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The Hyades: distance, structure, dynamics, and age
Brown, A. G. A.; Crifo, F.; Gomez, A. +7 more
{We use absolute trigonometric parallaxes from the Hipparcos Catalogue to determine individual distances to members of the Hyades cluster, from which the 3-dimensional structure of the cluster can be derived. Inertially-referenced proper motions are used to rediscuss distance determinations based on convergent-point analyses. A combination of para…
Constraints on Cosmological Models from Hubble Space Telescope Observations of High-z Supernovae
Spyromilio, J.; Diercks, A.; Schmidt, B. P. +18 more
We have coordinated Hubble Space Telescope (HST) photometry with ground-based discovery for three supernovae: Type Ia supernovae near z~0.5 (SN 1997ce, SN 1997cj) and a third event at z=0.97 (SN 1997ck). The superb spatial resolution of HST separates each supernova from its host galaxy and leads to good precision in the light curves. We use these …
Nearby stars of the Galactic disk and halo
Fuhrmann, Klaus
Model atmosphere analyses of echelle spectra of some fifty nearby F- and G-type stars are presented. The sample is confined to the main-sequence, turnoff and subgiant region, regardless of the metal abundance. On the base of these data, spectroscopic parallaxes are calculated and compared to the Hipparcos astrometry to explore the reliability of t…
The structure and origin of magnetic clouds in the solar wind
Schwenn, R.; Bothmer, V.
Plasma and magnetic field data from the Helios 1/2 spacecraft have been used to investigate the structure of magnetic clouds (MCs) in the inner heliosphere. 46 MCs were identified in the Helios data for the period 1974-1981 between 0.3 and 1 AU. 85% of the MCs were associated with fast-forward interplanetary shock waves, supporting the close assoc…
SOHO/EIT observations of an Earth-directed coronal mass ejection on May 12, 1997
St. Cyr, O. C.; Plunkett, S. P.; Michels, D. J. +3 more
An earth-directed coronal mass ejection (CME) was observed on May 12, 1997 by the SOHO Extreme ultraviolet Imaging Telescope (EIT). The CME, originating north of the central solar meridian, was later observed by the Large Angle Spectrometric Coronagraph (LASCO) as a “halo” CME: a bright expanding ring centered about the occulting disk. Beginning a…
The Evolution of Early-Type Galaxies in Distant Clusters
Dickinson, Mark; Eisenhardt, Peter R.; Stanford, S. A.
We present results from an optical-infrared photometric study of early-type (E+S0) galaxies in 19 galaxy clusters out to z = 0.9. The galaxy sample is selected on the basis of morphologies determined from Hubble Space Telescope (HST) WFPC2 images and is photometrically defined in the K band in order to minimize redshift-dependent selection biases.…
A Hubble Space Telescope Imaging Survey of Nearby Active Galactic Nuclei
Gorjian, Varoujan; Malkan, Matthew A.; Tam, Raymond
We have obtained WFPC2 images of 256 of the nearest (z <= 0.035) Seyfert 1, Seyfert 2, and starburst galaxies. Our 500 s broadband (F606W) exposures reveal much fine-scale structure in the centers of these galaxies, including dust lanes and patches, bars, rings, wisps, and filaments, and tidal features such as warps and tails. Most of this fine…
Indication, from Pioneer 10/11, Galileo, and Ulysses Data, of an Apparent Anomalous, Weak, Long-Range Acceleration
Anderson, John D.; Nieto, Michael Martin; Turyshev, Slava G. +3 more
Radio metric data from the Pioneer 10/11, Galileo, and Ulysses spacecraft indicate an apparent anomalous, constant, acceleration acting on the spacecraft with a magnitude ~8.5×10-8 cm/s2, directed towards the Sun. Two independent codes and physical strategies have been used to analyze the data. A number of potential causes ha…
Star Formation in R136: A Cluster of O3 Stars Revealed by Hubble Space Telescope Spectroscopy
Massey, Philip; Hunter, Deidre A.
The R136 cluster in 30 Doradus is the prototype ``super star cluster,'' and the only example sufficiently close that its massive star content can be studied directly. We have used the Hubble Space Telescope to obtain spectra of 65 of the bluest, most luminous stars in R136 and find that the majority of these stars are of type O3, the hottest, most…
Multipolar Bubbles and Jets in Low-Excitation Planetary Nebulae: Toward a New Understanding of the Formation and Shaping of Planetary Nebulae
Trauger, John T.; Sahai, Raghvendra
First results from a Hubble Space Telescope Wide Field Planetary Camera 2 Hα imaging survey of young planetary nebulae (PNs) are reported. The PNs have been selected on the basis of their low excitation characteristics. All objects imaged so far show highly aspherical morphology, with a majority characterized by multipolar bubbles distributed roug…