1,747 research outputs found
Discovery of an Optical Counterpart to the Supersoft X-ray Source in the Globular Cluster M3
We report the detection, with HST, of an optical counterpart to the transient
supersoft X-ray source 1E 1339.8+2837, in the globular cluster M3. The
counterpart is found near the faint end of the subgiant branch in the V vs V-I
color magnitude diagram, but is extremely bright in U. Variability is detected
over a range of timescales suggesting the presence of an accretion disk and
perhaps also ellipsoidal variations of the subgiant secondary. The optical
colors of the binary are similar to those of cataclysmic variables recently
discovered in 47 Tucanae and NGC 6397. We suggest that magnetically channeled
accretion may explain the relatively low X-ray luminosity of this source's
supersoft state.Comment: 11 pages, 3 figures, 2 tables. Accepted for publication in Ap
Photometric follow-up of the transiting planet WASP-1b
We report on photometric follow-up of the recently discovered transiting
planet WASP-1b. We observed two transits with the Wise Observatory 1m
telescope, and used a variant of the EBOP code together with the Sys-Rem
detrending approach to fit the light curve. Assuming a stellar mass of 1.15
M_sun, we derived a planetary radius of R_p = 1.40 +- 0.06 R_J and mass of M_p
= 0.87 +- 0.07 M_J. An uncertainty of 15% in the stellar mass results in an
additional systematic uncertainty of 5% in the planetary radius and of 10% in
planetary mass. Our observations yielded a slightly better ephemeris for the
center of the transit: T_c [HJD] = (2454013.3127 +- 0.0004) + N_tr * (2.51996
+- 0.00002). The new planet is an inflated, low-density planet, similar to
HAT-P-1b and HD209458b.Comment: Revised version accepted for publication in MNRA
A multi-color and Fourier study of RR Lyrae variables in the globular cluster NGC 5272 (M3)
We have performed a detailed study of the pulsational and evolutionary
characteristics of 133 RR Lyrae stars in the globular cluster NGC5272 (M3)
using highly accurate BVI data taken on 5 separate epochs. M3 seems to contain
no less than ~32% of Blazhko stars, and the occurrence and characteristics of
the Blazhko effect have been analyzed in detail. We have identified a good
number (~ 14%) of overluminous RR Lyrae stars that are likely in a more
advanced evolutionary stage off the Zero Age Horizontal Branch (ZAHB). Physical
parameters (i.e. temperature, luminosity, mass) have been derived from (B--V)
colors and accurate color-temperature calibration, and compared with Horizontal
Branch evolutionary models and with the requirements of stellar pulsation
theory. Additional analysis by means of Fourier decomposition of the V light
curves confirms, as expected, that no metallicity spread is present in M3.
Evolution off the ZAHB does not affect [Fe/H] determinations, whereas Blazhko
stars at low amplitude phase do affect [Fe/H] distributions as they appear more
metal-rich. Absolute magnitudes derived from Fourier coefficients might provide
useful average estimates for groups of stars, if applicable, but do not give
reliable {\em individual} values. Intrinsic colors derived from Fourier
coefficients show significant discrepancies with the observed ones, hence the
resulting temperatures and temperature-related parameters are unreliable.Comment: 86 pages, 19 figures, 13 tables, in press A
Detection of a transit of the super-Earth 55 Cnc e with Warm Spitzer
We report on the detection of a transit of the super-Earth 55 Cnc e with warm
Spitzer in IRAC's 4.5-micron band. Our MCMC analysis includes an extensive
modeling of the systematic effects affecting warm Spitzer photometry, and
yields a transit depth of 410 +- 63 ppm, which translates to a planetary radius
of 2.08 +- 0.16 R_Earth as measured in IRAC 4.5-micron channel. A planetary
mass of 7.81 +- 0.58 M_Earth is derived from an extensive set of
radial-velocity data, yielding a mean planetary density of 4.8 +- 1.3 g cm-3.
Thanks to the brightness of its host star (V = 6, K = 4), 55 Cnc e is a unique
target for the thorough characterization of a super-Earth orbiting around a
solar-type star.Comment: Accepted for publication in A&A on 31 July 2011. 9 pages, 7 figures
and 3 tables. Minor changes. The revised version includes a baseline models
comparison and a new figure presenting the spatially- and time-dependent
terms of the model function used in Eq.
The TRAPPIST survey of southern transiting planets. I. Thirty eclipses of the ultra-short period planet WASP-43 b
We present twenty-three transit light curves and seven occultation light
curves for the ultra-short period planet WASP-43 b, in addition to eight new
measurements of the radial velocity of the star. Thanks to this extensive data
set, we improve significantly the parameters of the system. Notably, the
largely improved precision on the stellar density (2.41+-0.08 rho_sun) combined
with constraining the age to be younger than a Hubble time allows us to break
the degeneracy of the stellar solution mentioned in the discovery paper. The
resulting stellar mass and size are 0.717+-0.025 M_sun and 0.667+-0.011 R_sun.
Our deduced physical parameters for the planet are 2.034+-0.052 M_jup and
1.036+-0.019 R_jup. Taking into account its level of irradiation, the high
density of the planet favors an old age and a massive core. Our deduced orbital
eccentricity, 0.0035(-0.0025,+0.0060), is consistent with a fully circularized
orbit. We detect the emission of the planet at 2.09 microns at better than
11-sigma, the deduced occultation depth being 1560+-140 ppm. Our detection of
the occultation at 1.19 microns is marginal (790+-320 ppm) and more
observations are needed to confirm it. We place a 3-sigma upper limit of 850
ppm on the depth of the occultation at ~0.9 microns. Together, these results
strongly favor a poor redistribution of the heat to the night-side of the
planet, and marginally favor a model with no day-side temperature inversion.Comment: 14 pages, 6 tables, 11 figures. Accepted for publication in A&
Obese father's metabolic state, adiposity, and reproductive capacity indicate son's reproductive health
ObjectiveTo determine whether dietary and exercise regimes in obese males can provide a novel intervention window for improving the reproductive health of the next generation.DesignExperimental animal study.SettingUniversity research facilities.Animal(s)C57BL6 male and female mice.Intervention(s)Mice were fed a control diet (6% fat) or high-fat diet (21% fat) for 9 weeks. After the initial feeding, high-fat-diet males were allocated to diet and/or exercise interventions for a further 9 weeks. After intervention males were mated with females fed standard chow (4% fat) before and during pregnancy.Main outcome measure(s)F1 sperm motility, count, morphology, capacitation, mitochondrial function, and sperm binding and weight of reproductive organs.Result(s)Our primary finding was that diet intervention alone in founders improved offspring sperm motility and mitochondrial markers of sperm health (decreased reactive oxygen species and mitochondrial membrane potential), ultimately improving sperm binding. Sperm binding and capacitation was also improved in F1 males born to a combined diet and exercise intervention in founders. Founder sperm parameters and metabolic measures as a response to diet and/or exercise (i.e., lipid/glucose homeostasis, sperm count and morphology) correlated with offspring's sperm function, independent of founder treatment. This implicates paternal metabolic and reproductive status in predicting male offspring's reproductive function.Conclusion(s)This is the first study to show that improvements to both metabolic (lipids, glucose and insulin sensitivity) and reproductive function (sperm motility and morphology) in obese fathers via diet and exercise interventions can improve subsequent reproductive health in offspring.Nicole O. McPherson, Tod Fullston, Hassan W. Bakos, Brian P. Setchell and Michelle Lan
Rotation of planet-harbouring stars
The rotation rate of a star has important implications for the detectability,
characterisation and stability of any planets that may be orbiting it. This
chapter gives a brief overview of stellar rotation before describing the
methods used to measure the rotation periods of planet host stars, the factors
affecting the evolution of a star's rotation rate, stellar age estimates based
on rotation, and an overview of the observed trends in the rotation properties
of stars with planets.Comment: 16 pages, 4 figures: Invited review to appear in 'Handbook of
Exoplanets', Springer Reference Works, edited by Hans J. Deeg and Juan
Antonio Belmont
Transit Photometry as an Exoplanet Discovery Method
Photometry with the transit method has arguably been the most successful
exoplanet discovery method to date. A short overview about the rise of that
method to its present status is given. The method's strength is the rich set of
parameters that can be obtained from transiting planets, in particular in
combination with radial velocity observations; the basic principles of these
parameters are given. The method has however also drawbacks, which are the low
probability that transits appear in randomly oriented planet systems, and the
presence of astrophysical phenomena that may mimic transits and give rise to
false detection positives. In the second part we outline the main factors that
determine the design of transit surveys, such as the size of the survey sample,
the temporal coverage, the detection precision, the sample brightness and the
methods to extract transit events from observed light curves. Lastly, an
overview over past, current and future transit surveys is given. For these
surveys we indicate their basic instrument configuration and their planet
catch, including the ranges of planet sizes and stellar magnitudes that were
encountered. Current and future transit detection experiments concentrate
primarily on bright or special targets, and we expect that the transit method
remains a principal driver of exoplanet science, through new discoveries to be
made and through the development of new generations of instruments.Comment: Review chapte
HAT Variability Survey in the High Stellar Density "Kepler Field" with Millimagnitude Image Subtraction Photometry
The Hungarian-made Automated Telescope network (HATnet) is an ongoing project
to detect transiting extra-solar planets using small aperture (11 cm diameter),
robotic telescopes. In this paper we present the results from using image
subtraction photometry to reduce a crowded stellar field observed with one of
the HATnet telescopes (HAT-5). This field was chosen to overlap with the
planned Kepler mission. We obtained I-band light curves for 98,000 objects in a
8.3x8.3 square degree field of view, near the Galactic plane in the
constellations Cygnus and Lyra. These observations include 788 5-minute
exposures over 30 days. For the brightest stars (I~8.0) we achieved a precision
of 3.5 millimagnitudes, falling to 0.1 magnitudes at the faint end (I~14). From
these light curves we identify 1617 variable stars, of which 1439 are newly
discovered. The fact that nearly 90% of the variables were previously
undetected further demonstrates the vast number of variables yet to be
discovered even among fairly bright stars in our Galaxy. We also discuss some
of the most interesting cases. These include: V1171 Cyg, a triple system with
the inner two stars in P=1.462 day period eclipsing orbit and the outer star a
P=4.86 day Cepheid; HD227269, an eccentric eclipsing system with a P=4.86 day
period that also shows P=2.907 day pulsations; WW Cyg, a well studied eclipsing
binary; V482 Cyg, an RCB star; and V546 Cyg, a PV Tel Variable. We also detect
a number of small amplitude variables, in some cases with full amplitude as low
as 10 mmag.Comment: 44 pages, 19 figures. Accepted for publication in the Astronomical
Journal. Revised version, including updated matches to existing catalogs.
Data available at http://cfa-www.harvard.edu/~gbakos/HAT/LC/199
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