23 research outputs found
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
Detailed Spectral Modeling of a 3-D Pulsating Reverse Detonation Model: Too Much Nickel
We calculate detailed NLTE synthetic spectra of a Pulsating Reverse
Detonation (PRD) model, a novel explosion mechanism for Type Ia supernovae.
While the hydro models are calculated in 3-D, the spectra use an angle averaged
hydro model and thus some of the 3-D details are lost, but the overall average
should be a good representation of the average observed spectra. We study the
model at 3 epochs: maximum light, seven days prior to maximum light, and 5 days
after maximum light. At maximum the defining Si II feature is prominent, but
there is also a prominent C II feature, not usually observed in normal SNe Ia
near maximum. We compare to the early spectrum of SN 2006D which did show a
prominent C II feature, but the fit to the observations is not compelling.
Finally we compare to the post-maximum UV+optical spectrum of SN 1992A. With
the broad spectral coverage it is clear that the iron-peak elements on the
outside of the model push too much flux to the red and thus the particular PRD
realizations studied would be intrinsically far redder than observed SNe Ia. We
briefly discuss variations that could improve future PRD models.Comment: 15 pages, 4 figures, submitted to Ap
Axisymmetric smoothed particle hydrodynamics with self-gravity
The axisymmetric form of the hydrodynamic equations within the smoothed
particle hydrodynamics (SPH) formalism is presented and checked using idealized
scenarios taken from astrophysics (free fall collapse, implosion and further
pulsation of a sun-like star), gas dynamics (wall heating problem, collision of
two streams of gas) and inertial confinement fusion (ICF, -ablative implosion
of a small capsule-). New material concerning the standard SPH formalism is
given. That includes the numerical handling of those mass points which move
close to the singularity axis, more accurate expressions for the artificial
viscosity and the heat conduction term and an easy way to incorporate
self-gravity in the simulations. The algorithm developed to compute gravity
does not rely in any sort of grid, leading to a numerical scheme totally
compatible with the lagrangian nature of the SPH equations.Comment: 17 pages, 10 figures, 1 Table. Accepted for publication in MNRA
Constraining deflagration models of Type Ia supernovae through intermediate-mass elements
The physical structure of a nuclear flame is a basic ingredient of the theory
of Type Ia supernovae (SNIa). Assuming an exponential density reduction with
several characteristic times we have followed the evolution of a planar nuclear
flame in an expanding background from an initial density 6.6 10^7 g/cm3 down to
2 10^6 g/cm3. The total amount of synthesized intermediate-mass elements (IME),
from silicon to calcium, was monitored during the calculation. We have made use
of the computed mass fractions, X_IME, of these elements to give an estimation
of the total amount of IME synthesized during the deflagration of a massive
white dwarf. Using X_IME and adopting the usual hypothesis that turbulence
decouples the effective burning velocity from the laminar flame speed, so that
the relevant flame speed is actually the turbulent speed on the integral
length-scale, we have built a simple geometrical approach to model the region
where IME are thought to be produced. It turns out that a healthy production of
IME involves the combination of not too short expansion times, t_c > 0.2 s, and
high turbulent intensities. According to our results it could be difficult to
produce much more than 0.2 solar masses of intermediate-mass elements within
the deflagrative paradigma. The calculations also suggest that the mass of IME
scales with the mass of Fe-peak elements, making it difficult to conciliate
energetic explosions with low ejected nickel masses, as in the well observed
SN1991bg or in SN1998de. Thus a large production of Si-peak elements,
especially in combination with a low or a moderate production of iron, could be
better addressed by either the delayed detonation route in standard
Chandrasekhar-mass models or, perhaps, by the off-center helium detonation in
the sub Chandrasekhar-mass scenario.Comment: 9 pages, 5 figures, 2 table
Thermal Timescale Mass Transfer and the Evolution of White Dwarf Binaries
The evolution of binaries consisting of evolved main sequence stars (1 <
M_d/Msun < 3.5) with white dwarf companions (0.7 < M_wd/Msun < 1.2) is
investigated through the thermal mass transfer phase. Taking into account the
stabilizing effect of a strong, optically thick wind from the accreting white
dwarf surface, we have explored the formation of several evolutionary groups of
systems for progenitors with initial orbital periods of 1 and 2 days. The
numerical results show that CO white dwarfs can accrete sufficient mass to
evolve to a Type Ia supernova and ONeMg white dwarfs can be built up to undergo
accretion induced collapse for donors more massive than about 2 Msun. For
donors less massive than ~2 Msun the system can evolve to form a He and CO or
ONeMg white dwarf pair. In addition, sufficient helium can be accumulated (~0.1
Msun) in systems characterized by 1.6 < M_d/Msun < 1.9 and 0.8 < M_wd/Msun < 1
such that sub Chandrasekhar mass models for Type Ia supernovae, involving off
center helium ignition, are possible for progenitor systems evolving via the
Case A mass transfer phase. For systems characterized by mass ratios > 3 the
system likely merges as a result of the occurrence of a delayed dynamical mass
transfer instability. A semi-analytical model is developed to delineate these
phases which can be easily incorporated in population synthesis studies of
these systems.Comment: 9 pages, 6 figures, Latex, emulateapj style, ApJ accepte
Observations of SN2011fe with INTEGRAL
SN2011fe was detected by the Palomar Transient Factory on August 24th 2011 in
M101 few hours after the explosion. From the early spectra it was immediately
realized that it was a Type Ia supernova thus making this event the brightest
one discovered in the last twenty years. In this paper the observations
performed with the instruments on board of INTEGRAL (SPI, IBIS/ISGRI, JEM-X and
OMC) before and after the maximum of the optical light as well as the
interpretation in terms of the existing models of --ray emission from
such kind of supernovae are reported. All INTEGRAL high-energy have only been
able to provide upper limits to the expected emission due to the decay of
Ni. These bounds allow to reject explosions involving a massive white
dwarf in the sub--Chandrasekhar scenario. On the other hand, the optical light
curve obtained with the OMC camera suggests that the event was produced by a
delayed detonation of a CO white dwarf that produced M of
Ni. In this particular case, INTEGRAL would have only been able to
detect the early --ray emission if the supernova had occurred at a
distance of 2 -3 Mpc, although the brightest event could be visible up to
distances larger by a factor two.Comment: Proceedings of "An INTEGRAL view of the high-energy sky (the first 10
years)" the 9th INTEGRAL Workshop, October 15-19, 2012, Paris, France, in
Proceedings of Science (INTEGRAL 2012), Eds. A. Goldwurm, F. Lebrun and C.
Winkler, http://pos.sissa.it/cgi-bin/reader/conf.cgi?confid=176, id number
PoS (INTEGRAL 2012) 103 (2013
Interaction of hemispherical blast waves with inhomogeneous spheres: Probing the collision of a supernova ejecta with a nearby companion star in the laboratory
Past laboratory experiments at high energy density have provided insights into the physics of supernovae, supernova remnants, and the destruction of interstellar clouds. In a typical experimental setting, a laser-driven planar blast wave interacts with a compositionally homogeneous spherical or cylindrical target. In this work we propose a new laboratory platform that accounts for curvature of the impacting shock and density stratification of the target. Both characteristics reflect the conditions expected to exist shortly after a supernova explosion in a close binary system. We provide details of a proposed experimental design (laser drive, target configuration, diagnostic system), optimized to capture the key properties of recent ejectaâcompanion interaction models. Good qualitative agreement found between our experimental models and their astrophysical counterparts highlights the strong potential of the proposed design to probe details of the ejectaâcompanion interaction for broad classes of objects by means of laboratory experiments at high energy density
Observation of SN2011fe with INTEGRAL. I. Pre--maximum phase
SN2011fe was detected by the Palomar Transient Factory on August 24th 2011 in
M101 a few hours after the explosion. From the early optical spectra it was
immediately realized that it was a Type Ia supernova thus making this event the
brightest one discovered in the last twenty years. The distance of the event
offered the rare opportunity to perform a detailed observation with the
instruments on board of INTEGRAL to detect the gamma-ray emission expected from
the decay chains of Ni. The observations were performed in two runs, one
before and around the optical maximum, aimed to detect the early emission from
the decay of Ni and another after this maximum aimed to detect the
emission of Co. The observations performed with the instruments on board
of INTEGRAL (SPI, IBIS/ISGRI, JEMX and OMC) have been analyzed and compared
with the existing models of gamma-ray emission from such kind of supernovae. In
this paper, the analysis of the gamma-ray emission has been restricted to the
first epoch. Both, SPI and IBIS/ISGRI, only provide upper-limits to the
expected emission due to the decay of Ni. These upper-limits on the
gamma-ray flux are of 7.1 10 ph/s/cm for the 158 keV line
and of 2.3 10 ph/s/cm for the 812 keV line. These bounds
allow to reject at the level explosions involving a massive white
dwarf, M in the sub--Chandrasekhar scenario and specifically
all models that would have substantial amounts of radioactive Ni in the
outer layers of the exploding star responsible of the SN2011fe event. The
optical light curve obtained with the OMC camera also suggests that SN2011fe
was the outcome of the explosion, possibly a delayed detonation although other
models are possible, of a CO white dwarf that synthesized M
of Ni. For this specific model.Comment: Accepted for publication in A&A. 10 pages, 10 figure