Search Publications
Hubble Space Telescope ultraviolet spectroscopy of the supersoft X-ray binaries CAL83 and RXJ0513.9-6951
Gänsicke, B. T.; Beuermann, K.; de Martino, D. +1 more
We present Hubble Space Telescope ultraviolet observations with the Goddard High Resolution Spectrograph of the supersoft X-ray binaries CAL83 and RXJ0513.9-6951 in the Large Magellanic Cloud. Both sources show a remarkably similar spectrum with an almost flat continuum and weak \N V and \O V emission lines. The neutral hydrogen column densities d…
Surface gravities of very metal-poor stars from HIPPARCOS parallaxes
Fuhrmann, Klaus
We discuss some consequences for the determination of the surface gravity parameter of very metal-poor halo dwarfs in the new light shed upon these objects from the Hipparcos astrometry. Whereas it has become clear that standard spectroscopic LTE iron ionization equilibria are prone to systematic errors, in the sense, that stages of evolution are …
Effective temperature of detached eclipsing binaries from HIPPARCOS parallax
Ribas, I.; Jordi, C.; Torra, J. +2 more
Effective temperatures of detached eclipsing binaries computed through Hipparcos trigonometric parallaxes are compared with the photometric determinations. The former are based on the values of the radius, the apparent visual magnitude and the bolometric correction of the star, whereas the latter are obtained from standard calibrations using Strom…
Pulsation modes of Mira stars and questioning of linear modelling: indications from HIPPARCOS and the LMC
Barthes, D.
Thorough discussion of the previous theoretical works on the pulsation of Long Period Variables leads us to the conclusion that the mode periods predicted by linear models must significantly differ from the reality, and that, if one nevertheless relies upon such a modelling, it is at least necessary to change the mixing length. The hypothesis that…
Far-infrared ISOPHOT observations and the energy balance of a quiescent globule
Lemke, D.; Lehtinen, K.; Mattila, K. +1 more
We have observed a quiescent small globule, the Thumbprint Nebula, with the ISOPHOT far-infrared camera at 100 and 200mu m. The observed emission is optically thin thermal emission from dust at a temperature of ~ 14-16K. The energy budget of the cloud is studied by considering the energy input (interstellar radiation field, ISRF), and outputs (sca…
Doppler redistribution of anisotropic radiation and resonance polarization in moving scattering media. I. Theory revisited in the density matrix formalism
Bommier, V.; Feautrier, N.; Sahal-Brechot, S.
Under the light of recent developments of the theory of matter-radiation interaction in the presence of magnetic field applied to non-LTE spectropolarimetry in astrophysics, we have revisited the theory of anisotropic resonance line scattering in moving media by means of the density-matrix formulation. This has led us to present a theoretical meth…
Are solar acoustic modes correlated?
Roca Cortes, T.; Ulrich, R. K.; Boumier, P. +7 more
We have studied the statistical properties of the energy of individual acoustic modes, extracted from 310 days of GOLF data near the solar minimum. The exponential distribution of the energy of each mode is clearly seen. The modes are found to be uncorrelated with a partial 0.6% accuracy, thus supporting the hypothesis of stochastic excitation by …
HST/FOC observations confirm the presence of a spectral feature in the optical spectrum of Geminga
Caraveo, P. A.; Bignami, G. F.; Mignani, R. P.
New optical and near-UV HST observations of Geminga are presented. When compared with previous ground-based and HST imaging, the data confirm and better define the presence of an emission feature centered at ~ 6,000 Angstroms and superimposed on the thermal continuum best fitting the extreme-UV/soft X-ray data. This feature may be interpreted in t…
Observational evidence for coronal mass injection by ``evaporation" of spicular plasma
Glassmeier, K. -H.; Wilhelm, K.; Schroeder, K. -P. +1 more
Despite being a common feature of the solar chromosphere, spicules are still a poorly understood phenomenon. Not much is known about their impact on the physics of the transition region and corona, for which spicules are believed to be the dominant mechanism for mass injection. We recently observed the spatial plasma structure of polar spicules in…
HST mid-ultraviolet spectroscopy of comet 46P/Wirtanen during its approach to perihelion in 1996-1997
Parker, Joel Wm.; Bertaux, Jean-Loup; Stern, S. Alan +6 more
We have used the Hubble Space Telescope Faint Object Spectrograph to observe the mid-UV spectrum of the ROSETTA mission target comet, 46P/Wirtanen, on three dates during the comet's apparition in 1996 and early 1997. During this time the comet moved inward from a heliocentric distance near 2.7 AU to 1.3 AU. The first measurement (22.7 July 1996) d…