115 research outputs found
Maximum mass and universal relations of rotating relativistic hybrid hadron-quark stars
We construct equilibrium models of uniformly and differentially rotating
hybrid hadron-quark stars using equations of state (EOSs) with a first-order
phase transition that gives rise to a third family of compact objects. We find
that the ratio of the maximum possible mass of uniformly rotating
configurations - the supramassive limit - to the Tolman-Oppenheimer-Volkoff
(TOV) limit mass is not EOS-independent, and is between 1.15 and 1.31,in
contrast with the value of 1.20 previously found for hadronic EOSs. Therefore,
some of the constraints placed on the EOS from the observation of the
gravitational wave event GW170817 do not apply to hadron-quark EOSs. However,
the supramassive limit mass for the family of EOSs we treat is consistent with
limits set by GW170817, strengthening the possibility of interpreting GW170817
with a hybrid hadron-quark EOSs. We also find that along constant angular
momentum sequences of uniformly rotating stars, the third family maximum and
minimum mass models satisfy approximate EOS-independent relations, and the
supramassive limit of the third family is approximately 16.5 % larger than the
third family TOV limit. For differentially rotating spheroidal stars, we find
that a lower-limit on the maximum supportable rest mass is 123 % more than the
TOV limit rest mass. Finally, we verify that the recently discovered universal
relations relating angular momentum, rest mass and gravitational mass for
turning-point models hold for hybrid hadron-quark EOSs when uniform rotation is
considered, but have a clear dependence on the degree of differential rotation.Comment: 19 pages, 14 figures, submitted to EPJA Topical Issue "First joint
gravitational wave and electromagnetic observations: Implications for nuclear
and particle physics
Symmetries of CMB Temperature Correlation at Large Angular Separations
A new analysis is presented of the angular correlation function
of cosmic microwave background (CMB) temperature at large angular separation,
based on published maps derived from {\sl WMAP} and {\sl Planck} satellite
data, using different models of astrophysical foregrounds. It is found that
using a common analysis, the results from the two satellites are very similar.
In particular, it is found that previously published differences between
measured values of near arise mainly from
different choices of masks in regions of largest Galactic emissions, and that
demonstrated measurement biases are reduced by eliminating masks altogether.
Maps from both satellites are shown to agree with to within
estimated statistical and systematic errors, consistent with an exact symmetry
predicted in a new holographic quantum model of inflation.Comment: resubmitted to ApJ Letters, with revisions in response to referee
comment
X-ray/UVOIR Frequency-resolved Time Lag Analysis of Mrk 335 Reveals Accretion Disk Reprocessing
UV and optical continuum reverberation mapping is powerful for probing the
accretion disk and inner broad-line region. However, recent reverberation
mapping campaigns in the X-ray, UV, and optical have found lags consistently
longer than those expected from the standard disk reprocessing picture. The
largest discrepancy to-date was recently reported in Mrk 335, where UV/optical
lags are up to 12 times longer than expected. Here, we perform a
frequency-resolved time lag analysis of Mrk 335, using Gaussian processes to
account for irregular sampling. For the first time, we compare the Fourier
frequency-resolved lags directly to those computed using the popular
Interpolated Cross-Correlation Function (ICCF) method applied to both the
original and detrended light curves. We show that the anticipated disk
reverberation lags are recovered by the Fourier lags when zeroing in on the
short-timescale variability. This suggests that a separate variability
component is present on long timescales. If this separate component is modeled
as reverberation from another region beyond the accretion disk, we constrain a
size-scale of roughly 15 light-days from the central black hole. This is
consistent with the size of the broad line region inferred from H
reverberation lags. We also find tentative evidence for a soft X-ray lag, which
we propose may be due to light travel time delays between the hard X-ray corona
and distant photoionized gas that dominates the soft X-ray spectrum below 2
keV.Comment: Accepted for publication in ApJ, 8 figure
Mesoscopic Electron and Phonon Transport through a Curved Wire
There is great interest in the development of novel nanomachines that use
charge, spin, or energy transport, to enable new sensors with unprecedented
measurement capabilities. Electrical and thermal transport in these mesoscopic
systems typically involves wave propagation through a nanoscale geometry such
as a quantum wire. In this paper we present a general theoretical technique to
describe wave propagation through a curved wire of uniform cross-section and
lying in a plane, but of otherwise arbitrary shape. The method consists of (i)
introducing a local orthogonal coordinate system, the arclength and two locally
perpendicular coordinate axes, dictated by the shape of the wire; (ii)
rewriting the wave equation of interest in this system; (iii) identifying an
effective scattering potential caused by the local curvature; and (iv), solving
the associated Lippmann-Schwinger equation for the scattering matrix. We carry
out this procedure in detail for the scalar Helmholtz equation with both
hard-wall and stress-free boundary conditions, appropriate for the mesoscopic
transport of electrons and (scalar) phonons. A novel aspect of the phonon case
is that the reflection probability always vanishes in the long-wavelength
limit, allowing a simple perturbative (Born approximation) treatment at low
energies. Our results show that, in contrast to charge transport, curvature
only barely suppresses thermal transport, even for sharply bent wires, at least
within the two-dimensional scalar phonon model considered. Applications to
experiments are also discussed.Comment: 9 pages, 11 figures, RevTe
Coupling and Guided Propagation along Parallel Chains of Plasmonic Nanoparticles
Here, extending our previous work on this topic, we derive a dynamic
closed-form dispersion relation for a rigorous analysis of guided wave
propagation along coupled parallel linear arrays of plasmonic nanoparticles,
operating as optical 'two-line' waveguides. Compared to linear arrays of
nanoparticles, our results suggest that these waveguides may support longer
propagation lengths and more confined beams, operating analogously to
transmission-line segments at lower frequencies. Our formulation fully takes
into account the whole dynamic interaction among the infinite number of
nanoparticles composing the parallel arrays, considering also realistic
presence of losses and the frequency dispersion of the involved plasmonic
materials, providing further physical insights into the guidance properties
that characterize this geometry.Comment: 34 pages, 11 figure
Blow-up profile of rotating 2D focusing Bose gases
We consider the Gross-Pitaevskii equation describing an attractive Bose gas
trapped to a quasi 2D layer by means of a purely harmonic potential, and which
rotates at a fixed speed of rotation . First we study the behavior of
the ground state when the coupling constant approaches , the critical
strength of the cubic nonlinearity for the focusing nonlinear Schr{\"o}dinger
equation. We prove that blow-up always happens at the center of the trap, with
the blow-up profile given by the Gagliardo-Nirenberg solution. In particular,
the blow-up scenario is independent of , to leading order. This
generalizes results obtained by Guo and Seiringer (Lett. Math. Phys., 2014,
vol. 104, p. 141--156) in the non-rotating case. In a second part we consider
the many-particle Hamiltonian for bosons, interacting with a potential
rescaled in the mean-field manner w\int\_{\mathbb{R}^2} w(x) dx = 1\beta < 1/2a\_N \to a\_*N \to \infty$
Near-infrared Spectral Characterization of Solar-type Stars in the Northern Hemisphere
Although solar-analog stars have been studied extensively over the past few
decades, most of these studies have focused on visible wavelengths, especially
those identifying solar-analog stars to be used as calibration tools for
observations. As a result, there is a dearth of well-characterized solar
analogs for observations in the near-infrared, a wavelength range important for
studying solar system objects. We present 184 stars selected based on
solar-like spectral type and V-J and V-K colors whose spectra we have observed
in the 0.8-4.2 micron range for calibrating our asteroid observations. Each
star has been classified into one of three ranks based on spectral resemblance
to vetted solar analogs. Of our set of 184 stars, we report 145 as reliable
solar-analog stars, 21 as solar analogs usable after spectral corrections with
low-order polynomial fitting, and 18 as unsuitable for use as calibration
standards owing to spectral shape, variability, or features at low to medium
resolution. We conclude that all but 5 of our candidates are reliable solar
analogs in the longer wavelength range from 2.5 to 4.2 microns. The average
colors of the stars classified as reliable or usable solar analogs are
V-J=1.148, V-H=1.418, and V-K=1.491, with the entire set being distributed
fairly uniformly in R.A. across the sky between -27 and +67 degrees in decl.Comment: 19 pages, 8 figures, 2 table
Searching for Inflow Towards Massive Starless Clump Candidates Identified in the Bolocam Galactic Plane Survey
Recent Galactic plane surveys of dust continuum emission at long wavelengths
have identified a population of dense, massive clumps with no evidence for
on-going star formation. These massive starless clump candidates are excellent
sites to search for the initial phases of massive star formation before the
feedback from massive star formation effects the clump. In this study, we
search for the spectroscopic signature of inflowing gas toward starless clumps,
some of which are massive enough to form a massive star. We observed 101
starless clump candidates identified in the Bolocam Galactic Plane Survey
(BGPS) in HCO+ J = 1-0 using the 12m Arizona Radio Observatory telescope. We
find a small blue excess of E = (Nblue - Nred)/Ntotal = 0.03 for the complete
survey. We identified 6 clumps that are good candidates for inflow motion and
used a radiative transfer model to calculate mass inflow rates that range from
500 - 2000 M /Myr. If the observed line profiles are indeed due to large-scale
inflow motions, then these clumps will typically double their mass on a free
fall time. Our survey finds that massive BGPS starless clump candidates with
inflow signatures in HCO+ J = 1-0 are rare throughout our Galaxy.Comment: 14 pages, 9 figure
Measurement of the response of heat-and-ionization germanium detectors to nuclear recoils
The heat quenching factor Q' (the ratio of the heat signals produced by
nuclear and electron recoils of equal energy) of the heat-and-ionization
germanium bolometers used by the EDELWEISS collaboration has been measured. It
is explained how this factor affects the energy scale and the effective
quenching factor observed in calibrations with neutron sources. This effective
quenching effect is found to be equal to Q/Q', where Q is the quenching factor
of the ionization yield. To measure Q', a precise EDELWEISS measurement of Q/Q'
is combined with values of Q obtained from a review of all available
measurements of this quantity in tagged neutron beam experiments. The
systematic uncertainties associated with this method to evaluate Q' are
discussed in detail. For recoil energies between 20 and 100 keV, the resulting
heat quenching factor is Q' = 0.91+-0.03+-0.04, where the two errors are the
contributions from the Q and Q/Q' measurements, respectively. The present
compilation of Q values and evaluation of Q' represent one of the most precise
determinations of the absolute energy scale for any detector used in direct
searches for dark matter.Comment: 28 pages, 7 figures. Submitted to Phys. Rev.
X-ray Reverberation Mapping of Ark 564 using Gaussian Process Regression
Ark 564 is an extreme high-Eddington Narrow-line Seyfert 1 galaxy, known for
being one of the brightest, most rapidly variable soft X-ray AGN, and for
having one of the lowest temperature coronae. Here we present a 410-ks NuSTAR
observation and two 115-ks XMM-Newton observations of this unique source, which
reveal a very strong, relativistically broadened iron line. We compute the
Fourier-resolved time lags by first using Gaussian processes to interpolate the
NuSTAR gaps, implementing the first employment of multi-task learning for
application in AGN timing. By fitting simultaneously the time lags and the flux
spectra with the relativistic reverberation model RELTRANS, we constrain the
mass at , although additional components
are required to describe the prominent soft excess in this source. These
results motivate future combinations of machine learning, Fourier-resolved
timing, and the development of reverberation models.Comment: 19 pages, 9 figures. Accepted for publication in The Astrophysical
Journa
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