2,938 research outputs found
KSwAGS: A Swift X-ray and UV Survey of the Kepler Field. I
We introduce the first phase of the Kepler-Swift Active Galaxies and Stars
survey (KSwAGS), a simultaneous X-ray and UV survey of ~6 square degrees of the
Kepler field using the Swift XRT and UVOT. We detect 93 unique X-ray sources
with S/N>3 with the XRT, of which 60 have observed UV counterparts. We use the
Kepler Input Catalog (KIC) to obtain the optical counterparts of these sources,
and construct the X-ray to optical flux ratio as a first approximation of the
classification of the source. The survey produces a mixture of stellar sources,
extragalactic sources, and sources which we are not able to classify with
certainty. We have obtained optical spectra for thirty of these targets, and
are conducting an ongoing observing campaign to fully identify the sample. For
sources classified as stellar or AGN with certainty, we construct SEDs using
the 2MASS, UBV and GALEX data supplied for their optical counterparts by the
KIC, and show that the SEDs differ qualitatively between the source types, and
so can offer a method of classification in absence of a spectrum. Future papers
in this series will analyze the timing properties of the stars and AGN in our
sample separately. Our survey provides the first X-ray and UV data for a number
of known variable stellar sources, as well as a large number of new X-ray
detections in this well-studied portion of the sky. The KSwAGS survey is
currently ongoing in the K2 ecliptic plane fields.Comment: Accepted for publication in the Astronomical Journal. 19 pages, 8
figures, 3 table
Seizing the Moment: Realizing the Promise of Student-Centered Learning
This brief outlines policy recommendations for supporting student-centered learning at the local, state, and federal level
From genomes to systems
A report on the 2nd Conference of the Consortium for Post-Genome Science (CPGS) 'Genomes to Systems', Manchester, UK, 1-3 September 2004
Fortnightly tides and subtidal motions in a choked inlet
This paper is not subject to U.S. copyright. The definitive version was published in Estuarine, Coastal and Shelf Science 150, Pt.B (2014): 325-331, doi:10.1016/j.ecss.2014.03.025.Amplitudes of semi-diurnal tidal fluctuations measured at an ocean inlet system decay nearly linearly by 87% between the ocean edge of the offshore ebb-tidal delta and the backbay. A monochromatic, dynamical model for a tidally choked inlet separately reproduces the evolution of the amplitudes and phases of the semi-diurnal and diurnal tidal constituents observed between the ocean and inland locations. However, the monochromatic model over-predicts the amplitude and under-predicts the lag of the lower-frequency subtidal and fortnightly motions observed in the backbay. A dimensional model that considers all tidal constituents simultaneously, balances the along-channel pressure gradient with quadratic bottom friction, and that includes a time-varying channel water depth, is used to show that that these model-data differences are associated with nonlinear interactions between the tidal constituents that are not included in non-dimensional, monochromatic models. In particular, numerical simulations suggest that the nonlinear interactions induced by quadratic bottom friction modify the amplitude and phase of the subtidal and fortnightly backbay response. This nonlinear effect on the low-frequency (subtidal and fortnightly) motions increases with increasing high-frequency (semi-diurnal) amplitude. The subtidal and fortnightly motions influence water exchange processes, and thus backbay temperature and salinity.We thank the Office of Naval Research (N0001411WX20962; N0001412WX20498) for funding
The integration of grazing management and anthelmintic treatment to provide clean lambing paddocks in the northern tablelands region of NSW, Australia
The three experiments described in this thesis have been submitted as research articles to Veterinary Parasitology. Each research article has been included in the thesis as an experimental chapter, essentially as submitted for publication but with the abstract removed
Kepler Observations of V447 Lyr: An Eclipsing U Gem Cataclysmic Variable
We present the results of an analysis of data covering 1.5 years of the dwarf
nova V447 Lyr. We detect eclipses of the accretion disk by the mass donating
secondary star every 3.74 hrs which is the binary orbital period. V447 Lyr is
therefore the first dwarf nova in the Kepler field to show eclipses. We also
detect five long outbursts and six short outbursts showing V447 Lyr is a U Gem
type dwarf nova. We show that the orbital phase of the mid-eclipse occurs
earlier during outbursts compared to quiescence and that the width of the
eclipse is greater during outburst. This suggests that the bright spot is more
prominent during quiescence and that the disk is larger during outburst than
quiescence. This is consistent with an expansion of the outer disk radius due
to the presence of high viscosity material associated with the outburst,
followed by a contraction in quiescence due to the accretion of low angular
momentum material. We note that the long outbursts appear to be triggered by a
short outburst, which is also observed in the super-outbursts of SU UMa dwarf
novae as observed using Kepler.Comment: Accepted by MNRA
Recommended from our members
Kepler-4B: A Hot Neptune-Like Planet of A G0 Star Near Main-Sequence Turnoff
Early time-series photometry from NASA's Kepler spacecraft has revealed a planet transiting the star we term Kepler-4, at R.A. = 19(h)02(m)27.(s)68, delta = +50 degrees 08'08 '' 7. The planet has an orbital period of 3.213 days and shows transits with a relative depth of 0.87 x 10(-3) and a duration of about 3.95 hr. Radial velocity (RV) measurements from the Keck High Resolution Echelle Spectrometer show a reflex Doppler signal of 9.3(-1.9)(+1.1) m s(-1), consistent with a low-eccentricity orbit with the phase expected from the transits. Various tests show no evidence for any companion star near enough to affect the light curve or the RVs for this system. From a transit-based estimate of the host star's mean density, combined with analysis of high-resolution spectra, we infer that the host star is near turnoff from the main sequence, with estimated mass and radius of 1.223(-0.091)(+0.053) M(circle dot) and 1.487(-0.084)(+0.071) R(circle dot).We estimate the planet mass and radius to be {M(P), R(P)} = {24.5 +/- 3.8 M(circle plus), 3.99 +/- 0.21 R(circle plus)}. The planet's density is near 1.9 g cm(-3); it is thus slightly denser and more massive than Neptune, but about the same size.W. M. Keck FoundationNASA's Science Mission DirectorateAstronom
KOI-54: The Kepler Discovery of Tidally Excited Pulsations and Brightenings in a Highly Eccentric Binary
Kepler observations of the star HD 187091 (KIC 8112039, hereafter KOI-54) revealed a remarkable light curve exhibiting sharp periodic brightening events every 41.8 days with a superimposed set of oscillations forming a beating pattern in phase with the brightenings. Spectroscopic observations revealed that this is a binary star with a highly eccentric orbit, e = 0.83. We are able to match the Kepler light curve and radial velocities with a nearly face-on (i = 5 degrees.5) binary star model in which the brightening events are caused by tidal distortion and irradiation of nearly identical A stars during their close periastron passage. The two dominant oscillations in the light curve, responsible for the beating pattern, have frequencies that are the 91st and 90th harmonic of the orbital frequency. The power spectrum of the light curve, after removing the binary star brightening component, reveals a large number of pulsations, 30 of which have a signal-to-noise ratio greater than or similar to 7. Nearly all of these pulsations have frequencies that are either integer multiples of the orbital frequency or are tidally split multiples of the orbital frequency. This pattern of frequencies unambiguously establishes the pulsations as resonances between the dynamic tides at periastron and the free oscillation modes of one or both of the stars. KOI-54 is only the fourth star to show such a phenomenon and is by far the richest in terms of excited modes.NASA, Science Mission DirectorateNASA NNX08AR14GEuropean Research Council under the European Community 227224W.M. Keck FoundationMcDonald Observator
The Millimeter Astronomy Legacy Team 90 GHz (MALT90) Pilot Survey
We describe a pilot survey conducted with the Mopra 22-m radio telescope in
preparation for the Millimeter Astronomy Legacy Team Survey at 90 GHz (MALT90).
We identified 182 candidate dense molecular clumps using six different
selection criteria and mapped each source simultaneously in 16 different lines
near 90 GHz. We present a summary of the data and describe how the results of
the pilot survey shaped the design of the larger MALT90 survey. We motivate our
selection of target sources for the main survey based on the pilot detection
rates and demonstrate the value of mapping in multiple lines simultaneously at
high spectral resolution.Comment: Accepted to ApJS. 23 pages and 16 figures. Full resolution version
with an appendix showing all the data (12.1 MB) is available at
http://malt90.bu.edu/publications/Foster_2011_Malt90Pilot.pd
Serendipitous Kepler observations of a background dwarf nova of SU UMa type
We have discovered a dwarf nova (DN) of type SU UMa in Kepler data which is
7.0 arcsec from the G-type exoplanet survey target KIC 4378554. The DN appears
as a background source in the pixel aperture of the foreground G star. We
extracted only the pixels where the DN is present and observed the source to
undergo five outbursts -- one a superoutburst -- over a timespan of 22 months.
The superoutburst was triggered by a normal outburst, a feature that has been
seen in all DNe superoutburst observed by Kepler. Superhumps during the super
outburst had a period of 1.842+/-0.004 h and we see a transition from
disc-dominated superhump signal to a mix of disc and accretion stream impact.
Predictions of the number of DNe present in Kepler data based on previously
published space densities vary from 0.3 to 258. An investigation of the
background pixels targets would lead to firmer constraints on the space density
of DN.Comment: Accepted for publication in MNRA
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