Search Publications
First Three-dimensional Reconstructions of Coronal Loops with the STEREO A+B Spacecraft. IV. Magnetic Modeling with Twisted Force-free Fields
DeRosa, Marc L.; Nitta, Nariaki V.; Aschwanden, Markus J. +3 more
The three-dimensional coordinates of stereoscopically triangulated loops provide strong constraints for magnetic field models of active regions in the solar corona. Here, we use STEREO/A and B data from some 500 stereoscopically triangulated loops observed in four active regions (2007 April 30, May 9, May 19, and December 11), together with SOHO/M…
Probing Dynamical Processes in the Planet-forming Region with Dust Mineralogy
Manoj, P.; Watson, D. M.; Sargent, B. +6 more
We present Herschel Space Observatory PACS spectra of GQ Lup, a protoplanetary disk in the Lupus star-forming region. Through spectral energy distribution fitting from 0.3 µm to 1.3 mm, we construct a self-consistent model of this system's temperature and density structures, finding that although it is 3 Myr old, its dust has not settled to …
The Dynamics and Heating of Active Region Loops
Doschek, G. A.
I examine the dynamics of active regions using spectra obtained by the Extreme-ultraviolet Imaging Spectrometer (EIS) on the Hinode spacecraft. I show the relationship between non-thermal velocities, Doppler outflows and downflows, intensities, and electron density for two representative active regions out of a group of 18 active regions examined.…
The Hubble Space Telescope Cluster Supernova Survey. VI. The Volumetric Type Ia Supernova Rate
Gladders, M. D.; Panagia, N.; Huang, X. +41 more
We present a measurement of the volumetric Type Ia supernova (SN Ia) rate out to z ~= 1.6 from the Hubble Space Telescope Cluster Supernova Survey. In observations spanning 189 orbits with the Advanced Camera for Surveys we discovered 29 SNe, of which approximately 20 are SNe Ia. Twelve of these SNe Ia are located in the foregrounds and background…
On the Force-free Nature of Photospheric Sunspot Magnetic Fields as Observed from Hinode (SOT/SP)
Tiwari, Sanjiv Kumar
A magnetic field is force-free if there is no interaction between it and the plasma in the surrounding atmosphere, i.e., electric currents are aligned with the magnetic field, giving rise to zero Lorentz force. The computation of various magnetic parameters, such as magnetic energy (using the virial theorem), gradient of twist of sunspot magnetic …
On the Origin of the Supergiant H I Shell and Putative Companion in NGC 6822
Cannon, John M.; Dolphin, Andrew E.; Skillman, Evan D. +6 more
We present new Hubble Space Telescope Advanced Camera for Surveys imaging of six positions spanning 5.8 kpc of the H I major axis of the Local Group dIrr NGC 6822, including both the putative companion galaxy and the large H I hole. The resulting deep color-magnitude diagrams show that NGC 6822 has formed >50% of its stars in the last ~5 Gyr. T…
The Y SZ-YX Scaling Relation as Determined from Planck and Chandra
Vikhlinin, Alexey; More, Surhud; Rozo, Eduardo
Sunyaev-Zeldovich (SZ) clusters surveys, such as Planck, the South Pole Telescope, and the Atacama Cosmology Telescope, will soon be publishing several hundred SZ-selected systems. The key ingredient required to transport the mass calibration from current X-ray-selected cluster samples to these SZ systems is the Y SZ-YX scali…
A New Code for Nonlinear Force-free Field Extrapolation of the Global Corona
Feng, Xueshang; Jiang, Chaowei; Xiang, Changqing
Reliable measurements of the solar magnetic field are still restricted to the photosphere, and our present knowledge of the three-dimensional coronal magnetic field is largely based on extrapolations from photospheric magnetograms using physical models, e.g., the nonlinear force-free field (NLFFF) model that is usually adopted. Most of the current…
V900 Mon and Thommes' Nebula: A New FUor in Monoceros
Reipurth, Bo; Aspin, Colin; Herbig, G. H.
Detailed observations of a recently recognized eruptive variable, V900 Mon, are presented. The star is located in the small cloud L1656, a little-studied region of modest star formation activity in Monoceros, and is presently at a magnitude of r ~ 16, surrounded by a bright compact reflection nebula, where only a 20th magnitude star was seen on th…
Keck/NIRC2 Imaging of the Warped, Asymmetric Debris Disk around HD 32297
Currie, Thayne; Debes, John; Robitaille, Thomas +8 more
We present Keck/NIRC2 Ks -band high-contrast coronagraphic imaging of the luminous debris disk around the nearby, young A star HD 32297 resolved at a projected separation of r = 0farcs3-2farcs5 (≈35-280 AU). The disk is highly warped to the north and exhibits a complex, "wavy" surface brightness (SB) profile interior to r ≈ 110 AU, wher…