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Large Magellanic Cloud Planetary Nebula Morphology: Probing Stellar Populations and Evolution
Blades, J. Chris; Balick, Bruce; Shaw, Richard A. +1 more
Planetary nebulae (PNe) in the Large Magellanic Cloud (LMC) offer the unique opportunity to study both the population and evolution of low- and intermediate-mass stars, by means of the morphological type of the nebula. Using observations from our LMC PN morphological survey, and including images available in the Hubble Space Telescope Data Archive…
Decoupled nuclei and nuclear polar rings in regular spiral galaxies NGC 7217
Sil'chenko, O. K.; Afanasiev, V. L.
The regular isolated Sab galaxy NGC 7217 has been studied with the Multi-Pupil Fiber Spectrograph of the 6m telescope of the Special Astrophysical Observatory RAS (Nizhnij Arkhyz, Russia) in two spectral ranges, the blue one including the strong absorption lines Mg I and Fe I and the red one including the emission lines Hα and [N II]lambda 6583. W…
Nuclear Bar, Star Formation, and Gas Fueling in the Active Galaxy NGC 4303
Colina, Luis; Wada, Keiichi
A combination of Hubble Space Telescope Wide Field Planetary Camera 2 (WFPC2) and Near-Infrared Camera Multiobject Spectrograph (NICMOS) images are used to investigate the gas/dust and stellar structure inside the central 300 pc of the nearby active galaxy NGC 4303. The NICMOS H-band (F160W) image reveals a bright core and a nuclear-elongated barl…
The Preflight Photometric Calibration of the Extreme-Ultraviolet Imaging Telescope EIT
Delaboudinière, J. -P.; Dere, K. P.; Moses, J. D. +7 more
This paper presents the preflight photometric calibration of the Extreme-ultraviolet Imaging Telescope (EIT) aboard the Solar and Heliospheric Observatory (SOHO). The EIT consists of a Ritchey-Chrétien telescope with multilayer coatings applied to four quadrants of the primary and secondary mirrors, several filters and a backside-thinned CCD detec…
Compressibility of ion cyclotron and whistler waves: Can radio measurements detect high-frequency waves of solar origin in the corona?
Hollweg, Joseph V.
The ultraviolet coronagraph spectrometer on Solar and Heliospheric Observatory (SOHO) has provided several lines of evidence strongly suggesting that coronal holes and the high-speed solar wind are heated by resonant interactions with ion cyclotron waves. Related evidence has also been provided by the solar ultraviolet measurements of emitted radi…
Structure of a Large low-Latitude Coronal Hole
Dobrzycka, D.; Del Zanna, G.; Gopalswamy, N. +7 more
Coronal holes on the Sun are the source of high-speed solar wind streams that produce magnetic disturbances at the Earth. A series of multi-wavelength, multi-instrument observations obtained during the 1996 `Whole Sun Month' campaign examined a large coronal hole in greater detail than ever before. It appeared on the Sun in August, and extended fr…
ISO-SWS calibration and the accurate modelling of cool-star atmospheres. I. Method
Eriksson, K.; Gustafsson, B.; Decin, L. +5 more
A detailed spectroscopic study of the ISO-SWS data of the red giant alpha Tau is presented, which enables not only the accurate determination of the stellar parameters of alpha Tau, but also serves as a critical review of the ISO-SWS calibration. This study is situated in a broader context of an iterative process in which both accurate observation…
The infrared spectrum of the Be star gamma Cassiopeiae
de Graauw, Th.; Waters, L. B. F. M.; Hony, S. +6 more
We present the 2.4-45 µm ISO-SWS spectrum of the Be star gamma Cas (B0.5 IVe). The spectrum is characterised by a thermal continuum which can be well fit by a power-law Snu ~ nu 0.99 over the entire SWS wavelength range. For an isothermal disc of ionized gas with constant opening angle, this correponds to a density gra…
Probing Cosmology with the X-Ray Forest
Canizares, Claude R.; Fang, Taotao
There is a growing consensus that in the present universe most baryons reside in galaxy clusters and groups in the form of highly ionized gas at temperatures of 106-108 K. The H-like and He-like ions of the heavy elements can produce absorption features-the so-called ``X-ray forest''-in the X-ray spectrum of a background quas…
On the Nature of Andromeda IV
Gallagher, J. S.; Wyse, Rosemary F. G.; Ferguson, Annette M. N.
Lying at a projected distance of 40' or 9 kpc from the center of M31, Andromeda IV is an enigmatic object first discovered during van den Bergh's search for dwarf spheroidal companions to M31. Since it is bluer, more compact, and has a higher surface brightness than other known dwarf spheroidals, it has been suggested that And IV is either a relat…