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Hubble Space Telescope Spectroscopy of Spot 1 on the Circumstellar Ring of SN 1987A
Filippenko, Alexei V.; Pun, C. S. J.; Garnavich, Peter +15 more
We present ultraviolet and optical spectra of the first bright spot (P.A.=29deg) on SN 1987A's equatorial circumstellar ring taken with the Space Telescope Imaging Spectrograph. We interpret this spot as the emission produced by radiative shocks that occur where the supernova blast wave strikes an inward protrusion of the ring. The obse…
The latitudinal distribution of solar wind magnetic holes
Tsurutani, Bruce T.; Goldstein, Bruce E.; Neugebauer, Marcia +2 more
Using the fast latitude scan period of the Ulysses spacecraft, the occurrence of magnetic holes in the solar wind is investigated from -80° to +80° helio-latitude. Near the ecliptic, the large average value and the large variations of the hole count rate appear to be correlated with interaction regions. It is found, however, that at 30°north and s…
Comparison of Frequencies and Rotational Splittings of Solar Acoustic Modes of Low Angular Degree from Simultaneous MDI and GOLF Observations
Kosovichev, A. G.; Henney, C. J.; Scherrer, P. H. +8 more
During the years 1996 through 1998 the Michelson Doppler Imager (MDI) and the Global Oscillations at Low Frequency (GOLF) experiments on the Solar and Heliospheric Observatory (SOHO) mission have provided unique and nearly uninterrupted sequences of helioseismic observations. This paper describes the analysis carried out on power spectra from 759 …
Rapid intensity and velocity variations in solar transition region lines
Hansteen, V. H.; Carlsson, M.; Betta, R.
We have obtained short exposure (3 s) time series of strong upper chromospheric and transition region emission lines from the quiet Sun with the SUMER instrument onboard SOHO during two 1 hour periods in 1996. With a Nyqvist frequency of 167 mHz and relatively high count rates the dataset is uniquely suited for searching for high frequency variati…
High-resolution imaging X-ray spectrometers
Strüder, L.
The successful commissioning of the XMM-Newton focal plane detectors, radiation hard X-ray imaging spectroscopic CCDs, has attracted some attention: Reliably operating X-ray CCDs are delivering extraordinary images, recorded in a single-photon counting mode, imaged through the largest X-ray telescope ever built. The experimental boundary condition…
The optical spectrum of the planetary nebula NGC 6543
Feibelman, W. A.; de Koter, A.; Hyung, S. +2 more
With the Hamilton echelle spectrograph at the Lick Observatory, emission-rich spectral lines of the planetary nebula NGC 6543 were secured in the wavelength range from 3550 to 10100Å. We chose two bright regions, ~8arcsec east and ~13arcsec north of the central star, the physical conditions and chemical abundances of which may differ as a result o…
WN stars in the LMC: Parameters and atmospheric abundances
Hamann, W. -R.; Koesterke, L.
The spectra of 18 WN stars in the Large Magellanic Cloud (LMC) are quantitatively analyzed by means of "standard" Wolf-Rayet model atmospheres, using the helium and nitrogen lines as well as the spectral energy distribution. The hydrogen abundance is also determined. Carbon is included for a subset of 4 stars. The studied sample covers all spectra…
Unavoidable Selection Effects in the Analysis of Faint Galaxies in the Hubble Deep Field: Probing the Cosmology and Merger History of Galaxies
Yoshii, Yuzuru; Totani, Tomonori
We present a detailed analysis of the number count and photometric redshift distribution of faint galaxies in the Hubble Deep Field (HDF), paying special attention to selection effects, including the cosmological dimming of the surface brightness of galaxies, under the observational conditions employed in this field. We find a considerably differe…
VLT-detection of two edge-on Circumstellar Disks in the rho Oph dark cloud
Motohara, K.; Iwamuro, F.; Brandner, W. +7 more
Observations of the rho Ophiuchi star forming region with VLT ANTU and ISAAC under 0\farcs35 seeing conditions reveal two bipolar reflection nebulosities intersected by central dust lanes. The sources (OphE-MM3 and CRBR 2422.8-3423) can be identified as spatially resolved circumstellar disks viewed close to edge-on, similar to edge-on disk sources…
New photochemical model of Saturn's atmosphere
Ollivier, J. L.; Dobrijévic, M.; Parisot, J. P.
A new photochemical model of Saturn's atmosphere, which includes hydrocarbon (up to C 4 compounds) and oxygen compounds, is presented. This model derives from Neptune's model established by Dobrijévic et al. (2000. Planet. Space Sci., submitted). In this one-dimensional model, we consider vertical transport driven by molecular and eddy …