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On rapid binary mass transfer -- I. Physical model
No full textIn some semi-detached binary systems, the donor star may transfer mass to the companion at a very high rate. We propose that, at sufficiently high mass transfer rates such that the accretion disk around the companion becomes geometrically thick (or advection-dominated) near the disk outer radius, a large fraction of the transferred mass will be lost through the outer Lagrangian (L2) point. A physical model is constructed where the L2 mass loss fraction is given by the requirement that the remaining material in the disk has Bernoulli number equal to the L2 potential energy. Our model predicts significant L2 mass loss at mass transfer rates exceeding a few times 10^{-4} Msun/yr -- an equatorial circum-binary outflow (CBO) is formed in these systems. Implications for the orbital evolution and the observational appearance are discussed. In particular, (1) rapid angular momentum loss from the system tends to shrink the orbital separation and hence may increase the formation rate of mergers and gravitational-wave sources; (2) photons from the hot disk wind are reprocessed by the CBO into longer wavelength emission in the infrared bands, consistent with Spitzer observations of some ultra-luminous X-ray sources
The TESS Grand Unified Hot Jupiter Survey. I. Ten TESS Planets
No full textHot Jupiters—short-period giant planets—were the first extrasolar planets to be discovered, but many questions about their origin remain. NASA’s Transiting Exoplanet Survey Satellite (TESS), an all-sky search for transiting planets, presents an opportunity to address these questions by constructing a uniform sample of hot Jupiters for demographic study through new detections and unifying the work of previous ground-based transit surveys. As the first results of an effort to build this large sample of planets, we report here the discovery of 10 new hot Jupiters (TOI-2193A b, TOI-2207b, TOI-2236b, TOI-2421b, TOI-2567b, TOI-2570b, TOI-3331b, TOI-3540A b, TOI-3693b, TOI-4137b). All of the planets were identified as planet candidates based on periodic flux dips observed by TESS, and were subsequently confirmed using ground-based time-series photometry, high-angular-resolution imaging, and high-resolution spectroscopy coordinated with the TESS Follow-up Observing Program. The 10 newly discovered planets orbit relatively bright F and G stars (G < 12.5, T_(eff) between 4800 and 6200 K). The planets’ orbital periods range from 2 to 10 days, and their masses range from 0.2 to 2.2 Jupiter masses. TOI-2421b is notable for being a Saturn-mass planet and TOI-2567b for being a “sub-Saturn,” with masses of 0.322 ± 0.073 and 0.195 ± 0.030 Jupiter masses, respectively. We also measured a detectably eccentric orbit (e = 0.17 ± 0.05) for TOI-2207b, a planet on an 8 day orbit, while placing an upper limit of e < 0.052 for TOI-3693b, which has a 9 day orbital period. The 10 planets described here represent an important step toward using TESS to create a large and statistically useful sample of hot Jupiters
The COS Legacy Archive Spectroscopy Survey (CLASSY) Treasury Atlas
No full textFar-ultraviolet (FUV; ∼1200–2000 Å) spectra are fundamental to our understanding of star-forming galaxies, providing a unique window on massive stellar populations, chemical evolution, feedback processes, and reionization. The launch of the James Webb Space Telescope will soon usher in a new era, pushing the UV spectroscopic frontier to higher redshifts than ever before; however, its success hinges on a comprehensive understanding of the massive star populations and gas conditions that power the observed UV spectral features. This requires a level of detail that is only possible with a combination of ample wavelength coverage, signal-to-noise, spectral-resolution, and sample diversity that has not yet been achieved by any FUV spectral database. We present the Cosmic Origins Spectrograph Legacy Spectroscopic Survey (CLASSY) treasury and its first high-level science product, the CLASSY atlas. CLASSY builds on the Hubble Space Telescope (HST) archive to construct the first high-quality (S/N_(1500 Å) ≳ 5/resel), high-resolution (R ∼ 15,000) FUV spectral database of 45 nearby (0.002 z M_⋆(M_⊙)) M_⊙ yr⁻¹) < +1.6), direct gas-phase metallicity (7.0 < 12 + log(O/H) < 8.8), ionization (0.5 < O₃₂ < 38.0), reddening (0.02 < E(B − V) < 0.67), and nebular density (10 < nₑ (cm⁻³) < 1120). CLASSY is biased to UV-bright star-forming galaxies, resulting in a sample that is consistent with the z ∼ 0 mass–metallicity relationship, but is offset to higher star formation rates by roughly 2 dex, similar to z ≳ 2 galaxies. This unique set of properties makes the CLASSY atlas the benchmark training set for star-forming galaxies across cosmic time
SN 2016dsg: A Thermonuclear Explosion Involving a Thick Helium Shell
No full textA thermonuclear explosion triggered by a He-shell detonation on a carbon–oxygen white-dwarf core has been predicted to have strong UV line blanketing at early times due to the iron-group elements produced during He-shell burning. We present the photometric and spectroscopic observations of SN 2016dsg, a subluminous peculiar Type I supernova consistent with a thermonuclear explosion involving a thick He shell. With a redshift of 0.04, the i-band peak absolute magnitude is derived to be around −17.5. The object is located far away from its host, an early-type galaxy, suggesting it originated from an old stellar population. The spectra collected after the peak are unusually red, show strong UV line blanketing and weak O i λ7773 absorption lines, and do not evolve significantly over 30 days. An absorption line around 9700–10500 Å is detected in the near-infrared spectrum and is likely from the unburnt He in the ejecta. The spectroscopic evolution is consistent with the thermonuclear explosion models for a sub-Chandrasekhar-mass white dwarf with a thick He shell, while the photometric evolution is not well described by existing models
Predictable Effects of Visual Salience in Experimental Decisions and Games
No full textBottom-up stimulus-driven visual salience is largely automatic, effortless, and independent of a person’s “top-down” perceptual goals; it depends only on features of a visual stimulus. Algorithms have been carefully trained to predict stimulus-driven salience values for each pixel in any image. The economic question we address is whether these salience values help explain economic decisions. Our first experimental analysis shows that when people pick between sets of fruits that have artificially induced value, predicted salience (which is uncorrelated with value by design) leads to mistakes. Our second analysis uses evidence from games in which choices are locations in images. When players are trying to cooperatively match locations, predicted salience is highly correlated with the success of matching (r = .57). In competitive hider-seeker location games, players choose salient locations more often than predicted by the unique Nash equilibrium. This tendency creates a disequilibrium “seeker’s advantage” (seekers win more often than predicted in equilibrium). The result can be explained by level-k models in which predicted stimulus-driven salience influences level-0 choices and thereby influences overall perceptions, beliefs, and choices of higher-level players. The third analysis shows that there is an effect of visual salience in matrix games, but it is small and statistically weak. Applications to behavioral IO, price and tax salience, nudges and design, and visually influenced beliefs are suggested
NIHAO – XXVII. Crossing the green valley
No full textThe transition of high-mass galaxies from being blue and star-forming to being red and dead is a crucial step in galaxy evolution, yet not fully understood. In this work, we use the NIHAO (Numerical Investigation of a Hundred Astrophysical Objects) suite of galaxy simulations to investigate the relation between the transition time through the green valley and other galaxy properties. The typical green valley crossing time of our galaxies is approximately 400 Myr, somewhat shorter than observational estimates. The crossing of the green valley is triggered by the onset of active galactic nucleus (AGN) feedback and the subsequent shutdown of star formation. Interestingly, the time spent in the green valley is not related to any other galaxy properties, such as stellar age or metallicity, or the time at which the star formation quenching takes place. The crossing time is set by two main contributions: the ageing of the current stellar population and the residual star formation in the green valley. These effects are of comparable magnitude, while major and minor mergers have a negligible contribution. Most interestingly, we find the time that a galaxy spends to travel through the green valley is twice the e-folding time of the star formation quenching. This result is stable against galaxy properties and the exact numerical implementation of AGN feedback in the simulation. Assuming a typical crossing time of about 1 Gyr inferred from observations, our results imply that any mechanism or process aiming to quench star formation must do it on a typical time-scale of 500 Myr
Absorber Design and Optimization of Kinetic Inductance Detectors for the Terahertz Intensity Mapper
No full textWe discuss the design and optimization of the absorber for Terahertz Intensity Mapper, a balloon-borne kinetic inductance detector spectrometer. The novel “chain-link” absorber design offers excellent performance, independent optimization for both polarizations, and robust fabrication. Electromagnetic simulations indicate in-band absorption efficiency over ∼90% in both linear polarization modes. DC measurements on different film thicknesses indicate the desired sheet resistance
The Curiosity Rover’s Exploration of Glen Torridon, Gale crater, Mars: An Overview of the Campaign and Scientific Results
No full textThe Mars Science Laboratory rover, Curiosity, explored the clay mineral-bearing Glen Torridon region for one martian year between January 2019 and January 2021, including a short campaign onto the Greenheugh pediment. The Glen Torridon campaign sought to characterize the geology of the area, seek evidence of habitable environments, and document the onset of a potentially global climatic transition during the Hesperian era. Curiosity roved 5 km in total throughout Glen Torridon, from the Vera Rubin ridge to the northern margin of the Greenheugh pediment. Curiosity acquired samples from 11 drill holes during this campaign and conducted the first martian thermochemolytic-based organics detection experiment with the Sample Analysis at Mars instrument suite. The lowest elevations within Glen Torridon represent a continuation of lacustrine Murray formation deposits, but overlying widespread cross bedded sandstones indicate an interval of more energetic fluvial environments and prompted the definition of a new stratigraphic formation in the Mount Sharp group called the Carolyn Shoemaker formation. Glen Torridon hosts abundant phyllosilicates yet remains compositionally and mineralogically comparable to the rest of the Mount Sharp group. Glen Torridon samples have a great diversity and abundance of sulfur-bearing organic molecules, which are consistent with the presence of ancient refractory organic matter. The Glen Torridon region experienced heterogeneous diagenesis, with the most striking alteration occurring just below the Siccar Point unconformity at the Greenheugh pediment. Results from the pediment campaign show that the capping sandstone formed within the Stimson Hesperian aeolian sand sea that experienced seasonal variations in wind direction
A high-speed, modular display system for diverse neuroscience applications
No full textVisual stimulation of animals in the laboratory is a powerful technique for studying sensory control of complex behaviors. Since commercial displays are optimized for human vision, we established a novel display system based on custom-built modular LED panels that provides millisecond refresh, precise synchronization, customizable color combinations, and varied display configurations. This system simplifies challenging experiments. With variants of this display, we probed the speed limits of motion vision and examined the role of color vision in behavioral experiments with tethered flying Drosophila. Using 2-photon calcium imaging, we comprehensively mapped the tuning of visual projection neurons across the fly's field of view. Finally, using real-time behavior analysis, we developed low-latency interactive virtual environments and found that flying flies can independently control their navigation along two dimensions. This display system uniquely addresses most technical challenges of small animal vision experiments and is thoroughly documented for replicability
Spatially resolving the terminator: variation of Fe, temperature, and winds in WASP-76 b across planetary limbs and orbital phase
No full textExoplanet atmospheres are inherently three-dimensional systems in which thermal/chemical variation and winds can strongly influence spectra. Recently, the ultra-hot Jupiter WASP-76 b has shown evidence for condensation and asymmetric Fe absorption with time. However, it is currently unclear whether these asymmetries are driven by chemical or thermal differences between the two limbs, as precise constraints on variation in these have remained elusive due to the challenges of modelling these dynamics in a Bayesian framework. To address this, we develop a new model, HyDRA-2D, capable of simultaneously retrieving morning and evening terminators with day-night winds. We explore variations in Fe, temperature profile, winds, and opacity deck with limb and orbital phase using VLT/ESPRESSO observations of WASP-76 b. We find Fe is more prominent on the evening for the last quarter of the transit, with log(X_(Fe)) = −4.03^(+0.28)_(−0.31), but the morning shows a lower abundance with a wider uncertainty, log(X_(Fe)) = −4.59^(+0.85)_(−1.0), driven by degeneracy with the opacity deck and the stronger evening signal. We constrain 0.1-mbar temperatures ranging from 2950⁺¹¹¹₋₁₅₆ to 2615⁺²⁶⁶₋₂₇₅ K, with a trend of higher temperatures for the more irradiated atmospheric regions. We also constrain a day-night wind speed of 9.8^(+1.2)_(−1.1) km s⁻¹ for the last quarter, higher than 5.9^(+1.5)_(−1.1) km s⁻¹ for the first, in line with general circulation models. We find our new spatially and phase-resolved treatment is statistically favoured by 4.9σ over traditional 1D-retrievals, and thus demonstrate the power of such modelling for robust constraints with current and future facilities