Search Publications
Origin(s) of the Highly Ionized High-Velocity Clouds Based on Their Distances
Lehner, N.; Howk, J. C.
Previous Hubble Space Telescope and FUSE observations have revealed highly ionized high-velocity clouds (HVCs) or more generally low H I column HVCs along extragalactic sight lines over 70%-90% of the sky. The distances of these HVCs have remained largely unknown hindering from distinguishing a "Galactic" origin (e.g., outflow, inflow) from a "Loc…
Evidence of Solar Flare Triggering Due to Loop-loop Interaction Caused by Footpoint Shear Motion
Srivastava, A. K.; Erdélyi, R.; Kumar, Pankaj +3 more
We analyze multi-wavelength data of an M7.9/1N class solar flare which occurred on 2006 April 27 in AR NOAA 10875. GOES soft X-ray images provide the most likely signature of two interacting loops and their reconnection, which triggers the solar flare. TRACE 195 Å images also reveal the loop-loop interaction and the formation of "X" points with co…
A Statistical Study of the Post-impulsive-phase Acceleration of Flare-associated Coronal Mass Ejections
Cheng, X.; Ding, M. D.; Zhang, J. +1 more
It is now generally accepted that the impulsive acceleration of a coronal mass ejection (CME) in the inner corona is closely correlated in time with the main energy release of the associated solar flare. In this paper, we examine in detail the post-impulsive-phase acceleration of a CME in the outer corona, which is the phase of evolution immediate…
Whistler Turbulence Wavevector Anisotropies: Particle-in-cell Simulations
Saito, Shinji; Gary, S. Peter; Narita, Yasuhito
Two-dimensional electromagnetic particle-in-cell simulations of whistler turbulence in a magnetized, homogeneous, collisionless plasma of electrons and protons are carried out. Enhanced magnetic fluctuation spectra are initially imposed at relatively long wavelengths, and, as in previous such simulations, the temporal evolution shows a forward cas…
Keck/LRIS Spectroscopic Confirmation of Coma Cluster Dwarf Galaxy Membership Assignments
Ferguson, Henry C.; Marzke, Ronald O.; Chiboucas, Kristin +5 more
Keck/LRIS multi-object spectroscopy has been carried out on 140 of some of the lowest and highest surface brightness faint (19 < R < 22) dwarf galaxy candidates in the core region of the Coma Cluster. These spectra are used to measure redshifts and establish membership for these faint dwarf populations. The primary goal of the low surface br…
Formation of Coronal Holes on the Ashes of Active Regions
Karachik, Nina V.; Pevtsov, Alexei A.; Abramenko, Valentyna I.
We investigate the formation of isolated non-polar coronal holes (CHs) on the remnants of decaying active regions (ARs) at the minimum/early ascending phase of sunspot activity. We follow the evolution of four bipolar ARs and measure several parameters of their magnetic fields including total flux, imbalance, and compactness. As regions decay, the…
A Comprehensive Spectral Analysis of the X-Ray Pulsar 4U 1907+09 from Two Observations with the Suzaku X-ray Observatory
Fürst, Felix; Pottschmidt, Katja; Wilms, Jörn +7 more
We present results from two observations of the wind-accreting X-ray pulsar 4U 1907+09 using the Suzaku Observatory. The broadband time-averaged spectrum allows us to examine the continuum emission of the source and the cyclotron resonance scattering feature at ~19 keV. Additionally, using the narrow CCD response of Suzaku near 6 keV allows us to …
Massive Star Formation of the Sgr A East H II Regions Near the Galactic Center
Yusef-Zadeh, F.; Lacy, J. H.; Wardle, M. +4 more
A group of four compact H II regions associated with the well-known 50 km s-1 molecular cloud is the closest site of on-going star formation to the dynamical center of the Galaxy, at a projected distance of ~6 pc. We present a study of ionized gas based on the [Ne II] (12.8 µm) line, as well as multi-frequency radio continuum, Hub…
Absolute Timing of the Crab Pulsar with the INTEGRAL/SPI Telescope
Molkov, S.; Jourdain, E.; Roques, J. P.
We have investigated the pulse shape evolution of the Crab pulsar emission in the hard X-ray domain of the electromagnetic spectrum. In particular, we have studied the alignment of the Crab pulsar phase profiles measured in the hard X-rays and in other wavebands. To obtain the hard X-ray pulse profiles, we have used six years (2003-2009, with a to…
Enstatite-rich Warm Debris Dust Around HD165014
Nakagawa, Takao; Onaka, Takashi; Ootsubo, Takafumi +6 more
We present the Spitzer/Infrared Spectrograph spectrum of the main-sequence star HD165014, which is a warm (gsim200 K) debris disk candidate discovered by the AKARI All-Sky Survey. The star possesses extremely large excess emission at wavelengths longer than 5 µm. The detected flux densities at 10 and 20 µm are ~10 and ~30 times larger …