Search Publications
Interpretation of the ion mass spectra in the mass per charge range 25-35 amu/e obtained in the inner coma of Halley's comet by the HIS-sensor of the Giotto IMS experiment
Altwegg, K.; Balsiger, H.; Geiss, J. +6 more
The IMS-HIS double-focusing mass spectrometer that flew on the Giotto spacecraft covered the mass per charge range from 12 to 56 (amu/e). By comparing flight data, calibration data and results of model calculations of the ion population in the inner coma, the absolute mass scale is established, and ions in the mass range 25 to 35 are identified. I…
On the evolutionary link between white dwarfs and central stars of planetary nebulae : NLTE analysis of PG 1144+005.
Werner, K.; Heber, U.
Line-blanketed non-LTE (NLTE) model atmospheres are used to study the optical spectra of the hydrogen-deficient prewhite dwarf PG 1144 + 005 by means of a spectral analysis. The star is compared to a prototype PG 1159 star for the analysis, and the stellar parameters of the PG 1144 dwarf show that the N/O ratio is indicative of very strong nitroge…
Spatially resolved spectroscopy of WR ring nebulae. II. M 1-67.
Smith, L. J.; Esteban, C.; Manchado, A. +1 more
Detailed, high spatial resolution spectroscopy of the WR ring nebula M1-67 surrounding the WN 8 star WR 124 is presented. Abundances for 4 positions in M1-67 are derived and it is found that N is enhanced by a factor of 4 - 7.5, O is deficient by a factor of 5 - 7.5 and S has a normal H II region abundance. This remarkable abundance pattern leads …
EXOSAT observations of Cygnus X-1 : study of the soft X-ray excess.
Hasinger, G.; Balucinska, M.
The paper presents results of a spectral analysis of the Cyg X-1 data collected during 1984-1985 by the Medium Energy instrument onboard the Exosat satellite. Emphasis is on two issues: the soft X-ray excess in the range below 3 keV and the iron-line intensity. The presence of a soft component in addition to the high-energy power-law component is …
NLTE-analysis of sublimous O stars : KS 292.
Rauch, T.; Werner, K.; Heber, U. +2 more
High-resolution spectra of the southern Galactic sdO star KS 292 are analyzed using modern NLTE model atmospheres in order to determine the atmospheric parameters. The results indicate that KS 292 probably belongs to a newly discovered group of post-AGB stars which are characterized by effective temperatures and gravities typical for central stars…
An IUE and optical study of interstellar gas towards stars within the Cygnus OB1 and OB3 associations.
Smith, L. J.; St. -Louis, N.
The interstellar absorption lines formed towards 13 members of the Cyg OB1 and OB3 associations were examined in detail using IUE and optical spectra. Low (0 to +17 km/s), intermediate (-24 km/s), and high (-40 to -70 km/s) velocity components were detected toward most of the stars. It is found that the main component of the highly ionized species…
The Spacela-1 very wide field survey of UV-excess objects. II. Analysis of 7 stars of various nature.
Deleuil, M.; Bouchet, P.; Prevot, L. +2 more
Multiwavelength observations of seven stellar objects with strong UV excesses are presented. The observations are IUE spectrophotometry, Stromgren Vuvby optical photometry, Johnson JHK infrared photometry, intermediate resolution optical spectroscopy, and in one case a CORAVEL radial velocity survey. Three of the objects are field subdwarfs (one o…
The nebular stage of nova PW Vulpeculae.
Snijders, M. A. J.; Andreae, J.; Drechsel, H. +1 more
UV and optical nebular spectra of Nova PW Vul were used to derive plasma parameters of the ejected shell. From the visual lightcurve decay times of t2 = 83 days and t3 = 147 days are estimated, which indicate that PW Vul is a slow nova. A color excess of E(B - V) = 0.55 and a distance of about 1.3 kpc were derived. Emission line fluxes were deredd…
Oscillator strengths for Y III and Zr III in the IUE region
Redfors, A.
Oscillator strengths for Y III and Zr III in the region 1190-3100 A have been calculated for transitions from all levels below 13 eV. The presence of these spectra in IUE observations of chemically peculiar stars is discussed.
A study of the flaring and quiscent X-ray and UV emission from II Pegasi.
Tagliaferri, G.; White, N. E.; Doyle, J. G. +3 more
An investigation has been conducted of the rotational modulation of the transition-region UV and coronal X-ray emission for the RS CVn system II Pegasi. The X-ray light curve is dominated by a strong flare detected at orbital phase, where the minimum of the photometric wave occurred. The flare parameters derived show that the flare originates with…