Search Publications
The Flux-Rope Scaling of the Acceleration of Coronal Mass Ejections and Eruptive Prominences
Schuck, P. W.; Chen, J.; Vourlidas, A. +2 more
The new flux-rope scaling law of the acceleration of coronal mass ejections (CMEs) derived by Chen & Krall is quantitatively tested by comparing the theoretical prediction with the near-Sun acceleration profiles of 13 eruptive prominences (EPs) and four CMEs. A CME and associated EP are assumed to be organized by an underlying magnetic flux ro…
The Dwarf Novae during Quiescence
Sion, Edward M.; Urban, Joel A.
We present a synthetic spectral analysis of nearly the entire far-ultraviolet (FUV) IUE archive of spectra of dwarf novae (DNe) in or near their quiescence. We have examined all of the systems for which the signal-to-noise ratio permitted an analysis. The study includes 53 systems of all DN subtypes both above and below the period gap. The spectra…
Hubble Space Telescope STIS Spectroscopy and Modeling of the Long-Term Cooling of WZ Sagittae following the 2001 July Outburst
Szkody, Paula; Sion, Edward M.; Godon, Patrick +3 more
We present the latest Hubble Space Telescope Space Telescope Imaging Spectrograph (HST STIS) E140M far-ultraviolet (FUV) spectrum of the dwarf nova WZ Sge, obtained in 2004 July, 3 yr following the early superoutburst of 2001 July. With a temperature T~15,000 K, the white dwarf (WD) is still ~1500 K above its quiescent temperature, it has a FUV fl…
Microlensing of the Lensed Quasar SDSS 0924+0219
Kochanek, C. S.; Morgan, Nicholas D.; Morgan, Christopher W. +1 more
We analyze V-, I-, and H-band HST images and two seasons of R-band monitoring data for the gravitationally lensed quasar SDSS 0924+0219. We clearly see that image D is a point-source image of the quasar at the center of its host galaxy. We can easily track the host galaxy of the quasar close to image D because microlensing has provided a natural c…
Spectral Modeling of SNe Ia Near Maximum Light: Probing the Characteristics of Hydrodynamical Models
Baron, E.; Branch, David; Hauschildt, Peter H. +1 more
We have performed detailed non-local thermodynamic equilibrium (NLTE) spectral synthesis modeling of two types of one-dimensional hydrodynamical models: the very highly parameterized deflagration model W7, and two delayed-detonation models. We find that, overall, both models do about equally well at fitting well-observed SNe Ia near maximum light.…
Physical Conditions in Orion's Veil. II. A Multicomponent Study of the Line of Sight toward the Trapezium
Abel, N. P.; O'Dell, C. R.; Ferland, G. J. +2 more
Orion's Veil is an absorbing screen that lies along the line of sight to the Orion H II region. It consists of two or more layers of gas that must lie within a few parsecs of the Trapezium cluster. Our previous work considered the Veil as a whole and found that the magnetic field dominates the energetics of the gas in at least one component. Here …
Clustering of i775 Dropout Galaxies at z ~ 6 in GOODS and the UDF
Franx, Marijn; Illingworth, Garth D.; Bouwens, Rychard J. +1 more
We measured the angular clustering at z~6 from a large sample of i775 dropout galaxies (293 with z850<=27.5 from GOODS and 95 with z850<=29.0 from the UDF). Our largest and most complete subsample (having L>~0.5L*z=6) shows the presence of clustering at 94% significance. For this samp…
The Connection between Bar Strength and Circumnuclear Dust Structure
Martini, Paul; Peeples, Molly S.
We present a comparison of bar strength Qb and circumnuclear dust morphology for 75 galaxies in order to investigate how bars affect the centers of galaxies. We trace the circumnuclear dust morphology and amount of dust structure with structure maps generated from visible-wavelength HST data, finding that tightly wound nuclear dust spir…
The Structure and Star Formation History of Early-Type Galaxies in the Ultra Deep Field/GRAPES Survey
Daddi, E.; Panagia, N.; Koekemoer, A. M. +9 more
We present a two-pronged approach to the formation of early-type galaxies, using a sample of 18 galaxies at 0.5<~z<~1 from the HST ACS Ultra Deep Field and GRAPES surveys: (1) We combine slitless low-resolution spectroscopy from the GRAPES data set with simple models of galaxy formation to explore their star formation histories. (2) We also …
The Pulsar Wind Nebula of the Geminga Pulsar
Pavlov, G. G.; Zavlin, V. E.; Sanwal, D.
The superb spatial resolution of Chandra has allowed us to detect a 20" long tail behind the Geminga pulsar, with a hard spectrum (photon index Γ=1.0+/-0.2) and a luminosity of (1.3+/-0.2)×1029 ergs s-1 in the 0.5-8 keV band, for an assumed distance of 200 pc. The tail could be either a pulsar jet, confined by a toroidal magn…