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X-Ray and Ultraviolet Spectral Properties of the X-Ray Transient Quasar PG 0844+349
Matsuoka, M.; Brinkmann, W.; Wang, J. X. +2 more
Despite the fact that quasars are generally strong X-ray emitters, ROSAT discovered several objects with only very weak X-ray emission. In this paper, the X-ray data from ASCA and ROSAT and the UV spectra from Hubble Space Telescope (HST) and IUE of one of these quasars, PG 0844+349, are analyzed. The ROSAT spectrum can be well fitted by a single …
Blue stragglers in open clusters. Part II
Drilling, J. S.; Andrievsky, S. M.; Schönberner, D.
We present the results of a spectroscopic study of blue straggler and main sequence B and A - type stars in the open clusters NGC 3496, NGC 6475, NGC 6633 and IC 2602. A detailed analysis based on Kurucz's atmosphere models showed that the main sequence stars rotate rather rapidly and differ from a normal (solar) metallicity for only a few light e…
SOHO/Energetic and Relativistic Nucleon and Electron Experiment Measurements of Energetic H, He, O, and Fe Fluxes during the 1997 November 6 Solar Event
Teittinen, M.; Torsti, J.; Mäkelä, P. +1 more
A brilliant solar X-ray and Hα flare and a coronal mass ejection (CME) on 1997 November 6 were associated with high particle fluxes in interplanetary space at energies above MeV. The CME had an exceptionally high leading edge velocity (1560 km s-1) as observed by the Large Angle and Spectrometric Coronagraph (LASCO) on board the Solar a…
A unified image of dust grains for the warped spiral galaxy in the merger Centaurus A
Sauvage, M.; Block, D. L.
A unified view of dust grains of all sizes and temperatures in Centaurus A has been generated by combining ISOCAM mid-infrared images with optical data. In our unified V-15mu m ratio image, a symmetrical bar-like structure and spiral arms of size 1.5 kpc surround the nucleus. We have overlaid the (H-K) model colour map of \cite{quillen93} and find…
Simulation of resonance scattering helioseismometer signals from spatially resolved images: Application to the GOLF instrument on SOHO
Henney, C. J.; García, R. A.; Ulrich, R. K. +3 more
A step in the analysis of the data from the GOLF (Global Oscillations at Low Frequency) instrument on SOHO (SOlar and Heliospheric Observatory, an ESA/NASA Mission) involves the calculation of the sensitivity of the GOLF signal to the velocity at each point on the solar surface. A successful model of this sort will permit the intercomparison of da…
The Isocam Responsivity in Orbit. Standard star photometry
Altieri, B.; Blommaert, J. A. D. L.; Okumura, K. +5 more
An overview is given of the absolute flux calibration of the ISOCAM detectors. The flux calibration is based on observations of standard stars selected from the Ground Based Preparatory Programme, for which Kurucz stellar models are available. No dependencies of the responsivity on different configurations of the camera were found. No trend of cha…
The transient behaviour of the long wavelength channel of ISOCAM
Aussel, H.; Abergel, A.; Sauvage, M. +3 more
The detector of the long wavelength channel of the ISOCAM camera on-board the Infrared Space Observatory is a Gallium doped Silicon photo-conductor hybridized by Indium bump. It presents systematic memory effects of the response which can bias the photometry by a factor of typically 40%. The main features of the response after flux variations are …
Period Changes in Population II Cepheids: TX Del and W Vir
Percy, John R.; Hoss, Jonathan X.
We have used the Hipparcos database of epoch photometry to study the variability of two Population II Cepheids: TX Del and W Vir. We have constructed (O-c) diagrams for these stars, using the new data and data from the literature. The period of TX Del is decreasing, at a rate which is consistent with evolutionary predictions. THe periodchange of W…
Far-Infrared ISO Maps of Active Galaxies
Pérez García, A. M.; Rodríguez Espinosa, J. M.; Fuensalida, J. J.
Far-IR Infrared Space Observatory (ISO) maps of four Seyfert galaxies are presented and compared with their optical counterpart images. The far-IR maps resemble the optical images of these galaxies when degraded to the ISO resolution. The spatial extension of the far-IR maps is also comparable to the optical extension of these objects, an indicati…
IUE Spectra and Emission-Line Fluxes for Eight Planetary Nebulae
Feibelman, Walter A.
We present IUE spectra and observed emission-line fluxes for the planetary nebulae NGC 2438, NGC 2610, NGC 5307, NGC 6620, NGC 7354, K3-27, PB 8, and He 2-182. All data have been processed by the final archive NEWSIPS routines. PB 8 and He 2-182 display strong C IV λ1549 P Cygni profiles from which terminal wind velocities of -2835+/-500 km s…