Search Publications
Statistical Pattern Recognition for Labeling Solar Active Regions: Application to SOHO/MDI Imagery
Pap, J. M.; Turmon, M.; Mukhtar, S.
This paper presents a new application of statistical methods for identifying the various surface structures on the Sun that may contribute to observed changes in total and spectral solar irradiance. These structures are divided for our purposes into three types: quiet Sun, faculae, and sunspots (umbra and penumbra). Each region type is characteriz…
A Millisecond Pulsar Optical Counterpart with Large-Amplitude Variability in the Globular Cluster 47 Tucanae
Heinke, Craig O.; Gilliland, Ronald L.; Edmonds, Peter D. +2 more
Using extensive Hubble Space Telescope imaging, combined with Chandra X-ray and Parkes radio data, we have detected the optical binary companion to a second millisecond pulsar (MSP) in the globular cluster 47 Tucanae. This faint (V=22.3) blue (V-I=0.7) star shows a large-amplitude (60%-70%) sinusoidal variation in both V and I. The period (3.19066…
New Observational Results Concerning Jupiter's Great Red Spot
Achterberg, Richard K.; Flasar, F. Michael; Simon-Miller, Amy A. +4 more
The changing size and aspect ratio of the Great Red Spot from 1880 to 2000 are reviewed, indicating that the length of the system has decreased significantly over the last 100 years and continues to decrease at present at a rate of 0.19 degrees per year. Voyager IRIS maps of para hydrogen fraction and potential temperature over the system are pres…
The Nature of the Progenitor of the Type II-P Supernova 1999em
Hodgkin, Simon T.; Smartt, Stephen J.; Gilmore, Gerard F. +1 more
The masses and the evolutionary states of the progenitors of core-collapse supernovae (SNe) are not well constrained by direct observations. Stellar evolution theory generally predicts that massive stars with initial masses less than about 30 Msolar should undergo core collapse when they are cool M-type supergiants. However, the only tw…
Progress in planetary lightning
Russell, C. T.; Borucki, W. J.; Bar-Nun, A. +1 more
We review the progress in the last decade in the field of planetary lightning. We provide background covering terrestrial lightning and newly discovered associated phenomena such as sprites. We concentrate on the theory and observations regarding lightning at Jupiter, especially the discoveries made by the Galileo orbiter and entry probe. Recent o…
Internal Velocities in the Orion Nebula: Large Proper-Motion Features
Hartigan, Patrick; O'Dell, C. R.; Doi, Takao
The proper motions of Herbig-Haro (HH) objects in the Orion Nebula were measured with a +/-10 km s-1 accuracy using the Hubble Space Telescope Wide Field Planetary Camera 2 images in [S II], [N II], Hα, and [O III], taken 4-6 yr apart. Seven HH flows in the outer region as well as seven HH objects in the inner region of the BN-KL comple…
Kinematics of Star Clusters in M33: Distinct Populations
Chandar, Rupali; Sarajedini, Ata; Bianchi, Luciana +1 more
We present velocity measurements for 107 star clusters in the nearby, low-luminosity spiral galaxy M33, from a homogeneous data set taken with the WIYN HYDRA spectrograph. The target clusters were chosen primarily from our previous catalogs based on multiband Hubble Space Telescope WFPC2 imaging and therefore have previous age estimates based on i…
Automated Galaxy Morphology: A Fourier Approach
Odewahn, S. C.; Windhorst, R. A.; Cohen, S. H. +1 more
We use automated surface photometry and pattern classification techniques to morphologically classify galaxies. The two-dimensional light distribution of a galaxy is reconstructed using Fourier series fits to azimuthal profiles computed in concentric elliptical annuli centered on the galaxy. Both the phase and amplitude of each Fourier component h…
An XMM-Newton Observation of NGC 1399 Reveals Two Phases of Hot Gas and Supersolar Abundances in the Central Regions
Buote, David A.
We present an initial analysis of a new XMM-Newton observation of NGC 1399, the central elliptical galaxy of the Fornax group. Spectral fitting of the spatially resolved spectral data of the European Photon Imaging Camera MOS and pn CCDs reveals that a two-temperature (2T) model of the hot gas is favored over single-phase and cooling flow models w…
XMM-NEWTON observation of Abell 1835: Temperature, mass and gas mass fraction profiles
Reiprich, T. H.; Majerowicz, S.; Neumann, D. M.
We present a study of the medium distant cluster of galaxies Abell 1835 based on XMM-NEWTON data. The high quality of XMM-NEWTON data enable us to perform spectro-imaging of the cluster up to large radii. We determine the gas and total mass profiles based on the hydrostatic approach using the beta-model and the temperature profile. For the determi…