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Kinematics and CMD of the globular cluster NGC 4147
Chen, L.; Geffert, M.; Wang, J. J. +2 more
Astrometry and BVRI CCD photometry of 115 stars down to B=17.6 in the region of about 11' x 11' around the globular cluster NGC 4147 was performed. In the astrometric reduction, three earlier epoch plates taken at Sheshan, Shanghai, China, in 1958 and four recent epoch B-passband CCD frames taken at Kavalur, India, were used.…
The Surface Temperatures of White Dwarf Accretors in Dwarf Novae: The Active Dwarf Nova CN Orionis during Quiescence
Mittal, R.; Urban, J.; Lyons, K. +3 more
We have carried out a synthetic spectral analysis of five IUE NEWSIPS archival spectra of the peculiar, very active dwarf nova CN Orionis taken at the system's lowest flux levels during quiescence. AAVSO data indicate the visual magnitude V~14 for CN Ori at this time. On the assumption that the white dwarf contributes significantly to the far-UV l…
Connecting the Sun and the solar wind: Source regions of the fast wind observed in interplanetary space
Habbal, Shadia Rifai; Woo, Richard
Highly sensitive radio occultation and white light measurements of path-integrated density have shown that the solar corona comprises three distinct morphological regions, streamer, quiet Sun, and polar coronal hole, which except for the streamer region, extend radially into interplanetary space from 1.15Rs to at least 30Rs. …
X-Ray Afterglow Detection of the Short Gamma-Ray Burst GRB 991014
Piro, L.; Antonelli, L. A.; Frontera, F. +14 more
GRB 991014 is one of the shortest gamma-ray bursts detected so far with the Wide Field Cameras aboard BeppoSAX, in both gamma rays and X-rays. The duration is 9.6 s in 2-28 keV and 3.2 s in 40 to 700 keV (as measured between the times when 5% and 95% of the burst photons have been accumulated). We have refined the InterPlanetary Network annulus of…
Complex Extended Line Emission in the CD Galaxy in Abell 2390
Balogh, M. L.; Hutchings, J. B.
This paper reports maps of the cD galaxy in the rich z=0.23 cluster Abell 2390 at UV, [O II], Lyα, and Hα wavelengths. Spatially resolved UV and optical spectra were obtained with Space Telescope Imaging Spectrograph on the Hubble Space Telescope; the 2" wide slit was aligned close to the long axis and blue lane of the galaxy and includes all the …
Empirical Luminosities and Radii of Early-Type Stars after Hipparcos
Jerzykiewicz, M.; Molenda-Zakowicz, J.
Using Hipparcos parallaxes we derive empirical luminosities and radii of the early-type stars for which the effective temperatures are known from directly measured angular diameters and total absolute fluxes. The empirical luminosities allow a direct comparison of the position of these stars in the fundamental HR diagram with evolutionary tracks. …
Why is the Sun's corona so hot? Views from SOHO, Yohkoh and solar eclipses
Phillips, Kenneth J. H.
It has been known for over 50 years that the outer atmosphere of the Sun, the so-called corona, has a temperature of 106 K (~0.1 keV) yet the exact reasons for this are still being debated. The magnetic field that pervades the corona is certainly the source of the heating, but the question is whether the field energy is dissipated via n…
A-shell stars in the Geneva system
Jaschek, C.; Hauck, B.
Among the various kinds of A stars having a peculiar spectrum, we find the A-shell stars. Many questions are still open concerning these stars, including their evolutionary status. In the present study we have used data from the Hipparcos catalogue to examine this point. We have found that the majority of A-shell stars are well above the main sequ…
Optical Positions for a Sample of ICRF Sources
Assafin, M.; Andrei, A. H.; Martins, R. Vieira +1 more
The aim of this paper is to present a large, coherent set of astrometric optical positions for ICRF sources in the Hipparcos reference frame. For this, we present positions for 315 ICRF sources measured in Digitized Sky Survey (DSS) images, with positions referred to the ACT, Hipparcos, and Tycho catalogs. The reductions were made relative to Hubb…
Optimal Masks for Low-Degree Solar Acoustic Modes
Kosovichev, A. G.; Toutain, T.
We suggest a solution to an important problem in observational helioseismology of the separation of lines of solar acoustic (p) modes of low angular degree in oscillation power spectra by constructing optimal masks for Doppler images of the Sun. Accurate measurements of oscillation frequencies of low-degree modes are essential for the determinatio…