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The extragalactic Cepheid bias: significant influence on the cosmic distance scale
Paturel, G.; Teerikorpi, P.
The unique measurements with the Hubble Space Telescope of Cepheid variable stars in nearby galaxies led to extragalactic distances that made the HST Key Project conclude that the Hubble constant is H0 = 72 km s-1 Mpc-1. The idea that H0 is now known is widely spread among the astronomical community. Som…
Photographic Zenith Tubes Observations to Improve HIPPARCOS Proper Motion in Declination of Some Stars
Damljanovic, G.
A procedure of calculation and results of an attempt to improve proper motions in declination for some HIPPARCOS stars are presented. A long series of optical observations of these stars observed with Photographic Zenith Tubes (PZT) are used. The HIPPARCOS ESA mission (ESA 1997) was nearly 4 years long, but each of the different Earth rotation pro…
First detections of the cataclysmic variable AE Aquarii in the near to far infrared with ISO and IRAS: Investigating the various possible thermal and non-thermal contributions
de Martino, D.; Schulz, B.; Fender, R. +13 more
We have used ISO to observe the Magnetic Cataclysmic Variable AE Aquarii in the previously unexplored range from 4.8 µm up to 170 µm in the framework of a coordinated multi-wavelength campaign from the radio to optical wavelengths. We have obtained for the first time a spectrum between 4.8 and 7.3 µm with ISOCAM and ISOPHOT-P: th…
A Martian PFS average spectrum: Comparison with ISO SWS
Lellouch, E.; Encrenaz, T.; Piccioni, G. +13 more
The evaluation of the planetary Fourier spectrometer performance at Mars is presented by comparing an average spectrum with the ISO spectrum published by Lellouch et al. [2000. Planet. Space Sci. 48, 1393.]. First, the average conditions of Mars atmosphere are compared, then the mixing ratios of the major gases are evaluated. Major and minor bands…
An Astrometric Study of the Binary Star α Ophiuchi
Gatewood, George
The work reported here combines data from the Multichannel Astrometric Photometer (MAP), the European astrometric satellite, Hipparcos, and infrared speckle observations of the nearby subgiant binary star system α Oph. The A5 IV primary is found to have a mass of 2.84+/-0.19 Msolar, while the approximately K2 V companion has a mass of 0…
A Possible High Nova Rate for Two Local Group Dwarf Galaxies: M32 and NGC 205
Shara, Michael M.; Neill, James D.
We report the results of a preliminary nova survey of Local Group dwarf elliptical galaxies. We used the 15' field-of-view CCD camera on the 0.8 m telescope at the Tenagra Observatory to observe M32, NGC 205, NGC 147, and NGC 185 in their entirety every clear night over a 4.5 month interval and discovered one nova in M32 and a candidate nova in NG…
On the determination of energy spectra of MeV electrons by the Ulysses COSPIN/KET
Fichtner, H.; Ferreira, S. E. S.; Heber, B. +1 more
The Ulysses mission has provided a wealth of data, particularly regarding the transport of low-energy cosmic ray electrons. These data have been used to derive significant constraints for the anisotropic spatial diffusion of these particles. Detailed model simulations allowed, in addition, to determine the relative contributions of galactic and Jo…
BS Indi: An enigmatic object in the Tucana association
Guenther, E. W.; Alcalá, J. M.; Esposito, M. +2 more
BS Ind (=HD 202947) is a young K0V star in the Tucana association. Photometric observations with the Hipparcos satellite show an eclipse-like light-curve with primary and secondary eclipse. The eclipsing binary has a period of 0.435338 days and a circular orbit. Our spectroscopic observations however show that the K0V primary is a single-line spec…
Spacecraft potential control for Double Star
Escoubet, C. P.; Baumjohann, W.; Zhao, H. +12 more
The spacecraft potential of Double Star TC-1 is positive in large parts of the orbits due to the photo-effect from solar EUV irradiation. These positive potentials typically disturb low energy plasma measurements on board. The potential can be reduced, and thereby the particle measurements improved, by emitting a positive ion beam. This method has…
Thermal response of Iapetus to an eclipse by Saturn's rings
Nicholson, P. D.; Matthews, K.; Soifer, B. T. +3 more
Measurements of Iapetus as seen at 20 and 2.2 µm in the shadow of Saturn's ring are given, providing the thermal response to a rapidly varying heat input. The 20 µm thermal emission follows the 2.2 µm flux input closely. The observations, plus a simple diffusion calculation, imply that the surface of Iapetus is made of material h…