Search Publications
Scaling Behavior of Structure Functions of the Longitudinal Magnetic Field in Active Regions on the Sun
Wang, H.; Goode, P. R.; Abramenko, V. I. +2 more
In the framework of a refined Kolmogorov hypothesis, the scaling behavior of the Bz-component of the photospheric magnetic field is analyzed and compared with flaring activity in solar active regions. We use Solar and Heliospheric Observatory Michelson Doppler Imager, Huairou (China), and Big Bear measurements of the Bz-compo…
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…
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…
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…
Does the Sun Have a Full-Time COmosphere?
Ayres, Thomas R.
Off-limb emissions of solar 4.7 µm rovibrational bands of carbon monoxide, recorded under excellent observing conditions with the Infrared Imaging Spectrograph at the McMath-Pierce telescope, are compared with theoretical translimb CO simulations based on time slices from the Carlsson & Stein dynamical model of chromospheric ``K grains.'…
The Far-Infrared Energy Distributions of Seyfert and Starburst Galaxies in the Local Universe: Infrared Space Observatory Photometry of the 12 Micron Active Galaxy Sample
Spinoglio, Luigi; Malkan, Matthew A.; Andreani, Paola
New far-infrared photometry with ISOPHOT aboard the Infrared Space Observatory (ISO) is presented for 58 galaxies with homogeneous published data for another 32 galaxies, all belonging to the 12 µm galaxy sample-in total, 29 Seyfert 1 galaxies, 35 Seyfert 2 galaxies, and 12 starburst galaxies, or about half of the 12 µm active galaxy s…
Reddening, Emission-Line, and Intrinsic Absorption Properties in the Narrow-Line Seyfert 1 Galaxy Arakelian 564
Brandt, W. N.; Clavel, J.; Kriss, G. A. +14 more
We use Hubble Space Telescope UV and optical spectra of the narrow-line Seyfert 1 (NLS1) galaxy Ark 564 to investigate its internal reddening and properties of its emission-line and intrinsic UV absorption gas. We find that the extinction curve of Ark 564, derived from a comparison of its UV/optical continuum to that of an unreddened NLS1, lacks a…