8,164 research outputs found
Heat capacity mapping mission project HCM-051
There are no author-identified significant results in this report
Pulsar timing arrays as imaging gravitational wave telescopes: angular resolution and source (de)confusion
Pulsar timing arrays (PTAs) will be sensitive to a finite number of
gravitational wave (GW) "point" sources (e.g. supermassive black hole
binaries). N quiet pulsars with accurately known distances d_{pulsar} can
characterize up to 2N/7 distant chirping sources per frequency bin \Delta
f_{gw}=1/T, and localize them with "diffraction limited" precision \delta\theta
\gtrsim (1/SNR)(\lambda_{gw}/d_{pulsar}). Even if the pulsar distances are
poorly known, a PTA with F frequency bins can still characterize up to
(2N/7)[1-(1/2F)] sources per bin, and the quasi-singular pattern of timing
residuals in the vicinity of a GW source still allows the source to be
localized quasi-topologically within roughly the smallest quadrilateral of
quiet pulsars that encircles it on the sky, down to a limiting resolution
\delta\theta \gtrsim (1/SNR) \sqrt{\lambda_{gw}/d_{pulsar}}. PTAs may be
unconfused, even at the lowest frequencies, with matched filtering always
appropriate.Comment: 7 pages, 1 figure, matches Phys.Rev.D versio
Heat Capacity Mapping Mission
The Tasman Front was delineated by airborne expendable bathythermograph survey; and an Heat Capacity Mapping Mission (HCMM) IR image on the same day shows the same principal features as determined from ground-truth. It is clear that digital enhancement of HCMM images is necessary to map ocean surface temperatures and when done, the Tasman Front and other oceanographic features can be mapped by this method, even through considerable scattered cloud cover
Line Broadening in Field Metal-poor Red Giant and Red Horizontal Branch Stars
We report 349 radial velocities for 45 metal-poor field red giant and red
horizontal branch stars. We have have identified one new spectroscopic binary,
HD 4306, and one possible such system, HD 184711. We also report 57 radial
velocities for 11 of the 91 stars reported on previously by Carney et al.
(2003). As was found in the previous study, radial velocity "jitter" is present
in many of the most luminous stars. Excluding stars showing spectroscopic
binary orbital motion, all 7 of the red giants with M(V) <= -2.0 display
jitter, as well as 3 of the 14 stars with -2.0 <= M(V) <= -1.4. We have also
measured line broadening in all of the new spectra, using synthetic spectra as
templates. The most luminous red giants show significant line broadening, as do
many of the red horizontal branch stars, and we discuss briefly possible
causes.Comment: To appear in the Astronomical Journa
A Photometric Survey for Variables and Transits in the Field of Praesepe with KELT
The Kilodegree Extremely Little Telescope (KELT) project is a small aperture,
wide-angle search for planetary transits of solar-type stars. In this paper, we
present the results of a commissioning campaign with the KELT telescope to
observe the open cluster Praesepe for 34 nights in early 2005. Lightcurves were
obtained for 69,337 stars, out of which we identify 58 long period variables
and 152 periodic variables. Sixteen of these are previously known as variable,
yielding 194 newly discovered variable stars for which we provide properties
and lightcurves. We also searched for planetary-like transits, finding four
transit candidates. Follow-up observations indicate that two of the candidates
are astrophysical false positives, with two candidates remaining as potential
planetary transits.Comment: 45 pages, 16 figures. Submitted to AJ. PDF version with full
resolution figures located at
http://www.astronomy.ohio-state.edu/~pepper/kelt.pd
Remote sensing of vigor loss in conifers due to dwarf mistletoe
The initial operation of a multiband/multidate tower-tramway test site in northeastern Minnesota for the development of specifications for subsequent multiband aerial photography of more extensive study areas was completed. Multiband/multidate configurations suggested by the tower-tramway studies were and will be flown with local equipment over the Togo test site. This site was photographed by the NASA RB57F aircraft in August and September 1971. It appears that, of all the film/filter combinations attempted to date (including optical recombining of several spectral band images via photo enhancement techniques), Ektachrome infrared film with a Wratten 12 filter is the best for detecting dwarf mistletoe, and other tree diseases as well. Using this film/filter combination, infection centers are easily detectable even on the smallest photo scale (1:100,000) obtained on the Togo site
Transits and Occultations of an Earth-Sized Planet in an 8.5-Hour Orbit
We report the discovery of an Earth-sized planet () in
an 8.5-hour orbit around a late G-type star (KIC 8435766, Kepler-78). The
object was identified in a search for short-period planets in the {\it Kepler}
database and confirmed to be a transiting planet (as opposed to an eclipsing
stellar system) through the absence of ellipsoidal light variations or
substantial radial-velocity variations. The unusually short orbital period and
the relative brightness of the host star ( = 11.5) enable robust
detections of the changing illumination of the visible hemisphere of the
planet, as well as the occultations of the planet by the star. We interpret
these signals as representing a combination of reflected and reprocessed light,
with the highest planet dayside temperature in the range of 2300 K to 3100 K.
Follow-up spectroscopy combined with finer sampling photometric observations
will further pin down the system parameters and may even yield the mass of the
planet.Comment: Accepted for publication, ApJ, 10 pages and 6 figure
Blue Dots Team Transits Working Group Review
Transiting planet systems offer an unique opportunity to observationally
constrain proposed models of the interiors (radius, composition) and
atmospheres (chemistry, dynamics) of extrasolar planets. The spectacular
successes of ground-based transit surveys (more than 60 transiting systems
known to-date) and the host of multi-wavelength, spectro-photometric follow-up
studies, carried out in particular by HST and Spitzer, have paved the way to
the next generation of transit search projects, which are currently ongoing
(CoRoT, Kepler), or planned. The possibility of detecting and characterizing
transiting Earth-sized planets in the habitable zone of their parent stars
appears tantalizingly close. In this contribution we briefly review the power
of the transit technique for characterization of extrasolar planets, summarize
the state of the art of both ground-based and space-borne transit search
programs, and illustrate how the science of planetary transits fits within the
Blue Dots perspective.Comment: 9 pages, 3 figures, to be published in the proceedings (ASP Conf.
Ser.) of the "Pathways Towards Habitable Planets" conference, held in
Barcelona (14-18 Sep 2009
Speckle Interferometry of Metal-Poor Stars in the Solar Neighborhood. I
We report the results of speckle-interferometric observations of 109 high
proper-motion metal-poor stars made with the 6-m telescope of the Special
Astrophysical Observatory of the Russian Academy of Sciences. We resolve eight
objects -- G102-20, G191-55, BD+19~1185A, G89-14, G87-45, G87-47,
G111-38, and G114-25 -- into individual components and we are the first to
astrometrically resolve seven of these stars. New resolved systems included two
triple (G111-38, G87-47) and one quadruple (G89-14) star. The ratio of
single-to-binary-to-triple-to-quadruple systems among the stars of our sample
is equal to 71:28:6:1.Comment: 8 pages, 4 figures, accepted to Astrophysical Bulleti
Novel use Of Hydroxyurea in an African Region with Malaria (NOHARM): a trial for children with sickle cell anemia
Hydroxyurea treatment is recommended for children with sickle cell anemia (SCA) living in high-resource malaria-free regions, but its safety and efficacy in malaria-endemic sub-Saharan Africa, where the greatest sickle-cell burden exists, remain unknown. In vitro studies suggest hydroxyurea could increase malaria severity, and hydroxyurea-associated neutropenia could worsen infections. NOHARM (Novel use Of Hydroxyurea in an African Region with Malaria) was a randomized, double-blinded, placebo-controlled trial conducted in malaria-endemic Uganda, comparing hydroxyurea to placebo at 20 ± 2.5 mg/kg per day for 12 months. The primary outcome was incidence of clinical malaria. Secondary outcomes included SCA-related adverse events (AEs), clinical and laboratory effects, and hematological toxicities. Children received either hydroxyurea (N = 104) or placebo (N = 103). Malaria incidence did not differ between children on hydroxyurea (0.05 episodes per child per year; 95% confidence interval [0.02, 0.13]) vs placebo (0.07 episodes per child per year [0.03, 0.16]); the hydroxyurea/placebo malaria incidence rate ratio was 0.7 ([0.2, 2.7]; P = .61). Time to infection also did not differ significantly between treatment arms. A composite SCA-related clinical outcome (vaso-occlusive painful crisis, dactylitis, acute chest syndrome, splenic sequestration, or blood transfusion) was less frequent with hydroxyurea (45%) than placebo (69%; P = .001). Children receiving hydroxyurea had significantly increased hemoglobin concentration and fetal hemoglobin, with decreased leukocytes and reticulocytes. Serious AEs, sepsis episodes, and dose-limiting toxicities were similar between treatment arms. Three deaths occurred (2 hydroxyurea, 1 placebo, and none from malaria). Hydroxyurea treatment appears safe for children with SCA living in malaria-endemic sub-Saharan Africa, without increased severe malaria, infections, or AEs. Hydroxyurea provides SCA-related laboratory and clinical efficacy, but optimal dosing and monitoring regimens for Africa remain undefined. This trial was registered at www.clinicaltrials.gov as #NCT01976416
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