Search Publications
Variability in Protoplanetary Nebulae: VII. Light-curve Studies of Five Medium-bright, Oxygen-rich, or Mixed-chemistry Post-AGB/Post-RGB Objects
Lu, Wenxian; Volk, Kevin; Hrivnak, Bruce J. +3 more
We have monitored over a 10-year interval the light variations of five evolved stars with very large mid-infrared excesses. All five objects appear to have oxygen-rich or mixed oxygen-rich and carbon-rich chemistries. They all vary in light: four over a small range of ∼0.2 mag and the fifth over a larger range of ∼0.7 mag. Spectral types range fro…
The Composite X-Ray Spectrum of 3CRR Quasars
Gu, Minfeng; Zhou, Minhua
The reason for the difference between the composite X-ray spectrum for radio-loud quasars (RLQs) versus radio-quiet quasars (RQQs) is still unclear. To study this difference, we built a new composite X-ray spectrum of RLQs using Chandra X-ray data and Sloan Digital Sky Survey optical data for the sample of 3CRR quasars. We find the X-ray spectra o…
Study of the Dynamics of Convective Turbulence in the Solar Granulation by Spectral Line Broadening and Asymmetry
Katsukawa, Yukio; Ishikawa, Ryohtaroh T.; Oba, Takayoshi +3 more
In quiet regions on the solar surface, turbulent convective motions of granulation play an important role in creating small-scale magnetic structures, as well as in energy injection into the upper atmosphere. The turbulent nature of granulation can be studied using spectral line profiles, especially line broadening, which contain information on th…
Flare Properties of A-type Stars in Kepler Data
Esamdin, Ali; Bai, Jian-Ying
We analyzed the long-cadence (LC) light curves of 5435 stars with effective temperatures of 7000-10,500 K in Data Release 25 of Kepler to extend the samples of A-type flare stars and study their flare properties. A total of 103 flare stars are detected, of which 72 have the Large Sky Area Multi-Object fiber Spectroscopic Telescope spectral types, …
Herschel SPIRE Discovery of Far-infrared Excess Synchrotron Emission from the West Hot Spot of the Radio Galaxy Pictor A
Isobe, Naoki; Pearson, Chris; Tashiro, Makoto +4 more
A far-infrared counterpart to the west hot spot of the radio galaxy Pictor A is discovered with the Spectral and Photometric Imaging REceiver (SPIRE) on board Herschel. The color-corrected flux density of the source is measured as 70.0 ± 9.9 mJy at the wavelength of 350 µm. A close investigation into its radio-to-optical spectrum indicates t…
Peak Temperatures of Large Solar X-Ray Flares and Associated CME Speeds and Widths
Kahler, S. W.; Ling, A. G.
We recently repeated an earlier analysis by Garcia showing that large (≥M3.0) solar X-ray flares associated with solar energetic particle (SEP) events have significantly lower peak X-ray flux ratios R = (0.04-0.5 nm)/(0.1-0.8 nm), proxies for flare peak temperatures, than those without SEP events. As we expect SEP events to be produced by shocks a…
A Mean Density of 112 M⊙ pc-3 for Central Molecular Zone Clumps—Evidences for Shear-enabled Pressure Equilibrium in the Galactic Center
Zhang, Chuan-Peng; Li, Guang-Xing
We carry out a systematic study of the density structure of gas in the Central Molecular Zone (CMZ) in the Galactic center by extracting clumps from the APEX Telescope Large Area Survey of the Galaxy survey at 870 µm. We find that the clumps follow a scaling of m = ρ0r3, which corresponds to a characteristic density of …
A Dust Trap in the Young Multiple System HD 34700
Wilner, David J.; Zhang, Qizhou; Rich, Evan A. +6 more
Millimeter observations of disks around young stars reveal substructures indicative of gas pressure traps that may aid grain growth and planet formation. We present Submillimeter Array observations of HD 34700: two Herbig Ae stars in a close binary system (Aa/Ab, ∼0.25 au), surrounded by a disk presenting a large cavity and spiral arms seen in sca…
Identification of Two Distinct Electron Populations in an Impulsive Solar Energetic Electron Event
Wang, L.; Zhao, L.; Li, G. +2 more
We examine the release times of energetic electrons in the 2001 April 25 event. An M2.7 flare occurred on 2001 April 25, from AR 09433, located at N18W09. The flare was observed in X-rays by GOES and the Yohkoh spacecraft. The Yohkoh observation also included hard X-ray (HXR) images for all four energy channels: L, M1, M2, and H. We use Yohkoh obs…
Comparing Observed Stellar Kinematics and Surface Densities in a Low-latitude Bulge Field to Galactic Population Synthesis Models
Anderson, Jay; Penny, Matthew T.; Bennett, David P. +3 more
We present an analysis of Galactic bulge stars from Hubble Space Telescope Wide Field Camera 3 observations of the Stanek window (l, b = [0.25, -2.15]) from two epochs approximately two years apart. This data set is adjacent to the provisional Wide-field Infrared Survey Telescope (WFIRST) microlensing field. Proper motions are measured for approxi…