10,803 research outputs found
Expanding direction of the period doubling operator
We prove that the period doubling operator has an expanding direction at the
fixed point. We use the induced operator, a ``Perron-Frobenius type operator'',
to study the linearization of the period doubling operator at its fixed point.
We then use a sequence of linear operators with finite ranks to study this
induced operator. The proof is constructive. One can calculate the expanding
direction and the rate of expansion of the period doubling operator at the
fixed point
Hanbury-Brown--Twiss Analysis in a Solvable Model
The analysis of meson correlations by Hanbury-Brown--Twiss interferometry is
tested with a simple model of meson production by resonance decay. We derive
conditions which should be satisfied in order to relate the measured momentum
correlation to the classical source size. The Bose correlation effects are
apparent in both the ratio of meson pairs to singles and in the ratio of like
to unlike pairs. With our parameter values, we find that the single particle
distribution is too distorted by the correlation to allow a straightforward
analysis using pair correlation normalized by the singles rates. An analysis
comparing symmetrized to unsymmetrized pairs is more robust, but nonclassical
off-shell effects are important at realistic temperatures.Comment: 21 pages + 9 figures (tarred etc. using uufiles, submitted
separately), REVTeX 3.0, preprint number: DOE/ER/40561-112/INT93-00-3
Field of a Radiation Distributuion
General relativistic spherically symmetric matter field with a vanishing
stress energy scalar is analyzed. Procedure for generating exact solutions of
the field equations for such matter distributions is given. It is further
pointed out that all such type I spherically symmetric fields with distinct
eignvalues in the radial two space can be treated as a mixture of isotropic and
directed radiations. Various classes of exact solutions are given. Junction
conditions for such a matter field to the possible exterior solutions are also
discussed.Comment: Latex file, 13 pages, no figures. Accepted for publication in Phys.
Rev.
A multi-wavelength investigation of the radio-loud supernova PTF11qcj and its circumstellar environment
We present the discovery, classification, and extensive panchromatic (from
radio to X-ray) follow-up observations of PTF11qcj, a supernova discovered by
the Palomar Transient Factory. PTF11qcj is located at a distance of dL ~ 124
Mpc. Our observations with the Karl G. Jansky Very Large Array show that this
event is radio-loud: PTF11qcj reached a radio peak luminosity comparable to
that of the famous gamma-ray-burst-associated supernova 1998bw (L_{5GHz} ~
10^{29} erg/s/Hz). PTF11qcj is also detected in X-rays with the Chandra
observatory, and in the infrared band with Spitzer. Our multi-wavelength
analysis probes the supernova interaction with circumstellar material. The
radio observations suggest a progenitor mass-loss rate of ~10^{-4} Msun/yr x
(v_w/1000 km/s), and a velocity of ~(0.3-0.5)c for the fastest moving ejecta
(at ~10d after explosion). However, these estimates are derived assuming the
simplest model of supernova ejecta interacting with a smooth circumstellar
material characterized by radial power-law density profile, and do not account
for possible inhomogeneities in the medium and asphericity of the explosion.
The radio light curve shows deviations from such a simple model, as well as a
re-brightening at late times. The X-ray flux from PTF11qcj is compatible with
the high-frequency extrapolation of the radio synchrotron emission (within the
large uncertainties). An IR light echo from pre-existing dust is in agreement
with our infrared data. Our analysis of pre-explosion data from the Palomar
Transient Factory suggests that a precursor eruption of absolute magnitude M_r
~ -13 mag may have occurred ~ 2.5 yr prior to the supernova explosion. Based on
our panchromatic follow-up campaign, we conclude that PTF11qcj fits the
expectations from the explosion of a Wolf-Rayet star. Precursor eruptions may
be a feature characterizing the final pre-explosion evolution of such stars.Comment: 43 pages, 15 figures; this version matches the one published in ApJ
(includes minor changes that address the Referee's comments.
Interaction-powered supernovae: Rise-time vs. peak-luminosity correlation and the shock-breakout velocity
Interaction of supernova (SN) ejecta with the optically thick circumstellar
medium (CSM) of a progenitor star can result in a bright, long-lived shock
breakout event. Candidates for such SNe include Type IIn and superluminous SNe.
If some of these SNe are powered by interaction, then there should be a
relation between their peak luminosity, bolometric light-curve rise time, and
shock-breakout velocity. Given that the shock velocity during shock breakout is
not measured, we expect a correlation, with a significant spread, between the
rise time and the peak luminosity of these SNe. Here, we present a sample of 15
SNe IIn for which we have good constraints on their rise time and peak
luminosity from observations obtained using the Palomar Transient Factory. We
report on a possible correlation between the R-band rise time and peak
luminosity of these SNe, with a false-alarm probability of 3%. Assuming that
these SNe are powered by interaction, combining these observables and theory
allows us to deduce lower limits on the shock-breakout velocity. The lower
limits on the shock velocity we find are consistent with what is expected for
SNe (i.e., ~10^4 km/s). This supports the suggestion that the early-time light
curves of SNe IIn are caused by shock breakout in a dense CSM. We note that
such a correlation can arise from other physical mechanisms. Performing such a
test on other classes of SNe (e.g., superluminous SNe) can be used to rule out
the interaction model for a class of events.Comment: Accepted to ApJ, 6 page
Fatty acid control of growth of human cervical and endometrial cancer cells.
Stearic acid and iodo-stearic and inhibited cell growth in a cervical cancer cell line (HOG-1) in a dose-related manner, with a half maximal effect at 50 microM stearic acid. Addition of oleic acid abrogated the effect of stearic acid. EGF-stimulated DNA synthesis and growth of HOG-1 cells was inhibited in the presence of stearic acid without any apparent effect on EGF receptor number or affinity
An outburst from a massive star 40 days before a supernova explosion
Various lines of evidence suggest that very massive stars experience extreme
mass-loss episodes shortly before they explode as a supernova. Interestingly,
several models predict such pre-explosion outbursts. Establishing a causal
connection between these mass-loss episodes and the final supernova explosion
will provide a novel way to study pre-supernova massive-star evolution. Here we
report on observations of a remarkable mass-loss event detected 40 days prior
to the explosion of the Type IIn supernova SN 2010mc (PTF 10tel). Our
photometric and spectroscopic data suggest that this event is a result of an
energetic outburst, radiating at least 6x10^47 erg of energy, and releasing
about 0.01 Solar mass at typical velocities of 2000 km/s. We show that the
temporal proximity of the mass-loss outburst and the supernova explosion
implies a causal connection between them. Moreover, we find that the outburst
luminosity and velocity are consistent with the predictions of the wave-driven
pulsation model and disfavor alternative suggestions.Comment: Nature 494, 65, including supplementary informatio
The Palomar Transient Factory photometric catalog 1.0
We construct a photometrically calibrated catalog of non-variable sources
from the Palomar Transient Factory (PTF) observations. The first version of
this catalog presented here, the PTF photometric catalog 1.0, contains
calibrated R_PTF-filter magnitudes for about 21 million sources brighter than
magnitude 19, over an area of about 11233 deg^2. The magnitudes are provided in
the PTF photometric system, and the color of a source is required in order to
convert these magnitudes into other magnitude systems. We estimate that the
magnitudes in this catalog have typical accuracy of about 0.02 mag with respect
to magnitudes from the Sloan Digital Sky Survey. The median repeatability of
our catalog's magnitudes for stars between 15 and 16 mag, is about 0.01 mag,
and it is better than 0.03 mag for 95% of the sources in this magnitude range.
The main goal of this catalog is to provide reference magnitudes for
photometric calibration of visible light observations. Subsequent versions of
this catalog, which will be published incrementally online, will be extended to
a larger sky area and will also include g_PTF-filter magnitudes, as well as
variability and proper motion information.Comment: 6 pages, 6 figures, PASP in pres
Light curves of hydrogen-poor Superluminous Supernovae from the Palomar Transient Factory
We investigate the light-curve properties of a sample of 26 spectroscopically
confirmed hydrogen-poor superluminous supernovae (SLSNe-I) in the Palomar
Transient Factory (PTF) survey. These events are brighter than SNe Ib/c and SNe
Ic-BL, on average, by about 4 and 2~mag, respectively. The peak absolute
magnitudes of SLSNe-I in rest-frame band span ~mag, and these peaks are not powered by radioactive Ni,
unless strong asymmetries are at play. The rise timescales are longer for SLSNe
than for normal SNe Ib/c, by roughly 10 days, for events with similar decay
times. Thus, SLSNe-I can be considered as a separate population based on
photometric properties. After peak, SLSNe-I decay with a wide range of slopes,
with no obvious gap between rapidly declining and slowly declining events. The
latter events show more irregularities (bumps) in the light curves at all
times. At late times, the SLSN-I light curves slow down and cluster around the
Co radioactive decay rate. Powering the late-time light curves with
radioactive decay would require between 1 and 10 of Ni masses.
Alternatively, a simple magnetar model can reasonably fit the majority of
SLSNe-I light curves, with four exceptions, and can mimic the radioactive decay
of Co, up to days from explosion. The resulting spin values do
not correlate with the host-galaxy metallicities. Finally, the analysis of our
sample cannot strengthen the case for using SLSNe-I for cosmology.Comment: 120 pages, 48 figures, 78 tables. ApJ in pres
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