Search Publications
Orion's Veil. IV. H2 Excitation and Geometry
Abel, N. P.; O'Dell, C. R.; Ferland, G. J. +1 more
The foreground Veil of material that lies in front of the Orion Nebula is the best studied sample of the interstellar medium because we know where it is located, how it is illuminated, and the balance of thermal and magnetic energy. In this work, we present high-resolution STIS observations toward the Trapezium, with the goal of better understandi…
Formation and Evolution of Blue Stragglers in 47 Tucanae
Heyl, Jeremy; Richer, Harvey; Kalirai, Jason +2 more
Blue stragglers (BSS) are stars whose position in the color-magnitude diagram (CMD) places them above the main sequence (MS) turn-off (TO) point of a star cluster. Using data from the core of 47 Tuc in the ultraviolet (UV), we have identified various stellar populations in the CMD, and used their radial distributions to study the evolution and ori…
Investigating the Conditions of the Formation of a Type II Radio Burst on 2014 January 8
Cheng, X.; Ding, M. D.; Chen, P. F. +3 more
It is believed that type II radio bursts are generated by shock waves. In order to understand the generation conditions of type II radio bursts, we analyze the physical parameters of a shock front. The type II radio burst we selected was observed by the Siberian Solar Radio Telescope (SSRT) and Learmonth radio station and was associated with a lim…
Spatially Resolved Spectroscopy of a Balmer-dominated Shock in the Cygnus Loop: An Extremely Thin Cosmic-Ray Precursor?
Katsuda, Satoru; Lee, Jae-Joon; Raymond, John C. +9 more
We present high-resolution long-slit spectroscopy of a Balmer-dominated shock in the northeastern limb of the Cygnus Loop with the Subaru high dispersion spectrograph. By setting the slit angle along the shock normal, we investigate variations of the flux and profile of the Hα line from preshock to postshock regions with a spatial resolution of ∼4…
A Study of the Elements Copper through Uranium in Sirius A: Contributions from STIS and Ground-Based Spectra
Wahlgren, G. M.; Castelli, F.; Monier, R. +3 more
We determine abundances or upper limits for all of the 55 stable elements from copper to uranium for the A1 Vm star Sirius. The purpose of the study is to assemble the most complete picture of elemental abundances with the hope of revealing the chemical history of the brightest star in the sky, apart from the Sun. We also explore the relationship …
A Deep Chandra ACIS Survey of M51
Kuntz, K. D.; Long, Knox S.; Kilgard, Roy E.
We have obtained a deep X-ray image of the nearby galaxy M51 using Chandra. Here we present the catalog of X-ray sources detected in these observations and provide an overview of the properties of the point-source population. We find 298 sources within the D 25 radii of NGC 5194/5, of which 20% are variable, a dozen are classical transi…
Narrowband Gyrosynchrotron Bursts: Probing Electron Acceleration in Solar Flares
Kontar, Eduard P.; Fleishman, Gregory D.; Nita, Gelu M. +1 more
Recently, in a few case studies we demonstrated that gyrosynchrotron microwave emission can be detected directly from the acceleration region when the trapped electron component is insignificant. For the statistical study reported here, we have identified events with steep (narrowband) microwave spectra that do not show a significant trapped compo…
Analysis of Flows inside Quiescent Prominences as Captured by Hinode/Solar Optical Telescope
Longcope, D. W.; McKenzie, D. E.; Freed, M. S. +1 more
Developing an understanding of how magnetic fields can become entangled in a prominence is important for predicting a possible eruption. This work investigates the kinetic energy and vorticity associated with plasma motion residing inside quiescent prominences (QPs). These plasma flow characteristics can be utilized to improve our understanding of…
Association of 3He-Rich Solar Energetic Particles with Large-scale Coronal Waves
Mason, Glenn M.; Bučík, Radoslav; Wiedenbeck, Mark E. +1 more
Small, 3He-rich solar energetic particle (SEP) events have been commonly associated with extreme-ultraviolet (EUV) jets and narrow coronal mass ejections (CMEs) that are believed to be the signatures of magnetic reconnection, involving field lines open to interplanetary space. The elemental and isotopic fractionation in these events are…
Relationship Between Chromospheric Evaporation and Magnetic Field Topology in an M-Class Solar Flare
Kosovichev, Alexander G.; Sadykov, Viacheslav M.; Sharykin, Ivan N. +2 more
Chromospheric evaporation is observed as Doppler blueshift during solar flares. It plays a key role in the dynamics and energetics of solar flares; however, its mechanism is still unknown. In this paper, we present a detailed analysis of spatially resolved multi-wavelength observations of chromospheric evaporation during an M 1.0-class solar flare…