Search Publications
A Self-Consistent Nonlinear Force-Free Solution for a Solar Active Region Magnetic Field
Régnier, S.; Wheatland, M. S.
Nonlinear force-free solutions for the magnetic field in the solar corona constructed using photospheric vector magnetic field boundary data suffer from a basic problem: the observed boundary data are inconsistent with the nonlinear force-free model. Specifically, there are two possible choices of boundary conditions on vertical current provided b…
Spitzer View of Young Massive Stars in the Large Magellanic Cloud H II Complex N 44
Gordon, Karl D.; Chu, You-Hua; Gruendl, Robert A. +2 more
The H II complex N 44 in the Large Magellanic Cloud (LMC) provides an excellent site to perform a detailed study of star formation in a mild starburst, as it hosts three regions of star formation at different evolutionary stages, and it is not as complicated and confusing as the 30 Doradus giant H II region. We have obtained Spitzer Space Telescop…
Revealing the Structure of a Pre-Transitional Disk: The Case of the Herbig F Star SAO 206462 (HD 135344B)
Ménard, F.; Apai, D.; Hamaguchi, K. +23 more
SAO 206462 (HD 135344B) has previously been identified as a Herbig F star with a circumstellar disk with a dip in its infrared excess near 10 µm. In combination with a low accretion rate estimated from Br γ, it may represent a gapped, but otherwise primordial or "pre-transitional" disk. We test this hypothesis with Hubble Space Telescope cor…
Current Buildup in Emerging Serpentine Flux Tubes
Aulanier, G.; Masson, S.; Pariat, E.
The increase of magnetic flux in the solar atmosphere during active-region formation involves the transport of the magnetic field from the solar convection zone through the lowest layers of the solar atmosphere, through which the plasma β changes from >1 to <1 with altitude. The crossing of this magnetic transition zone requires the magnetic…
The NGC 300 Transient: An Alternative Method for Measuring Progenitor Masses
Williams, Benjamin F.; Dolphin, Andrew; Dalcanton, Julianne J. +3 more
We present an alternative technique for measuring the precursor masses of transient events in stars undergoing late stage stellar evolution. We use the well-established techniques of stellar population modeling to age-date the stars surrounding the site of the recent transient event in NGC 300 (NGC 300 OT2008-1). The surrounding stars must share a…
Correlated X-Ray and Very High Energy Emission in the Gamma-Ray Binary LS I +61 303
Maraschi, L.; Covino, S.; Antonelli, L. A. +153 more
The discovery of very high energy (VHE) gamma-ray emitting X-ray binaries has triggered an intense effort to better understand the particle acceleration, absorption, and emission mechanisms in compact binary systems, which provide variable conditions along eccentric orbits. Despite this, the nature of some of these systems, and of the accelerated …
Some Like It Hot: Coronal Heating Observations from Hinode X-ray Telescope and RHESSI
Lin, L.; Golub, L.; Schmelz, J. T. +7 more
We have used Hinode X-Ray Telescope observations and RHESSI upper limits together to characterize the differential emission measure (DEM) from a quiescent active region. We find a relatively smooth DEM curve with the expected active region peak at log T = 6.4. We also find a high-temperature component with significant emission measure at log T gsi…
New Observation of Failed Filament Eruptions: The Influence of Asymmetric Coronal Background Fields on Solar Eruptions
Liu, Y.; Shibata, K.; Lin, H. +3 more
Failed filament eruptions not associated with a coronal mass ejection (CME) have been observed and reported as evidence for solar coronal field confinement on erupting flux ropes. In those events, each filament eventually returns to its origin on the solar surface. In this Letter, a new observation of two failed filament eruptions is reported whic…
Global Star Formation Rate Density over 0.7 < z < 1.9
Henry, Alaina; Shim, Hyunjin; Teplitz, Harry +4 more
We determine the global star formation rate (SFR) density at 0.7 < z < 1.9 using emission-line-selected galaxies identified in Hubble Space Telescope-Near Infrared Camera and Multi-Object Spectrograph (HST-NICMOS) grism spectroscopy observations. Observing in a pure parallel mode throughout HST Cycles 12 and 13, our survey covers ~104 arcmin…
Simultaneous Multiwavelength Observations of Markarian 421 During Outburst
Maraschi, L.; Covino, S.; Antonelli, L. A. +226 more
We report on the results of two coordinated multiwavelength campaigns that focused on the blazar Markarian 421 during its 2006 and 2008 outbursts. These campaigns obtained UV and X-ray data using the XMM-Newton satellite, while the gamma-ray data were obtained utilizing three imaging atmospheric Cerenkov telescopes, the Whipple 10 m telescope and …