Absolute Magnitude Research Articles

Life beyond 30: Probing the −20 < M UV < −17 Luminosity Function at 8 < z < 13 with the NIRCam Parallel Field of the MIRI Deep Survey

We present the ultraviolet luminosity function and an estimate of the cosmic star formation rate density at 8 < z < 13 derived from deep NIRCam observations taken in parallel with the MIRI Deep Survey of the Hubble Ultra Deep Field (HUDF), NIRCam covering the parallel field 2. Our deep (40 hr) NIRCam observations reach an F277W magnitude of 30.8 (5σ), more than 2 mag deeper than JWST public data sets already analyzed to find high-redshift galaxies. We select a sample of 44 z > 8 galaxy candidates based on their dropout nature in the F115W and/or F150W filters, a high probability for their photometric redshifts, estimated with three different codes, being at z > 8, good fits based on χ 2 calculations, and predominant solutions compared to z < 8 alternatives. We find mild evolution in the luminosity function from z ∼ 13 to z ∼ 8, i.e., only a small increase in the average number density of ∼0.2 dex, while the faint-end slope and absolute magnitude of the knee remain approximately constant, with values α = − 2.2 ± 0.1, and M * = − 20.8 ± 0.2 mag. Comparing our results with the predictions of state-of-the-art galaxy evolution models, we find two main results: (1) a slower increase with time in the cosmic star formation rate density compared to a steeper rise predicted by models; (2) nearly a factor of 10 higher star formation activity concentrated in scales around 2 kpc in galaxies with stellar masses ∼108 M ⊙ during the first 350 Myr of the universe, z ∼ 12, with models matching better the luminosity density observational estimations ∼150 Myr later, by z ∼ 9.

Laboratory evaluation of organic aerosol relative ionization efficiencies in the aerodyne aerosol mass spectrometer and aerosol chemical speciation monitor

Organic aerosol (OA) mass concentrations measured by the Aerodyne Aerosol Mass Spectrometer (AMS) and Aerosol Chemical Species Monitor (ACSM) depend on particle relative ionization efficiency (RIEOA). Here, a series of laboratory experiments were conducted to investigate how RIEOA differs for different classes of OA and between AMS and ACSM instruments. For OA surrogates with high oxidation state ( OSc¯), the measured RIEOA is 1.60 ± 0.56 for all instruments. However, for OA surrogates with lower OSc¯, the absolute magnitude and the variability of the measured RIEOA increases. The increase in RIEOA is different between the AMS and ACSMs due to differences in m/z-dependent ion transmission/detection efficiencies in the mass spectrometers. A new metric is introduced to explore RIEOA—the fractional contribution of ions at less than or equal to m/z 50 (fΣm/z50 ). When fΣm/z50 is high (>64%, similar to ambient OA), the average RIEOA is 1.23 ± 0.62. This supports the use of a default RIEOA of 1.4 for typical ambient conditions, where secondary OA dominates the OA budget. When fΣm/z50 is less than 64%, the RIEOA increases as higher m/z ions contribute more to the total signal. These observations reflect the fact that the observed RIEOA is a combination of multiple processes. The fΣm/z50 may be used as a metric to determine if primary-like OA is contributing significantly to total OA. Overall, the results indicate that changes in RIEOA are most important for studies measuring primary-like OA, and the magnitude of the changes will depend on the instrument being used to measure the OA.

Does diversity foster individualism? The relation of racial-ethnic diversity to individualism-collectivism across the 50 American States

ABSTRACT Recent longitudinal research by others analyzing the relation between racial-ethnic diversity and individualism-collectivism in the 50 American states over the period 2000–2018 suggests that racial-ethnic diversity promotes individualism. The present study used a cross-sectional approach based on 2013 data to determine whether a relation mirroring the longitudinal pattern exists between racial-ethnic diversity and individualism-collectivism across the 50 states. Two measures of state racial-ethnic diversity were related to four measures of state individualism-collectivism using Pearson correlation and partial correlation controlling for state socioeconomic status. All correlations between diversity and individualism were negative and all those between diversity and collectivism were positive. The absolute magnitudes ranged from .43 to .68 for the Pearson correlations and from .43 to .67 for the partial correlations. Contrary to the earlier longitudinal findings, the current results show that states with higher racial-ethnic diversity are less individualistic and more collectivistic.

The use of double-mode RR Lyrae stars as robust distance and metallicity indicators

AbstractRR Lyrae stars are one of the primary distance indicators for old stellar populations such as globular clusters, dwarf galaxies and galaxies. Typically, fundamental-mode RR Lyr stars are used for distance measurements, and their accuracy is strongly limited by the dependence of absolute magnitudes on metallicity, in both the optical and infrared bands. Here, we report the discovery of a period–(period ratio)–metallicity relation for double-mode RR Lyr stars, which can predict metallicity as accurately as the low-resolution spectra. With theoretical and observational evidence, we propose that the period–luminosity relation of double-mode RR Lyr stars is not affected by the metallicity. Combining the Large Magellanic Cloud distance and Gaia parallaxes, we calibrate the zero point of the period–luminosity relation to an error of 0.022 mag, which means that in the best case double-mode RR Lyr stars can anchor galaxy distances to an accuracy of 1.0%. For four globular clusters and two dwarf galaxies, we obtain distances using double-mode RR Lyr stars with a distance accuracy of 2–3% and 1–2%, respectively. With future telescopes such as the China Space Station Telescope and the Vera C. Rubin Observatory, double-mode RR Lyr stars will be established as an independent distance ladder in the near-field universe.

SN 2017fzw: A Fast-Expanding Type Ia Supernova with Transitional Features

In this study, we analyzed the optical observations of a subluminous Type Ia supernova (SN Ia) 2017fzw, which exhibited high photospheric velocity (HV) at B-band maximum light. The absolute B-band peak magnitude was determined to be MmaxB=−18.65±0.13 mag, similar to 91bg-like SNe Ia. An estimation of the rate of decline for the B-band light curve was determined to be Δm15(B)=1.60±0.06 mag. The spectra of SN 2017fzw were similar to those of 91bg-like SNe Ia, with prominent Ti ii and Si ii λ5972 features at early phases, gradually transitioning to spectra resembling normal (mainly HV subclass) SNe Ia at later phases, with a stronger Ca ii NIR feature. Notably, throughout all phases of observation, SN 2017fzw displayed spectral evolution characteristics that were comparable to those of HV SNe Ia, and at peak brightness, the Si ii λ6355 velocity was determined to be 13,800 ± 415 km s−1 and a more pronounced Ca ii NIR feature was also detected. Based on these findings, we classify SN 2017fzw as a transitional object with properties of both normal and 91bg-like SNe Ia, providing support for the hypothesis of a continuous distribution of supernovae between these two groups.

Broad-emission-line dominated hydrogen-rich luminous supernovae

ABSTRACT Hydrogen-rich Type II supernovae (SNe II) are the most frequently observed class of core-collapse SNe (CCSNe). However, most studies that analyse large samples of SNe II lack events with absolute peak magnitudes brighter than −18.5 mag at rest-frame optical wavelengths. Thanks to modern surveys, the detected number of such luminous SNe II (LSNe II) is growing. There exist several mechanisms that could produce luminous SNe II. The most popular propose either the presence of a central engine (a magnetar gradually spinning down or a black hole accreting fallback material) or the interaction of supernova ejecta with circumstellar material (CSM) that turns kinetic energy into radiation energy. In this work, we study the light curves and spectral series of a small sample of six LSNe II that show peculiarities in their H α profile, to attempt to understand the underlying powering mechanism. We favour an interaction scenario with CSM that is not dense enough to be optically thick to electron scattering on large scales – thus, no narrow emission lines are observed. This conclusion is based on the observed light curve (higher luminosity, fast decline, blue colours) and spectral features (lack of persistent narrow lines, broad H α emission, lack of H α absorption, weak, or non-existent metal lines) together with comparison to other luminous events available in the literature. We add to the growing evidence that transients powered by ejecta–CSM interaction do not necessarily display persistent narrow emission lines.

A novel systems solution for accurate colorimetric measurement through smartphone-based augmented reality.

Quantifying the colors of objects is useful in a wide range of applications, including medical diagnosis, agricultural monitoring, and food safety. Accurate colorimetric measurement of objects is a laborious process normally performed through a color matching test in the laboratory. A promising alternative is to use digital images for colorimetric measurement, due to their portability and ease of use. However, image-based measurements suffer from errors caused by the non-linear image formation process and unpredictable environmental lighting. Solutions to this problem often perform relative color correction among multiple images through discrete color reference boards, which may yield biased results due to the lack of continuous observation. In this paper, we propose a smartphone-based solution, that couples a designated color reference board with a novel color correction algorithm, to achieve accurate and absolute color measurements. Our color reference board contains multiple color stripes with continuous color sampling at the sides. A novel correction algorithm is proposed to utilize a first-order spatial varying regression model to perform the color correction, which leverages both the absolute color magnitude and scale to maximize the correction accuracy. The proposed algorithm is implemented as a "human-in-the-loop" smartphone application, where users are guided by an augmented reality scheme with a marker tracking module to take images at an angle that minimizes the impact of non-Lambertian reflectance. Our experimental results show that our colorimetric measurement is device independent and can reduce up to 90% color variance for images collected under different lighting conditions. In the application of reading pH values from test papers, we show that our system performs 200% better than human reading. The designed color reference board, the correction algorithm, and our augmented reality guiding approach form an integrated system as a novel solution to measure color with increased accuracy. This technique has the flexibility to improve color reading performance in systems beyond existing applications, evidenced by both qualitative and quantitative experiments on example applications such as pH-test reading.

Spectral type and geometric albedo of (98943) 2001 CC21, the Hayabusa2# mission target

ABSTRACT We conducted optical polarimetry and near-infrared spectroscopy of Japan Aerospace Exploration Agency (JAXA)’s Hayabusa2# mission target, (98943) 2001 CC21, in early 2023. Our new observations indicate that this asteroid has a polarimetric inversion angle of ∼20°, absorption bands around 0.9 and 1.9 μm, and a geometric albedo of 0.23 ± 0.04. All these features are consistent with those of S types but inconsistent with L types. Based on this evidence, we conclude that JAXA’s Hayabusa2# spacecraft will explore an S-type asteroid (more specifically, an L or LL chondrite-like object) with albedo and size (0.44–0.53 km when we assume the absolute magnitude of 18.8) similar to (25143) Itokawa.

IONOSPHERIC TOTAL ELECTRON CONTENT VARIATIONS CAUSED BY THE TONGA VOLCANO EXPLOSION ON JANUARY 15, 2022

The capability of volcanoes to generate powerful explosive eruptions influencing the state of the ionosphere became known back in the 1980th. The Hunga-Tonga-Hunga-Ha’apai (Tonga for short) volcano explosion on January 15, 2022, has shown a surge of renewed interest in investigating effects in the Earth — atmosphere — ionosphere — magnetosphere system since this volcano can be rightfully classified as unique. A number of papers have already dealt with the ionospheric effects generated by the Tonga volcano. The temporal variations in the total electron content (TEC) were used to determine the number of volcano explosions to be five. The second and third explosions were the strongest, with the second being the most intense. The response of the ionosphere to the Tonga volcano explosion has been studied on local and global scales by making use of the Global Positioning System satellite constellation and measurements onboard the Swarm satellite network. In the vicinity of the volcano explosion, disturbances in TEC attained 5—10 TECU. In addition to the local effect, traveling ionospheric disturbances were observed to propagate, which were due to the generation and propagation of atmospheric gravity waves with speeds of 180 m/s to 1,050 m/s. Of particular importance to global-scale perturbations is the Lamb wave, which propagated with a speed of 315 m/s. At nighttime, plasma depletions of the equatorial ionosphere were revealed over the tropical Pacific Ocean when the electron density at 400—500 km altitude showed a decrease by 2-3 orders of magnitude. The length of these formations in longitude exceeded ~10 Mm, and they were observed for more than 4—5 h. The scientific objective of this study is further analysis of aperiodic and quasi-periodic perturbations in the ionosphere, which were caused by the Tonga volcano explosion, in a wide range of distances from the source of disturbance (from ~0.1 Mm to 5 Mm). To reveal the ionospheric response to the Tonga volcano explosion, the records of signals from Global Positioning System satellites have been analyzed. The intercomparison of temporal variations in TEC observed on the reference days and on the day when the volcano explosion occurred has resulted in the determination of basic principles of the generation of ionospheric perturbations and the estimation of numerical magnitudes of the parameters of the perturbations. Four groups of disturbances have been detected, each of which arrived at different time delays with respect to the moment of the volcano explosion. It is important to note that the time delay increases with increasing distance from the volcano to the observational instruments. The first group of speeds included the disturbances traveling with a speed close to 1,000 m/s and having an N-shaped profile. This perturbation was generated by a blast wave whose speed depended on the excess pressure and a priori exceeded the speed of sound. In the second group, the speed varied in the 336 m/s to 500 m/s range, within which the speeds of atmospheric gravity waves are found. The speeds in the third group exhibited variability within the 260—318 m/s limits, within which the Lamb wave propagates. The speed in the fourth group was estimated to be 190—220 m/s, which is a characteristic speed of the tsunami that was caused directly by the volcano explosion. The period of quasi-periodic perturbations varied from ~10 min to 20 min, while their amplitudes were from 0.5 TECU to 1 TECU. The observed ionospheric «hole» was proved to be produced by the volcano explosion directly, with the modules of the absolute and relative magnitudes of disturbances showing a tendency for decreasing with increasing distance from the explosion epicenter, from ~10 TECU to 2 TECU and from 37 % to 7 %, respectively. Contrary to the amplitude, the «hole» time delay and its duration exhibited an increase with distance from the volcano to the observational sensors, from 35 min to 100 min and from ~ 30—40 min to 120— 150 min, respectively. A mechanism for generating the ionospheric «hole» has been advanced, which is based on both the electric and non-electric processes (cracking, the friction of particles, condensation of water vapor, coagulation of water droplets, attachment of electrons, gravity segregation, etc.). The ionospheric «hole» is formed as a result of perturbing the global electric circuit, arising external electric currents, an increase in the electric field strengths by orders of magnitude in the atmosphere and the ionosphere, diffusion of the ionospheric plasma down to lower altitudes where the recombination processes become fast. The basic numerical characteristics have been established of the disturbances, whose fluctuations account for local time, the dusk terminator, sensor geographic locations, the location of subionospheric points on the satellite to receiver ray paths with respect to the equatorial anomaly, etc.

Smoothing the [formula omitted] tension with a phantom dynamical dark energy model

The discrepancy between Planck data and direct measurements of the current expansion rate H0 and the matter fluctuation amplitude S8 has become one of the most intriguing puzzles in cosmology nowadays. The H0 tension has reached 5σ in the context of standard cosmology i.e ΛCDM. Therefore, explanations to this issue are mandatory to unveil its secrets. Despite its success, ΛCDM is unable to give a satisfying explanation to the tension problem. Unless some systematic errors are hidden in the observable measurements, physics beyond the standard model of cosmology must be advocated. In this perspective, we study a phantom dynamical dark energy model as an alternative to ΛCDM in order to explain the aforementioned issues. This phantom model is characterized by one extra parameter, Ωpdde, compared to ΛCDM. We obtain a strong positive correlation between H0 and Ωpdde, for all data combinations. Using Planck18 measurements together with BAO and Pantheon, we find that the H0 and the S8 tensions are 3.4σ and 2.75σ, respectively. By introducing a prior on the absolute magnitude, MB, of the SN Ia, the H0 tension decreases to 2.49σ with H0=69.7−0.86+0.83 km s−1 Mpc−1 and the S8 tension reaches the value 2.51σ with S8=0.82650.012+0.011.

Multiscale stellar associations across the star formation hierarchy in PHANGS–HST nearby galaxies: methodology and properties

ABSTRACT We develop a method to identify and determine the physical properties of stellar associations using Hubble Space Telescope (HST) NUV−U−B−V−I imaging of nearby galaxies from the Physics at High Angular Resolution in Nearby GalaxieS with the Hubble Space Telescope (PHANGS–HST) survey. We apply a watershed algorithm to density maps constructed from point source catalogues Gaussian smoothed to multiple physical scales from 8 to 64 pc. We develop our method on two galaxies that span the distance range in the PHANGS–HST sample: NGC 3351 (10 Mpc) and NGC 1566 (18 Mpc). We test our algorithm with different parameters such as the choice of detection band for the point source catalogue (NUV or V), source density image filtering methods, and absolute magnitude limits. We characterize the properties of the resulting multiscale associations, including sizes, number of tracer stars, number of associations, and photometry, as well as ages, masses, and reddening from spectral energy distribution fitting. Our method successfully identifies structures that occupy loci in the UBVI colour–colour diagram consistent with previously published catalogues of clusters and associations. The median ages of the associations increase from log(age/yr) = 6.6 to log(age/yr) = 6.9 as the spatial scale increases from 8 to 64 pc for both galaxies. We find that the youngest stellar associations, with ages &amp;lt;3 Myr, indeed closely trace H ii regions in H α imaging, and that older associations are increasingly anticorrelated with the H α emission. Owing to our new method, the PHANGS–HST multiscale associations provide a far more complete census of recent star formation activity than found with previous cluster and compact association catalogues.

Orbital eccentricity and inclination distribution of main-belt asteroids—The Statistical model revisited

The distribution and evolution of the Main-belt Asteroid (MBA) orbital eccentricity and inclination provide clues for a deeper understanding of the dynamic evolution of our solar system. This paper presents an analysis of the orbital eccentricity and inclination of 460,000 known MBAs and fits MBA eccentricities and inclinations to a distribution model and further onto a dynamic model. We find that outer-belt MBAs fully fit a Rayleigh distribution; the orbital inclination grouped by the absolute magnitude generally not fully conformed to a Rayleigh distribution. Three evolutionary models of the MBAs were built; Model 1 follows the assumptions of a Rayleigh distribution and Model 2 follows the assumptions of a 2D Cauchy distribution; for the only orbital inclination, a Gaussian distribution was assumed as Model 3. For eccentricity, the distribution mode parameter fits by about 0.074∼0.086 in Model 1 and about 0.03 in Model 2 for the cases grouped by the absolute magnitude, the excitation parameter decreases as the magnitude increases. For the cases grouped by the heliocentric distance, the Model 1 fits the samples better than Model 2; the outer belt also fits Model 1 well, and its fit goodness is about 0.21. For inclination, when the samples were grouped by the absolute magnitude, the distribution mode and excitation parameters were consistent as well. Model 3 overall fits the data better than Models 1 and 2. In summary, the MBA excitation mechanism appears basically consistent with all models when the MBAs were classified by absolute magnitude for both eccentricity and inclination. The cases grouped by absolute magnitude can be fit well in Model 1 for eccentricities and Model 3 for inclinations. When the samples classified by heliocentric distance, the eccentricity and inclination distribution mode was correlated with heliocentric distance, and the influence of excitation was highly related to that distance as well.

Separating the blue cloud and the red sequence using Otsu’s method for image segmentation

The observed colour bimodality allows a classification of the galaxies into two distinct classes: the ‘blue cloud’ and the ‘red sequence’. Such classification is often carried out using empirical cuts in colour and other galaxy properties that lack solid mathematical justifications. We propose a method for separating the galaxies in the ‘blue cloud’ and the ‘red sequence’ using Otsu’s thresholding technique for image segmentation. We show that this technique is insensitive to the choice of binning. It provides a robust and parameter-free method for the classification of the red and blue galaxies based on the minimization of the intra-class variance and maximization of the inter-class variance. We also apply an iterative triclass thresholding technique based on Otsu’s method to improve the classification. The galaxy colour is known to depend on the stellar mass and the luminosity of galaxies. We obtain the dividing lines between the two populations in the colour–stellar mass plane and the colour–absolute magnitude plane by employing these methods in a number of independent stellar mass bins and absolute magnitude bins.

Quadrature-Averaged Homodyne Detection for Estimating Cavity Parameters

Balanced homodyne interferometry is a well-known detection technique that allows for sensitive characterization of light fields. Conventionally a homodyne interferometer is operated by locking the relative phase of a reference beam to the signal beam by means of an active feedback loop. A less often used method is to perform a slow continuous modulation of the reference beam arm length that corresponds to averaging all relative phases during the measurement. Here we show theoretically and experimentally that this quadrature averaging can be advantageous in estimating the parameters of a resonant optical cavity. We demonstrate that the averaging turns the transduction function, from cavity frequency fluctuations into the interferometer signal, into a simple function of the laser detuning that, notably, does not depend on the parameters of possible nonresonant channels present in the system. The method needs no active feedback and gives results that are easy to interpret. Moreover, the phase-averaged measurement allows characterization of the absolute magnitude of a cavity frequency modulation.

OSSOS. XXVII. Population Estimates for Theoretically Stable Centaurs between Uranus and Neptune

We calculate the upper bounds of the population of theoretically stable Centaur orbits between Uranus and Neptune. These small bodies are on low-eccentricity, low-inclination orbits in two specific bands of semimajor axis, centered at ∼24.6 and ∼25.6 au. They exhibit unusually long Gyr-stable lifetimes in previously published numerical integrations, orders of magnitude longer than that of a typical Centaur. Despite the increased breadth and depth of recent Solar System surveys, no such objects have been found. Using the Outer Solar System Origins Survey simulator to calculate the detection efficiency for these objects in an ensemble of fully characterized surveys, we determine that a population of 72 stable Centaurs with absolute magnitude H r ≤ 10 (95% confidence upper limit) could remain undetected. The upcoming Legacy Survey of Space and Time will be able to detect this entire intrinsic population, due to its complete coverage of the ecliptic plane. If detected, these objects will be interesting dynamically accessible mission targets—especially as comparison of the stable Centaur orbital phase space to the outcomes of several modern planetary migration simulations suggests that these objects could be close to primordial in nature.

Measuring the Orbit Drift of Near-Earth Asteroids by the Yarkovsky Effect

The Yarkovsky effect causes the semimajor axis drift of near-Earth asteroids. The drift can be detected by a precise orbit determination process. Using the proposed algorithm, 2233 out of 27,078 near-Earth asteroids are chosen as the initial candidates. Out of these initial candidates, 769 have a measurable Yarkovsky effect with a signal-to-noise ratio (S/N) larger than 1, and 166 have a measurable Yarkovsky effect with an S/N larger than 3. The ratio between retrograde and prograde near-Earth asteroids is plotted with respect to their size. An average ratio of 2 is found for asteroids with an absolute magnitude between 14 and 21. The measurement work is carried out based on orbit determination software developed by the authors that considers a high-precision dynamical model.

Preatmospheric Detection of a Meter-sized Earth Impactor

On 2020 September 18 U.S. Government (USG) sensors detected a bolide with peak bolometric magnitude of −19 over the Western Pacific. The impact was also detected by the Geostationary Lightning Mapper instrument on the GOES-17 satellite and infrasound sensors in Hawaii. The USG measurements reported a steep entry angle of 67° from horizontal from a radiant 13° east of north and an impact speed of 11.7 km s−1. Interpretation of all energy yields produces a preferred energy estimate of 0.4 kt TNT, corresponding to a 23,000 kg, 3 m diameter meteoroid. A postimpact search of telescopic images found that the Asteroid Terrestrial-impact Last Alert System survey captured the object just 10 minutes prior to impact at an Earth-centered distance of nearly 11,900 km with apparent magnitude m = 12.5. The object appears as a 0.44° streak originating on the eastern edge of the image, extending one-third of the USG state-vector-based prediction of 1.26° over the 30 s exposure. The streak shows brightness variability consistent with small asteroid rotation. The position of Earth’s shadow, the object’s size, and its consistency with the reported USG state vector confirm the object is likely natural. This is the eighth preatmospheric detection of a near-Earth asteroid (NEA) impactor and the closest initial telescopic detection prior to impact. The high altitude of peak fireball brightness suggests it was a weak object comparable in many respects with 2008 TC3 (the Almahata Sitta meteorite), with an absolute magnitude H = 32.5 and likely low albedo. Therefore, we suggest the NEA was a C-complex asteroid.

GaiaData Release 3

Context.The astrophysical characterisation of sources is among the major new data products in the thirdGaiaData Release (DR3). In particular, there are stellar parameters for 471 million sources estimated from low-resolution BP/RP spectra.Aims.We present the General Stellar Parameterizer from Photometry (GSP-Phot), which is part of the astrophysical parameters inference system (Apsis). GSP-Phot is designed to produce a homogeneous catalogue of parameters for hundreds of millions of single non-variable stars based on their astrometry, photometry, and low-resolution BP/RP spectra. These parameters are effective temperature, surface gravity, metallicity, absoluteMGmagnitude, radius, distance, and extinction for each star.Methods.GSP-Phot uses a Bayesian forward-modelling approach to simultaneously fit the BP/RP spectrum, parallax, and apparentGmagnitude. A major design feature of GSP-Phot is the use of the apparent flux levels of BP/RP spectra to derive, in combination with isochrone models, tight observational constraints on radii and distances. We carefully validate the uncertainty estimates by exploiting repeatGaiaobservations of the same source.Results.The data release includes GSP-Phot results for 471 million sources withG &lt;  19. Typical differences to literature values are 110 K forTeffand 0.2–0.25 for log g, but these depend strongly on data quality. In particular, GSP-Phot results are significantly better for stars with good parallax measurements (ϖ/σϖ &gt;  20), mostly within 2 kpc. Metallicity estimates exhibit substantial biases compared to literature values and are only useful at a qualitative level. However, we provide an empirical calibration of our metallicity estimates that largely removes these biases. ExtinctionsA0andABPshow typical differences from reference values of 0.07–0.09 mag. MCMC samples of the parameters are also available for 95% of the sources.Conclusions.GSP-Phot provides a homogeneous catalogue of stellar parameters, distances, and extinctions that can be used for various purposes, such as sample selections (OB stars, red giants, solar analogues etc.). In the context of asteroseismology or ground-based interferometry, where targets are usually bright and have good parallax measurements, GSP-Phot results should be particularly useful for combined analysis or target selection.

The Type II-P Supernova 2019mhm and Constraints on its Progenitor System

We present pre- and postexplosion observations of the Type II-P supernova (SN II-P) 2019mhm located in NGC 6753. Based on optical spectroscopy and photometry, we show that SN 2019mhm exhibits broad lines of hydrogen with a velocity of −8500 ± 200 km s−1 and a 111 ± 2 day extended plateau in its luminosity, typical of the Type II-P subclass. We also fit its late-time bolometric light curve and infer that it initially produced a 56Ni mass of 1.3 × 10−2 ± 5.5 × 10−4 M ⊙. Using imaging from the Wide Field Planetary Camera 2 on the Hubble Space Telescope obtained 19 yr before explosion, we aligned to a postexplosion Wide Field Camera 3 image and demonstrate that there is no detected counterpart to the SN to a limit of >24.53 mag in F814W, corresponding to an absolute magnitude limit of M F814W < −7.7 mag. Comparing to massive-star evolutionary tracks, we determine that the progenitor star had a maximum zero-age main-sequence mass <17.5 M ⊙, consistent with other SN II-P progenitor stars. SN 2019mhm can be added to the growing population of SNe II-P with both direct constraints on the brightness of their progenitor stars and well-observed SN properties.

Aerosol Particle Size Influences the Infectious Dose and Disease Severity in a Golden Syrian Hamster Model of Inhalational COVID-19.

Background: Significant evidence suggests that SARS-CoV-2 can be transmitted via respiratory aerosols, which are known to vary as a function of respiratory activity. Most animal models examine disease presentation following inhalation of small-particle aerosols similar to those generated during quiet breathing or speaking. However, despite evidence that particle size can influence dose-infectivity relationships and disease presentation for other microorganisms, no studies have examined the infectivity of SARS-CoV-2 contained in larger particle aerosols similar to those produced during coughing, singing, or talking. Therefore, the aim of the present study was to assess the influence of aerodynamic diameter on the infectivity and virulence of aerosols containing SARS-CoV-2 in a hamster model of inhalational COVID-19. Methods: Dose-response relationships were assessed for two different aerosol particle size distributions, with mass median aerodynamic diameters (MMADs) of 1.3 and 5.2 μm in groups of Syrian hamsters exposed to aerosols containing SARS-CoV-2. Results: Disease was characterized by viral shedding in oropharyngeal swabs, increased respiratory rate, decreased activity, and decreased weight gain. Aerosol particle size significantly influenced the median doses to induce seroconversion and viral shedding, with both increasing ∼30-fold when the MMAD was increased. In addition, disease presentation was dose-dependent, with seroconversion and viral shedding occurring at lower doses than symptomatic disease characterized by increased respiratory rate and decreased activity. Conclusions: These results suggest that aerosol particle size may be an important factor influencing the risk of COVID-19 transmission and needs to be considered when developing animal models of disease. This result agrees with numerous previous studies with other microorganisms and animal species, suggesting that it would be generally translatable across different species. However, it should be noted that the absolute magnitude of the observed shifts in the median doses obtained with the specific particle sizes utilized herein may not be directly applicable to other species.