5,042 research outputs found
The timing and location of dust formation in the remnant of SN 1987A
The discovery with the {\it Herschel Space Observatory} of bright far
infrared and submm emission from the ejecta of the core collapse supernova
SN\,1987A has been interpreted as indicating the presence of some
0.4--0.7\,M of dust. We have constructed radiative transfer models of
the ejecta to fit optical to far-infrared observations from the literature at
epochs between 615 days and 24 years after the explosion, to determine when and
where this unexpectedly large amount of dust formed.
We find that the observations by day 1153 are consistent with the presence of
310M of dust. Although this is a larger amount than has
previously been considered possible at this epoch, it is still very small
compared to the amount present in the remnant after 24 years, and significantly
higher dust masses at the earlier epochs are firmly ruled out by the
observations, indicating that the majority of the dust must have formed at very
late times. By 8515-9200 days after the explosion, 0.6--0.8\,M of dust
is present, and dust grains with radii greater than 2\,m are required to
obtain a fit to the observed SED. This suggests that the dust mass increase at
late times was caused by accretion onto and coagulation of the dust grains
formed at earlier epochs.
These findings provide further confirmation that core collapse supernovae can
create large quantities of dust, and indicate that the reason for small dust
masses being estimated in many cases is that the vast majority of the dust
forms long after most supernovae have been detectable at mid-infrared
wavelengths.Comment: 13 pages, 16 figures. Accepted for publication in MNRA
A Microscopic Mechanism for Muscle's Motion
The SIRM (Stochastic Inclined Rods Model) proposed by H. Matsuura and M.
Nakano can explain the muscle's motion perfectly, but the intermolecular
potential between myosin head and G-actin is too simple and only repulsive
potential is considered. In this paper we study the SIRM with different complex
potential and discuss the effect of the spring on the system. The calculation
results show that the spring, the effective radius of the G-actin and the
intermolecular potential play key roles in the motion. The sliding speed is
about calculated from the model which well agrees with
the experimental data.Comment: 9 pages, 6 figure
The superwind mass-loss rate of the metal-poor carbon star LI-LMC 1813 in the LMC cluster KMHK 1603
LI-LMC 1813 is a dust-enshrouded Asymptotic Giant Branch (AGB) star, located
in the small open cluster KMHK 1603 near the rim of the Large Magellanic Cloud
(LMC). Optical and infrared photometry between 0.5 and 60 micron is obtained to
constrain the spectral energy distribution of LI-LMC 1813. Near-infrared
spectra unambiguously show it to be a carbon star. Modelling with the radiation
transfer code Dusty yields accurate values for the bolometric luminosity, L=1.5
x 10^4 Lsun, and mass-loss rate, Mdot=3.7(+/-1.2) x 10^-5 Msun/yr. On the basis
of colour-magnitude diagrams, the age of the cluster KMHK 1603 is estimated to
be t=0.9-1.0 Gyr, which implies a Zero-Age Main Sequence mass for LI-LMC 1813
of M(ZAMS)=2.2+/-0.1 Msun. This makes LI-LMC 1813 arguably the object with the
most accurately and reliably determined (circum)stellar parameters amongst all
carbon stars in the superwind phase.Comment: Accepted for publication in MNRAS (better quality figure 1 on request
from jacco
Localization on the D-brane, two-dimensional gauge theory and matrix models
We consider the effective topological field theory on Euclidean D-strings
wrapping on a 2-cycle in the internal space. We evaluate the vev of a suitable
operator corresponding to the chemical potential of vortices bounded to the
D-strings, and find that it reduces to the partition function of generalized
two-dimensional Yang-Mills theory as a result of localization. We argue that
the partition function gives a grand canonical ensemble of multi-instanton
corrections for four-dimensional N=2 gauge theory in a suitable large N limit.
We find two-dimensional gauge theories that provide the instanton partition
function for four-dimensional N=2 theories with the hypermultiplets in the
adjoint and fundamental representations. We also propose a partition function
that gives the instanton contributions to four-dimensional N=2 quiver gauge
theory. We discuss the relation between Nekrasov's instanton partition function
and the Dijkgraaf-Vafa theory in terms of large N phase transitions of the
generalized two-dimensional Yang-Mills theory.Comment: 40 pages, 5 figures, LaTeX2e, typos corrected, references added,
Final version to appear in Physical Review
Next to leading order evolution of SIDIS processes in the forward region
We compute the order quark initiated corrections to
semi-inclusive deep inelastic scattering extending the approach developed
recently for the gluon contributions. With these corrections we complete the
order QCD description of these processes, verifying explicitly the
factorization of collinear singularities. We also obtain the corresponding NLO
evolution kernels, relevant for the scale dependence of fracture functions. We
compare the non-homogeneous evolution effects driven by these kernels with
those obtained at leading order accuracy and discuss their phenomenological
implications.Comment: 18 pages, 4 ps figures, uses revtex4 and feynmf. Accepted for
publication in Nuclear Physics
Avaliação de banana-passa obtida de frutos de diferentes genótipos de bananeira.
A industrialização pode ser uma opção para o aproveitamento de excedentes de produção e de frutos com aparência comprometida para consumo in natura, proporcionando aumento da vida-de-prateleira e agregação de valor ao produto. Frutos de diferentes variedades de bananeira (Musa spp.), obtidas em programas de melhoramento genético, podem apresentar características diferenciadas no que se refere à adequação à determinada forma de processamento. O presente trabalho teve o objetivo de avaliar o produto banana-passa obtido a partir de frutos de diferentes genótipos de bananeira: ?Caipira?; ?Nanica?; ?Pacovan? e seus híbridos PV03-44 e PV03-76; ?Prata Anã? e seus híbridos ?FHIA-18?, ?Pioneira? e ?Prata Graúda?. O processamento da banana-passa incluiu a aplicação de um tratamento antioxidante, contendo ácido ascórbico (0,25%) e ácido cítrico (0,30%), e uma desidratação osmótica, com sacarose (40%, a 70°C). A desidratação foi completada em secador de cabine com circulação forçada de ar. Os produtos obtidos foram avaliados quanto a aspectos físicos, físico-químicos, químicos e sensoriais. O maior rendimento de produção foi obtido utilizando-se a cultivar Pacovan. As bananas-passa tiveram boa aceitação sensorial, com médias superiores a 6 para os atributos aparência, cor, aroma, sabor e textura. A ?Pioneira? foi o genótipo com maior aceitação sensorial
A decade of ejecta dust formation in the Type IIn SN 2005ip
In order to understand the contribution of core-collapse supernovae to the
dust budget of the early universe, it is important to understand not only the
mass of dust that can form in core-collapse supernovae but also the location
and rate of dust formation. SN 2005ip is of particular interest since dust has
been inferred to have formed in both the ejecta and the post-shock region
behind the radiative reverse shock. We have collated eight optical archival
spectra that span the lifetime of SN 2005ip and we additionally present a new
X-shooter optical-near-IR spectrum of SN 2005ip at 4075d post-discovery. Using
the Monte Carlo line transfer code DAMOCLES, we have modelled the blueshifted
broad and intermediate width H, H and He I lines from 48d to
4075d post-discovery using an ejecta dust model. We find that dust in the
ejecta can account for the asymmetries observed in the broad and intermediate
width H, H and He I line profiles at all epochs and that it is
not necessary to invoke post-shock dust formation to explain the blueshifting
observed in the intermediate width post-shock lines. Using a Bayesian approach,
we have determined the evolution of the ejecta dust mass in SN 2005ip over 10
years presuming an ejecta dust model, with an increasing dust mass from
~10 M at 48d to a current dust mass of 0.1 M.Comment: Accepted by MNRAS, 17 pages, 11 figures. Author accepted manuscript.
Accepted on 04/03/19. Deposited on 07/03/1
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