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3C 236: Radio Source, Interrupted?
Koekemoer, Anton M.; Baum, Stefi A.; O'Dea, Christopher P. +5 more
We present new Hubble Space Telescope Space Telescope Imaging Spectrograph MAMA near-UV images and archival Wide Field Planetary Camera 2 (WFPC2) V- and R-band images that reveal the presence of four star-forming regions in an arc along the edge of the dust lane in the giant (4 Mpc) radio galaxy 3C 236. Two of the star-forming regions are relative…
Infrared Properties of Weak Radio Sources in the ρ Ophiuchi Molecular Cloud
André, Philippe; Greene, Thomas P.; Wilking, Bruce A. +2 more
We report mid-infrared ISOCAM observations for a sample of radio continuum sources in the ρ Ophiuchi molecular cloud core with unknown or poorly studied infrared counterparts. These data are combined with existing infrared photometry, including recently published ISOCAM data, for previously studied radio sources to investigate the evolutionary sta…
Direct multi-wavelength limb-darkening measurements of three late-type giants with the Navy Prototype Optical Interferometer
Hajian, A. R.; Wittkowski, M.; Hummel, C. A. +3 more
We present direct measurements of the limb-darkened intensity profiles of the late-type giant stars HR 5299, HR 7635, and HR 8621 obtained with the Navy Prototype Optical Interferometer (NPOI) at the Lowell Observatory. A triangle of baselines with lengths of 18.9 m, 22.2 m, and 37.5 m was used. We utilized squared visibility amplitudes beyond the…
Subarcsecond Mid-Infrared Structure of the Dust Shell around IRAS 22272+5435
Ueta, Toshiya; Fazio, Giovanni G.; Meixner, Margaret +6 more
We report subarcsecond imaging of extended mid-IR emission from a proto-planetary nebula (PPN), IRAS 22272+5435, performed at the MMT observatory with its newly upgraded 6.5 m aperture telescope and at the Keck observatory. The mid-IR emission structure is resolved into two emission peaks separated by 0.5"-0.6" in the MMT 11.7 µm image and i…
The Relative Star Formation Histories of Spiral Bulges and Elliptical Galaxies in the Hubble Deep Fields
Dickinson, Mark; Ellis, Richard S.; Abraham, Roberto G.
Hierarchical galaxy formation models make specific predictions concerning the relative assembly rates and star formation histories of spiral bulges and field ellipticals. Independently of the cosmological model and initial power spectrum of fluctuations, at all epochs the stellar populations in spiral bulges should be older and redder than those i…
Cluster AgeS Experiment. CCD photometry of SX Phoenicis variables in the globular cluster M 55
Thompson, I. B.; Schwarzenberg-Czerny, A.; Kaluzny, J. +2 more
We present CCD photometry of SX Phe variables in the field of the globular cluster M 55. We have discovered 27 variables, three of which are probable members of the Sagittarius dwarf galaxy. All of the SX Phe stars in M 55 lie in the blue straggler region of the cluster color-magnitude diagram. Using period ratio information we have identified the…
Cluster PEACE observations of electrons during magnetospheric flux transfer events
Coates, A. J.; Balogh, A.; Wilson, R. J. +9 more
During the first quarter of 2001 the apogees of the Cluster spacecraft quartet precessed through midday local times. This provides the first opportunity for 4 spacecraft studies of the bow shock, magnetosheath and the dayside magnetopause current layer and boundary layers. In this paper, we present observations of electrons in the energy range ~ 1…
The Solar Helium Abundance in the Outer Corona Determined from Observations with SUMER/SOHO
Feldman, U.; Laming, J. M.
At altitudes of about 1.05 Rsolar or more, the corona above quiet solar regions becomes essentially isothermal. This obviates many of the difficulties associated with the inverse problem of determining emission measure distributions and allows for fairly straightforward relative element abundance measurements. We present new values for …
High-Resolution Imaging of Proto-Planetary Nebulae: The Effects of Orientation
Kwok, Sun; Hrivnak, Bruce J.; Su, Kate Y. L.
Deep Hubble Space Telescope (HST) F814W images were obtained of six proto-planetary nebulae (PPNs), each of which shows a bipolar morphology but with a difference in orientation. Two of these (IRAS 17245-3951 and IRAS 22574+6609) show a dark lane separating bipolar lobes and appear to be seen approximately edge-on. The other four (IRAS 16594-4656,…
Preliminary Astrometric Masses for Proposed Extrasolar Planetary Companions
Han, Inwoo; Gatewood, George; Black, David C.
As a first step in the implementation of an astrometric survey, we have reduced the Hipparcos intermediate astrometric data (IAD) for 30 stars that currently exhibit small-amplitude periodic radial velocity variations. We consider only systems with periods longer than 10 days, where the motion is attributed to the presence of an ``extrasolar plane…