Search Publications

Implementing TOPbase/Iron Project: continuous absorption from FeII

Bautista, Manuel; Cowley, Charles R.

We discuss implementation of TOPbase and Iron Project opacities for stellar spectral codes. We use a technique employed by Peach, where a Boltzmann-averaged cross-section is calculated for selected temperatures, and the opacity obtained from double interpolation in temperature and wavelength. It is straightforward to include all levels for which c…

The Operational Environment of the Hipparcos Mission

van Leeuwen, Floor; Penston, Margaret J.

We investigate links between the observational environment as experienced by the Hipparcos satellite and the performance of the spacecraft and payload instrumentation, with particular emphasis on finding out whether some of these effects may have been inadequately represented in instrument calibrations and could thus have affected the scientific r…

ISO observations of four active galaxies

Rigopoulou, D.; Dennefeld, M.; Spoon, H. W. W. +1 more

We present ISO PHOT-S spectra of four galaxies known or suspected to host a central AGN. Two of them are selected, among several others, from the initial Iras/Rosat sample of Boller et al. (\cite{Boller92}) because of their substantial X-ray emission, while no obvious Seyfert features was present in their optical spectra: IRAS 14201+2956 and IRAS …

In-flight performance of the IBIS calibration unit

Malaguti, G.; Bird, A. J.; Ubertini, P. +3 more

We describe the in-flight performance of the on-board calibration unit for the IBIS telescope on INTEGRAL. Both intrinsic performance and the quality of the calibration signals provided to the IBIS detector planes are discussed. The calibration unit intrinsic performance is assessed based on the diagnostic information in IBIS housekeeping. The flu…

Spectroscopic diagnostics of UV power and accretion in T Tauri stars

Brooks, D. H.; Costa, V. M.

It is known that in the upper atmospheres of the Sun and some late-type stars there is a systematic relationship between the optically thin total radiated power and the power emitted by single spectral lines. Using recently derived emission-measure distributions from IUE spectra for BP Tau, CV Cha, RY Tau, RU Lupi and GW Ori, we demonstrate that t…

Coronal densities and temperatures for cool stars in different stages of activity

Schmitt, J. H. M. M.; Audard, M.; Güdel, M. +1 more

With the advent of the new X-ray missions Chandra and XMM-Newton, high-resolution spectroscopy has become available for studies of stellar coronae. Individual lines can be used as diagnostic tools for measuring densities and temperatures in coronal plasma. In addition to the overall X-ray luminosity, spectroscopic properties can be used for a clas…

XMM-Newton observation of the Marano Field

Hasinger, G.; Wilms, J.; Staubert, R. +2 more

Physical Conditions in the O⁺⁺ Zone from ISO and HST Data: NGC 6543 Revisited

Luridiana, V.; Cerviño, M.; Pérez, E.

We revise the physical conditions in the O⁺⁺ zone of the planetary nebula NGC 6543, obtaining two different estimates of the electron temperature (T_e) and one estimate of the electron density (N_e). The electron temperature is computed by means of two independent methods, the nebular-to-auroral ratio [O III] λ5007/λ…

A comparison between the CaII(k₃), H_alpha , SOHO/MDI and radio-enhanced temperature regions of the Sun

Pohjolainen, S.; Valtaoja, E.; Riehokainen, A.

We present a comparison of the enhanced temperature regions (ETRs) in the radio emission of the Sun with other manifestations of solar activity over 5 days. The radio observations at 87 GHz were observed with the Metsähovi Radio Telescope (Finland). We superposed the intensity contours of the full-disk radio maps on the Meudon spectroheliograph Ca…

Introduction to a Further Examination of the Hipparcos Data

van Leeuwen, Floor; Fantino, Elena

We present an introduction to four papers on further analysis of the raw Hipparcos data. This analysis has lead to the recognition of how orbit, radiation and temperature conditions did or didn't affect the scientific results of the Hipparcos mission. It also led the way to a new reduction of the scientific data that shows from its initial results…