Search Publications
The Effect of Magnetic Reconnection and Writhing in a Partial Filament Eruption
Liu, Rui; Alexander, David; Gilbert, Holly R. +1 more
We present observations from 2007 March 2 of a partial filament eruption characterized by two distinct phases of writhing motions: a quasi-static, slowly evolving phase followed by a rapid kinking phase showing a bifurcation of the filament. The quasi-static kinking motions are observed before there is any heating or flaring evident in EUV or soft…
The Shape of Cas A
Wheeler, J. Craig; Maund, Justyn R.; Couch, Sean M.
On the basis of optical, IR, and X-ray studies of Cas A, we propose a geometry for the remnant based on a "jet-induced" scenario with significant systematic departures from axial symmetry. In this model, the main jet axis is oriented in the direction of strong blueshifted motion at an angle of 110°-120° east of north and about 40°-50° to the east …
Spatial Distribution of Magnetic Reconnection in the 2006 December 13 Solar Flare as Observed by Hinode
Jing, Ju; Wang, Haimin; Chae, Jongchul
A massive two-ribbon flare and its source magnetic field region were well captured by the Solar Optical Telescope (SOT) on board Hinode in the Ca II H spectral line and by the Spectro-Polarimeter of SOT, respectively. Using the high-resolution Hinode data sets, we compare the spatial distribution of the local magnetic reconnection rate and the ene…
An Ultraluminous Supersoft X-Ray Source in M81: An Intermediate-Mass Black Hole?
Liu, Jifeng; Di Stefano, Rosanne
Ultraluminous supersoft X-ray sources (ULSSSs) exhibit supersoft spectra with blackbody temperatures of 50-100 eV and bolometric luminosities above 1039 ergs s-1 and are possibly intermediate-mass black holes (IMBHs) of >=103 M⊙ or massive white dwarfs that are progenitors of Type Ia supernovae. In th…
The Nature and Geometry of the Light Echo from SN 2006X
Crotts, Arlin P. S.; Yourdon, David
We report on the discovery of the geometry producing the light echo emanating from supernova 2006X, a nearby but underluminous Type Ia supernova (SN Ia) in M100 (=NGC 4321). This offers a rare chance to study the environment of a SN Ia. Contrary to previous reports, there is little evidence of a circumstellar component in the light echo morphology…
Modeling X-Ray Loops and EUV "Moss" in an Active Region Core
Winebarger, Amy R.; Warren, Harry P.; Falconer, David A.
The soft X-ray intensity of loops in active region cores and the corresponding footpoint, or moss, intensity observed in the EUV remain steady for several hours of observation. The steadiness of the emission has prompted many to suggest that the heating in these loops must also be steady, although no direct comparison between the observed X-ray an…
Theoretical Fits of the δ Cephei Light, Radius, and Radial Velocity Curves
Marconi, Marcella; Bono, Giuseppe; Natale, Giovanni
We present a theoretical investigation of the light, radius, and radial velocity variations of the prototype δ Cephei. We find that the best-fit model accounts for luminosity and velocity amplitudes with an accuracy better than 0.8 σ, and for the radius amplitude with an accuracy of 1.7 σ. The chemical composition of this model suggests a decrease…
The Initial Mass Function of the Stellar Association NGC 602 in the Small Magellanic Cloud with Hubble Space Telescope ACS Observations
Henning, Thomas; Gouliermis, Dimitrios A.; Dolphin, Andrew E. +1 more
We present our photometric study of the stellar association NGC 602 in the wing of the Small Magellanic Cloud (SMC). The data were taken in the filters F555W and F814W using the Advanced Camera for Surveys (ACS) on board the Hubble Space Telescope (HST). Photometry was performed using the ACS module of the stellar photometry package DOLPHOT. We de…
Simultaneous Estimation of Time Delays and Quasar Structure
Kochanek, C. S.; Morgan, Nicholas D.; Meylan, G. +5 more
We expand our Bayesian Monte Carlo method for analyzing the light curves of gravitationally lensed quasars to simultaneously estimate time delays and the sizes of quasar continuum emission regions including their mutual uncertainties. We apply the method to HE1104-1805 and QJ0158-4325, two doubly imaged quasars with microlensing and intrinsic vari…
On the White Dwarf Cooling Sequence of the Globular Cluster ω Centauri
Degl'Innocenti, S.; Marchetti, E.; Pulone, L. +16 more
We present deep and precise photometry (F435W, F625W, F658N) of ω Cen collected with the Advanced Camera for Surveys (ACS) on board the Hubble Space Telescope (HST). We have identified ≈6500 white dwarf (WD) candidates, and the ratio of WD to main-sequence (MS) star counts is found to be at least a factor of 2 larger than the ratio of CO-core WD c…