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NGC 6543: The Rings Around the Cat's Eye
Balick, Bruce; Hajian, Arsen R.; Wilson, Jeanine
Hubble archival images of NGC 6543 reveal a series of at least nine regularly spaced concentric circular rings that surround the famous nebular core, known as the Cat's Eye Nebula. The rings are almost certainly spherical bubbles of periodic isotropic nuclear mass pulsations that preceded the formation of the core. The bubbles are detected solely …
The Stellar Content of the Super-Star Clusters in NGC 1569
Aloisi, Alessandra; Leitherer, Claus; Origlia, Livia +2 more
We discuss HST Faint Object Spectrograph (FOS) ultraviolet spectroscopy and Near-Infrared Camera and Multiobject Spectrometer (NICMOS) photometry of four young super-star clusters in the central region of the irregular starburst galaxy NGC 1569. The new observations, coupled with previous HST WFPC2 photometry and ground-based optical spectroscopy,…
The phenomenology of solar-cycle-induced acoustic eigenfrequency variations: a comparative and complementary analysis of GONG, BiSON and VIRGO/LOI data
Chaplin, W. J.; Elsworth, Y.; Appourchaux, T. +2 more
We use high-quality helioseismic data collected by three different observational programmes during the declining phase of activity cycle 22,Q7 and a substantial portion of the rising phase of the current cycle (23), to study the phenomenological nature of the cycle-induced (centroid) eigenfrequency variations. We have analysed the frequency depend…
Hubble Space Telescope photometry of globular clusters in the Sombrero galaxy
Forbes, Duncan A.; Brodie, Jean P.; Larsen, Søren S.
We explore the rich globular cluster (GC) system of the nearby Sa galaxy M104, the `Sombrero' (NGC 4594), using archive Wide Field Planetary Camera 2 data. The GC colour distribution is found to be bimodal at the >99 per cent confidence level, with peaks at (V-I)0=0.96+/-0.03 and 1.21+/-0.03. The inferred metallicities are very simil…
The Hipparcos observations and the mass of sub-stellar objects
Pourbaix, D.
The Hipparcos Intermediate Astrometric Data have been used lately to estimate the inclination of the orbital plane of candidate extrasolar planets. Whereas most of these investigations derive almost face-on orbits, we show that the astrometric data are seldom precise enough to undertake such studies and that the ``face-on'' result might be just a …
An XMM-Newton Detection of the Z=5.80 X-Ray-Weak Quasar SDSSP J104433.04-012502.2
Brandt, W. N.; Clavel, J.; Strauss, Michael A. +5 more
We report on an XMM-Newton observation of the most distant known quasar, SDSSp J104433.04-012502.2, at z=5.80. We have detected this quasar with high significance in the rest-frame 3.4-13.6 keV band, making it the most distant cosmic object detected in X-rays 32+/-9 counts were collected. SDSSp J104433.04-012502.2 is notably X-ray-weak relative to…
NOTE: The Merger of Two Giant Anticyclones in the Atmosphere of Jupiter
Colas, F.; Orton, G. S.; Lecacheux, J. +10 more
Two giant ovals in Jupiter's southern atmosphere, vortices of counterclockwise-rotating winds, merged in a 3-week period, starting in March 2000. One of the ovals called FA was more than 60 years old; the other called BE was the product of two 60-year-old ovals (BC and DE) that merged in 1998 (A. Sanchez-Lavega et al. 1999, Icarus142, 116-124). Th…
Analysis of the Hipparcos Observations of the Extrasolar Planets and the Brown Dwarf Candidates
Mazeh, Tsevi; Zucker, Shay
We analyzed the Hipparcos astrometric observations of 47 stars that were discovered to harbor giant planets and 14 stars with brown dwarf secondary candidates. The Hipparcos measurements were used together with the corresponding stellar radial velocity data to derive an astrometric orbit for each system. To find out the significance of the derived…
Optical photometry of the PSR B0656+14 and its neighborhood
Zharikov, S. V.; Shibanov, Yu. A.; Kurt, V. G. +3 more
We present the results of broad-band photometry of the nearby middle-aged radio pulsar PSR B0656+14 and its neighborhood obtained with the 6-meter telescope of the SAO RAS and with the Hubble Space Telescope. The broad-band spectral flux F_nu of the pulsar decreases with increasing frequency in the near-IR range and increases with frequency in the…
The Star Formation History of NGC 6822
Wyder, Ted K.
Images of five fields in the Local Group dwarf irregular galaxy NGC 6822 obtained with the Hubble Space Telescope in the F555W and F814W filters are presented. Three of the fields lie mostly within the central bar of NGC 6822, where most of the sites of current star formation are concentrated, while two other fields sample more of the outer region…