Search Publications
Evidence for Non-Maxwellian Electron Energy Distributions in the Solar Transition Region: Si III Line Ratios from SUMER
Wilhelm, K.; Curdt, W.; Mathioudakis, M. +3 more
Recent calculations of Si III emission-line strengths are compared with SUMER observations from a quiet solar region, a coronal hole, and an active region. Diagnostic line ratios are used to derive Te and Ne for the emitting plasma in each region, and good agreement between theory and observations is found. A major enhancemen…
The Distribution of Collisionally Induced Blue Stragglers in the Color-Magnitude Diagram
Sills, Alison; Bailyn, Charles D.
A primary production mechanism for blue stragglers in globular clusters is thought to be collisionally induced mergers, perhaps mediated by dynamical encounters involving binary stars. We model the formation and evolution of such blue stragglers and produce theoretical distributions of them in the color-magnitude diagram. We use a crude representa…
Star Clusters in M33. I. Detection, Morphology, and Photometry
Chandar, Rupali; Bianchi, Luciana; Ford, Holland C.
In this paper we present the discovery of 60 star clusters in 20 multiband Hubble Space Telescope (HST) WFPC2 fields in M33. The fields sample a variety of environments, from outer regions to spiral arms and central regions, as well as a range of galactocentric distances. The HST spatial resolution allowed us to penetrate the crowded, spiral arm r…
Variations of Photospheric Magnetic Field Associated with Flares and CMEs
Kosovichev, A. G.; Zharkova, V. V.
Using high-cadence magnetograms from the SOHO/MDI we have investigated variations of the photospheric magnetic field during solar flares and CMEs. In the case of a strong X-class flare of May 2, 1998, we have detected variations of magnetic field in a form of a rapidly propagating magnetic wave. During the impulsive phase of the flare we have obse…
Mercury in the HgMn Stars χ Lupi and HR 7775
Wahlgren, Glenn M.; Brandt, John C.; Proffitt, Charles R. +5 more
Observations of mercury lines in the HgMn stars χ Lupi and HR 7775 made with the Hubble Space Telescope Goddard High Resolution Spectrograph are presented and analyzed. In χ Lupi we find that all observed lines are consistent with the same isotopic mixture (essentially pure 204Hg). Strong ionization anomalies are present, with UV Hg I l…
High-Resolution Infrared Imaging and Spectroscopy of the Pistol Nebula: Evidence for Ejection
Rich, R. Michael; Serabyn, Eugene; Geballe, T. R. +5 more
We present new infrared images, obtained with the Hubble Space Telescope (HST) Near-Infrared Camera and Multiobject Spectrometer (NICMOS), and Brα (4.05 µm) spectroscopy, obtained using CGS4 on UKIRT, of the Pistol Star and its associated nebula. We find strong evidence to support the hypothesis that the Pistol Nebula was ejected from the Pi…
The NTT SUSI deep field
Fontana, A.; Cristiani, S.; Giallongo, E. +3 more
We present a deep BVrI multicolor catalog of galaxies in a 5.62 sq.arcmin field 80 arcsec south of the high redshift (z=4.7) quasar BR 1202-0725, derived from observations with the direct CCD camera SUSI at the ESO NTT. The formal 5sigma magnitude limits (in 2x FWHM apertures) are 26.9, 26.5, 25.9 and 25.3 in B, V, r and I respectively. Counts, co…
NICMOS Narrowband Images of OMC-1
O'Dell, C. R.; Schultz, A. S. B.; Young, E. T. +5 more
We present images of a 90''×90'' field centered on the Becklin-Neugebauer object (BN) in OMC-1, taken with the Near-Infrared Camera and Multiobject Spectrometer (NICMOS) aboard the Hubble Space Telescope. The observed lines are H2 1-0 S(1), Paα, [Fe II] 1.64 µm, and the adjacent continua. The region is rich i…
First Extragalactic Direct Detection of Large-Scale Molecular Hydrogen in the Disk of NGC 891
van der Werf, Paul P.; Valentijn, Edwin A.
We present direct observations of molecular hydrogen in the disk of the nearby edge-on spiral galaxy NGC 891. With Infrared Space Observatory's Short-Wavelength Spectrometer (SWS) it has been possible, for the first time, to observe the lowest pure rotational lines of H2 [S(0) at 28.2 µm and S(1) at 17.0 µm] at eight positio…
Infrared Space Observatory-Long Wavelength Spectrometer Detection of the 112 Micron HD J = 1 --> 0 Line toward the Orion Bar
van Dishoeck, Ewine F.; Wright, Christopher M.; Kessler, Martin F. +2 more
We report the first detection outside of the solar system of the lowest pure rotational J=1-->0 transition of the HD molecule at 112 µm. The detection was made toward the Orion Bar using the Fabry-Pérot interferometer of the Long Wavelength Spectrometer (LWS) on board the Infrared Space Observatory. The line appears in emission with an in…