Search Publications

A Transient Sub-Eddington Black Hole X-Ray Binary Candidate in the Dust Lanes of Centaurus A

Sarazin, Craig L.; Jordán, Andrés; Kainulainen, Jouni +18 more

We report the discovery of a bright X-ray transient CXOU J132527.6-430023 in the nearby early-type galaxy NGC 5128. The source was first detected over the course of five Chandra observations in 2007, reaching an unabsorbed outburst luminosity of (1-2) × 10³⁸ erg s^-1 in the 0.5-7.0 keV band before returning to quiescence. Such…

The Morphologic Properties of Magnetic Networks over the Solar Cycle 23

Li, Gang; Tan, Baolin; Zhang, Yin +2 more

The morphologic properties of the magnetic networks during Carrington Rotations (CRs) 1955-2091 (from 1999 to 2010) have been analyzed by applying the watershed algorithm to magnetograms observed by the Michelson Doppler Interferometer on board the Solar and Heliospheric Observatory spacecraft. We find that the average area of magnetic cells on th…

Maximizing Magnetic Energy Storage in the Solar Corona

Wolfson, Richard; Drake, Christina; Kennedy, Max

The energy that drives solar eruptive events such as coronal mass ejections (CMEs) almost certainly originates in coronal magnetic fields. Such energy may build up gradually on timescales of days or longer before its sudden release in an eruptive event, and the presence of free magnetic energy capable of rapid release requires nonpotential magneti…

Proper Motions and Internal Dynamics in the Core of the Globular Cluster M71

Richer, Harvey B.; Thanjavur, Karun; Goldsbury, Ryan +4 more

We have used Gemini North together with the NIRI-ALTAIR adaptive optics imager in the H and K bands to explore the core of the Galactic globular cluster M71 (NGC 6838). We obtained proper motions for 217 stars and have resolved its internal proper motion dispersion. Using a 3.8 year baseline, the proper motion dispersion in the core is found to be…

Are Decaying Magnetic Fields Above Active Regions Related to Coronal Mass Ejection Onset?

Li, Y.; Welsch, B. T.; Suzuki, J.

Coronal mass ejections (CMEs) are powered by magnetic energy stored in non-potential (current-carrying) coronal magnetic fields, with the pre-CME field in balance between outward magnetic pressure of the proto-ejecta and inward magnetic tension from overlying fields that confine the proto-ejecta. In studies of global potential (current-free) model…

The Swift BAT Survey Detects Two Optical Broad Line, X-Ray Heavily Obscured Active Galaxies: NVSS 193013+341047 and IRAS 05218-1212

Reynolds, Christopher S.; Mushotzky, Richard F.; Winter, Lisa M. +2 more

The Swift Burst Alert Telescope (BAT) is discovering interesting new objects while monitoring the sky in the 14-195 keV band. Here we present the X-ray properties and spectral energy distributions (SEDs) for two unusual active galactic nucleus sources. Both NVSS 193013+341047 and IRAS 05218-1212 are absorbed, Compton-thin, but heavily obscured (N …

Investigating the Optical Counterpart Candidates of Four INTEGRAL Sources Localized with Chandra

Rahoui, Farid; Kalemci, Emrah; Bodaghee, Arash +5 more

We report on the optical spectroscopic follow-up observations of the candidate counterparts to four INTEGRAL sources: IGR J04069+5042, IGR J06552-1146, IGR J21188+4901, and IGR J22014+6034. The candidate counterparts were determined with Chandra, and the optical observations were performed with 1.5 m RTT-150 telescope (TÜBİTAK National Observatory…

Coronal Mass Ejection Reconstruction from Three Viewpoints via Simulation Morphing. I. Theory and Examples

Frazin, Richard A.

The problem of reconstructing the three-dimensional (3D) density distribution of a coronal mass ejection (CME) from three simultaneous coronagraph observations is timely in that the COR1 and COR2 coronagraphs on the dual-spacecraft STEREO mission complement the LASCO coronagraphs on the SOHO satellite and the Mk4 on Mauna Loa. While the separation…

Erratum: "The Herschel and IRAM CHESS Spectral Surveys of the Protostellar Shock L1157-B1: Fossil Deuteration" (2012, ApJ, 757, L9)

Codella, C.; Ceccarelli, C.; Caselli, P. +9 more

Global Optimization Methods for Gravitational Lens Systems with Regularized Sources

Rogers, Adam; Fiege, Jason D.

Several approaches exist to model gravitational lens systems. In this study, we apply global optimization methods to find the optimal set of lens parameters using a genetic algorithm. We treat the full optimization procedure as a two-step process: an analytical description of the source plane intensity distribution is used to find an initial appro…