3,486 research outputs found
Properties of Type II Plateau Supernova SNLS-04D2dc: Multicolor Light Curves of Shock Breakout and Plateau
Shock breakout is the brightest radiative phenomenon in a Type II supernova
(SN). Although it was predicted to be bright, the direct observation is
difficult due to the short duration and X-ray/ultraviolet-peaked spectra. First
entire observations of the shock breakouts of Type II Plateau SNe (SNe IIP)
were reported in 2008 by ultraviolet and optical observations by the {\it
GALEX} satellite and supernova legacy survey (SNLS), named SNLS-04D2dc and
SNLS-06D1jd. We present multicolor light curves of a SN IIP, including the
shock breakout and plateau, calculated with a multigroup radiation
hydrodynamical code {\sc STELLA} and an evolutionary progenitor model. The
synthetic multicolor light curves reproduce well the observations of
SNLS-04D2dc. This is the first study to reproduce the ultraviolet light curve
of the shock breakout and the optical light curve of the plateau consistently.
We conclude that SNLS-04D2dc is the explosion with a canonical explosion energy
ergs and that its progenitor is a star with a zero-age
main-sequence mass and a presupernova radius . The
model demonstrates that the peak apparent -band magnitude of the shock
breakout would be mag if a SN being identical to
SNLS-04D2dc occurs at a redshift , which can be reached by 8m-class
telescopes. The result evidences that the shock breakout has a great potential
to detect SNe IIP at z\gsim1.Comment: 5 pages, 5 figures. Accepted for publication in the Astrophysical
Journal Letter
First Detection of Ar-K Line Emission from the Cygnus Loop
We observed the Cygnus Loop with XMM-Newton (9 pointings) and Suzaku (32
pointings) between 2002 and 2008. The total effective exposure time is 670.2
ks. By using all of the available data, we intended to improve a
signal-to-noise ratio of the spectrum. Accordingly, the accumulated spectra
obtained by the XIS and the EPIC show some line features around 3 keV that are
attributed to the S He and Ar He lines, respectively. Since the
Cygnus Loop is an evolved (10,000 yr) supernova remnant whose temperature
is relatively low (1 keV) compared with other young remnants, its spectrum
is generally faint above 3.0 keV, no emission lines, such as the Ar-K line have
ever been detected. The detection of the Ar-K line is the first time and we
found that its abundance is significantly higher than that of the solar value;
9.0 and 8.4 (in units of solar), estimated from
the XIS and the EPIC spectra, respectively. We conclude that the Ar-K line
originated from the ejecta of the Cygnus Loop. Follow-up X-ray observations to
tightly constrain the abundances of Ar-rich ejecta will be useful to accurately
estimate the progenitor's mass.Comment: 12 pages, 9 figures, accepted for publication in PAS
A strong neutron burst in jet-like supernovae of spinstars
Some metal-poor stars have abundance patterns which are midway between the
slow (s) and rapid (r) neutron capture processes. We show that the helium shell
of a fast rotating massive star experiencing a jet-like explosion undergoes two
efficient neutron capture processes: one during stellar evolution and one
during the explosion. It eventually provides a material whose chemical
composition is midway between the s- and r-process. A low metallicity
40~ model with an initial rotational velocity of ~km~s was computed from birth to pre-supernova with a nuclear
network following the slow neutron capture process. A 2D hydrodynamic
relativistic code was used to model a ~erg relativistic jet-like
explosion hitting the stellar mantle. The jet-induced nucleosynthesis was
calculated in post-processing with a network of 1812 nuclei. During the star's
life, heavy elements from are produced thanks to an
efficient s-process, which is boosted by rotation. At the end of evolution, the
helium shell is largely enriched in trans-iron elements and in (unburnt)
Ne, whose abundance is times higher than in a non-rotating
model. During the explosion, the jet heats the helium shell up to
GK. It efficiently activates () reactions, such as
Ne(), and leads to a strong n-process with neutron densities
of ~cm during ~second. This has the effect
of shifting the s-process pattern towards heavier elements (e.g. Eu). The
resulting chemical pattern is consistent with the abundances of the
carbon-enhanced metal-poor r/s star CS29528-028, provided the ejecta of the jet
model is not homogeneously mixed. This is a new astrophysical site which can
explain at least some of the metal-poor stars showing abundance patterns midway
between the s- and r-process.Comment: 9 pages, 12 figures, accepted in A&
The evolution of the peculiar Type Ia supernova SN 2005hk over 400 days
photometry and medium resolution optical spectroscopy of peculiar
Type Ia supernova SN 2005hk are presented and analysed, covering the
pre-maximum phase to around 400 days after explosion. The supernova is found to
be underluminous compared to "normal" Type Ia supernovae. The photometric and
spectroscopic evolution of SN 2005hk is remarkably similar to the peculiar Type
Ia event SN 2002cx. The expansion velocity of the supernova ejecta is found to
be lower than normal Type Ia events. The spectra obtained \gsim 200 days
since explosion do not show the presence of forbidden [\ion{Fe}{ii}],
[\ion{Fe}{iii}] and [\ion{Co}{iii}] lines, but are dominated by narrow,
permitted \ion{Fe}{ii}, NIR \ion{Ca}{ii} and \ion{Na}{i} lines with P-Cygni
profiles. Thermonuclear explosion model with Chandrasekhar mass ejecta and a
kinetic energy smaller (\KE = 0.3 \times 10^{51} {\rm ergs}) than that of
canonical Type Ia supernovae is found to well explain the observed bolometric
light curve. The mass of \Nifs synthesized in this explosion is 0.18 \Msun.
The early spectra are successfully modeled with this less energetic model with
some modifications of the abundance distribution. The late spectrum is
explained as a combination of a photospheric component and a nebular component.Comment: Accepted for publication in The Astrophysical Journal. Minor
revision, discussion section adde
The Nucleosynthetic Imprint of 15-40 Solar Mass Primordial Supernovae on Metal-Poor Stars
The inclusion of rotationally-induced mixing in stellar evolution can alter
the structure and composition of presupernova stars. We survey the effects of
progenitor rotation on nucleosynthetic yields in Population III and II
supernovae using the new adaptive mesh refinement (AMR) code CASTRO. We examine
spherical explosions in 15, 25 and 40 solar mass stars at Z = 0 and 10^-4 solar
metallicity with three explosion energies and two rotation rates. Rotation in
the Z = 0 models resulted in primary nitrogen production and a stronger
hydrogen burning shell which led all models to die as red supergiants. On the
other hand, the Z=10^-4 solar metallicity models that included rotation ended
their lives as compact blue stars. Because of their extended structure, the
hydrodynamics favors more mixing and less fallback in the metal free stars than
the Z = 10^-4 models. As expected, higher energy explosions produce more
enrichment and less fallback than do lower energy explosions, and less massive
stars produce more enrichment and leave behind smaller remnants than do more
massive stars. We compare our nucleosynthetic yields to the chemical abundances
in the three most iron-poor stars yet found and reproduce the abundance pattern
of one, HE 0557-4840, with a zero metallicity 15 solar mass, 2.4 x 10^51 erg
supernova. A Salpeter IMF averaged integration of our yields for Z=0 models
with explosion energies of 2.4x10^51 ergs or less is in good agreement with the
abundances observed in larger samples of extremely metal-poor stars, provided
15 solar mass stars are included. Since the abundance patterns of extremely
metal-poor stars likely arise from a representative sample of progenitors, our
yields suggest that low-mass supernovae contributed the bulk of the metals to
the early universe.Comment: 16 pages, 11 figures; submitted to Ap
B^0-\bar{B}^0 mixing with quenched lattice NRQCD
We present our recent results for the B-parameters, which parameterize the
\Delta B=2 transition amplitudes. Calculations are made in quenched QCD at
\beta=5.7, 5.9, and 6.1, using NRQCD for heavy quark and the -improved
action for light quark. The operators are perturbatively renormalized including
corrections of O(\alpha_s/am_Q). We examine scaling behavior of the
B-parameters in detail, and discuss the systematic uncertainties using scatter
of results with different analysis procedures adopted. As a result, we find
B_{B_d}(m_b)=0.84(2)(8), B_{B_s}/B_{B_d}=1.017(10)(^{+4}_{-0}) and
B_{S_s}(m_b)=0.87(1)(9)(^{+1}_{-0}) in the quenched approximation.Comment: Lattice 2000 (Heavy Quark Physics), 4 pages, 4 eps-figures, Latex,
typo correcte
Heavy quark expansion parameters from lattice NRQCD
Using the lattice NRQCD action for heavy quark, we calculate the heavy quark
expansion parameters and for heavy-light mesons and
heavy-light-light baryons. The results are compared with the mass differences
among heavy hadrons to test the validity of HQET relations on the lattice.Comment: Lattice2001(heavyquark), 3 pages, 4 figure
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