Search Publications
Modeling the Initiation of the 2006 December 13 Coronal Mass Ejection in AR 10930: The Structure and Dynamics of the Erupting Flux Rope
Fan, Yuhong
We carry out a 3D magnetohydrodynamic simulation to model the initiation of the coronal mass ejection (CME) on 2006 December 13 in the emerging δ-sunspot active region NOAA 10930. The setup of the simulation is similar to a previous simulation by Fan, but with a significantly widened simulation domain to accommodate the wide CME. The simulation sh…
Transition Region Abundance Measurements During Impulsive Heating Events
Warren, Harry P.; Doschek, George A.; Brooks, David H. +1 more
It is well established that elemental abundances vary in the solar atmosphere and that this variation is organized by first ionization potential (FIP). Previous studies have shown that in the solar corona, low-FIP elements such as Fe, Si, Mg, and Ca, are generally enriched relative to high-FIP elements such as C, N, O, Ar, and Ne. In this paper we…
Evidence for Reflected Light from the Most Eccentric Exoplanet Known
Butler, R. Paul; Mahadevan, Suvrath; Henry, Gregory W. +16 more
Planets in highly eccentric orbits form a class of objects not seen within our solar system. The most extreme case known among these objects is the planet orbiting HD 20782, with an orbital period of 597 days and an eccentricity of 0.96. Here we present new data and analysis for this system as part of the Transit Ephemeris Refinement and Monitorin…
IC 3639—a New Bona Fide Compton-Thick AGN Unveiled by NuSTAR
Harrison, F. A.; Stern, D.; Zhang, W. W. +19 more
We analyze high-quality NuSTAR observations of the local (z = 0.011) Seyfert 2 active galactic nucleus (AGN) IC 3639, in conjunction with archival Suzaku and Chandra data. This provides the first broadband X-ray spectral analysis of the source, spanning nearly two decades in energy (0.5-30 keV). Previous X-ray observations of the source below 10 k…
Constraints on the Binary Companion to the SN Ic 1994I Progenitor
Van Dyk, Schuyler D.; de Mink, Selma E.; Zapartas, Emmanouil
Core-collapse supernovae (SNe), which mark the deaths of massive stars, are among the most powerful explosions in the universe and are responsible, e.g., for a predominant synthesis of chemical elements in their host galaxies. The majority of massive stars are thought to be born in close binary systems. To date, putative binary companions to the p…
Compact Galactic Planetary Nebulae: An HST/WFC3 Morphological Catalog, and a Study of Their Role in the Galaxy
Villaver, Eva; Shaw, Richard A.; Stanghellini, Letizia
We present the images of a Hubble Space Telescope (HST/WFC3) snapshot program of angularly compact Galactic planetary nebulae (PNe), acquired with the aim of studying their size, evolutionary status, and morphology. PNe that are smaller than ∼4″ are underrepresented in most morphological studies, and today they are less well studied than their imm…
The Star Formation Rate Efficiency of Neutral Atomic-dominated Hydrogen Gas in the Outskirts of Star-forming Galaxies from z ~ 1 to z ~3
Koekemoer, Anton M.; Gardner, Jonathan P.; Teplitz, Harry I. +5 more
Current observational evidence suggests that the star formation rate (SFR) efficiency of neutral atomic hydrogen gas measured in damped Lyα systems (DLAs) at z∼ 3 is more than 10 times lower than predicted by the Kennicutt-Schmidt (KS) relation. To understand the origin of this deficit, and to investigate possible evolution with redshift and galax…
Enhancement of a Sunspot Light Wall with External Disturbances
Yang, Shuhong; Zhang, Jun; Erdélyi, Robert
Based on the Interface Region Imaging Spectrograph observations, we study the response of a solar sunspot light wall to external disturbances. A flare occurrence near the light wall caused material to erupt from the lower solar atmosphere into the corona. Some material falls back to the solar surface and hits the light bridge (I.e., the base of th…
First Detection of a Pulsar Bow Shock Nebula in Far-UV: PSR J0437-4715
Pavlov, George G.; Kargaltsev, Oleg; Rangelov, Blagoy +3 more
Pulsars traveling at supersonic speeds are often accompanied by cometary bow shocks seen in Hα. We report on the first detection of a pulsar bow shock in the far-ultraviolet (FUV). We detected it in FUV images of the nearest millisecond pulsar J0437-4715 obtained with the Hubble Space Telescope. The images reveal a bow-like structure positionally …
H II Region Ionization of the Interstellar Medium: A Case Study of NGC 7538
Anderson, L. D.; Bania, T. M.; Balser, Dana S. +2 more
Using data from the Green Bank Telescope, we analyze the radio continuum (free-free) and radio recombination line (RRL) emission of the compact H II region NGC 7538 (Sharpless 158). We detect extended radio continuum and hydrogen RRL emission beyond the photodissociation region (PDR) toward the north and east, but a sharp decrease in emission towa…