1,001 research outputs found
New Models for X-Ray Synchrotron Radiation from the Remnant of Supernova 1006 AD
Galactic cosmic rays up to energies of around 10^15 eV are assumed to
originate in supernova remnants (SNRs). The shock wave of a young SNR like SN
1006 AD can accelerate electrons to energies greater than 1 TeV, where they can
produce synchrotron radiation in the X-ray band. A new model (SRESC) designed
to model synchrotron X-rays from Type Ia supernovae can constrain values for
the magnetic-field strength and electron scattering properties, with
implications for the acceleration of the unseen ions which dominate the
cosmic-ray energetics. New observations by ASCA, ROSAT, and RXTE have provided
enormously improved data, which now extend to higher X-ray energies. These data
allow much firmer constraints. We will describe model fits to these new data on
SN 1006 AD, emphasizing the physical constraints that can be placed on SNRs and
on the cosmic-ray acceleration process.Comment: 10 pages, 2 figures. to appear in "Cosmic Explosions", proceeding of
the 10th Annual October Astrophysics Conference (ed. S.S. Holt and W. W.
Zhang) LaTex aipproc.st
Exploring the Physics of Type Ia Supernovae Through the X-ray Spectra of their Remnants
We present the results of an ongoing project to use the X-ray observations of
Type Ia Supernova Remnants to constrain the physical processes involved in Type
Ia Supernova explosions. We use the Tycho Supernova Remnant (SN 1572) as a
benchmark case, comparing its observed spectrum with models for the X-ray
emission from the shocked ejecta generated from different kinds of Type Ia
explosions. Both the integrated spectrum of Tycho and the spatial distribution
of the Fe and Si emission in the remnant are well reproduced by delayed
detonation models with stratified ejecta. All the other Type Ia explosion
models fail, including well-mixed deflagrations calculated in three dimensions.Comment: 5 pages, 3 figures, to appear in the proceedings of the "Stellar end
products" workshop, 13-15 April 2005, Granada, Spain, ed. M.A. Perez-Torres,
Vol. 77 (Jan 2006) of MmSA
Thermal X-Ray Emission from Shocked Ejecta in Type Ia Supernova Remnants II: Parameters Affecting the Spectrum
The supernova remnants left behind by Type Ia supernovae provide an excellent
opportunity for the study of these enigmatic objects. In a previous work, we
showed that it is possible to use the X-ray spectra of young Type Ia supernova
remnants to explore the physics of Type Ia supernovae and identify the relevant
mechanism underlying these explosions. Our simulation technique is based on
hydrodynamic and nonequilibrium ionization calculations of the interaction of a
grid of Type Ia explosion models with the surrounding ambient medium, coupled
to an X-ray spectral code. In this work we explore the influence of two key
parameters on the shape of the X-ray spectrum of the ejecta: the density of the
ambient medium around the supernova progenitor and the efficiency of
collisionless electron heating at the reverse shock. We also discuss the
performance of recent 3D simulations of Type Ia SN explosions in the context of
the X-ray spectra of young SNRs. We find a better agreement with the
observations for Type Ia supernova models with stratified ejecta than for 3D
deflagration models with well mixed ejecta. We conclude that our grid of Type
Ia supernova remnant models can improve our understanding of these objects and
their relationship to the supernovae that originated them.Comment: Accepted for publication in Ap
Supernova Ejecta in the Youngest Galactic Supernova Remnant G1.9+0.3
G1.9+0.3 is the youngest known Galactic supernova remnant (SNR), with an
estimated supernova (SN) explosion date of about 1900, and most likely located
near the Galactic Center. Only the outermost ejecta layers with free-expansion
velocities larger than about 18,000 km/s have been shocked so far in this
dynamically young, likely Type Ia SNR. A long (980 ks) Chandra observation in
2011 allowed spatially-resolved spectroscopy of heavy-element ejecta. We
denoised Chandra data with the spatio-spectral method of Krishnamurthy et al.,
and used a wavelet-based technique to spatially localize thermal emission
produced by intermediate-mass elements (IMEs: Si and S) and iron. The spatial
distribution of both IMEs and Fe is extremely asymmetric, with the strongest
ejecta emission in the northern rim. Fe Kalpha emission is particularly
prominent there, and fits with thermal models indicate strongly oversolar Fe
abundances. In a localized, outlying region in the northern rim, IMEs are less
abundant than Fe, indicating that undiluted Fe-group elements (including 56Ni)
with velocities larger than 18,000 km/s were ejected by this SN. But in the
inner west rim, we find Si- and S-rich ejecta without any traces of Fe, so
high-velocity products of O-burning were also ejected. G1.9+0.3 appears similar
to energetic Type Ia SNe such as SN 2010jn where iron-group elements at such
high free-expansion velocities have been recently detected. The pronounced
asymmetry in the ejecta distribution and abundance inhomogeneities are best
explained by a strongly asymmetric SN explosion, similar to those produced in
some recent 3D delayed-detonation Type Ia models.Comment: 6 pages, 3 figures, submitted to ApJ Letter
Nonuniform Expansion of the Youngest Galactic Supernova Remnant G1.9+0.3
We report measurements of X-ray expansion of the youngest Galactic supernova
remnant, G1.9+0.3, using Chandra observations in 2007, 2009, and 2011. The
measured rates strongly deviate from uniform expansion, decreasing radially by
about 60% along the X-ray bright SE-NW axis from 0.84% +/- 0.06% per yr to
0.52% +/- 0.03% per yr. This corresponds to undecelerated ages of 120-190 yr,
confirming the young age of G1.9+0.3, and implying a significant deceleration
of the blast wave. The synchrotron-dominated X-ray emission brightens at a rate
of 1.9% +/- 0.4% per yr. We identify bright outer and inner rims with the blast
wave and reverse shock, respectively. Sharp density gradients in either ejecta
or ambient medium are required to produce the sudden deceleration of the
reverse shock or the blast wave implied by the large spread in expansion ages.
The blast wave could have been decelerated recently by an encounter with a
modest density discontinuity in the ambient medium, such as found at a wind
termination shock, requiring strong mass loss in the progenitor. Alternatively,
the reverse shock might have encountered an order-of-magnitude density
discontinuity within the ejecta, such as found in pulsating delayed-detonation
Type Ia models. We demonstrate that the blast wave is much more decelerated
than the reverse shock in these models for remnants at ages similar to
G1.9+0.3. Similar effects may also be produced by dense shells possibly
associated with high-velocity features in Type Ia spectra. Accounting for the
asymmetry of G1.9+0.3 will require more realistic 3D Type Ia models.Comment: 6 pages, 4 figures, accepted for publication in ApJ Letters, minor
revision
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