2,191 research outputs found
High-Spatial-Resolution K-Band Imaging of Select K2 Campaign Fields
NASA's K2 mission began observing fields along the ecliptic plane in 2014.
Each observing campaign lasts approximately 80 days, during which
high-precision optical photometry of select astrophysical targets is collected
by the Kepler spacecraft. Due to the 4 arcsec pixel scale of the Kepler
photometer, significant blending between the observed targets can occur
(especially in dense fields close to the Galactic plane). We undertook a
program to use the Wide Field Camera (WFCAM) on the 3.8 m United Kingdom
InfraRed Telescope (UKIRT) to collect high-spatial-resolution near-infrared
images of targets in select K2 campaign fields, which we report here. These 0.4
arcsec resolution K-band images offer the opportunity to perform a variety of
science, including vetting exoplanet candidates by identifying nearby stars
blended with the target star and estimating the size, color, and type of
galaxies observed by K2.Comment: 2 pages, Published by Research Notes of the American Astronomical
Societ
Nuclear Equation of State from Observations of Short Gamma-Ray Burst Remnants
The favoured progenitor model for short -ray bursts (SGRBs) is the
merger of two neutron stars that triggers an explosion with a burst of
collimated -rays. Following the initial prompt emission, some SGRBs
exhibit a plateau phase in their -ray light curves that indicates additional
energy injection from a central engine, believed to be a rapidly rotating,
highly magnetised neutron star. The collapse of this `protomagnetar' to a black
hole is likely to be responsible for a steep decay in -ray flux observed at
the end of the plateau. In this letter, we show that these observations can be
used to effectively constrain the equation of state of dense matter. In
particular, we show that the known distribution of masses in binary neutron
star systems, together with fits to the -ray light curves, provide
constraints that exclude the softest and stiffest plausible equations of state.
We further illustrate how a future gravitational wave observation with Advanced
LIGO/Virgo can place tight constraints on the equation of state, by adding into
the picture a measurement of the chirp mass of the SGRB progenitor.Comment: accepted for publication in Phys. Rev.
Weather, Timing, and Promotions in Minor League Baseball: An Examination of Attendance in the International League
Understanding the different factors that impact attendance at sporting events is a timely and relevant topic for researchers and practitioners alike. The present study examines the effects of different types of promotions, weather, and selected temporal elements on attendance in Minor League Baseball. Using data for teams participating in the International League during the 2010 season, results from a multiple regression analysis revealed that special events, promotional giveaways, and non-workdays have a positive impact on attendance; while suboptimal weather conditions have a negative impact. These findings contribute to our understanding of the factors that impact attendance in professional baseball and hold useful implications for future research and managerial practice
The Mid-Infrared Spectrum of the Short Orbital Period Polar EF Eridani from the Spitzer Space Telescope
We present the first mid-infrared (5.5-14.5 micron) spectrum of a highly
magnetic cataclysmic variable, EF Eridani, obtained with the Infrared
Spectrograph on the Spitzer Space Telescope. The spectrum displays a relatively
flat, featureless continuum. A spectral energy distribution model consisting of
a 9500 K white dwarf, L5 secondary star, cyclotron emission corresponding to a
B~13 MG white dwarf magnetic field, and an optically thin circumbinary dust
disk is in reasonable agreement with the extant 2MASS, IRAC, and IRS
observations of EF Eri. Cyclotron emission is ruled out as a dominant
contributor to the infrared flux density at wavelengths >3 microns. The
spectral energy distribution longward of ~5 microns is dominated by dust
emission. Even longer wavelength observations would test the model's prediction
of a continuing gradual decline in the circumbinary disk-dominated region of
the spectral energy distribution.Comment: To be published in The Astrophysical Journa
Rapidly Reconfigurable Optically Induced Photonic Crystals in Hot Rubidium Vapor
Through periodic index modulation, we create two different types of photonic structures in a heated rubidium vapor for controlled reflection, transmission, and diffraction of light. The modulation is achieved through the use of the ac Stark effect resulting from a standing-wave control field. The periodic intensity structures create translationally invariant index profiles analogous to photonic crystals in spectral regions of steep dispersion. Experimental results are consistent with modeling
Modeling Multi-Wavelength Stellar Astrometry. I. SIM Lite Observations of Interacting Binaries
Interacting binaries consist of a secondary star which fills or is very close
to filling its Roche lobe, resulting in accretion onto the primary star, which
is often, but not always, a compact object. In many cases, the primary star,
secondary star, and the accretion disk can all be significant sources of
luminosity. SIM Lite will only measure the photocenter of an astrometric
target, and thus determining the true astrometric orbits of such systems will
be difficult. We have modified the Eclipsing Light Curve code (Orosz &
Hauschildt 2000) to allow us to model the flux-weighted reflex motions of
interacting binaries, in a code we call REFLUX. This code gives us sufficient
flexibility to investigate nearly every configuration of interacting binary. We
find that SIM Lite will be able to determine astrometric orbits for all
sufficiently bright interacting binaries where the primary or secondary star
dominates the luminosity. For systems where there are multiple components that
comprise the spectrum in the optical bandpass accessible to SIM Lite, we find
it is possible to obtain absolute masses for both components, although
multi-wavelength photometry will be required to disentangle the multiple
components. In all cases, SIM Lite will at least yield accurate inclinations,
and provide valuable information that will allow us to begin to understand the
complex evolution of mass-transferring binaries. It is critical that SIM Lite
maintains a multi-wavelength capability to allow for the proper deconvolution
of the astrometric orbits in multi-component systems.Comment: 12 pages, 6 figures, 6 tables. Accepted for publication in the
Astrophysical Journa
Nebular-Phase Spectra of Nearby Type Ia Supernovae
We present late-time spectra of eight Type Ia supernovae (SNe Ia) obtained at
days after peak brightness using the Gemini South and Keck telescopes.
All of the SNe Ia in our sample were nearby, well separated from their host
galaxy's light, and have early-time photometry and spectroscopy from the Las
Cumbres Observatory (LCO). Parameters are derived from the light curves and
spectra such as peak brightness, decline rate, photospheric velocity, and the
widths and velocities of the forbidden nebular emission lines. We discuss the
physical interpretations of these parameters for the individual SNe Ia and the
sample in general, including comparisons to well-observed SNe Ia from the
literature. There are possible correlations between early-time and late-time
spectral features that may indicate an asymmetric explosion, so we discuss our
sample of SNe within the context of models for an offset ignition and/or white
dwarf collisions. A subset of our late-time spectra are uncontaminated by host
emission, and we statistically evaluate our nondetections of H emission
to limit the amount of hydrogen in these systems. Finally, we consider the
late-time evolution of the iron emission lines, finding that not all of our SNe
follow the established trend of a redward migration at days after
maximum brightness.Comment: 20 pages, 8 figures, 9 tables; accepted to MNRA
The Gravitational Wave Treasure Map: A Tool to Coordinate, Visualize, and Assess the Electromagnetic Follow-Up of Gravitational Wave Events
We present the Gravitational Wave Treasure Map, a tool to coordinate,
visualize, and assess the electromagnetic follow-up of gravitational wave (GW)
events. With typical GW localization regions of hundreds to thousands of square
degrees and dozens of active follow-up groups, the pursuit of electromagnetic
(EM) counterparts is a challenging endeavor, but the scientific payoff for
early discovery of any counterpart is clear. With this tool, we provide a
website and API interface that allows users to easily see where other groups
have searched and better inform their own follow-up search efforts. A strong
community of Treasure Map users will increase the overall efficiency of EM
counterpart searches and will play a fundamental role in the future of
multi-messenger astronomy.Comment: 14 pages, 8 figures, Accepted to Ap
Revised Stellar Properties of Kepler Targets for the Q1-17 (DR25) Transit Detection Run
The determination of exoplanet properties and occurrence rates using Kepler
data critically depends on our knowledge of the fundamental properties (such as
temperature, radius and mass) of the observed stars. We present revised stellar
properties for 197,096 Kepler targets observed between Quarters 1-17 (Q1-17),
which were used for the final transiting planet search run by the Kepler
Mission (Data Release 25, DR25). Similar to the Q1--16 catalog by Huber et al.
the classifications are based on conditioning published atmospheric parameters
on a grid of Dartmouth isochrones, with significant improvements in the adopted
methodology and over 29,000 new sources for temperatures, surface gravities or
metallicities. In addition to fundamental stellar properties the new catalog
also includes distances and extinctions, and we provide posterior samples for
each stellar parameter of each star. Typical uncertainties are ~27% in radius,
~17% in mass, and ~51% in density, which is somewhat smaller than previous
catalogs due to the larger number of improved logg constraints and the
inclusion of isochrone weighting when deriving stellar posterior distributions.
On average, the catalog includes a significantly larger number of evolved
solar-type stars, with an increase of 43.5% in the number of subgiants. We
discuss the overall changes of radii and masses of Kepler targets as a function
of spectral type, with particular focus on exoplanet host stars.Comment: 19 pages, 13 figures. ApJS in pres
The Kepler Follow-up Observation Program
The Kepler Mission was launched on March 6, 2009 to perform a photometric
survey of more than 100,000 dwarf stars to search for terrestrial-size planets
with the transit technique. Follow-up observations of planetary candidates
identified by detection of transit-like events are needed both for
identification of astrophysical phenomena that mimic planetary transits and for
characterization of the true planets and planetary systems found by Kepler. We
have developed techniques and protocols for detection of false planetary
transits and are currently conducting observations on 177 Kepler targets that
have been selected for follow-up. A preliminary estimate indicates that between
24% and 62% of planetary candidates selected for follow-up will turn out to be
true planets.Comment: 12 pages, submitted to the Astrophysical Journal Letter
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