2,502 research outputs found
Continuous wave detector has wide frequency range
Portable battery-operated detector indicates the presence of steady state signals exceeding a predetermined value over a wide frequency range by the closure of output relay contacts. It was designed to monitor electronic equipment used in the Saturn 2 program
LRG-BEASTS III: Ground-based transmission spectrum of the gas giant orbiting the cool dwarf WASP-80
We have performed ground-based transmission spectroscopy of the hot Jupiter
orbiting the cool dwarf WASP-80 using the ACAM instrument on the William
Herschel Telescope (WHT) as part of the LRG-BEASTS programme. This is the third
paper of a ground-based transmission spectroscopy survey of hot Jupiters using
low-resolution grism spectrographs. We observed two transits of the planet and
have constructed transmission spectra spanning a wavelength range of
4640-8840A. Our transmission spectrum is inconsistent with a previously claimed
detection of potassium in WASP-80b's atmosphere, and is instead most consistent
with a haze. We also do not see evidence for sodium absorption at a resolution
of 100A.Comment: 11 pages, 9 figures. Accepted for publication in MNRA
The shared evaporation history of three sub-Neptunes spanning the radius-period valley of a Hyades star
We model the evaporation histories of the three planets around K2-136, a
K-dwarf in the Hyades open cluster with an age of 700 Myr. The star hosts three
transiting planets, with radii of 1.0, 3.0 and 1.5 Earth radii, where the
middle planet lies above the radius-period valley and the inner and outer
planets are below. We use an XMM-Newton observation to measure the XUV
radiation environment of the planets, finding that the X-ray activity of K2-136
is lower than predicted by models but typical of similar Hyades members. We
estimate the internal structure of each planet, and model their evaporation
histories using a range of structure and atmospheric escape formulations. While
the precise X-ray irradiation history of the system may be uncertain, we
exploit the fact that the three planets must have shared the same history. We
find that the Earth-sized K2-136b is most likely rocky, with any primordial
gaseous envelope being lost within a few Myr. The sub-Neptune, K2-136c, has an
envelope contributing 1-1.7% of its mass that is stable against evaporation
thanks to the high mass of its rocky core, whilst the super-Earth, K2-136d,
must have a mass at the upper end of the allowed range in order to retain any
of its envelope. Our results are consistent with all three planets beginning as
sub-Neptunes that have since been sculpted by atmospheric evaporation to their
current states, stripping the envelope from planet b and removing most from
planet d whilst preserving planet c above the radius-period valley.Comment: Accepted for publication on MNRA
The XUV irradiation and likely atmospheric escape of the super-Earth Men c
Men c was recently announced as the first confirmed exoplanet from the
TESS mission. The planet has a radius of just 2 R and it transits
a nearby Sun-like star of naked-eye brightness, making it the ideal target for
atmospheric characterisation of a super-Earth. Here we analyse archival
and observations of Men in order to
determine the X-ray and extreme-ultraviolet irradiation of the planetary
atmosphere and assess whether atmospheric escape is likely to be on-going. We
find that Men has a similar level of X-ray emission to the Sun, with
. However, due to
its small orbital separation, the high-energy irradiation of the super-Earth is
around 2000 times stronger than suffered by the Earth. We show that this is
sufficient to drive atmospheric escape at a rate greater than that readily
detected from the warm Neptune GJ 436b. Furthermore, we estimate Men to
be four times brighter at Ly than GJ 436. Given the small atmospheric
scale heights of super-Earths, together with their potentially cloudy
atmospheres, and the consequent difficulty in measuring transmission spectra,
we conclude that ultraviolet absorption by material escaping Men c
presents the best opportunity currently to determine the atmospheric
composition of a super-Earth.Comment: 5 pages, 3 figures, 3 tables; accepted for publication in MNRAS
Letter
An XMM-Newton observation of the nova-like variable UX UMa: spatially and spectrally resolved two-component X-ray emission
In the optical and ultraviolet regions of the electromagnetic spectrum, UX
Ursae Majoris is a deeply eclipsing cataclysmic variable. However, no soft
X-ray eclipse was detected in ROSAT observations. We have obtained a 38 ksec
XMM-Newton observation to further constrain the origin of the X-rays. The
combination of spectral and timing information allows us to identify two
components in the X-ray emission of the system. The soft component, dominant
below photon energies of 2 keV, can be fitted with a multi-temperature plasma
model and is uneclipsed. The hard component, dominant above 3 keV, can be
fitted with a kT ~ 5 keV plasma model and appears to be deeply eclipsed. We
suggest that the most likely source of the hard X-ray emission in UX UMa, and
other systems in high mass transfer states, is the boundary layer.Comment: To appear in MNRAS Letter
K2 Variable Catalogue II: Machine Learning Classification of Variable Stars and Eclipsing Binaries in K2 Fields 0-4
We are entering an era of unprecedented quantities of data from current and
planned survey telescopes. To maximise the potential of such surveys, automated
data analysis techniques are required. Here we implement a new methodology for
variable star classification, through the combination of Kohonen Self
Organising Maps (SOM, an unsupervised machine learning algorithm) and the more
common Random Forest (RF) supervised machine learning technique. We apply this
method to data from the K2 mission fields 0-4, finding 154 ab-type RR Lyraes
(10 newly discovered), 377 Delta Scuti pulsators, 133 Gamma Doradus pulsators,
183 detached eclipsing binaries, 290 semi-detached or contact eclipsing
binaries and 9399 other periodic (mostly spot-modulated) sources, once class
significance cuts are taken into account. We present lightcurve features for
all K2 stellar targets, including their three strongest detected frequencies,
which can be used to study stellar rotation periods where the observed
variability arises from spot modulation. The resulting catalogue of variable
stars, classes, and associated data features are made available online. We
publish our SOM code in Python as part of the open source PyMVPA package, which
in combination with already available RF modules can be easily used to recreate
the method.Comment: Accepted for publication in MNRAS, 16 pages, 13 figures. Updated with
proof corrections. Full catalogue tables available at
https://www2.warwick.ac.uk/fac/sci/physics/research/astro/people/armstrong/
or at the CD
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