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Allen, N. H., Espinoza, N., Jordan, A., Lopez-Morales, M., Apai, D., Rackham, B. V., et al. (2022). ACCESS: Tentative Detection of H2O in the Ground-based Optical Transmission Spectrum of the Low-density Hot Saturn HATS-5b. Astron. J., 164(4), 153.
Abstract: We present a precise ground-based optical transmission spectrum of the hot Saturn HATS-5b (T (eq) = 1025 K), obtained as part of the ACCESS survey with the IMACS multi-object spectrograph mounted on the Magellan Baade Telescope. Our spectra cover the 0.5-0.9 mu m region and are the product of five individual transits observed between 2014 and 2018. We introduce the usage of additional second-order light in our analyses, which allows us to extract an “extra” transit light curve, improving the overall precision of our combined transit spectrum. We find that the favored atmospheric model for this transmission spectrum is a solar-metallicity atmosphere with subsolar C/O, whose features are dominated by H2O and with a depleted abundance of Na and K. If confirmed, this would point to a “clear” atmosphere at the pressure levels probed by transmission spectroscopy for HATS-5b. Our best-fit atmospheric model predicts a rich near-IR spectrum, which makes this exoplanet an excellent target for future follow-up observations with the James Webb Space Telescope, both to confirm this H2O detection and to superbly constrain the atmosphere's parameters.
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Bhat, S. M., Ahmed, S., Bahar, A. N., Wahid, K. A., Otsuki, A., & Singh, P. (2023). Design of Cost-Efficient SRAM Cell in Quantum Dot Cellular Automata Technology. Electronics, 12(2), 367.
Abstract: SRAM or Static Random-Access Memory is the most vital memory technology. SRAM is fast and robust but faces design challenges in nanoscale CMOS such as high leakage, power consumption, and reliability. Quantum-dot Cellular Automata (QCA) is the alternative technology that can be used to address the challenges of conventional SRAM. In this paper, a cost-efficient single layer SRAM cell has been proposed in QCA. The design has 39 cells with a latency of 1.5 clock cycles and achieves an overall improvement in cell count, area, latency, and QCA cost compared to the reported designs. It can therefore be used to design nanoscale memory structures of higher order.
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Brahm, R., Ulmer-Moll, S., Hobson, M. J., Jordan, A., Henning, T., Trifonov, T., et al. (2023). Three Long-period Transiting Giant Planets from TESS. Astron. J., 165(6), 227.
Abstract: We report the discovery and orbital characterization of three new transiting warm giant planets. These systems were initially identified as presenting single-transit events in the light curves generated from the full-frame images of the Transiting Exoplanet Survey Satellite. Follow-up radial velocity measurements and additional light curves were used to determine the orbital periods and confirm the planetary nature of the candidates. The planets orbit slightly metal-rich late F- and early G-type stars. We find that TOI 4406b has a mass of M ( P ) = 0.30 +/- 0.04 M (J), a radius of R ( P ) = 1.00 +/- 0.02 R (J), and a low-eccentricity orbit (e = 0.15 +/- 0.05) with a period of P = 30.08364 +/- 0.00005 days. TOI 2338b has a mass of M ( P ) = 5.98 +/- 0.20 M (J), a radius of R ( P ) = 1.00 +/- 0.01 R (J), and a highly eccentric orbit (e = 0.676 +/- 0.002) with a period of P = 22.65398 +/- 0.00002 days. Finally, TOI 2589b has a mass of M ( P ) = 3.50 +/- 0.10 M (J), a radius of R ( P ) = 1.08 +/- 0.03 R (J), and an eccentric orbit (e = 0.522 +/- 0.006) with a period of P = 61.6277 +/- 0.0002 days. TOI 4406b and TOI 2338b are enriched in metals compared to their host stars, while the structure of TOI 2589b is consistent with having similar metal enrichment to its host star.
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Brems, A., Caceres, G., Dewil, R., Baeyens, J., & Pitie, E. (2013). Heat transfer to the riser-wall of a circulating fluidised bed (CFB). Energy, 50, 493–500.
Abstract: The circulating fluidized bed is of increasing importance for gas-solid and gas-catalytic reactions, for drying, and recently its use in solar energy capture and storage has been advocated. In all applications, the supply or withdrawal of heat is a major issue, and the heat transfer coefficient from the gas-solid suspension to the heat transfer surface needs to be determined as design parameter. The present paper investigates the heat transfer coefficient for different operating gas velocity and solids circulation flux, whilst covering the different hydrodynamic solid flow regimes of dilute, core-annulus or dense mode. Measured values of the wall-to-bed heat transfer coefficients are compared with empirical predictions of both Molodstof and Muzyka, and Golriz and Grace. The application of a packet renewal mechanism at the wall is also investigated, and introducing the predicted solid contact time at the wall provides a very fair estimate of the heat transfer coefficient. Crown Copyright (C) 2012 Published by Elsevier Ltd. All rights reserved.
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Efraimidis, I., Gaona, J., Hernandez, R., & Venegas, O. (2017). On harmonic Bloch-type mappings. Complex Var. Elliptic Equ., 62(8), 1081–1092.
Abstract: Let f be a complex-valued harmonicmapping defined in the unit disk D. We introduce the following notion: we say that f is a Bloch-type function if its Jacobian satisfies This gives rise to a new class of functions which generalizes and contains the well-known analytic Bloch space. We give estimates for the schlicht radius, the growth and the coefficients of functions in this class. We establish an analogue of the theorem which, roughly speaking, states that for. analytic log. is Bloch if and only if. is univalent.
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Feinstein, A. D., Radica, M., Welbanks, L., Murray, C. A., Ohno, K., Coulombe, L. P., et al. (2023). Early Release Science of the exoplanet WASP-39b with JWST NIRISS. Nature, Early Access.
Abstract: The Saturn-mass exoplanet WASP-39b has been the subject of extensive efforts to determine its atmospheric properties using transmission spectroscopy(1-4). However, these efforts have been hampered by modelling degeneracies between composition and cloud properties that are caused by limited data quality(5-9). Here we present the transmission spectrum of WASP-39b obtained using the Single-Object Slitless Spectroscopy (SOSS) mode of the Near Infrared Imager and Slitless Spectrograph (NIRISS) instrument on the JWST. This spectrum spans 0.6-2.8 mu m in wavelength and shows several water-absorption bands, the potassium resonance doublet and signatures of clouds. The precision and broad wavelength coverage of NIRISS/SOSS allows us to break model degeneracies between cloud properties and the atmospheric composition of WASP-39b, favouring a heavy-element enhancement ('metallicity') of about 10-30 times the solar value, a sub-solar carbon-to-oxygen (C/O) ratio and a solar-to-super-solar potassium-to-oxygen (K/O) ratio. The observations are also best explained by wavelength-dependent, non-grey clouds with inhomogeneous coverageof the planet's terminator.
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Fernandes, R. B., Mulders, G. D., Pascucci, I., Bergsten, G. J., Koskinen, T. T., Hardegree-Ullman, K. K., et al. (2022). pterodactyls: A Tool to Uniformly Search and Vet for Young Transiting Planets in TESS Primary Mission Photometry. Astron. J., 164(3), 78.
Abstract: Kepler's short-period exoplanet population has revealed evolutionary features such as the Radius Valley and the Hot Neptune desert that are likely sculpted by atmospheric loss over time. These findings suggest that the primordial planet population is different from the Gyr-old Kepler population, and motivates exoplanet searches around young stars. Here, we present pterodactyls, a data reduction pipeline specifically built to address the challenges in discovering exoplanets around young stars and to work with TESS Primary Mission 30-minute cadence photometry, since most young stars were not preselected TESS two-minute cadence targets. pterodactyls builds on publicly available and tested tools in order to extract, detrend, search, and vet transiting young planet candidates. We search five clusters with known transiting planets: the Tucana-Horologium Association, IC 2602, Upper Centaurus Lupus, Ursa Major, and Pisces-Eridani. We show that pterodactyls recovers seven out of the eight confirmed planets and one out of the two planet candidates, most of which were initially detected in two-minute cadence data. For these clusters, we conduct injection-recovery tests to characterize our detection efficiency, and compute an intrinsic planet occurrence rate of 49% +/- 20% for sub-Neptunes and Neptunes (1.8-6 R (circle plus)) within 12.5 days, which is higher than Kepler's Gyr-old occurrence rates of 6.8% +/- 0.3%. This potentially implies that these planets have shrunk with time due to atmospheric mass loss. However, a proper assessment of the occurrence of transiting young planets will require a larger sample unbiased to planets already detected. As such, pterodactyls will be used in future work to search and vet for planet candidates in nearby clusters and moving groups.
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Hartman, J. D., Bakos, G. A., Csubry, Z., Howard, A. W., Isaacson, H., Giacalone, S., et al. (2023). TOI 4201 b and TOI 5344 b: Discovery of Two Transiting Giant Planets around M-dwarf Stars and Revised Parameters for Three Others. Astron. J., 166(4), 163.
Abstract: We present the discovery from the TESS mission of two giant planets transiting M-dwarf stars: TOI 4201 b and TOI 5344 b. We also provide precise radial velocity measurements and updated system parameters for three other M dwarfs with transiting giant planets: TOI 519, TOI 3629, and TOI 3714. We measure planetary masses of 0.525 +/- 0.064 MJ, 0.243 +/- 0.020 M-J, 0.689 +/- 0.030 M-J, 2.57 +/- 0.15 M-J, and 0.412 +/- 0.040 M-J for TOI 519 b, TOI 3629 b, TOI 3714 b, TOI 4201 b, and TOI 5344 b, respectively. The corresponding stellar masses are 0.372 +/- 0.018 M-circle dot, 0.635 +/- 0.032 M-circle dot, 0.522 +/- 0.028 M-circle dot, 0.626 +/- 0.033 M-circle dot, and 0.612 +/- 0.034 M-circle dot. All five hosts have supersolar metallicities, providing further support for recent findings that, like for solar-type stars, close-in giant planets are preferentially found around metal-rich M-dwarf host stars. Finally, we describe a procedure for accounting for systematic errors in stellar evolution models when those models are included directly in fitting a transiting planet system.
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Hobson, M. J., Jordan, A., Bryant, E. M., Brahm, R., Bayliss, D., Hartman, J. D., et al. (2023). TOI-3235 b: A Transiting Giant Planet around an M4 Dwarf Star. Astrophys. J. Lett., 946(1), L4.
Abstract: We present the discovery of TOI-3235 b, a short-period Jupiter orbiting an M dwarf with a stellar mass close to the critical mass at which stars transition from partially to fully convective. TOI-3235 b was first identified as a candidate from TESS photometry and confirmed with radial velocities from ESPRESSO and ground-based photometry from HATSouth, MEarth-South, TRAPPIST-South, LCOGT, and ExTrA. We find that the planet has a mass of 0.665 +/- 0.025 M-J and a radius of 1.017 +/- 0.044 R-J. It orbits close to its host star, with an orbital period of 2.5926 days but has an equilibrium temperature of approximate to 604 K, well below the expected threshold for radius inflation of hot Jupiters. The host star has a mass of 0.3939 +/- 0.0030 M-circle dot, a radius of 0.3697 +/- 0.0018 R-circle dot;, an effective temperature of 3389 K, and a J-band magnitude of 11.706 +/- 0.025. Current planet formation models do not predict the existence of gas giants such as TOI-3235 b around such low-mass stars. With a high transmission spectroscopy metric, TOI-3235 b is one of the best-suited giants orbiting M dwarfs for atmospheric characterization.
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Jenkins, J. S., Diaz, M. R., Kurtovic, N. T., Espinoza, N., Vines, J. I., Rojas, P. A. P., et al. (2020). An ultrahot Neptune in the Neptune desert. Nat. Astron., 4(12), 1148–1157.
Abstract: 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-circle plus), or apparently rocky planets smaller than 2 R-circle plus. 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-circle plus and a mass of 29 M-circle plus, 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).
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Kirk, J., Rackham, B. V., MacDonald, R. J., Lopez-Morales, M., Espinoza, N., Lendl, M., et al. (2021). ACCESS and LRG-BEASTS: A Precise New Optical Transmission Spectrum of the Ultrahot Jupiter WASP-103b. Astron. J., 162(1), 34.
Abstract: We present a new ground-based optical transmission spectrum of the ultrahot Jupiter WASP-103b (Teq=2484
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Pinto-Rios, J., Calderon, F., Leiva, A., Hermosilla, G., Beghelli, A., Borquez-Paredes, D., et al. (2023). Resource Allocation in Multicore Elastic Optical Networks: A Deep Reinforcement Learning Approach. Complexity, 2023, 4140594.
Abstract: A deep reinforcement learning (DRL) approach is applied, for the first time, to solve the routing, modulation, spectrum, and core allocation (RMSCA) problem in dynamic multicore fiber elastic optical networks (MCF-EONs). To do so, a new environment was designed and implemented to emulate the operation of MCF-EONs – taking into account the modulation format-dependent reach and intercore crosstalk (XT) – and four DRL agents were trained to solve the RMSCA problem. The blocking performance of the trained agents was compared through simulation to 3 baselines RMSCA heuristics. Results obtained for the NSFNet and COST239 network topologies under different traffic loads show that the best-performing agent achieves, on average, up to a four-times decrease in blocking probability with respect to the best-performing baseline heuristic method.
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Saunders, N., Grunblatt, S. K., Huber, D., Collins, K. A., Jensen, E. L. N., Vanderburg, A., et al. (2022). TESS Giants Transiting Giants. I.: A Noninflated Hot Jupiter Orbiting a Massive Subgiant. Astron. J., 163(2), 53.
Abstract: While the population of confirmed exoplanets continues to grow, the sample of confirmed transiting planets around evolved stars is still limited. We present the discovery and confirmation of a hot Jupiter orbiting TOI-2184 (TIC 176956893), a massive evolved subgiant (M-* = 1.53 +/- 0.12 M-circle dot, R-* = 2.90 +/- 0.14 R-circle dot) in the Transiting Exoplanet Survey Satellite (TESS) Southern Continuous Viewing Zone. The planet was flagged as a false positive by the TESS Quick-Look Pipeline due to periodic systematics introducing a spurious depth difference between even and odd transits. Using a new pipeline to remove background scattered light in TESS Full Frame Image data, we combine space-based TESS photometry, ground-based photometry, and ground-based radial velocity measurements to report a planet radius of R (p) = 1.017 +/- 0.051 R (J) and mass of M (p) = 0.65 +/- 0.16 M (J) . For a planet so close to its star, the mass and radius of TOI-2184b are unusually well matched to those of Jupiter. We find that the radius of TOI-2184b is smaller than theoretically predicted based on its mass and incident flux, providing a valuable new constraint on the timescale of post-main-sequence planet inflation. The discovery of TOI-2184b demonstrates the feasibility of detecting planets around faint (TESS magnitude > 12) post-main-sequence stars and suggests that many more similar systems are waiting to be detected in the TESS FFIs, whose confirmation may elucidate the final stages of planetary system evolution.
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