Search Publications
The luminosity of the B2 hypergiant HD 80077.
de Jager, C.; Nieuwenhuijzen, H.; Carpay, J.
The extremely bright and relatively stable hypergiant HD 80077 is an enigmatic object. Since the star is assumed to have a luminosity of 2 x 10 exp 6, considerable variability and a large mass loss rate would be expected. However, its mass loss rate of (5 +10/-3) x 10 exp -6 solar mass/yr and its variability are very low with respect to its lumino…
Quasr link conditions for Hipparcos.
Ducourant, C.; Brosche, P.; Geffert, M. +2 more
Fictitious proper motions of quasars and of their surrounding stars have been determined based on plates with epoch differences of up to 90 yrs. From the fact that the true proper motions of the quasar are vanishingly small, we obtain conditions for the extragalactic calibration of the preliminary Hipparcos system. We present results for the field…
Velocity of individual large dust particles ejected from Comet P/Halley
Keller, H. U.; Curdt, W.; Richter, K.
Five discrete events are presented which provide accurate information about the impact locations relative to the comet and lower mass limits of the individual particles. Ejection velocities of about 40 m/s were found for two particles in the 1-mg mass range and of not more than 10 m/s for particles in the 10-mg range for the most probable scenario…
The chromospheric Lyman-alpha emission of ALTAIR (A7 IV-V).
Catalano, S.; Gouttebroze, P.; Marilli, E. +1 more
The definition of the spectral type along the main sequence where chromospheres appear is of crucial importance for the study of the stellar structure and the chromospheric heating mechanism. Due to the bright UV continuum and the fast rotation typical of early type stars, the Ly-alpha emission core remains the only good chromospheric indicator in…
Studies of symbiotic stars. IV. IUE-optical-IR observations of AS 360.
Munari, U.; Buson, L. M.
Observations of the symbiotic star are reported and compared to similar objects to determine the consistent properties of interacting binaries. Absolute spectrophotometry is conducted at the wavelengths 1200-11,100 A, and UBV photometric observations are also taken. AS 360 is found to be an interacting binary made up of a dust-free M 4.0 III with …
Trace hydrogen in DB white dwarfs : GD 408 - the lowest H abundance case.
Koester, D.; Weidemann, V.
Improved IUE observations revealed the presence of trace hydrogen in the helium atmosphere of GD408, a DB star at Teff of 13,500 K. The hydrogen abundance determined by spectroscopic analysis, log H/He = -6, is considerably smaller than the value determined for other DB stars, which are classified DBA due to the presence of visible hydrogen lines.…
Search for fast ultraviolet variability in NGC 5548 and non-linearities in IUE's SWP camera.
Walter, R.; Courvoisier, T. J. -L.
, Large observation campaigns of Seyfert galaxies give the opportunity to check the linearity of IUE short wavelength camera at low flux number and moderate background. In particular, many pairs of quasi simultaneous observations of NGC 5548 have been obtained with IUE. We selected pairs of spectra which include one well exposed and one poorly exp…
Carbon and nitrogen abundances in the BN supergiant HD 93840, and their implications for normal galactic supergiants.
Massa, D.; Lamers, H. J. G. L. M.; Altner, B. +1 more
It is demonstrated how carbon and nitrogen abundances of luminous B stars can be determined by a combined analysis of their UV photospheric and wind lines. It is shown that HD 93840 has nearly the same temperature and surface gravity as the normal B1 Ib star Zeta Per. These two stars are compared on the basis of their UV photospheric silicon spect…
Observations of X-ray spectra of two nearby QSO's : MRK 205 and MRK 1148.
Singh, K. P.; Rao, A. R.; Vahia, M. N.
The 0.1 - 10 keY X-ray spectra of two nearby quasistellar objects (QSO's) known as Markarian 205 (Mrk 205) and Mrk 1148 (PG 0049+171), are presented based on observations with the EXOSAT Observatory. Simple power law models with the line of sight absorption consistent with the values obtained from the 21 cm surveys are sufficient to explain the ob…
Rotationalmodulation and flares on RS Canum Venaticorum and BY Draconis stars. XVI. IUE spectroscopy and VLA observations of GL 182 (=V 1005 Orionis) in October 1983.
Doyle, J. G.; Linsky, J. L.; Mathioudakis, M. +7 more
A large flare was detected simultaneously with IUE and VLA on Gl 182 on October 5, 1983, this event showing the largest C IV flare enhancement yet observed by IUE. A smaller flare was also detected on October 4, although only with the IUE satellite. Line ratio and emission measure techniques are used to derive various physical parameters of the fl…