Search Publications
Three-dimensional Geometry of a Current Sheet in the High Solar Corona: Evidence for Reconnection in the Late Stage of the Coronal Mass Ejections
Vourlidas, Angelos; Kwon, Ryun-Young; Webb, David
Motivated by the standard flare model, ray-like structures in the wake of coronal mass ejections (CMEs) have been often interpreted as proxies of the reconnecting current sheet connecting the CME with the postflare arcade. We present the three-dimensional properties of a post-CME ray derived from white light images taken from three different viewi…
The Unusual Galactic Center Radio Source N3
Morris, M. R.; Mills, E. A. C.; Mutel, R. +4 more
Here, we report on new multi-wavelength radio observations of the unusual point source “N3” that appears to be located in the vicinity of the Galactic Center (GC). VLA observations between 2 and 50 GHz reveal that N3 is a compact and bright source (56 mJy at 10 GHz) with a non-thermal spectrum superimposed upon the non-thermal radio filaments (NTF…
Testing the Effects of Expansion on Solar Wind Turbulence
Chen, Christopher H. K.; Vech, Daniel
We present a multi-spacecraft approach to test the predictions of recent studies on the effect of solar wind expansion on the radial spectral, variance, and local 3D anisotropies of the turbulence. We found that on small scales (5000-10,000 km) the power levels of the B-trace structure functions do not depend on the sampling direction with respect…
Multi-spacecraft Analysis of Energetic Heavy Ion and Interplanetary Shock Properties in Energetic Storm Particle Events near 1 au
Jian, L. K.; Mason, G. M.; Desai, M. I. +3 more
We examine the longitude distribution of and relationship between interplanetary (IP) shock properties and ∼0.1-20 MeV nucleon-1 O and Fe ions during seven multi-spacecraft energetic storm particle (ESP) events at 1 au. These ESP events were observed at two spacecraft and were primarily associated with low Mach number, quasi-perpendicul…
Analysis of the Herschel/Hexos Spectral Survey Toward Orion South: A Massive Protostellar Envelope with Strong External Irradiation
Menten, K. M.; Pagani, L.; Lis, D. C. +14 more
We present results from a comprehensive submillimeter spectral survey toward the source Orion South, based on data obtained with the Heterodyne Instrument for the Far-Infrared instrument on board the Herschel Space Observatory, covering the frequency range of 480 to 1900 GHz. We detect 685 spectral lines with signal-to-noise ratios (S/Ns) > 3σ,…
M Dwarf Activity in the Pan-STARRS1 Medium-Deep Survey: First Catalog and Rotation Periods
Berger, E.; Rest, A.; Chambers, K. C. +10 more
We report on an ongoing project to investigate activity in the M dwarf stellar population observed by the Pan-STARRS1 Medium-Deep Survey (PS1-MDS). Using a custom-built pipeline, we refine an initial sample of ∼4 million sources in PS1-MDS to a sample of 184,148 candidate cool stars using color cuts. Motivated by the well-known relationship betwee…
A Perturbative Analysis of Synchrotron Spectral Index Variation over the Microwave Sky
Aluri, Pavan K.; Saha, Rajib
In this paper, we implement a perturbative approach, first proposed by Bouchet & Gispert, to estimate the variation of the spectral index of galactic polarized synchrotron emission, using a linear combination of simulated Stokes Q polarization maps of selected frequency bands from WMAP and Planck observations on a region of sky dominated by th…
Isolating the Young Stellar Population in the Outer Disk of NGC 300
Dolphin, Andrew E.; Skillman, Evan D.; Williams, Benjamin F. +2 more
The recent star formation history (SFH) in the outer disk of NGC 300 is presented through the analysis of color-magnitude diagrams (CMDs). We analyze resolved stellar photometry by creating CMDs from four Hubble Space Telescope fields containing a combination of images from the Advanced Camera for Surveys and the UVIS imager aboard the Wide Field …
Of Genes and Machines: Application of a Combination of Machine Learning Tools to Astronomy Data Sets
Kumar, S.; Chambers, K. C.; Flewelling, H. +8 more
We apply a combination of genetic algorithm (GA) and support vector machine (SVM) machine learning algorithms to solve two important problems faced by the astronomical community: star-galaxy separation and photometric redshift estimation of galaxies in survey catalogs. We use the GA to select the relevant features in the first step, followed by op…
Panchromatic Imaging of a Transitional Disk: The Disk of GM Aur in Optical and FUV Scattered Light
Apai, D.; Hamaguchi, K.; Henning, Th. +18 more
We have imaged GM Aurigae with the Hubble Space Telescope, detected its disk in scattered light at 1400 and 1650 Å, and compared these with observations at 3300 Å, 5550 Å, 1.1 µm, and 1.6 µm. The scattered light increases at shorter wavelengths. The radial surface brightness profile at 3300 Å shows no evidence of the 24 au radius cavit…