9,605 research outputs found
Asteroseismic modeling of 16 Cyg A & B using the complete Kepler data set
Asteroseismology of bright stars with well-determined properties from
parallax measurements and interferometry can yield precise stellar ages and
meaningful constraints on the composition. We substantiate this claim with an
updated asteroseismic analysis of the solar-analog binary system 16 Cyg A & B
using the complete 30-month data sets from the Kepler space telescope. An
analysis with the Asteroseismic Modeling Portal (AMP), using all of the
available constraints to model each star independently, yields the same age
( Gyr) and composition (, ) for both stars, as expected for a binary system. We quantify the
accuracy of the derived stellar properties by conducting a similar analysis of
a Kepler-like data set for the Sun, and we investigate how the reliability of
asteroseismic inference changes when fewer observational constraints are
available or when different fitting methods are employed. We find that our
estimates of the initial helium mass fraction are probably biased low by
0.02-0.03 from neglecting diffusion and settling of heavy elements, and we
identify changes to our fitting method as the likely source of small shifts
from our initial results in 2012. We conclude that in the best cases reliable
stellar properties can be determined from asteroseismic analysis even without
independent constraints on the radius and luminosity.Comment: 5 emulateapj pages, 1 table, 1 figure. ApJ Letters, accepte
Kinematics of Clustering
The dynamical system for inertial particles in fluid flow has both attracting
and repelling regions, the interplay of which can localize particles. In
laminar flow experiments we find that particles, initially moving throughout
the fluid domain, can undergo an instability and cluster into subdomains of the
fluid when the flow Reynolds number exceeds a critical value that depends on
particle and fluid inertia. We derive an expression for the instability
boundary and for a universal curve that describes the clustering rate for all
particles.Comment: 13 pages, 6 figure
The Impact of Popular Music Education in Building and Maintaining Rural East Tennessee High School Band Programs
Despite existing research in popular music education, a gap exists in the literature concerning popular music education for rural East Tennessee high school band programs. The purpose of this qualitative research was to address the history of societal acceptance of popular music styles as well as changes within the field of music education philosophy that allowed for popular music study. A review of music education literature concerning popular music education and praxis was conducted to find applications for rural East Tennessee high school band programs. Further research was conducted through student and band director surveys which were distributed to rural East Tennessee high school band programs with the assistance of the Tennessee Secondary Schools Band Directors Association. The survey items were examined for themes that aided the researcher in determining the value of popular music education according to students within rural East Tennessee high school band programs. Findings included an increase in student interest in the band program, a positive outlook upon continued membership, and possible appeal to students who are not current members of the band program. The implications suggested that the embrace of popular music and the provision of skills for making music beyond the classroom were important. Research suggested that rural East Tennessee high school band programs can remove the disconnection between classroom music and the world beyond the classroom to improve growth and maintenance by using popular music education (PME)
An asteroseismic test of diffusion theory in white dwarfs
The helium-atmosphere (DB) white dwarfs are commonly thought to be the
descendants of the hotter PG1159 stars, which initially have uniform He/C/O
atmospheres. In this evolutionary scenario, diffusion builds a pure He surface
layer which gradually thickens as the star cools. In the temperature range of
the pulsating DB white dwarfs (T_eff ~ 25,000 K) this transformation is still
taking place, allowing asteroseismic tests of the theory. We have obtained
dual-site observations of the pulsating DB star CBS114, to complement existing
observations of the slightly cooler star GD358. We recover the 7 independent
pulsation modes that were previously known, and we discover 4 new ones to
provide additional constraints on the models. We perform objective global
fitting of our updated double-layered envelope models to both sets of
observations, leading to determinations of the envelope masses and pure He
surface layers that qualitatively agree with the expectations of diffusion
theory. These results provide new asteroseismic evidence supporting one of the
central assumptions of spectral evolution theory, linking the DB white dwarfs
to PG1159 stars.Comment: 7 pages, 3 figures, 3 tables, accepted for publication in A&
Gamma-ray bursts and X-ray melting of material as a potential source of chondrules and planets
The intense radiation from a gamma-ray burst (GRB) is shown to be capable of
melting stony material at distances up to 300 light years which subsequently
cool to form chondrules. These conditions were created in the laboratory for
the first time when millimeter sized pellets were placed in a vacuum chamber in
the white synchrotron beam at the European Synchrotron Radiation Facility
(ESRF). The pellets were rapidly heated in the X-ray and gamma-ray furnace to
above 1400 C melted and cooled. This process heats from the inside unlike
normal furnaces. The melted spherical samples were examined with a range of
techniques and found to have microstructural properties similar to the
chondrules that come from meteorites. This experiment demonstrates that GRBs
can melt precursor material to form chondrules that may subsequently influence
the formation of planets. This work extends the field of laboratory
astrophysics to include high power synchrotron sources.Comment: 8 pages, 10 figures. Proceedings of the 5th INTEGRAL Workshop, Munich
16-20 February 2004. High resolution figures available at
http://bermuda.ucd.ie/%7Esmcbreen/papers/duggan_01.pd
A Stellar Model-fitting Pipeline for Solar-like Oscillations
Over the past two decades, helioseismology has revolutionized our
understanding of the interior structure and dynamics of the Sun.
Asteroseismology will soon place this knowledge into a broader context by
providing structural data for hundreds of Sun-like stars. Solar-like
oscillations have already been detected from the ground in several stars, and
NASA's Kepler mission is poised to unleash a flood of stellar pulsation data.
Deriving reliable asteroseismic information from these observations demands a
significant improvement in our analysis methods. We report the initial results
of our efforts to develop an objective stellar model-fitting pipeline for
asteroseismic data. The cornerstone of our automated approach is an
optimization method using a parallel genetic algorithm. We describe the details
of the pipeline and we present the initial application to Sun-as-a-star data,
yielding an optimal model that accurately reproduces the known solar
properties.Comment: 5 pages, 2 figs, Stellar Pulsation: Challenges for Theory and
Observation (proceedings to be published by AIP
A ring galaxy at z=1 lensed by the cluster Abell 370
We present a study of a very peculiar object found in the field of the
cluster-lens Abell 370. This object displays, in HST imaging, a spectacular
morphology comparable to nearby ring-galaxies. From spectroscopic observations
at the CFHT, we measured a redshift of based on the identification of
[O ii] 3727 \AA and [Ne v] 3426 \AA emission lines. These emission lines are
typical of starburst galaxies hosting a central active nucleus and are in good
agreement with the assumption that this object is a ring-galaxy. This object is
also detected with ISO in the LW2 and LW3 filters, and the mid Infra-Red (MIR)
flux ratio favors a Seyfert 1 type. The shape of the ring is gravitationally
distorted by the cluster-lens, and most particularly by a nearby cluster
elliptical galaxy. Using the cluster mass model, we can compute its intrinsic
shape. Requiring that the outer ring follows an ellipse we put constraints on
the M/L ratio of the nearby galaxy and derive a magnification factor of 2.5
0.2. The absolute luminosities of the source are then $L_B = 1.3 \
10^{12} L_{B \odot}\nu_\nu \simeq 4. 10^{10}_\odot$ in the
mid-IR.Comment: 5 pages, 5 figures, uses aa.cls, accepted to A&A Letters. Minor
changes, Figure 1 revisited and typos adde
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