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Interferometric Astrometry of the Low-Mass Binary GL 791.2 (= HU Del) UsingHubble Space Telescope Fine Guidance Sensor 3: Parallax and Component Masses
Henry, Todd J.; Wasserman, Lawrence H.; Benedict, G. Fritz +2 more
With fourteen epochs of fringe-tracking data spanning 1.7 yr from Fine Guidance Sensor 3 we have obtained a parallax (πabs=113.1+/-0.3 mas) and perturbation orbit for Gl 791.2A. Contemporaneous fringe-scanning observations yield only three clear detections of the secondary on both interferometer axes. They provide a mean component magni…
UBVI Color-Magnitude Diagrams in Baade's Window Metallicity Range, Implications for the Red Clump Method, Color "Anomaly" and the Distances to the Galactic Center and the Large Magellanic Cloud
Stanek, K. Z.; Kaluzny, J.; Wysocka, A. +1 more
We analyze the UBVI color-magnitude diagrams towards the Galactic bulge in a relatively low-reddening region of Baade's Window. The dereddened red giant branch is very wide [approx 1.0 mag in (U-B)_0 and approx 0.4 mag in (B-V)_0 and (V-I)_0], indicating a significant dispersion of stellar metallicities, which by comparison with the theoretical is…
The Hubble Space Telescope Key Project on the Extragalactic Distance Scale. XXI. The Cepheid Distance to NGC 1425
Kelson, Daniel D.; Illingworth, Garth D.; Huchra, John P. +22 more
The distance to NGC 1425 has been derived from Cepheid variables, as part of the Hubble Space Telescope Key Project on the Extragalactic Distance Scale. Thirteen F555W (V) and eight F814W (I) epochs of cosmic-ray-split Wide Field Planetary Camera 2 observations were obtained. Twenty-nine Cepheids were discovered, with periods ranging from 16 to 63…
ISO SWS-LWS observations of the prototypical reflection nebula NGC 7023
Cernicharo, J.; Gerin, M.; Fuente, A. +2 more
We present SWS and LWS ISO observations towards a strip across the photodissociation region (PDR) in the reflection nebula NGC 7023. SWS02 and LWS01 spectra have been taken towards the star and the brightest infrared filaments located NW and SW from the star (hereafter NW and SW PDRs). In addition, SWS02 spectra have been taken towards two interme…
Calculation of the sun's acoustic impulse response by multi-dimensional spectral factorization
Rickett, J. E.; Claerbout, J. F.
Calculation of time-distance curves in helioseismology can be formulated as a blind-deconvolution (or system identification) problem. A classical solution in one-dimensional space is Kolmogorov's Fourier domain spectral-factorization method. The helical coordinate system maps two-dimensions to one. Likewise a three-dimensional volume is representa…
Metal abundances of field A and Am stars
Hui-Bon-Hoa, A.
Detailed abundances of 9 field A and Am stars are derived for Mg, Ca, Sc, Cr, Fe, and Ni using high resolution spectroscopy. Most of our sample Am stars show the characteristic deficiencies of Ca and Sc on one hand, and the overabundances of the iron peak elements on the other, which is consistent with the predictions of the diffusion model for Ma…
Comparison of the 1998 April 29 M6.8 and 1998 November 5 M8.4 Flares
Yang, Guo; Denker, Carsten; Wang, Haimin +6 more
We combined, and analyzed in detail, the Hα and magnetograph data from Big Bear Solar Observatory (BBSO), full-disk magnetograms from the Michelson Doppler Imager (MDI) on board Solar and Heliospheric Observatory (SOHO), coronagraph data from the Large Angle Spectrometric Coronagraph (LASCO) of SOHO, Fe XII 195 Å data from the Extreme ultraviolet …
OB association members in the ACT and TRC catalogues
Hoogerwerf, Ronnie
The Hipparcos Catalogue contains members of nearby OB associations brighter than 12th magnitude in V. However, membership lists are complete only to magnitude V=7.3. In this paper we discuss whether proper motions listed in the `Astrographic Catalogue+Tycho' reference catalogue (ACT) and the Tycho Reference Catalogue (TRC), which are complete to V…
Hipparcos astrometry for 257 stars using Tycho-2 data
Makarov, V. V.; Fabricius, C.
We present improved Hipparcos astrometry for 257 Hipparcos stars, resolved into 342 components. For 64 of the stars no astrometry was obtained in the Hipparcos Catalogue, while for the remaining stars additional components have been added by this solution or the positions have been revised considerably. We have used the published Hipparcos transit…
Interception of comet Hyakutake's ion tail at a distance of 500 million kilometres
Balsiger, H.; Geiss, J.; Schwadron, N. A. +6 more
Remote sensing observations and the direct sampling of material from a few comets have established the characteristic composition of cometary gas. This gas is ionized by solar ultraviolet radiation and the solar wind to form `pick-up' ions, ions in a low ionization state that retain the same compositional signatures as the original gas. The pick-u…