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"Bryant, Edward M."
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Wild cards III : Jokers Wild
\"The journey into high adventure soars on! Let the secret history of the world be told--of the alien virus that struck Earth after World War II, and of the handful of survivors who found they now possessed superhuman powers. Some were called Aces, endowed with powerful mental and physical prowess. The others were Jokers, tormented by bizarre mind or body disfigurements. Some served humanity. Others wreaked terror. Now, forty years later, under the streets of Manhattan an evil genius unleashes the powers of darkness--and Aces and Jokers alike must fight for their lives. Here, in the third volume of the Wild Cards series, seven of science fiction's most gifted writers take you on a journey of wonder and excitement.Includes stories by:Edward Bryant, Leanne C. Harper, George R. R. Martin, John J. Miller, Lewis Shiner ,Walter Simons, Melinda M. Snodgrass\"-- Provided by publisher.
Book
Early Release Science of the exoplanet WASP-39b with JWST NIRCam
Measuring the metallicity and carbon-to-oxygen (C/O) ratio in exoplanet atmospheres is a fundamental step towards constraining the dominant chemical processes at work and, if in equilibrium, revealing planet formation histories. Transmission spectroscopy (for example, refs.
1
,
2
) provides the necessary means by constraining the abundances of oxygen- and carbon-bearing species; however, this requires broad wavelength coverage, moderate spectral resolution and high precision, which, together, are not achievable with previous observatories. Now that JWST has commenced science operations, we are able to observe exoplanets at previously uncharted wavelengths and spectral resolutions. Here we report time-series observations of the transiting exoplanet WASP-39b using JWST’s Near InfraRed Camera (NIRCam). The long-wavelength spectroscopic and short-wavelength photometric light curves span 2.0–4.0 micrometres, exhibit minimal systematics and reveal well defined molecular absorption features in the planet’s spectrum. Specifically, we detect gaseous water in the atmosphere and place an upper limit on the abundance of methane. The otherwise prominent carbon dioxide feature at 2.8 micrometres is largely masked by water. The best-fit chemical equilibrium models favour an atmospheric metallicity of 1–100-times solar (that is, an enrichment of elements heavier than helium relative to the Sun) and a substellar C/O ratio. The inferred high metallicity and low C/O ratio may indicate significant accretion of solid materials during planet formation (for example, refs.
3
,
4
,
) or disequilibrium processes in the upper atmosphere (for example, refs.
5
,
6
).
Time-series observations from the JWST of the transiting exoplanet WASP-39b show gaseous water in the planet’s atmosphere and place an upper limit on the abundance of methane.
Journal Article
A remnant planetary core in the hot-Neptune desert
The interiors of giant planets remain poorly understood. Even for the planets in the Solar System, difficulties in observation lead to large uncertainties in the properties of planetary cores. Exoplanets that have undergone rare evolutionary processes provide a route to understanding planetary interiors. Planets found in and near the typically barren hot-Neptune ‘desert’ (a region in mass–radius space that contains few planets) have proved to be particularly valuable in this regard. These planets include HD149026b, which is thought to have an unusually massive core, and recent discoveries such as LTT9779b and NGTS-4b, on which photoevaporation has removed a substantial part of their outer atmospheres. Here we report observations of the planet TOI-849b, which has a radius smaller than Neptune’s but an anomalously large mass of 39.1(+2.7−2.6) Earth masses and a density of 5.2(+0.7−0.8) grams per cubic centimetre, similar to Earth’s. Interior-structure models suggest that any gaseous envelope of pure hydrogen and helium consists of no more than 3.9(+0.8−0.9) per cent of the total planetary mass. The planet could have been a gas giant before undergoing extreme mass loss via thermal self-disruption or giant planet collisions, or it could have avoided substantial gas accretion, perhaps through gap opening or late formation. Although photoevaporation rates cannot account for the mass loss required to reduce a Jupiter-like gas giant, they can remove a small (a few Earth masses) hydrogen and helium envelope on timescales of several billion years, implying that any remaining atmosphere on TOI-849b is likely to be enriched by water or other volatiles from the planetary interior. We conclude that TOI-849b is the remnant core of a giant planet.
Journal Article
Author Correction: An ultrahot Neptune in the Neptune desert
An amendment to this paper has been published and can be accessed via a link at the top of the paper.
Journal Article
An ultrahot Neptune in the Neptune desert
About 1 out of 200 Sun-like stars has a planet with an orbital period shorter than one day: an ultrashort-period planet
1
,
2
. All of the previously known ultrashort-period planets are either hot Jupiters, with sizes above 10 Earth radii (
R
⊕
), or apparently rocky planets smaller than 2
R
⊕
. Such lack of planets of intermediate size (the ‘hot Neptune desert’) has been interpreted as the inability of low-mass planets to retain any hydrogen/helium (H/He) envelope in the face of strong stellar irradiation. Here we report the discovery of an ultrashort-period planet with a radius of 4.6
R
⊕
and a mass of 29
M
⊕
, firmly in the hot Neptune desert. Data from the Transiting Exoplanet Survey Satellite
3
revealed transits of the bright Sun-like star LTT 9779 every 0.79 days. The planet’s mean density is similar to that of Neptune, and according to thermal evolution models, it has a H/He-rich envelope constituting 9.0
−
2.9
+
2.7
% of the total mass. With an equilibrium temperature around 2,000 K, it is unclear how this ‘ultrahot Neptune’ managed to retain such an envelope. Follow-up observations of the planet’s atmosphere to better understand its origin and physical nature will be facilitated by the star’s brightness (
V
mag
= 9.8).
LTT 9779 b is Neptune-sized planet rotating around its star with a period of 0.79 days and an equilibrium temperature of 2,000 K. It is not clear how it retained its atmospheric envelope, which contains ~10% of H/He, as it should have been photoevaporated by now.
Journal Article
Revisiting WASP-47 with ESPRESSO and TESS
WASP-47 hosts a remarkable planetary system containing a hot Jupiter (WASP-47 b; P = 4.159 days) with an inner super-Earth (WASP-47 e; P = 0.7896 days), a close-orbiting outer Neptune (WASP-47 d; P = 9.031 days), and a long period giant planet (WASP-47 c; P = 588.4 days). We use the new TESS photometry to refine the orbital ephemerides of the transiting planets in the system, particularly the hot Jupiter WASP-47 b, for which we find an update equating to a 17.4 min shift in the transit time. We report new radial velocity measurements from the ESPRESSO spectrograph for WASP-47, which we use to refine the masses of WASP-47 d and WASP-47 e, with a high cadence observing strategy aimed to focus on the super-Earth WASP-47 e. We detect a periodic modulation in the K2 photometry that corresponds to a 32.5\\(\\pm\\)3.9 day stellar rotation, and find further stellar activity signals in our ESPRESSO data consistent with this rotation period. For WASP-47 e we measure a mass of 6.77\\(\\pm\\)0.57 M\\(_{\\oplus}\\) and a bulk density of 6.29\\(\\pm\\)0.60 gcm\\(^{-3}\\), giving WASP-47 e the second most precisely measured density to date of any super-Earth. The mass and radius of WASP-47 e, combined with the exotic configuration of the planetary system, suggest the WASP-47 system formed through a mechanism different to systems with multiple small planets or more typical isolated hot Jupiters.
Paper
The occurrence rate of giant planets orbiting low-mass stars with TESS
We present a systematic search for transiting giant planets (\\(0.6 R_{\\rm J} \\leq R_{\\rm P} \\leq 2.0 R_{\\rm J}\\)) orbiting nearby low-mass stars (\\(M_{*} \\leq 0.71 M_{\\odot}\\)). The formation of giant planets around low-mass stars is predicted to be rare by the core-accretion planet formation theory. We search 91,306 low-mass stars in the TESS 30 minute cadence photometry detecting fifteen giant planet candidates, including seven new planet candidates which were not known planets or identified as TOIs prior to our search. Our candidates present an exciting opportunity to improve our knowledge of the giant planet population around the lowest mass stars. We perform planet injection-recovery simulations and find that our pipeline has a high detection efficiency across the majority of our targeted parameter space. We measure the occurrence rates of giant planets with host stars in different stellar mass ranges spanning our full sample. We find occurrence rates of \\(0.137 \\pm 0.097\\)% (0.088 - 0.26 \\(M_{\\odot}\\)), \\(0.108 \\pm 0.083\\)% (0.26 - 0.42 \\(M_{\\odot}\\)), and \\(0.29 \\pm 0.15\\)% (0.42 - 0.71 \\(M_{\\odot}\\)). For our full sample (0.088 - 0.71 \\(M_{\\odot}\\)) we find a giant planet occurrence rate of \\(0.194 \\pm 0.072\\)%. We have measured for the first time the occurrence rate for giant planets orbiting stars with \\(M_{*} \\leq 0.4 M_{\\odot}\\) and we demonstrate this occurrence rate to be non-zero. This result contradicts currently accepted planet formation models and we discuss some possibilities for how these planets could have formed.
Paper
Planet Hunters NGTS: New Planet Candidates from a Citizen Science Search of the Next Generation Transit Survey Public Data
We present the results from the first two years of the Planet Hunters NGTS citizen science project, which searches for transiting planet candidates in data from the Next Generation Transit Survey (NGTS) by enlisting the help of members of the general public. Over 8,000 registered volunteers reviewed 138,198 light curves from the NGTS Public Data Releases 1 and 2. We utilize a user weighting scheme to combine the classifications of multiple users to identify the most promising planet candidates not initially discovered by the NGTS team. We highlight the five most interesting planet candidates detected through this search, which are all candidate short-period giant planets. This includes the TIC-165227846 system that, if confirmed, would be the lowest-mass star to host a close-in giant planet. We assess the detection efficiency of the project by determining the number of confirmed planets from the NASA Exoplanet Archive and TESS Objects of Interest (TOIs) successfully recovered by this search and find that 74% of confirmed planets and 63% of TOIs detected by NGTS are recovered by the Planet Hunters NGTS project. The identification of new planet candidates shows that the citizen science approach can provide a complementary method to the detection of exoplanets with ground-based surveys such as NGTS.
Paper
The discovery of three hot Jupiters, NGTS-23b, 24b and 25b, and updated parameters for HATS-54b from the Next Generation Transit Survey
We report the discovery of three new hot Jupiters with the Next Generation Transit Survey (NGTS) as well as updated parameters for HATS-54b, which was independently discovered by NGTS. NGTS-23b, NGTS-24b and NGTS-25b have orbital periods of 4.076, 3.468, and 2.823 days and orbit G-, F- and K-type stars, respectively. NGTS-24 and HATS-54 appear close to transitioning off the main-sequence (if they are not already doing so), and therefore are interesting targets given the observed lack of Hot Jupiters around sub-giant stars. By considering the host star luminosities and the planets' small orbital separations (0.037 - 0.050 au), we find that all four hot Jupiters are above the minimum irradiance threshold for inflation mechanisms to be effective. NGTS-23b has a mass of 0.61 \\(M_{J}\\) and radius of 1.27 \\(R_{J}\\) and is likely inflated. With a radius of 1.21 \\(R_{J}\\) and mass of 0.52 \\(M_{J}\\), NGTS-24b has a radius larger than expected from non-inflated models but its radius is smaller than the predicted radius from current Bayesian inflationary models. Finally, NGTS-25b is intermediate between the inflated and non-inflated cases, having a mass of 0.64 \\(M_{J}\\) and a radius of 1.02 \\(R_{J}\\). The physical processes driving radius inflation remain poorly understood, and by building the sample of hot Jupiters we can aim to identify the additional controlling parameters, such as metallicity and stellar age.
Paper
NGTS-21b: An Inflated Super-Jupiter Orbiting a Metal-poor K dwarf
We report the discovery of NGTS-21b, a massive hot Jupiter orbiting a low-mass star as part of the Next Generation Transit Survey (NGTS). The planet has a mass and radius of \\(2.36 \\pm 0.21\\) M\\(_{\\rm J}\\), and \\(1.33 \\pm 0.03\\) R\\(_{\\rm J}\\), and an orbital period of 1.543 days. The host is a K3V (\\(T_{\\rm eff}=4660 \\pm 41\\), K) metal-poor (\\({\\rm [Fe/H]}=-0.26 \\pm 0.07\\), dex) dwarf star with a mass and radius of \\(0.72 \\pm 0.04\\), M\\(_{\\odot}\\),and \\(0.86 \\pm 0.04\\), R\\(_{\\odot}\\). Its age and rotation period of \\(10.02^{+3.29}_{-7.30}\\), Gyr and \\(17.88 \\pm 0.08\\), d respectively, are in accordance with the observed moderately low stellar activity level. When comparing NGTS-21b with currently known transiting hot Jupiters with similar equilibrium temperatures, it is found to have one of the largest measured radii despite its large mass. Inflation-free planetary structure models suggest the planet's atmosphere is inflated by \\(\\sim21\\%\\), while inflationary models predict a radius consistent with observations, thus pointing to stellar irradiation as the probable origin of NGTS-21b's radius inflation. Additionally, NGTS-21b's bulk density (\\(1.25 \\pm 0.15\\), g/cm\\(^3\\)) is also amongst the largest within the population of metal-poor giant hosts ([Fe/H] < 0.0), helping to reveal a falling upper boundary in metallicity-planet density parameter space that is in concordance with core accretion formation models. The discovery of rare planetary systems such as NGTS-21 greatly contributes towards better constraints being placed on the formation and evolution mechanisms of massive planets orbiting low-mass stars.
Paper