Search Publications
Evidence of Impulsive Heating in Active Region Core Loops
Tripathi, Durgesh; Mason, Helen E.; Klimchuk, James A.
Using a full spectral scan of an active region from the Extreme-Ultraviolet Imaging Spectrometer (EIS) we have obtained emission measure EM(T) distributions in two different moss regions within the same active region. We have compared these with theoretical transition region EMs derived for three limiting cases, namely, static equilibrium, strong …
A Far-ultraviolet Survey of M80: X-Ray Source Counterparts, Strange Blue Stragglers, and the Recovery of Nova T Sco
Zurek, David R.; Long, Knox S.; Knigge, Christian +2 more
Using the Advanced Camera for Surveys on Hubble Space Telescope, we have surveyed the far-ultraviolet (FUV) and near-ultraviolet (NUV) populations in the core region of M80. The color-magnitude diagram (CMD) reveals large numbers of blue and extreme horizontal branch stars and blue stragglers, as well as ≈60 objects lying in the region of the CMD …
New X-ray Observations of the Geminga Pulsar Wind Nebula
Pavlov, George G.; Zavlin, Vyacheslav E.; Bhattacharyya, Sudip
Previous observations of the middle-aged pulsar Geminga with XMM-Newton and Chandra have shown an unusual pulsar wind nebula (PWN), with a 20'' long central (axial) tail directed opposite to the pulsar's proper motion and two 2' long, bent lateral (outer) tails. Here, we report on a deeper Chandra observation (78 ks exposure) and a few additional …
Stationarity in Solar Wind Flows
Perri, S.; Balogh, A.
By using single-point measurements in space physics it is possible to study a phenomenon only as a function of time. This means that we cannot have direct access to information about spatial variations of a measured quantity. However, the investigation of the properties of turbulence and of related phenomena in the solar wind widely makes use of a…
Exoplanetary Transits of Limb-brightened Lines: Tentative Si IV Absorption by HD 209458b
Schlawin, E.; Agol, E.; Walkowicz, L. M. +2 more
Transit light curves for stellar continua have only one minimum and a "U" shape. By contrast, transit curves for optically thin chromospheric emission lines can have a "W" shape because of stellar limb brightening. We calculate light curves for an optically thin shell of emission and fit these models to time-resolved observations of Si IV absorpti…
A Detailed look at Chemical Abundances in Magellanic Cloud Planetary Nebulae. I. The Small Magellanic Cloud
Villaver, Eva; Balick, Bruce; Shaw, Richard A. +8 more
We present an analysis of elemental abundances of He, N, O, Ne, S, and Ar in Magellanic Cloud planetary nebulae (PNe) and focus initially on 14 PNe in the Small Magellanic Cloud (SMC). We derive the abundances from a combination of deep, high-dispersion optical spectra, as well as mid-infrared (IR) spectra from the Spitzer Space Telescope. A detai…
Ultra-compact Dwarfs in the Core of the Coma Cluster
Ferguson, Henry C.; Spitler, Lee R.; Forbes, Duncan A. +6 more
We have discovered both a red and a blue subpopulation of ultra-compact dwarf (UCD) galaxy candidates in the Coma galaxy cluster. We analyzed deep F475W (Sloan g) and F814W (I) Hubble Space Telescope images obtained with the Advanced Camera for Surveys Wide Field Channel as part of the Coma Cluster Treasury Survey and have fitted the light profile…
Radioheliograph Observations of Metric Type II Bursts and the Kinematics of Coronal Mass Ejections
Kartha, Sreeja S.; Ramesh, R.; Kathiravan, C. +1 more
Assuming that metric type II radio bursts from the Sun are due to magnetohydrodynamic shocks driven by coronal mass ejections (CMEs), we estimate the average CME acceleration from its source region up to the position of the type II burst. The acceleration values are in the range ≈600-1240 m s^{-2}, which are consistent with values obtained using n…
Coronal Fuzziness Modeled with Pulse-heated Multi-stranded Loop Systems
Reale, Fabio; Peres, Giovanni; Guarrasi, Massimiliano
Coronal active regions are observed to get increasingly fuzzy (i.e., increasingly confused and uniform) in increasingly hard energy bands or lines. We explain this as evidence of fine multi-temperature structure of coronal loops. To this end, we model bundles of loops made of thin strands, each heated by short and intense heat pulses. For simplici…
Spatial and Temporal Distributions of Transient Horizontal Magnetic Fields with Deep Exposure
Tsuneta, Saku; Ishikawa, Ryohko
We obtained a long-exposure vector magnetogram of the quiet Sun photosphere at the disk center with a wide field of view of 51'' × 82''. The observation was performed at Fe I 525.0 nm with the shutterless mode of the Narrow Band Filter Imager of the Solar Optical Telescope (SOT) on board the Hinode satellite. We summed the linear polarization (LP)…