202 research outputs found
Early X-ray emission from Type Ia supernovae originating from symbiotic progenitors or recurrent novae
One of the key observables for determining the progenitor nature of Type Ia
supernovae is provided by their immediate circumstellar medium, which according
to several models should be shaped by the progenitor binary system. So far,
X-ray and radio observations indicate that the surroundings are very tenuous,
producing severe upper-limits on the mass loss from winds of the progenitors.
In this study, we perform numerical hydro-dynamical simulations of the
interaction of the SN ejecta with circumstellar structures formed by possible
mass outflows from the progenitor systems and we estimate numerically the
expected numerical X-ray luminosity. We consider two kinds of circumstellar
structures: a) A circumstellar medium formed by the donor star's stellar wind,
in case of a symbiotic binary progenitor system; b) A circumstellar medium
shaped by the interaction of the slow wind of the donor star with consecutive
nova outbursts for the case of a symbiotic recurrent nova progenitor system.
For the hydro-simulations we used well-known Type Ia supernova explosion
models, as well as an approximation based on a power law model for the density
structure of the outer ejecta. We confirm the strict upper limits on stellar
wind mass loss, provided by simplified interpretations of X-ray upper limits of
Type Ia supernovae. However, we show that supernova explosions going off in the
cavities created by repeated nova explosions, provide a possible explanation
for the lack of X-ray emission from supernovae originating from symbiotic
binaries. Moreover, the velocity structure of circumstellar medium, shaped by a
series of nova explosion matches well with the Na absorption features seen in
absorption toward several Type Ia supernovae.Comment: 11 pages, 12 figures, submitted to MNRA
The many sides of RCW 86: a type Ia supernova remnant evolving in its progenitor's wind bubble
We present the results of a detailed investigation of the Galactic supernova
remnant RCW 86 using the XMM-Newton X-ray telescope. RCW 86 is the probable
remnant of SN 185 A.D, a supernova that likely exploded inside a wind-blown
cavity. We use the XMM-Newton Reflection Grating Spectrometer (RGS) to derive
precise temperatures and ionization ages of the plasma, which are an indication
of the interaction history of the remnant with the presumed cavity. We find
that the spectra are well fitted by two non-equilibrium ionization models,
which enables us to constrain the properties of the ejecta and interstellar
matter plasma. Furthermore, we performed a principal component analysis on EPIC
MOS and pn data to find regions with particular spectral properties. We present
evidence that the shocked ejecta, emitting Fe-K and Si line emission, are
confined to a shell of approximately 2 pc width with an oblate spheroidal
morphology. Using detailed hydrodynamical simulations, we show that general
dynamical and emission properties at different portions of the remnant can be
well-reproduced by a type Ia supernova that exploded in a non-spherically
symmetric wind-blown cavity. We also show that this cavity can be created using
general wind properties for a single degenerate system. Our data and
simulations provide further evidence that RCW 86 is indeed the remnant of SN
185, and is the likely result of a type Ia explosion of single degenerate
origin.Comment: Accepted for publication in MNRAS. 16 pages, 13 figure
Progenitor's signatures in Type Ia supernova remnants
The remnants of Type Ia supernovae can provide important clues about their
progenitor-histories. We discuss two well-observed supernova remnants (SNRs)
that are believed to result from a Type Ia SN and use various tools to shed
light on the possible progenitor history. We find that Kepler's SNR is
consistent with a symbiotic binary progenitor consisted of a white dwarf and an
AGB star. Our hydrosimulations can reproduce the observed kinematic and
morphological properties. For Tycho's remnant we use the characteristics of the
X-ray spectrum and the kinematics to show that the ejecta has likely interacted
with dense circumstellar gas.Comment: 4 pages, 9 figures, proceedings for IAU Symposium 281, Padova, July
201
Modeling the interaction of thermonuclear supernova remnants with circumstellar structures: The case of Tycho's supernova remnant
The well-established Type Ia remnant of Tycho's supernova (SN 1572) reveals
discrepant ambient medium density estimates based on either the measured
dynamics or on the X-ray emission properties. This discrepancy can potentially
be solved by assuming that the supernova remnant (SNR) shock initially moved
through a stellar wind bubble, but is currently evolving in the uniform
interstellar medium with a relatively low density.
We investigate this scenario by combining hydrodynamical simulations of the
wind-loss phase and the supernova remnant evolution with a coupled X-ray
emission model, which includes non-equilibrium ionization. For the explosion
models we use the well-known W7 deflagration model and the delayed detonation
model that was previously shown to provide good fits to the X-ray emission of
Tycho's SNR.
Our simulations confirm that a uniform ambient density cannot simultaneously
reproduce the dynamical and X-ray emission properties of Tycho. In contrast,
models that considered that the remnant was evolving in a dense, but small,
wind bubble reproduce reasonably well both the measured X-ray emission spectrum
and the expansion parameter of Tycho's SNR. Finally, we discuss possible mass
loss scenarios in the context of single- and double-degenerate models which
possible could form such a small dense wind bubble.Comment: 12 pages, 7 figures, accepted for publication in MNRA
The Interaction of Type Ia Supernovae with Planetary Nebulae: the Case of Kepler's Supernova Remnant
One of the key methods for determining the unknown nature of Type Ia
supernovae (SNe Ia) is the search for traces of interaction between the SN
ejecta and the circumstellar structures at the resulting supernova remnants
(SNRs Ia). So far, the observables that we receive from well-studied SNRs Ia
cannot be explained self-consistently by any model presented in the literature.
In this study, we suggest that the circumstellar medium (CSM) being observed to
surround several SNRs Ia was mainly shaped by planetary nebulae (PNe) that
originated from one or both progenitor stars. Performing two-dimensional
hydrodynamic simulations, we show that the ambient medium shaped by PNe can
account for several properties of the CSM that have been found to surround SNe
Ia and their remnants. Finally, we model Kepler's SNR considering that the SN
explosion occurred inside a bipolar PN. Our simulations show good agreement
with the observed morphological and kinematic properties of Kepler's SNR. In
particular, our model reproduces the current expansion parameter of Kepler's
SNR, the partial interaction of the remnant with a dense CSM at its northern
region and finally the existence of two opposite protrusions (`ears') at the
equatorial plane of the SNR.Comment: Accepted for publication in Galaxies, 7 page
Unconventional Control of Electromagnetic Waves with Applications in Electrically Small Antennas, Nondiffracting Waves, and Metasurfaces
Although electromagnetics is a well-established field within physics and engineering, it is also a rather dynamic one. Our ever increasing need for connectivity and the rise of medical and military applications constantly create new challenges for researchers in electromagnetics. In this thesis, unconventional methods are proposed for tackling some of these challenges by manipulating the electromagnetic fields in different regions: reactive near field, radiative near field, and far field.
The first topic examined pertains to the development of antennas for Internet of Things (IoT) nodes with extremely small form factors and low power consumption. As a result, they require small and relatively efficient antennas that can be tightly integrated within the node. The antennas should be able to operate with lossy and metallic components in their near field, while maintaining adequate performance. A type of antenna, called a 3D loop, is designed to fulfill these specifications, and is used in two compact IoT systems.
The second thrust aims at developing devices that generate Bessel beams and X waves in their radiative near field. Bessel beams are a class of exotic beams with nondiffracting and self-healing properties. Here, two radiator designs are presented, capable of generating Bessel beams with minimal deviation of their parameters over a broad bandwidth. This allows the generation of nondiffracting and nondispersive pulses (X waves) that remain highly localized within the device’s radiative near field.
The final topic examined aims at analytically modeling the electromagnetic properties of patterned metallic sheets. Such sheets are the building blocks of metasurfaces, which are two dimensional devices that manipulate the properties of a propagating wavefront (amplitude, phase, polarization). Having analytical models for sheets that realize arbitrary electromagnetic properties significantly expedites their design, as opposed to relying on databases of simulated geometries.PHDElectrical EngineeringUniversity of Michigan, Horace H. Rackham School of Graduate Studieshttps://deepblue.lib.umich.edu/bitstream/2027.42/150024/1/nchiot_1.pd
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