1,189 research outputs found
Absolute dimensions of detached eclipsing binaries. I. The metallic-lined system WW Aurigae
WW Aurigae is a detached eclipsing binary composed of two metallic-lined
A-type stars orbiting each other every 2.5 days. We have determined the masses
and radii of both components to accuracies of 0.4 and 0.6 percent,
respectively. From a cross-correlation analysis of high-resolution spectra we
find masses of 1.964 +/- 0.007 Msun for the primary star and 1.814 +/- 0.007
Msun for the secondary star. From an analysis of photoelectric uvby and UBV
light curves we find the radii of the stars to be 1.927 +/- 0.011 Rsun and
1.841 +/- 0.011 Rsun, where the uncertainties have been calculated using a
Monte Carlo algorithm. Fundamental effective temperatures of the two stars have
been derived, using the Hipparcos parallax of WW Aur and published ultraviolet,
optical and infrared fluxes, and are 7960 +/- 420 and 7670 +/- 410 K. The
masses, radii and effective temperatures of WW Aur are only matched by
theoretical evolutionary models for a fractional initial metal abundance, Z, of
approximately 0.06 and an age of roughly 90 Myr. This seems to be the highest
metal abundance inferred for a well-studied detached eclipsing binary, but we
find no evidence that it is related to the metallic-lined nature of the stars.
The circular orbit of WW Aur is in conflict with the circularization timescales
of both the Tassoul and the Zahn tidal theories and we suggest that this is due
to pre-main-sequence evolution or the presence of a circular orbit when the
stars were formed.Comment: Accepted for publication in MNRAS (14 pages, 8 figures). Photometric
data will be made available at the CDS once the final version appear
Accurate fundamental parameters of eclipsing binary stars
The study of detached eclipsing binaries is one of the most powerful ways to
investigate the properties of individual stars and stellar systems. We present
preliminary masses, radii and effective temperatures for the eclipsing binary
WW Aurigae, which is composed of two metallic-lined A-type stars. We also
reanalyse the data on HD 23642, an A-type eclipsing binary member of the
Pleiades open cluster with a metallic-lined component, and determine its
distance to be 139 +/- 4 pc. This is in agreement with the traditional Pleiades
distance, but in disagreement with distance to the Pleiades, and to HD 23642
itself, derived from Hipparcos trigonometrical parallaxes.Comment: 15 pages, 11 figures, Poster presented at IAU Symposium 224 "The A
Star Puzzle", 7-13 July 2004, Poprad, Slovaki
Solutions for 10,000 Eclipsing Binaries in the Bulge Fields of OGLE II Using DEBiL
We have developed a fully-automated pipeline for systematically identifying
and analyzing eclipsing binaries within large datasets of light curves. The
pipeline is made up of multiple tiers which subject the light curves to
increasing levels of scrutiny. After each tier, light curves that did not
conform to a given criteria were filtered out of the pipeline, reducing the
load on the following, more computationally intensive tiers. As a central
component of the pipeline, we created the fully automated Detached Eclipsing
Binary Light curve fitter (DEBiL), which rapidly fits large numbers of light
curves to a simple model. Using the results of DEBiL, light curves of interest
can be flagged for follow-up analysis. As a test case, we analyzed the 218699
light curves within the bulge fields of the OGLE II survey and produced 10862
model fits. We point out a small number of extreme examples as well as
unexpected structure found in several of the population distributions. We
expect this approach to become increasingly important as light curve datasets
continue growing in both size and number.Comment: Accepted for publication in ApJ, 36 pages, 15 figures, 5 tables. See
http://cfa-www.harvard.edu/~jdevor/DEBiL.html for high-resolution figures and
further informatio
MECI: A Method for Eclipsing Component Identification
We describe an automated method for assigning the most probable physical
parameters to the components of an eclipsing binary, using only its photometric
light curve and combined colors. With traditional methods, one attempts to
optimize a multi-parameter model over many iterations, so as to minimize the
chi-squared value. We suggest an alternative method, where one selects pairs of
coeval stars from a set of theoretical stellar models, and compares their
simulated light curves and combined colors with the observations. This approach
greatly reduces the parameter space over which one needs to search, and allows
one to estimate the components' masses, radii and absolute magnitudes, without
spectroscopic data. We have implemented this method in an automated program
using published theoretical isochrones and limb-darkening coefficients. Since
it is easy to automate, this method lends itself to systematic analyses of
datasets consisting of photometric time series of large numbers of stars, such
as those produced by OGLE, MACHO, TrES, HAT, and many others surveys.Comment: 25 pages, 7 figures, accepted for publication in Ap
Upper Limits on a Stochastic Background of Gravitational Waves
The Laser Interferometer Gravitational-Wave Observatory has performed a third science run with much improved sensitivities of all three interferometers. We present an analysis of approximately 200 hours of data acquired during this run, used to search for a stochastic background of gravitational radiation. We place upper bounds on the energy density stored as gravitational radiation for three different spectral power laws. For the flat spectrum, our limit of Ω_0<8.4Ă10^(-4) in the 69â156 Hz band is ~10^5 times lower than the previous result in this frequency range
Independent confirmation and refined parameters of the hot Jupiter XO-5b
We present HATNet observations of XO-5b, confirming its planetary nature
based on evidence beyond that described in the announcement of Burke et al.
(2008), namely, the lack of significant correlation between spectral bisector
variations and orbital phase. In addition, using extensive spectroscopic
measurements spanning multiple seasons, we investigate the relatively large
scatter in the spectral line bisectors. We also examine possible blended
stellar configurations (hierarchical triples, chance alignments) that can mimic
the planet signals, and we are able to show that none are consistent with the
sum of all the data. The analysis of the S activity index shows no significant
stellar activity. Our results for the planet parameters are consistent with
values in Burke et al. (2008), and we refine both the stellar and planetary
parameters using our data. XO-5b orbits a slightly evolved, late G type star
with mass M_s = 0.88 +/- 0.03, radius R_s = 1.08 +/- 0.04, and metallicity
close to solar. The planetary mass and radius are M_p = 1.059 +/- 0.028 M_Jup
and R_p = 1.109 +/- 0.050 R_Jup, respectively, corresponding to a mean density
of 0.96 -0.11 +0.14 g/cm^3. The ephemeris for the orbit is P = 4.187757 +/-
0.000011, E= 2454552.67168 +/- 0.00029 (BJD) with transit duration of 0.1307
+/- 0.0013 d. By measuring four individual transit centers, we found no signs
for transit timing variations. The planet XO-5b is notable for its anomalously
high Safronov number, and has a high surface gravity when compared to other
transiting exoplanets with similar period.Comment: Accepted for publication in ApJ, 8 pages in emulateapj styl
Yoga at Every Size: A Preliminary Evaluation of a Brief Online Size-Inclusive Yoga and Body Gratitude Journaling Intervention to Enhance Positive Embodiment in Higher Weight College Women
The present pilot randomized controlled trial (RCT) evaluated the feasibility, acceptability, and preliminary efficacy of a 4-week online yoga and body gratitude journaling intervention for strengthening positive embodiment among racially-diverse higher weight college women. Seventy-five participants were initially randomized to either the yoga condition (n = 36) or to a wait-list control (n = 39). Participants completed measures of positive and negative body image, weight bias internalization, self-compassion, drive for leanness, and physical activity acceptance at both baseline and post. Preliminary results among the 42 analyzed completers (mean age = 20.9, SD = 2.4; 30% Black or African American) revealed acceptable feasibility given the low-intensity nature of the intervention reflected in a 36% attrition rate. Self-reported adherence was strong for the yoga component with 81% of participants indicating that they practiced with the videos â„3â4 times per week as suggested. Although 71% reported completing the body gratitude journal â„1â2 times per week, daily adherence was minimal. Acceptability was also high among participants randomized to the yoga condition as indicated by 86% expressing at least moderate levels of satisfaction with the overall program. Qualitative feedback from participants further supported the acceptability of the program and pointed to important areas in further refining the protocol in the future. Preliminary efficacy was supported by significant reductions in internal body shame and gains in body appreciation, functional body appreciation, functional body satisfaction, functional body awareness, and behavioral commitment to physical activity engagement among the yoga vs. wait-list control participants. These promising findings once replicated in larger, higher-powered trials may have important implications for extending the reach and accessibility of mind-body wellness practices like yoga to benefit racially-/ethnically-diverse college women of higher weight. This research is further responsive to the growing need for efficacious remotely-delivered, and scalable behavioral health interventions in the ongoing era of the COVID-19 pandemic. However, additional research is warranted to explore ways of enhancing engagement of participants with lower levels of positive embodiment and to further incentivize the journaling component of the intervention
Limits on Gravitational-Wave Emission from Selected Pulsars Using LIGO Data
We place direct upper limits on the amplitude of gravitational waves from 28 isolated radio pulsars by a coherent multidetector analysis of the data collected during the second science run of the LIGO interferometric detectors. These are the first direct upper limits for 26 of the 28 pulsars. We use coordinated radio observations for the first time to build radio-guided phase templates for the expected gravitational-wave signals. The unprecedented sensitivity of the detectors allows us to set strain upper limits as low as a few times 10^(-24). These strain limits translate into limits on the equatorial ellipticities of the pulsars, which are smaller than 10^(-5) for the four closest pulsars
Search for Gravitational-wave Inspiral Signals Associated with Short Gamma-ray Bursts During LIGO's Fifth and Virgo's First Science Run
Progenitor scenarios for short gamma-ray bursts (short GRBs) include coalescenses of two neutron stars or a neutron star and black hole, which would necessarily be accompanied by the emission of strong gravitational waves. We present a search for these known gravitational-wave signatures in temporal and directional coincidence with 22 GRBs that had sufficient gravitational-wave data available in multiple instruments during LIGO's fifth science run, S5, and Virgo's first science run, VSR1. We find no statistically significant gravitational-wave candidates within a [ â 5, + 1) s window around the trigger time of any GRB. Using the Wilcoxon-Mann-Whitney U-test, we find no evidence for an excess of weak gravitational-wave signals in our sample of GRBs. We exclude neutron star-black hole progenitors to a median 90% confidence exclusion distance of 6.7 Mpc
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