Search Publications
UV (IUE) spectra of the central stars of high latitude planetary nebulae Hb7 and Sp3
Parthasarathy, M.; Nakada, Y.; Gauba, G. +1 more
We present an analysis of the UV (IUE) spectra of the central stars of Hb7 and Sp3. Comparison with the IUE spectrum of the standard star HD 93205 leads to a spectral classification of O3V for these stars, with an effective temperature of 50 000 K. From the P-Cygni profiles of CIV (1550 Å), we derive stellar wind velocities and mass loss rates of …
On the Wilson-Bappu relationship in the Mg II k line
Badiali, M.; Cardini, D.; Altamore, A. +1 more
An investigation is carried out on the Wilson-Bappu effect in the Mg Ii k line at 2796.34 Å. The work is based on a selection of 230 stars observed by both the IUE and HIPPARCOS satellites, covering a wide range of spectral types (F to M) and absolute visual magnitudes (-5.4<= MV <=9.0). A semi-automatic procedure is used to measu…
The relation between cyclotron heating and energetic particles on open coronal field lines
Laitinen, T.; Vainio, R.
Cyclotron resonance with high-frequency Alfvén waves has been proposed as an ion heating mechanism for producing high-speed winds and large ion temperatures in coronal holes. In the simplest version of the model (cyclotron sweep model), the waves propagate without interacting until they hit a resonance with the plasma ions at distance, where the i…
ISO observations of symbiotic stars. I. HM Sge
Schild, H.; Eyres, S. P. S.; Salama, A. +1 more
We present ISO SWS and LWS observations of the symbiotic star HM Sge. The infrared emission longward of ~ 5 mu m is dominated by a silicate dust shell. There is a number of high ionization emission lines superimposed on the dust continuum. The ISO continuum spectra can be fitted with a single, optically thick silicate dust shell but such a model d…
A multi-wavelength study of solar coronal-hole regions showing radio enhancements
Wilhelm, K.; Gopalswamy, N.; Dammasch, I. E. +1 more
We observed 17 GHz microwave-enhanced regions in equatorial coronal holes (ECH) together with extreme-ultraviolet (EUV), far-ultraviolet (FUV) and visible emissions in a search for temperature increases which might explain the bright spots in radio wavelengths. The ultraviolet (UV) observations span a wide range of formation temperatures (8000 K t…
Detection of X-ray line emission from the shell of SNR B0540-69.3 with XMM-Newton RGS
Kaastra, J. S.; Branduardi-Raymont, G.; Paerels, F. +2 more
We present X-ray observations of PSR 0540-69.3 with the XMM-Newton observatory. The spectra obtained with the Reflection Grating Spectrometer reveal, for the first time, emission from ionized species of O, Ne and Fe originating from the SNR shell. Analysis of the emission line spectrum allows us to derive estimates of the temperature, ionization t…
V - (V-I) distance to Lupus 2
Knude, J.; Nielsen, A. S.
We report a possible distance to the star forming cloud Lupus 2 of 360 pc, at least 150 pc larger than previously suggested. Despite the cloud's small angular size and remoteness this distance estimate is corroborated by Hipparcos/Tycho data for field stars. The increased distance changes the mass estimate from 100 to ~ 600 cal Msun mor…
Singular value decomposition: A tool to separate elementary contributions in ISOCAM spectral maps
Joblin, C.; Boissel, P.; Pernot, P.
Singular value decomposition (SVD) is applied to a mid-infrared ISOCAM spectral map of NGC 7023. As a first result, this decomposition provides a mathematical analysis of the map in terms of a linear combination of elementary spectra. After further processing, it is shown that the spectrum observed on each pixel can be described as the physical su…
Spectra of binaries classified as lambda Bootis stars
Bonifacio, P.; Gerbaldi, M.; François, P. +1 more
High angular resolution observations have shown that some stars classified as lambda Boo are binaries with low values of angular separation and magnitude difference of the components; therefore the observed spectrum of these objects is a combination of those two components. These composite spectra have been used to define spectroscopic criteria ab…
An analytical representation of the systematic differences HIPPARCOS-FK5
Schwan, H.
In the present paper we present an analytical representation of the relations between the systems of the HIPPARCOS catalogue and the Basic FK5 catalogue. These relations were used in the construction of the ``Sixth Catalogue of Fundamental Stars (FK6)'' for the reduction of the FK5 to the HIPPARCOS system. A comparison has been made between the pr…