared observations of Abell 1689, an exceptionally rich cluster of galaxies at intermediate redshift (z^simeq 0.181). It was observed with ISOCAM, at 6.7 mum and 15 mum , and ISOPHOT at 200 mum from the Infrared Space Observatory (ISO). The cluster galaxies detected above a sensitivity limit of 0.15 mJy in the 6.7 mum …
Damped Lyman alpha systems at z=0.68 and z=1.15 towards HE 1122-1649 and HE 0515-4414
Reimers, D.; Burles, S.; Tytler, D. +2 more
Detailed analysis of the spectral lines from two low redshift damped Lyman alpha absorbers (DLA) confirms that they are a heterogeneous population. Both systems have low metal abundances of approximately 0.05 to 0.1 solar. The abundance pattern of the DLA at z=1.15 towards HE 0515-4414 shows dust depletion comparable to that found in our Galaxy, w…
Testing the photoionization models of powerful radio galaxies: mixed line-emitting media in 3C 321
Tadhunter, C. N.; Axon, D. J.; Robinson, A. +1 more
The photoionization models for the narrow emission-line regions of powerful radio galaxies have yet to be tested in depth. To this end, we present high-quality long-slit spectroscopy of the powerful double-nucleus radio galaxy 3C 321. The data have good enough spatial resolution to be able to trace the variation in emission-line properties on kpc …
A Chemical Model of the Neutral Envelope of the Planetary Nebula NGC 7027
Hasegawa, Tatsuhiko; Volk, Kevin; Kwok, Sun
In response to the recent molecular observations by ISO and millimeter-wave telescopes, we have developed a spherically symmetric, steady state chemical model for the planetary nebula NGC 7027. In our model, the neutral envelope consists of a geometrically thin, high-density shell of constant density and an outer stellar wind region with an invers…
Atomic diffusion in metal poor stars. The influence on the Main Sequence fitting distance scale, subdwarfs ages and the value of Delta Y/ Delta Z
Salaris, M.; Weiss, A.; Groenewegen, M. A. T.
The effect of atomic diffusion on the Main Sequence (MS) of metal-poor low mass stars is investigated. Since diffusion alters the stellar surface chemical abundances with respect to their initial values, one must ensure - by calibrating the initial chemical composition of the theoretical models - that the surface abundances of the models match the…
Morphology and Kinematics of Planetary Nebulae. II. A Diabolo Model for NGC 3132
Morisset, C.; Monteiro, H.; Gruenwald, R. +1 more
We use a three-dimensional photoionization modeling tool to study the morphokinematic properties of the planetary nebula NGC 3132. We show that it is possible to reproduce the low-resolution observations (spectra and images) with an ellipsoidal shell. However, high-resolution observations, as those showing a density variation along the nebula and …
A Search for Rotational Modulation of X-Ray Centers on the Classical BE Star γ Cassiopeiae
Smith, Myron A.; Robinson, Richard D.
In this paper we discuss X-ray observations of γ Cas obtained in 1998 November with the Rossi X-Ray Timing Explorer (RXTE). The data were obtained nearly continuously over 54 hr, which is about twice the expected rotational period. An earlier RXTE light curve obtained in 1996 March over a 27 hr period showed X-ray flux arising from short-duration …