1,023 research outputs found
Optimal interactions of light with magnetic and electric resonant particles
This work studies the limits of far and near-field electromagnetic response
of sub-wavelength scatterers, like the unitary limit and of lossless
scatterers, and the ideal absorption limit of lossy particles. These limit
behaviors are described in terms of analytic formulas that approximate finite
size effects while rigorously including radiative corrections. This analysis
predicts the electric and/or magnetic limit responses of both metallic and
dielectric nanoparticles while quantitatively describing near-field
enhancements.Comment: 9 pages, 8 figures, 2 table
Servicing the service industries: lifelong education as human capital investments for Hong Kong
published_or_final_versio
The Doppler Shadow of WASP-3b: A tomographic analysis of Rossiter-McLaughlin observations
Hot-Jupiter planets must form at large separations from their host stars
where the temperatures are cool enough for their cores to condense. They then
migrate inwards to their current observed orbital separations. Different
theories of how this migration occurs lead to varying distributions of orbital
eccentricity and the alignment between the rotation axis of the star and the
orbital axis of the planet. The spin-orbit alignment of a transiting system is
revealed via the Rossiter-McLaughlin effect, which is the anomaly present in
the radial velocity measurements of the rotating star during transit due to the
planet blocking some of the starlight. In this paper we aim to measure the
spin-orbit alignment of the WASP-3 system via a new way of analysing the
Rossiter-McLaughlin observations. We apply a new tomographic method for
analysing the time variable asymmetry of stellar line profiles caused by the
Rossiter-McLaughlin effect. This new method eliminates the systematic error
inherent in previous methods used to analyse the effect. We find a value for
the projected stellar spin rate of v sin i = 13.9 \pm 0.03 km/s which is in
agreement with previous measurements but has a much higher precision. The
system is found to be well aligned which favours an evolutionary history for
WASP-3b involving migration through tidal interactions with a protoplanetary
disc. Using gyrochronology we estimate the age of the star to be ~300 Myr with
an upper limit of 2 Gyr from comparison with isochrones.Comment: Accepted for publication in A&A, 8 pages, 4 figures, 2 table
WASP-29b: A Saturn-sized transiting exoplanet
We report the discovery of a Saturn-sized planet transiting a V = 11.3, K4
dwarf star every 3.9 d. WASP-29b has a mass of 0.24+/-0.02 M_Jup and a radius
of 0.79+/-0.05 R_Jup, making it the smallest planet so far discovered by the
WASP survey, and the exoplanet most similar in mass and radius to Saturn. The
host star WASP-29 has an above-Solar metallicity and fits a possible
correlation for Saturn-mass planets such that planets with higher-metallicity
host stars have higher core masses and thus smaller radii.Comment: 6 pages, submitted to ApJ
BLAST: The Mass Function, Lifetimes, and Properties of Intermediate Mass Cores from a 50 Square Degree Submillimeter Galactic Survey in Vela (l = ~265)
We present first results from an unbiased 50 deg^2 submillimeter Galactic
survey at 250, 350, and 500 micron from the 2006 flight of the Balloon-borne
Large Aperture Submillimeter Telescope (BLAST). The map has resolution ranging
from 36 arcsec to 60 arcsec in the three submillimeter bands spanning the
thermal emission peak of cold starless cores. We determine the temperature,
luminosity, and mass of more than one thousand compact sources in a range of
evolutionary stages and an unbiased statistical characterization of the
population. From comparison with C^(18)O data, we find the dust opacity per gas
mass, kappa r = 0.16 cm^2 g^(-1) at 250 micron, for cold clumps. We find that
2% of the mass of the molecular gas over this diverse region is in cores colder
than 14 K, and that the mass function for these cold cores is consistent with a
power law with index alpha = -3.22 +/- 0.14 over the mass range 14 M_sun < M <
80 M_sun. Additionally, we infer a mass-dependent cold core lifetime of t_c(M)
= 4E6 (M/20 M_sun)^(-0.9) years - longer than what has been found in previous
surveys of either low or high mass cores, and significantly longer than free
fall or likely turbulent decay times. This implies some form of non-thermal
support for cold cores during this early stage of star formation.Comment: Accepted for publication in the Astrophysical Journal. Maps available
at http://blastexperiment.info
Rossiter-McLaughlin Effect Measurements for WASP-16, WASP-25 and WASP-31
We present new measurements of the Rossiter-McLaughlin (RM) effect for three
WASP planetary systems, WASP-16, WASP-25 and WASP-31, from a combined analysis
of their complete sets of photometric and spectroscopic data. We find a low
amplitude RM effect for WASP-16 (Teff = 5700 \pm 150K), suggesting that the
star is a slow rotator and thus of an advanced age, and obtain a projected
alignment angle of lambda = -4.2 degrees +11.0 -13.9. For WASP-25 (Teff =
5750\pm100K) we detect a projected spin-orbit angle of lambda = 14.6 degrees
\pm6.7. WASP-31 (Teff = 6300\pm100K) is found to be well-aligned, with a
projected spin-orbit angle of lambda = 2.8degrees \pm3.1. A circular orbit is
consistent with the data for all three systems, in agreement with their
respective discovery papers. We consider the results for these systems in the
context of the ensemble of RM measurements made to date. We find that whilst
WASP-16 fits the hypothesis of Winn et al. (2010) that 'cool' stars (Teff <
6250K) are preferentially aligned, WASP-31 has little impact on the proposed
trend. We bring the total distribution of the true spin-orbit alignment angle,
psi, up to date, noting that recent results have improved the agreement with
the theory of Fabrycky & Tremaine (2007) at mid-range angles. We also suggest a
new test for judging misalignment using the Bayesian Information Criterion,
according to which WASP-25 b's orbit should be considered to be aligned.Comment: 20 pages, 14 tables, 10 figures. Accepted to MNRA
WASP-42 b and WASP-49 b: two new transiting sub-Jupiters
We report the discovery of two new transiting planets from the WASP survey.
WASP-42 b is a 0.500 +/- 0.035 M_jup planet orbiting a K1 star at a separation
of 0.0548 +/- 0.0017 AU with a period of 4.9816872 +/- 7.3 x 10^-6 days. The
radius of WASP-42 b is 1.080 +/- 0.057 R_jup while its equilibrium temperature
is T_eq = 995 +/- 34 K. We detect some evidence for a small but non-zero
eccentricity of e=0.060 +/- 0.013. WASP-49 b is a 0.378 +/- 0.027 M_jup planet
around an old G6 star. It has a period of 2.7817387 +/- 5.6 x 10^-6 days and a
separation of 0.0379 +/- 0.0011 AU. This planet is slightly bloated, having a
radius of 1.115 +/- 0.047 R_jup and an equilibrium temperature of T_eq = 1369
+/- 39 K. Both planets have been followed up photometrically, and in total we
have obtained 5 full and one partial transit light curves of WASP-42 and 4 full
and one partial light curves of WASP-49 using the Euler-Swiss, TRAPPIST and
Faulkes South telescopes
WASP-26b : a 1-Jupiter-mass planet around an early-G-type star
We report the discovery of WASP-26b, a moderately over-sized Jupiter-mass exoplanet transiting its 11.3-mag early-G-type host star (1SWASP J001824.70-151602.3; TYC 5839-876-1) every 2.7566 days. A simultaneous fit to transit photometry and radial-velocity measurements yields a planetary mass of 1.02 ± 0.03 MJup and radius of 1.32 ± 0.08 RJup. The host star, WASP-26, has a mass of
1.12 ± 0.03 M and a radius of 1.34 ± 0.06 R and is in a visual double with a fainter K-type star. The two stars are at least a common-proper motion pair with a common distance of around 250 ± 15 pc and an age of 6 ± 2 Gy
WASP-30b: a 61 Mjup brown dwarf transiting a V=12, F8 star
We report the discovery of a 61-Jupiter-mass brown dwarf, which transits its
F8V host star, WASP-30, every 4.16 days. From a range of age indicators we
estimate the system age to be 1-2 Gyr. We derive a radius (0.89 +/- 0.02 RJup)
for the companion that is consistent with that predicted (0.914 RJup) by a
model of a 1-Gyr-old, non-irradiated brown dwarf with a dusty atmosphere. The
location of WASP-30b in the minimum of the mass-radius relation is consistent
with the quantitative prediction of Chabrier & Baraffe (2000), thus confirming
the theory.Comment: As accepted for publication in ApJL (6 pages, 2 figures, 3 tables
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