4,658 research outputs found
Spitzer Phase Curves of KELT-1b and the Signatures of Nightside Clouds in Thermal Phase Observations
We observed two full orbital phase curves of the transiting brown dwarf
KELT-1b, at 3.6um and 4.5um, using the Spitzer Space Telescope. Combined with
previous eclipse data from Beatty et al. (2014), we strongly detect KELT-1b's
phase variation as a single sinusoid in both bands, with amplitudes of
ppm at 3.6um and ppm at 4.5um, and confirm the secondary
eclipse depths measured by Beatty et al. (2014). We also measure noticeable
Eastward hotspot offsets of degrees at 3.6um and
degrees at 4.5um. Both the day-night temperature contrasts and the hotspot
offsets we measure are in line with the trends seen in hot Jupiters (e.g.,
Crossfield 2015), though we disagree with the recent suggestion of an offset
trend by Zhang et al. (2018). Using an ensemble analysis of Spitzer phase
curves, we argue that nightside clouds are playing a noticeable role in
modulating the thermal emission from these objects, based on: 1) the lack of a
clear trend in phase offsets with equilibrium temperature, 2) the sharp
day-night transitions required to have non-negative intensity maps, which also
resolves the inversion issues raised by Keating & Cowan (2017), 3) the fact
that all the nightsides of these objects appear to be at roughly the same
temperature of 1000K, while the dayside temperatures increase linearly with
equilibrium temperature, and 4) the trajectories of these objects on a Spitzer
color-magnitude diagram, which suggest colors only explainable via nightside
clouds.Comment: AJ in press. Updated to reflect the accepted versio
Spitzer and z' Secondary Eclipse Observations of the Highly Irradiated Transiting Brown Dwarf KELT-1b
We present secondary eclipse observations of the highly irradiated transiting
brown dwarf KELT-1b. These observations represent the first constraints on the
atmospheric dynamics of a highly irradiated brown dwarf, and the atmospheres of
irradiated giant planets at high surface gravity. Using the Spitzer Space
Telescope, we measure secondary eclipse depths of 0.195+/-0.010% at 3.6um and
0.200+/-0.012% at 4.5um. We also find tentative evidence for the secondary
eclipse in the z' band with a depth of 0.049+/-0.023%. These measured eclipse
depths are most consistent with an atmosphere model in which there is a strong
substellar hotspot, implying that heat redistribution in the atmosphere of
KELT-1b is low. While models with a more mild hotspot or even with dayside heat
redistribution are only marginally disfavored, models with complete heat
redistribution are strongly ruled out. The eclipse depths also prefer an
atmosphere with no TiO inversion layer, although a model with TiO inversion is
permitted in the dayside heat redistribution case, and we consider the
possibility of a day-night TiO cold trap in this object. For the first time, we
compare the IRAC colors of brown dwarfs and hot Jupiters as a function of
effective temperature. Importantly, our measurements reveal that KELT-1b has a
[3.6]-[4.5] color of 0.07+/-0.11, identical to that of isolated brown dwarfs of
similarly high temperature. In contrast, hot Jupiters generally show redder
[3.6]-[4.5] colors of ~0.4, with a very large range from ~0 to ~1. Evidently,
despite being more similar to hot Jupiters than to isolated brown dwarfs in
terms of external forcing of the atmosphere by stellar insolation, KELT-1b has
an atmosphere most like that of other brown dwarfs. This suggests that surface
gravity is very important in controlling the atmospheric systems of substellar
mass bodies.Comment: 14 pages, 3 tables, 11 figures. Accepted by ApJ. Updated to reflect
the accepted versio
Observations of Microwave Continuum Emission from Air Shower Plasmas
We investigate a possible new technique for microwave measurements of
ultra-high energy cosmic ray (UHECR) extensive air showers which relies on
detection of expected continuum radiation in the microwave range, caused by
free-electron collisions with neutrals in the tenuous plasma left after the
passage of the shower. We performed an initial experiment at the AWA (Argonne
Wakefield Accelerator) laboratory in 2003 and measured broadband microwave
emission from air ionized via high energy electrons and photons. A follow-up
experiment at SLAC (Stanford Linear Accelerator Center) in summer of 2004
confirmed the major features of the previous AWA observations with better
precision and made additional measurements relevant to the calorimetric
capabilities of the method. Prompted by these results we built a prototype
detector using satellite television technology, and have made measurements
indicating possible detection of cosmic ray extensive air showers. The method,
if confirmed by experiments now in progress, could provide a high-duty cycle
complement to current nitrogen fluorescence observations of UHECR, which are
limited to dark, clear nights. By contrast, decimeter microwave observations
can be made both night and day, in clear or cloudy weather, or even in the
presence of moderate precipitation.Comment: 15 pages, 13 figure
Blaming the victim, all over again: Waddell and Aylward's biopsychosocial (BPS) model of disability
The biopsychosocial (BPS) model of mental distress, originally conceived by the American psychiatrist George Engel in the 1970s and commonly used in psychiatry and psychology, has been adapted by Gordon Waddell and Mansell Aylward to form the theoretical basis for current UK Government thinking on disability. Most importantly, the Waddell and Aylward version of the BPS has played a key role as the Government has sought to reform spending on out-of- work disability benefits. This paper presents a critique of Waddell and Aylward’s model, examining its origins, its claims and the evidence it employs. We will argue that its potential for genuine inter-disciplinary cooperation and the holistic and humanistic benefits for disabled people as envisaged by Engel are not now, if they ever have been, fully realized. Any potential benefit it may have offered has been eclipsed by its role in Coalition/Conservative government social welfare policies that have blamed the victim and justified restriction of entitlements
Planning the Future of U.S. Particle Physics (Snowmass 2013): Chapter 4: Cosmic Frontier
These reports present the results of the 2013 Community Summer Study of the
APS Division of Particles and Fields ("Snowmass 2013") on the future program of
particle physics in the U.S. Chapter 4, on the Cosmic Frontier, discusses the
program of research relevant to cosmology and the early universe. This area
includes the study of dark matter and the search for its particle nature, the
study of dark energy and inflation, and cosmic probes of fundamental
symmetries.Comment: 61 page
Observational Constraints on the Ultra-high Energy Cosmic Neutrino Flux from the Second Flight of the ANITA Experiment
The Antarctic Impulsive Transient Antenna (ANITA) completed its second
long-duration balloon flight in January 2009, with 31 days aloft (28.5 live
days) over Antarctica. ANITA searches for impulsive coherent radio Cherenkov
emission from 200 to 1200 MHz, arising from the Askaryan charge excess in
ultra-high energy neutrino-induced cascades within Antarctic ice. This flight
included significant improvements over the first flight in the payload
sensitivity, efficiency, and a flight trajectory over deeper ice. Analysis of
in-flight calibration pulses from surface and sub-surface locations verifies
the expected sensitivity. In a blind analysis, we find 2 surviving events on a
background, mostly anthropogenic, of 0.97+-0.42 events. We set the strongest
limit to date for 1-1000 EeV cosmic neutrinos, excluding several current
cosmogenic neutrino models.Comment: 6 pages, 5 figures, submitted to Phys. Rev.
Indirect search for dark matter with micrOMEGAs2.4
We present a new module of micrOMEGAs devoted to the computation of indirect
signals from dark matter annihilation in any new model with a stable weakly
interacting particle. The code provides the mass spectrum, cross-sections,
relic density and exotic fluxes of gamma rays, positrons and antiprotons. The
propagation of charged particles in the Galactic halo is handled with a new
module that allows to easily modify the propagation parameters.Comment: 24 pages, 6 figures, typos corrected, acknowledgements modifie
Status of ANITA and ANITA-lite
We describe a new experiment to search for neutrinos with energies above 3 x
10^18 eV based on the observation of short duration radio pulses that are
emitted from neutrino-initiated cascades. The primary objective of the
ANtarctic Impulse Transient Antenna (ANITA) mission is to measure the flux of
Greisen-Zatsepin-Kuzmin (GZK) neutrinos and search for neutrinos from Active
Galactic Nuclei (AGN). We present first results obtained from the successful
launch of a 2-antenna prototype instrument (called ANITA-lite) that circled
Antarctica for 18 days during the 03/04 Antarctic campaign and show preliminary
results from attenuation length studies of electromagnetic waves at radio
frequencies in Antarctic ice. The ANITA detector is funded by NASA, and the
first flight is scheduled for December 2006.Comment: 9 pages, 8 figures, to be published in Proceedings of International
School of Cosmic Ray Astrophysics, 14th Course: "Neutrinos and Explosive
Events in the Universe", Erice, Italy, 2-13 July 200
The Energy Spectra and Relative Abundances of Electrons and Positrons in the Galactic Cosmic Radiation
Observations of cosmic-ray electrons and positrons have been made with a new
balloon-borne detector, HEAT (the "High-Energy Antimatter Telescope"), first
flown in 1994 May from Fort Sumner, NM. We describe the instrumental approach
and the data analysis procedures, and we present results from this flight. The
measurement has provided a new determination of the individual energy spectra
of electrons and positrons from 5 GeV to about 50 GeV, and of the combined
"all-electron" intensity (e+ + e-) up to about 100 GeV. The single power-law
spectral indices for electrons and positrons are alpha = 3.09 +/- 0.08 and 3.3
+/- 0.2, respectively. We find that a contribution from primary sources to the
positron intensity in this energy region, if it exists, must be quite small.Comment: latex2e file, 30 pages, 15 figures, aas2pp4.sty and epsf.tex needed.
To appear in May 10, 1998 issue of Ap.
KELT-3b: A Hot Jupiter Transiting A V=9.8 Late-F Star
We report the discovery of KELT-3b, a moderately inflated transiting hot Jupiter with a mass of 1.477(-0.067)(+0.066) M-J, radius of 1.345 +/- 0.072 R-J, and an orbital period of 2.7033904 +/- 0.000010 days. The host star, KELT-3, is a V = 9.8 late F star with M-* = 1.278(-0.061)(+0.063) M-circle dot, R-* = 1.472(-0.067)(+0.065) R-circle dot, T-eff = 6306(-49)(+50) K, log(g) = 4.209(-0.031)(+0.033), and [Fe/H] = 0.044(-0.082)(+0.080), and has a likely proper motion companion. KELT-3b is the third transiting exoplanet discovered by the KELT survey, and is orbiting one of the 20 brightest known transiting planet host stars, making it a promising candidate for detailed characterization studies. Although we infer that KELT-3 is significantly evolved, a preliminary analysis of the stellar and orbital evolution of the system suggests that the planet has likely always received a level of incident flux above the empirically identified threshold for radius inflation suggested by Demory & Seager
- …