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HST observations of the very young SMC ``blob'' N 88A
Heydari-Malayeri, M.; Charmandaris, V.; Zinnecker, H. +2 more
High-resolution Hubble Space Telescope images have allowed us for the first time to resolve the compact SMC ionized ``blob'' N 88A (diameter ~ ,3''.5 or 1 pc). This very young H ii,region, which is hatching from its natal molecular cloud, is heavily affected by absorbing dust associated with the cloud. The interstellar reddening towards N 88A is o…
Energetic particle cross-field diffusion: Interaction with Magnetic Decreases (MDs)
Lakhina, G. S.; Tsurutani, B. T.; Galvan, C. +3 more
Magnetic field Decreases (MDs) are detected in the heliospheric polar regions. The MDs have minimum spatial scales sizes of 25 proton thermal gyroradii, and are typically bounded by tangential or rotational discontinuities. The distribution of the magnitudes of the decreases within AIDs is a continuum, with the smallest decreases being most freque…
The Hubble Space Telescope Key Project on the Extragalactic Distance Scale. XVII. The Cepheid Distance to NGC 4725
Kelson, Daniel D.; Illingworth, Garth D.; Huchra, John P. +22 more
The distance to NGC 4725 has been derived from Cepheid variables as part of the Hubble Space Telescope Key Project on the Extragalactic Distance Scale. Thirteen F555W (V) and four F814W (I) epochs of cosmic-ray-split Wide Field and Planetary Camera 2 observations were obtained. Twenty Cepheids were discovered, with periods ranging from 12 to 49 da…
EUV and radio observations of an equatorial coronal hole
Kerdraon, A.; Fludra, A.; Landi, E. +1 more
EUV and radio data of an equatorial coronal hole, observed in October 1996 at its central meridian transit, are compared. EUV lines were observed by the CDS instrument onboard SOHO and the radio emission by the Nancay Radioheliograph (France) in the frequency range 164-410 MHz. Using the Differential Emission Measure (DEM), derived from EUV line i…
Relationship between Ulysses plasma observations and solar observations during the Whole Sun Month campaign
Luhmann, J. G.; Thompson, B. J.; Hoeksema, J. T. +7 more
In this report, we summarize measurements made by the plasma experiment on the Ulysses spacecraft during the period designated as ``Whole Sun Month'' (WSM, August 10 to September 8, 1996). This interval coincided with the return of solar wind variability at Ulysses. Ulysses was located at ~28°N heliographic latitude, at a heliocentric distance of …
A Near-Infrared Stellar Census of the Blue Compact Dwarf Galaxy VII ZW 403
Greggio, Laura; Hopp, Ulrich; Schulte-Ladbeck, Regina E. +1 more
We present near-infrared single-star photometry for the low-metallicity blue compact dwarf galaxy VII Zw 403. We achieve limiting magnitudes of F110W~25.5 and F160W~24.5 using one of the NICMOS cameras with the Hubble Space Telescope equivalents of the ground-based J and H filters. The data have a high photometric precision (0.1 mag) and are more …
Ultraviolet Spectral Classification of O and B Stars in the Large Magellanic Cloud
Bruhweiler, Frederick C.; Smith Neubig, Margaret M.
In this extension of our previous ultraviolet classification study of Small Magellanic Cloud stars, we construct an ultraviolet classification system for stars of the Large Magellanic Cloud, a galaxy with a metallicity intermediate to those of the Milky Way and the SMC. Employing the same method as was used for the SMC, we compile a set of LMC spe…
Optical and Infrared Observations of the Bipolar Proto-Planetary Nebula Henize 401
García-Lario, Pedro; Riera, Angels; Manchado, Arturo
Based on optical and near-infrared ground-based spectroscopy and optical and near-infrared Hubble Space Telescope (HST) images, we confirm the classification of Hen 401 as a bipolar proto-planetary nebula. HST images reveal a highly elongated morphology, consisting of two main bipolar lobes of unequal surface brightness separated by a dark lane of…
The Hubble Space Telescope Key Project on the Extragalactic Distance Scale. XXII. The Discovery of Cepheids in NGC 1326A
Kelson, Daniel D.; Illingworth, Garth D.; Huchra, John P. +17 more
We report on the detection of Cepheids and the first distance measurement to the spiral galaxy NGC 1326A, a member of the Fornax Cluster of galaxies. We have employed data obtained with the Wide Field and Planetary Camera 2 on board the Hubble Space Telescope. Over a 49 day interval, a total of 12 V-band (F555W) and eight I-band (F814W) epochs of …
The dwarf spheroidal galaxy DDO 44: stellar populations and distance
Sarajedini, A.; Dolphin, A. E.; Grebel, E. K. +7 more
We have ground-based and HST WFPC2 imaging of the nearby low surface brightness dwarf spheroidal galaxy DDO 44. For the first time DDO 44 was resolved into stars. The resulting color-magnitude diagram for about 1290 stars show the red giant branch with a tip at I = 23.55+/-0.15, which yields the distance DMW= 3.2+/-0.2 Mpc consistent wi…