33,904 research outputs found
GMRT Low Frequency Observations of Extrasolar Planetary Systems
Extrasolar planets are expected to emit detectable low frequency radio
emission. In this paper we present results from new low frequency observations
of two extrasolar planetary systems (Epsilon Eridani and HD 128311) taken at
150 MHz with the Giant Metrewave Radio Telescope (GMRT). These two systems have
been chosen because the stars are young (with ages < 1 Gyr) and are likely to
have strong stellar winds, which will increase the expected radio flux. The
planets are massive (presumably) gas giant planets in longer period orbits, and
hence will not be tidally locked to their host star (as is likely to be the
case for short period planets) and we would expect them to have a strong
planetary dynamo and magnetic field. We do not detect either system, but are
able to place tight upper limits on their low frequency radio emission, at
levels comparable to the theoretical predictions for these systems. From these
observations we have a 2.5sigma limit of 7.8 mJy for Epsilon Eri and 15.5 mJy
for HD 128311. In addition, these upper limits also provide limits on the low
frequency radio emission from the stars themselves. These results are discussed
and also the prospects for the future detection of radio emission from
extrasolar planets.Comment: 6 pages, 2 figures, accepted for publication in MNRA
Capillary waves at the liquid-vapor interface and the surface tension of water models
Capillary waves occurring at the liquid-vapor interface of water are studied
using molecular dynamics simulations. In addition, the surface tension,
determined thermodynamically from the difference in the normal and tangential
pressure at the liquid-vapor interface, is compared for a number of standard
three- and four-point water models. We study four three-point models (SPC/E,
TIP3P, TIP3P-CHARMM, and TIP3P-Ew) and two four-point models (TIP4P and
TIP4P-Ew). All of the models examined underestimate the surface tension; the
TIP4P-Ew model comes closest to reproducing the experimental data. The surface
tension can also be determined from the amplitude of capillary waves at the
liquid-vapor interface by varying the surface area of the interface. The
surface tensions determined from the amplitude of the logarithmic divergence of
the capillary interfacial width and from the traditional thermodynamic method
agree only if the density profile is fitted to an error function instead of a
hyperbolic tangent function.Comment: 11 pages, 8 figures, 7 tables. Accepted for publication in J. Chem.
Phys. [v2: Added references, corrected minor errors
The supercuspidal representations of p-adic classical groups
Let G be a unitary, symplectic or special orthogonal group over a locally
compact non-archimedean local field of odd residual characteristic. We
construct many new supercuspidal representations of G, and Bushnell-Kutzko
types for these representations. Moreover, we prove that every irreducible
supercuspidal representation of G arises from our constructions.Comment: 55 pages -- minor changes from 1st version (mostly in sections 2.2,
4.2 and 6.2). To appear in Inventiones mathematicae, 2008 (DOI is not yet
active as at 12 Nov 2007
Testing of typical spacecraft materials in a simulated substorm environment
The test specimens were spacecraft paints, silvered Teflon, thermal blankets, and solar array segments. The samples, ranging in size from 300 to 1000 sq cm were exposed to monoenergetic electron energies from 2 to 20 keV at a current density of 1 NA/sq cm. The samples generally behaved as capacitors with strong voltage gradient at their edges. The charging characteristics of the silvered Teflon, Kapton, and solar cell covers were controlled by the secondary emission characteristics. Insulators that did not discharge were the spacecraft paints and the quartz fiber cloth thermal blanket sample. All other samples did experience discharges when the surface voltage reached -8 to -16kV. The discharges were photographed. The breakdown voltage for each sample was determined and the average energy lost in the discharge was computed
A theoretical study of the aerodynamic characteristics of lifting-body entry vehicles Summary report, Mar. 1965 - Mar. 1966
Aerodynamic characteristics of lifting-body entry vehicle
Asteroseismology of red giants: photometric observations of Arcturus by SMEI
We present new results on oscillations of the K1.5 III giant Arcturus (alpha
Boo), from analysis of just over 2.5 yr of precise photometric observations
made by the Solar Mass Ejection Imager (SMEI) on board the Coriolis satellite.
A strong mode of oscillation is uncovered by the analysis, having frequency
3.51+/-0.03 micro-Hertz. By fitting its mode peak, we are able offer a highly
constrained direct estimate of the damping time (tau = 24+/-1 days). The data
also hint at the possible presence of several radial-mode overtones, and maybe
some non-radial modes. We are also able to measure the properties of the
granulation on the star, with the characteristic timescale for the granulation
estimated to be 0.50+/-0.05 days.Comment: 6 pages, 5 figures; accepted for publication in MNRAS Letter
High spatial resolution observations of CUDSS14A: a SCUBA-selected ultraluminous galaxy at high redshift
The definitive version is available at www.blackwell-synergy.com '. Copyright Blackwell Publishing DOI : 10.1046/j.1365-8711.2000.03822.xWe present a high-resolutionmillimetre interferometric image of the brightest SCUBA- selected galaxy from the Canada-UK deep SCUBA survey (CUDSS). We make a very clear detection at 1.3 mm, but fail to resolve any structure in the source.Peer reviewe
- …