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M Dwarfs from Hubble Space Telescope Star Counts. III. The Groth Strip
Gould, Andrew; Bahcall, John N.; Flynn, Chris
We analyze the disk M dwarfs found in 31 new fields observed with the Wide Field Camera 2 (WFC2) on the Hubble Space Telescope, together with the sample previously analyzed from 22 WFC2 fields and 162 prerepair Planetary Camera 1 fields. The new observations, which include the 28 high-latitude fields comprising the Large Area Multi-Color Survey (G…
The Star Cluster System of the Merger Remnant NGC 7252
Whitmore, Bradley C.; Fall, S. Michael; Miller, Bryan W. +1 more
We present new U, B, V, and I images of the prototypical merger remnant NGC 7252 obtained with the WFPC2 instrument of the Hubble Space Telescope. The photometry reaches about 3 mag deeper than the previous observations with WF/PC1 and we detect 499 cluster candidates, most of them previously undiscovered. We can distinguish three populations of s…
Spiral Galaxies with WFPC2.I.Nuclear Morphology, Bulges, Star Clusters, and Surface Brightness Profiles
Carollo, C. M.; Stiavelli, M.; de Zeeuw, P. T. +1 more
We report the analysis of HST WFPC2 F606W images of a sample of 35 spiral galaxies. We describe the optical morphological properties of the galaxies on scales of a few tens of parsecs, derive the surface brightness profiles for 18 of them, and present the results of analytical fits to these profiles. We find that: (I) Several galaxies, despite the…
Triggered Star Formation in a Massive Galaxy at z = 3.8: 4C 41.17
Dey, Arjun; Vacca, William D.; van Breugel, Wil +1 more
We present deep spectropolarimetric observations obtained with the W. M. Keck Telescope of the very high redshift (z = 3.79786 +/- 0.0024) radio galaxy 4C 41.17. We find that the bright, spatially extended rest-frame UV continuum emission from this galaxy, which is aligned with the radio axis, is unpolarized (P2σ < 2.4%). This implie…
Ultraviolet Coronagraph Spectrometer Observations of Density Fluctuations in the Solar Wind
Romoli, M.; Poletto, G.; Noci, G. +2 more
Recent Ultraviolet Coronagraph Spectrometer (UVCS) white-light channel (WLC) observations on board the Solar and Heliospheric Observatory (SOHO) indicate quasi-periodic variations in the polarized brightness (pB) in the polar coronal holes. This is the first observation of possible signatures of compressional waves high above the limb (at heliocen…
Infrared Space Observatory Measurements of [C II] Line Variations in Galaxies
Helou, G.; Stacey, G.; Malhotra, S. +11 more
We report measurements of the [C II] fine-structure line at 157.714 µm in 30 normal star-forming galaxies with the Long Wavelength Spectrometer (LWS) on the Infrared Space Observatory (ISO). The ratio of the line to total far-infrared (FIR) luminosity, L[CII]/LFIR, measures the ratio of the cooling of gas to that of dus…
On the Evolutionary Phase and Mass Loss of the Wolf-Rayet--like Stars in R136a
Hubeny, Ivan; Heap, Sara R.; de Koter, Alex
We report on a systematic study of the most massive stars, in which we analyzed the spectra of four very luminous stars in the Large Magellanic Cloud. The stars lie in the 30 Doradus complex, three of which are located in the core of the compact cluster, R136a (R136a1, R136a3, and R136a5), and the fourth (Melnick 42), located about 8" north of R13…
Geologic Mapping of Vesta from 1994 Hubble Space Telescope Images
Wells, Eddie N.; Storrs, Alex D.; Thomas, Peter C. +3 more
We utilize the 56 images of Asteroid 4 Vesta obtained through four mineralogically diagnostic filters by the Hubble Space Telescope (Zellneret al.1997,Icarus) to construct a geologic map. Vesta's surface is found to be geologically diverse and to be dichotomous at a hemispheric scale. The eastern hemisphere (longitude definition from Thomaset al.1…
SN IA light curves and radioactive decay
Turatto, M.; Cappellaro, E.; Benetti, S. +4 more
The absolute V light curves of 5 SNe Ia, selected to represent the known range of absolute luminosities at maximum for this class of objects, are presented. Comparison of the long term luminosity evolution shows that the differences seen at maximum persist, and actually increase with time, reinforcing the notion that intrinsic differences do exist…
EIT and LASCO Observations of the Initiation of a Coronal Mass Ejection
Llebaria, A.; St. Cyr, O. C.; Michels, D. J. +31 more
We present the first observations of the initiation of a coronal mass ejection (CME) seen on the disk of the Sun. Observations with the EIT experiment on SOHO show that the CME began in a small volume and was initially associated with slow motions of prominence material and a small brightening at one end of the prominence. Shortly afterward, the p…