7 research outputs found
Early emission from type Ia supernovae
A unique feature of deflagration-to-detonation (DDT) white dwarf explosion
models of SNe of type Ia is the presence of a strong shock wave propagating
through the outer envelope. We consider the early emission expected in such
models, which is produced by the expanding shock-heated outer part of the
ejecta and precedes the emission driven by radioactive decay. We expand on
earlier analyses by considering the modification of the pre-detonation density
profile by the weak-shocks generated during the deflagration phase, the time
evolution of the opacity, and the deviation of the post-shock equation of state
from that obtained for radiation pressure domination. A simple analytic model
is presented and shown to provide an acceptable approximation to the results of
1D numerical DDT simulations. Our analysis predicts a thousand second long
UV/optical flash with a luminosity of ~1 to 3*1e39 erg/s. Lower luminosity
corresponds to faster (turbulent) deflagration velocity. The predicted
luminosity of the UV flash is an order of magnitude lower than that of earlier
estimates, and is expected to be strongly suppressed at times longer than an
hour due to the deviation from pure radiation domination.Comment: 10 pages, 4 figure
Atom in a coherently controlled squeezed vacuum
A broadband squeezed vacuum photon field is characterized by a complex
squeezing function. We show that by controlling the wavelength dependence of
its phase it is possible to change the dynamics of the atomic polarization
interacting with the squeezed vacuum. Such a phase modulation effectively
produces a finite range temporal interaction kernel between the two quadratures
of the atomic polarization yielding the change in the decay rates as well as
the appearance of additional oscillation frequencies. We show that decay rates
slower than the spontaneous decay rate can be achieved even for a squeezed bath
in the classic regime. For linear and quadratic phase modulations the power
spectrum of the scattered light exhibits narrowing of the central peak due to
the modified decay rates. For strong phase modulations side lobes appear
symmetrically around the central peak reflecting additional oscillation
frequencies.Comment: 4 pages, 4 figure
The early UV/Optical emission from core-collapse supernovae
We derive a simple approximate model describing the early, hours to days,
UV/optical supernova emission, which is produced by the expansion of the outer
<~0.01 solar mass part of the shock-heated envelope, and precedes the optical
emission driven by radioactive decay. Our model includes an approximate
description of the time dependence of the opacity (due mainly to
recombination), and of the deviation of the emitted spectrum from a black body
spectrum. We show that the characteristics of the early UV/O emission constrain
the radius of the progenitor star, its envelope composition, and the ratio of
the ejecta energy to its mass, E/M. For He envelopes, neglecting the effect of
recombination may lead to an over estimate of progenitor radius by more than an
order of magnitude. We also show that the relative extinction at different
wavelengths may be inferred from the light-curves at these wave-lengths,
removing the uncertainty in the estimate of progenitor radius due to reddening
(but not the uncertainty in E/M due to uncertainty in absolute extinction). The
early UV/O observations of the type Ib SN2008D and of the type IIp SNLS-04D2dc
are consistent with our model predictions. For SN2008D we find progenitor
radius to be approx. 10^11 cm, and an indication that the He envelope contains
a significant C/O fraction.Comment: 18 pages, 13 figures. Expanded discussion of diffusio
Long wavelength unstable modes in the far upstream of relativistic collisionless shocks
The growth rate of long wavelength kinetic instabilities arising due to the
interaction of a collimated beam of relativistic particles and a cold
unmagnetized plasma are calculated in the ultra relativistic limit. For
sufficiently culminated beams, all long wave-length modes are shown to be
Weibel-unstable, and a simple analytic expression for their growth rate is
derived. For large transverse velocity spreads, these modes become stable. An
analytic condition for stability is given. These analytic results, which
generalize earlier ones given in the literature, are shown to be in agreement
with numerical solutions of the dispersion equation and with the results of
novel PIC simulations in which the electro-magnetic fields are restricted to a
given k-mode. The results may describe the interaction of energetic cosmic
rays, propagating into the far upstream of a relativistic collisionless shock,
with a cold unmagnetized upstream. The long wavelength modes considered may be
efficient in deflecting particles and could be important for diffusive shock
acceleration. It is shown that while these modes grow in relativistic shocks
propagating into electron-positron pair plasmas, they are damped in
relativistic shocks propagating into electron-proton plasmas with moderate
Lorenz factors \Gamma_{sh}\lesssim 100. If these modes dominate the deflection
of energetic cosmic rays in electron-positron shocks, it is argued that
particle acceleration is suppressed at shock frame energies that are larger
than the downstream thermal energy by a factor greater than the shock Lorentz
factor.Comment: 8 pages, 4 figure
PTF11eon/SN2011dh: Discovery of a Type IIb Supernova From a Compact Progenitor in the Nearby Galaxy M51
On May 31, 2011 UT a supernova (SN) exploded in the nearby galaxy M51 (the
Whirlpool Galaxy). We discovered this event using small telescopes equipped
with CCD cameras, as well as by the Palomar Transient Factory (PTF) survey, and
rapidly confirmed it to be a Type II supernova. Our early light curve and
spectroscopy indicates that PTF11eon resulted from the explosion of a
relatively compact progenitor star as evidenced by the rapid shock-breakout
cooling seen in the light curve, the relatively low temperature in early-time
spectra and the prompt appearance of low-ionization spectral features. The
spectra of PTF11eon are dominated by H lines out to day 10 after explosion, but
initial signs of He appear to be present. Assuming that He lines continue to
develop in the near future, this SN is likely a member of the cIIb (compact
IIb; Chevalier and Soderberg 2010) class, with progenitor radius larger than
that of SN 2008ax and smaller than the eIIb (extended IIb) SN 1993J progenitor.
Our data imply that the object identified in pre-explosion Hubble Space
Telescope images at the SN location is possibly a companion to the progenitor
or a blended source, and not the progenitor star itself, as its radius (~10^13
cm) would be highly inconsistent with constraints from our post-explosion
photometric and spectroscopic data
SN 2010mb: Direct Evidence for a Supernova Interacting with a Large Amount of Hydrogen-free Circumstellar Material
We present our observations of SN 2010mb, a Type Ic supernova (SN) lacking spectroscopic signatures of H and He. SN 2010mb has a slowly declining light curve (LC) (~600 days) that cannot be powered by ^(56)Ni/^(56)Co radioactivity, the common energy source for Type Ic SNe. We detect signatures of interaction with hydrogen-free circumstellar material including a blue quasi-continuum and, uniquely, narrow oxygen emission lines that require high densities (~10^9 cm^(–3)). From the observed spectra and LC, we estimate that the amount of material involved in the interaction was ~3 M_☉. Our observations are in agreement with models of pulsational pair-instability SNe described in the literature
SN 2010MB: Direct Evidence for A Supernova Interacting with A Large Amount of Hydrogen-Free Circumstellar Material
We present our observations of SN 2010mb, a Type Ic supernova (SN) lacking spectroscopic signatures of H and He. SN 2010mb has a slowly declining light curve (LC) (~600 days) that cannot be powered by 56Ni/56Co radioactivity, the common energy source for Type Ic SNe. We detect signatures of interaction with hydrogen-free circumstellar material including a blue quasi-continuum and, uniquely, narrow oxygen emission lines that require high densities (~109 cm–3). From the observed spectra and LC, we estimate that the amount of material involved in the interaction was ~3 M ☉. Our observations are in agreement with models of pulsational pair-instability SNe described in the literature