2,727 research outputs found
The Impact of Type Ia Supernova Ejecta on Binary Companions
We present adaptive mesh refinement (AMR) hydrodynamical simulations of the
interaction between Type Ia supernovae and their companion stars within the
context of the single-degenerate model. Results for 3D red-giant companions
without binary evolution agree with previous 2D results by Marietta et al. We
also consider evolved helium-star companions in 2D. For a range of helium-star
masses and initial binary separations, we examine the mass unbound by the
interaction and the kick velocity delivered to the companion star. We find that
unbound mass versus separation obeys a power law with index between -3.1 and
-4.0, consistent with previous results for hydrogen-rich companions. Kick
velocity also obeys a power-law relationship with binary separation, but the
slope differs from those found for hydrogen-rich companions. Assuming accretion
via Roche-lobe overflow, we find that the unbound helium mass is consistent
with observational limits. Ablation (shock heating) appears to be more
important in removing gas from helium-star companions than from hydrogen-rich
ones, though stripping (momentum transfer) dominates in both cases.Comment: 6 pages, 2 figures, to appear in the proceedings of the conference
"Binary Star Evolution: Mass Loss, Accretion, and Mergers" at Mykonos,
Greece, June 22-25, 201
A Direct Multigrid Poisson Solver for Oct-Tree Adaptive Meshes
We describe a finite-volume method for solving the Poisson equation on
oct-tree adaptive meshes using direct solvers for individual mesh blocks. The
method is a modified version of the method presented by Huang and Greengard
(2000), which works with finite-difference meshes and does not allow for shared
boundaries between refined patches. Our algorithm is implemented within the
FLASH code framework and makes use of the PARAMESH library, permitting
efficient use of parallel computers. We describe the algorithm and present test
results that demonstrate its accuracy.Comment: 10 pages, 6 figures, accepted by the Astrophysical Journal; minor
revisions in response to referee's comments; added char
Water Quality Project Evaluation A Handbook for Objectives-Based Evaluation of Water Quality Projects
PDF pages: 5
Effects of fresnel prisms on two clinical stereoscopic tests: An exploratory study
Effects of fresnel prisms on two clinical stereoscopic tests: An exploratory stud
Optical and X-ray Observations of the Afterglow to XRF030723
The X-ray-flash XRF030723 was detected by the HETE satellite and rapidly
disseminated, allowing for an optical transient to be detected ~1 day after the
burst. We discuss observations in the optical with Magellan, which confirmed
the fade of the optical transient. In a 2-epoch ToO observation with Chandra,
we discovered a fading X-ray source spatially coincident with the optical
transient. We present spectral fits to the X-ray data. We also discuss the
possibility that the source underwent a rebrightening in the X-rays, as was
observed in the optical. We find that the significance of a possible
rebrightening is very low (~1 sigma).Comment: 4 pages, 2 figures, to appear in Santa Fe GRB Conference Proceedings,
200
Observation and implications of the Epeak - Eiso correlation in Gamma-Ray Bursts
The availability of a few dozen GRB redshifts now allows studies of the
intrinsic properties of these high energy transients. Amati et al. recently
discovered a correlation between Epeak, the intrinsic peak energy of the spectrum, and Eiso, the isotropic equivalent energy radiated by the
source. Lamb et al. have shown that HETE-2 data confirm and extend this
correlation. We discuss here one of the consequences of this correlation: the
existence of a 'spectral standard candle', which can be used to construct a
simple redshift indicator for GRBs.Comment: Proceedings of the GRB 2003 Conference in SantaFe, 5 pages, 4 figure
X-ray Observations of Optically Selected Giant Elliptical-Dominated Galaxy Groups
We present a combined optical and X-ray analysis of three optically selected
X-ray bright groups with giant elliptical galaxies in the center. These massive
ellipticals were targeted for XMM-Newton X-ray observations based on their
large velocity dispersions and their proximity to a nearby ROSAT X-ray source.
Additionally, these targets are significantly brighter in the optical than
their nearest neighbors. We show that one of these systems meets the standard
criteria for a fossil group. While the other two systems have a prominent
magnitude gap in the E/S0 ridgeline, they do not appear to have reached the
fossil-like final stage of group evolution.Comment: 8 pages, 6 figures, Accepted for publication in Ap
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