2,997 research outputs found
A reddening-free method to estimate the Ni mass of Type Ia supernovae
The increase in the number of Type Ia supernovae (SNe\,Ia) has demonstrated
that the population shows larger diversity than has been assumed in the past.
The reasons (e.g. parent population, explosion mechanism) for this diversity
remain largely unknown. We have investigated a sample of SNe\,Ia near-infrared
light curves and have correlated the phase of the second maximum with the
bolometric peak luminosity. The peak bolometric luminosity is related to the
time of the second maximum (relative to the {\it B} light curve maximum) as
follows : .
Ni masses can be derived from the peak luminosity based on Arnett's
rule, which states that the luminosity at maximum is equal to instantaneous
energy generated by the nickel decay. We check this assumption against recent
radiative-transfer calculations of Chandrasekhar-mass delayed detonation models
and find this assumption is valid to within 10\% in recent radiative-transfer
calculations of Chandrasekhar-mass delayed detonation models.
The vs. relation is applied to a sample of 40 additional
SNe\,Ia with significant reddening ( 0.1 mag) and a reddening-free
bolometric luminosity function of SNe~Ia is established. The method is tested
with the Ni mass measurement from the direct observation of
rays in the heavily absorbed SN 2014J and found to be fully
consistent.
Super-Chandrasekhar-mass explosions, in particular SN\,2007if, do not follow
the relations between peak luminosity and second IR maximum. This may point to
an additional energy source contributing at maximum light.
The luminosity function of SNe\,Ia is constructed and is shown to be
asymmetric with a tail of low-luminosity objects and a rather sharp
high-luminosity cutoff, although it might be influenced by selection effects.Comment: 9 pages, 3 figures, Accepted to A&
Limits on stable iron in TypeIa supernovae from NIR spectroscopy
We obtained optical and near-infrared spectra of TypeIa supernovae
(SNeIa) at epochs ranging from 224 to 496 days after the explosion. The
spectra show emission lines from forbidden transitions of singly ionised iron
and cobalt atoms. We used non-local thermodynamic equilibrium (NLTE) modelling
of the first and second ionisation stages of iron, nickel, and cobalt to fit
the spectra using a sampling algorithm allowing us to probe a broad parameter
space. We derive velocity shifts, line widths, and abundance ratios for iron
and cobalt. The measured line widths and velocity shifts of the singly ionised
ions suggest a shared emitting region. Our data are fully compatible with
radioactive Ni decay as the origin for cobalt and iron. We compare the
measured abundance ratios of iron and cobalt to theoretical predictions of
various SNIa explosion models. These models include, in addition to
Ni, different amounts of Ni and stable Fe. We can
exclude models that produced only Fe or only Ni in addition to
Ni. If we consider a model that has Ni, Ni, and
Fe then our data imply that these ratios are Fe / Ni
and Ni / Ni .Comment: 10 pages, 7 figures, Accepted for publication in A&
Study of fragmentation using clusterization algorithm with realistic binding energies
We here study fragmentation using \emph{simulated annealing clusterization
algorithm} (SACA) with binding energy at a microscopic level. In an earlier
version, a constant binding energy (4 MeV/nucleon) was used. We improve this
binding energy criterion by calculating the binding energy of different
clusters using modified Bethe-Weizs\"{a}cker mass (BWM) formula. We also
compare our calculations with experimental data of ALADiN group. Nearly no
effect is visible of this modification
A Parallax Distance to the Microquasar GRS 1915+105 and a Revised Estimate of its Black Hole Mass
Using the Very Long Baseline Array, we have measured a trigonometric parallax
for the micro quasar GRS 1915+105, which contains a black hole and a K-giant
companion. This yields a direct distance estimate of 8.6 (+2.0,-1.6) kpc and a
revised estimate for the mass of the black hole of 12.4 (+2.0,-1.8) Msun. GRS
1915+105 is at about the same distance as some HII regions and water masers
associated with high-mass star formation in the Sagittarius spiral arm of the
Galaxy. The absolute proper motion of GRS 1915+105 is -3.19 +/- 0.03 mas/y and
-6.24 +/- 0.05 mas/y toward the east and north, respectively, which corresponds
to a modest peculiar speed of 22 +/-24 km/s at the parallax distance,
suggesting that the binary did not receive a large velocity kick when the black
hole formed. On one observational epoch, GRS 1915+105 displayed superluminal
motion along the direction of its approaching jet. Considering previous
observations of jet motions, the jet in GRS 1915+105 can be modeled with a jet
inclination to the line of sight of 60 +/- 5 deg and a variable flow speed
between 0.65c and 0.81c, which possibly indicates deceleration of the jet at
distances from the black hole >2000 AU. Finally, using our measurements of
distance and estimates of black hole mass and inclination, we provisionally
confirm our earlier result that the black hole is spinning very rapidly.Comment: 20 pages; 2 tables; 6 figure
THE ROLE OF X-RAYS IN THE TREATMENT OF GAS GANGRENE: A HISTORICAL ASSESSMENT
While the use of x-rays to treat patients with gas gangrene ended in the early 1940’s with the advent of antibiotics, x-ray had been widely accepted as a useful and highly effective treatment for this condition. The present paper re-assesses the historical foundations of this belief, the quality of the data, use of confirmatory animal models, and underlying mechanisms that might account for the therapeutic role of x-rays in the treatment of gas gangrene
THE HISTORICAL USE OF RADIOTHERAPY IN THE TREATMENT OF SINUS INFECTIONS
The aim of this paper is to assess the historical role of radiotherapy in the treatment of sinus infections. This assessment involved a literature-based review of how radiotherapy was used to treat sinus infections in the first half of the 20th century. Low doses of x-rays were used with considerable success to treat nearly 3,000 patients of sinus infection in a span of 12 years with these cases being reported in leading medical journals as case stud- ies. The mechanism of x-ray induced reduction of inflammation and increased tissue repair is uncertain but appears to be related to the development of a multifactorial and integrative anti-inflammatory phenotype
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EMP2 regulates angiogenesis in endometrial cancer cells through induction of VEGF.
Understanding tumor-induced angiogenesis is a challenging problem with important consequences for the diagnosis and treatment of cancer. In this study, we define a novel function for epithelial membrane protein-2 (EMP2) in the control of angiogenesis. EMP2 functions as an oncogene in endometrial cancer, and its expression has been linked to decreased survival. Using endometrial cancer xenografts, modulation of EMP2 expression resulted in profound changes to the tumor microvasculature. Under hypoxic conditions, upregulation of EMP2 promoted vascular endothelial growth factors (VEGF) expression through a HIF-1α-dependent pathway and resulted in successful capillary-like tube formation. In contrast, reduction of EMP2 correlated with reduced HIF-1α and VEGF expression with the net consequence of poorly vascularized tumors in vivo. We have previously shown that targeting of EMP2 using diabodies in endometrial cancer resulted in a reduction of tumor load, and since then we have constructed a fully human EMP2 IgG1. Treatment of endometrial cancer cells with EMP2-IgG1 reduced tumor load with a significant improvement in survival. These results support the role of EMP2 in the control of the tumor microenvironment and confirm the cytotoxic effects observed by EMP2 treatment in vivo
Nebular spectroscopy of SN 2014J: Detection of stable nickel in near infrared spectra
We present near infrared (NIR) spectroscopy of the nearby supernova 2014J
obtained 450 d after explosion. We detect the [Ni II] 1.939 m line
in the spectra indicating the presence of stable Ni in the ejecta. The
stable nickel is not centrally concentrated but rather distributed as the iron.
The spectra are dominated by forbidden [Fe II] and [Co II] lines. We use lines,
in the NIR spectra, arising from the same upper energy levels to place
constraints on the extinction from host galaxy dust. We find that that our data
are in agreement with the high and low found in earlier studies
from data near maximum light. Using a Ni mass prior from near maximum
light -ray observations, we find 0.05 M of stable nickel
to be present in the ejecta. We find that the iron group features are
redshifted from the host galaxy rest frame by 600 km s.Comment: 6 pages, 4 figures, submitted to A&
Potential signature of a quadrupolar Hubble expansion in Pantheon+ supernovae
The assumption of isotropy -- that the Universe looks the same in all
directions on large scales -- is fundamental to the standard cosmological
model. This model forms the building blocks of essentially all of our
cosmological knowledge to date. It is therefore critical to empirically test in
which regimes its core assumptions hold. Anisotropies in the cosmic expansion
are expected on small scales due to nonlinear structures in the late Universe,
however, the extent to which these anisotropies might impact our low-redshift
observations remains to be fully tested. In this paper, we use fully general
relativistic simulations to calculate the expected local anisotropic expansion
and identify the dominant multipoles in cosmological parameters to be the
quadrupole in the Hubble parameter and the dipole in the deceleration
parameter. We constrain these multipoles simultaneously in the new Pantheon+
supernova compilation. The fiducial analysis is done in the rest frame of the
CMB with peculiar velocity corrections. Under the fiducial range of redshifts
in the Hubble flow sample, we find a deviation from isotropy. We
constrain the eigenvalues of the quadrupole in the Hubble parameter to be
and
and place a upper limit on its amplitude of . We find no
significant dipole in the deceleration parameter, finding constraints of
. However, in the rest frame of the CMB
without corrections, we find , a
positive amplitude. We also investigate the impact of these anisotropies on the
Hubble tension. We find a maximal shift of km s Mpc in the
monopole of the Hubble parameter and conclude that local anisotropies are
unlikely to fully explain the observed tension.Comment: 12 pages, to be submitted to MNRA
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