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During its 2 yr Prime Mission, TESS observed over 232,000 stars at a 2 minute cadence across ∼70% of the sky. These data provide a record of photometric variability across a range of astrophysically interesting timescales, probing stellar rotation, stellar binarity, and pulsations. We have analyzed the TESS 2 minute light curves to identify periodic variability on timescales of 0.01–13 days, and explored the results across various stellar properties. We have identified over 46,000 periodic variables with high confidence, and another 38,000 with moderate confidence. These light curves show differences in variability type across the Hertzsprung–Russell diagram, with distinct groupings of rotational, eclipsing, and pulsational variables. We also see interesting patterns across period–luminosity space, with clear correlations between period and luminosity for high-mass pulsators, evolved stars, and contact binary systems, a discontinuity corresponding to the Kraft break, and a lower occurrence of periodic variability in main-sequence stars on timescales of 1.5–2 days. The variable stars identified in this work are cross-identified with several other variability catalogs, from which we find good agreement between the measured periods of variability. There are ∼65,000 variable stars that are newly identified in this work, which includes the rotation rates of low-mass stars, high-frequency pulsation periods for high-mass stars, and a variety of giant star variability.

An analysis of archival data reveals an observational correlation between stellar brightness variations and surface gravity, allowing a determination of surface gravity with a precision of better than 25 per cent for inactive Sun-like stars at main-sequence to giant stages of evolution. Measuring surface gravity in Sun-like stars Variations in the brightness of solar-type stars are driven by many factors including granulation, a consequence of heat convection below the photosphere. And as granulation is correlated with surface gravity, variations in brightness can be used as a measure of surface gravity. Fabienne Bastien et al . analyse archival data from NASA's Kepler mission and show that brightness fluctuations on timescales of less than 8 hours are correlated with the surface gravity in Sun-like stars in various evolutionary phases. Using straightforward measurements of this type it should be possible to determine the surface gravities of many of the stars observed by Kepler. Surface gravity is a basic stellar property, but it is difficult to measure accurately, with typical uncertainties of 25 to 50 per cent if measured spectroscopically 1 , 2 and 90 to 150 per cent if measured photometrically 3 . Asteroseismology measures gravity with an uncertainty of about 2 per cent but is restricted to relatively small samples of bright stars, most of which are giants 4 , 5 , 6 . The availability of high-precision measurements of brightness variations for more than 150,000 stars 7 , 8 provides an opportunity to investigate whether the variations can be used to determine surface gravities. The Fourier power of granulation on a star’s surface correlates physically with surface gravity 9 , 10 : if brightness variations on timescales of hours arise from granulation 11 , then such variations should correlate with surface gravity. Here we report an analysis of archival data that reveals an observational correlation between surface gravity and root mean squared brightness variations on timescales of less than eight hours for stars with temperatures of 4,500 to 6,750 kelvin, log surface gravities of 2.5 to 4.5 (cgs units) and overall brightness variations of less than three parts per thousand. A straightforward observation of optical brightness variations therefore allows a determination of the surface gravity with a precision of better than 25 per cent for inactive Sun-like stars at main-sequence to giant stages of evolution.

Residual stress is an intrinsic property of semicrystalline plastics such as polypropylene and polyethylene. However, there is no fundamental understanding of the role intrinsic residual stress plays in the generation of plastic pollutants that threaten the environment and human health. Here, we show that the processing-induced compressive residual stress typically found in polypropylene and polyethylene plastics forces internal nano and microscale segregation of low molecular weight (MW) amorphous polymer droplets onto the plastic’s surface. Squeeze flow simulations reveal this stress-driven volumetric flow is consistent with that of a Bingham plastic material, with a temperature-dependent threshold yield stress. We confirm that flow is thermally activated and stress dependent, with a reduced energy barrier at higher compressive stresses. Transfer of surface segregated droplets into water generates amorphous polymer micropollutants (APMPs) that are denatured, with structure and composition different from that of traditional polycrystalline microplastics. Studies with water-containing plastic bottles show that the highly compressed bottle neck and mouth regions are predominantly responsible for the release of APMPs. Our findings reveal a stress-induced mechanism of plastic degradation and underscore the need to modify current plastic processing technologies to reduce residual stress levels and suppress phase separation of low MW APMPs in plastics. Residual stresses are pervasive in most modern plastics. Here, the authors show that they promote the migration of low-molecular-weight amorphous polymer and additives from bulk plastics and release micropollutants into water.

A set of eclipsing binary systems exhibit a changing inclination over time due to the gravitational influence of a third stellar companion. These changing inclinations manifest in photometric observations over time as eclipse depth variations. To detect changing eclipse depths, it is advantageous to have a long time baseline of observations, which can be attained by combining data from multiple surveys. We collect ground-based photometry from the Kilodegree Extremely Little Telescope and space-based photometry from the Transiting Exoplanet Survey Satellite (TESS) for seven known changing-inclination eclipsing binaries: HS Hya, RW Per, IU Aur, AH Cep, SV Gem, V685 Cen, and SS Lac. We measure eclipse depth variations and eclipse timing variations in six systems; SS Lac no longer eclipses. As of observations presented here from TESS Sector 35, eclipses are no longer visible in HS Hya (as noted in J. R. A. Davenport et al. 2021). SV Gem, previously believed to have stopped eclipsing, exhibits eclipse-like features across all years of observation, as well as evidence of the negative “O’Connell Effect.” We also present high-resolution speckle imaging from Gemini-North, Gemini-South, and the NESSI instrument on the WIYN telescope for RW Per, AH Cep, SV Gem, and SS Lac, none of which revealed a third companion. Speckle imaging of IU Aur from NESSI revealed the presence of a third companion at an angular separation of ∼0 .″ 14; we report the details of this detection.

The transit method of exoplanet discovery and characterization has enabled numerous breakthroughs in exoplanetary science. These include measurements of planetary radii, mass-radius relationships, stellar obliquities, bulk density constraints on interior models, and transmission spectroscopy as a means to study planetary atmospheres. The Transiting Exoplanet Survey Satellite (TESS) has added to the exoplanet inventory by observing a significant fraction of the celestial sphere, including many stars already known to host exoplanets. Here we describe the science extraction from TESS observations of known exoplanet hosts during the primary mission. These include transit detection of known exoplanets, discovery of additional exoplanets, detection of phase signatures and secondary eclipses, transit ephemeris refinement, and asteroseismology as a means to improve stellar and planetary parameters. We provide the statistics of TESS known host observations during Cycle 1 and 2, and present several examples of TESS photometry for known host stars observed with a long baseline. We outline the major discoveries from observations of known hosts during the primary mission. Finally, we describe the case for further observations of known exoplanet hosts during the TESS extended mission and the expected science yield.

Both direct and indirect methods of exoplanet detection rely upon detailed knowledge of the potential host stars. Such stellar characterization allows for accurate extraction of planetary properties, as well as contributing to our overall understanding of exoplanetary system architecture. In this analysis, we examine the photometry of 264 known exoplanet host stars (harboring 337 planetary companions) that were observed during the Transiting Exoplanet Survey Satellite (TESS) Prime Mission. We identify periodic signatures in the lightcurves of these stars and make possible connections to stellar pulsations and their rotation periods, and compare the stellar variability to the published planetary orbital periods. From these comparisons, we quantify the effects of stellar variability on exoplanet detection, confirming that exoplanets detection is biased toward lower variability stars, but larger exoplanets dominate the population of exoplanets around variable stars. Exoplanet detection methods represented among these systems are distinct between stellar spectral types across the main sequence, though notable outliers exist. In addition, biases present in both the sourced data from TESS and the host star selection process, which strongly influences the representation of both stellar and planetary characteristics in the final populations. We also determine whether the host stars photometric variability affects or mimics the behavior or properties of the system’s planets. These results are discussed in the context of how the behavior of the host star is responsible for how we observe exoplanet characteristics, most notably their radii and atmospheric properties, and how the activity may alter our measurements or impact the evolution of planetary properties.

We present second observations by K2 of OJ 287 and seven other γ-ray active galactic nuclei (AGNs) obtained in 2017–2018, second and third observations of the lobe-dominated, steep-spectrum quasar 3C 207, and observations of nine additional blazars not previously observed with K2. The AGNs were observed simultaneously with K2 and the Fermi Large Area Telescope for 51–81 days. Our full sample, observed in 2014–2018, contained 16 BL Lacertae objects (BL Lacs), nine flat-spectrum radio quasars (FSRQs), and four other γ-ray AGNs. Twelve BL Lacs and seven FSRQs exhibited fast, jagged light curves, while four BL Lacs and two FSRQs had slow, smooth light curves. Some objects changed their red-noise character significantly between repeated K2 observations. The optical characteristics of OJ 287 derived from the short-cadence K2 light curves changed between observations made before and after the predicted passage of the suspected secondary supermassive black hole through the accretion disk of the primary supermassive black hole. The average slopes of the periodogram power spectral densities of the BL Lacs’ and FSRQs’ light curves differed significantly, by ≈12%, with the BL Lac slopes being steeper, and a Kolmogorov–Smirnov test with a p-value of 0.039 indicates that these samples probably come from different populations; however, this result is not as strongly supported by power spectral response (PSRESP) analyses. Differences in the origin of the jets from the ergosphere or accretion disk in these two classes could produce such a disparity, as could different sizes or locations of emission regions within the jets.

Background Specific symptom outcomes after craniovertebral decompression for patients with Chiari type 1 malformation, without accompanying syringomyelia, are not well characterised and poorly reported. Methods We performed a retrospective review of all patients diagnosed with Chiari type 1, without syringomyelia, who underwent craniovertebral decompression in our unit. Results We identified 129 individuals with a minimum of 2 years’ follow-up. The most common pre-operative symptoms were pressure dissociation headaches (78%), visual disturbances (33%), dizziness/balance disturbances (24%) and blackouts (17%). The symptoms most likely to respond to surgery included Valsalva-induced headache (74% response, p < 0.0001) and blackouts (86% response, p < 0.001). Conclusions After successful craniovertebral decompression, most patients presenting with pressure dissociation headaches and blackouts will improve. However, the large variety of other symptoms patients often present with may not improve after surgery.

We present the discovery of TOI-1994b, a low-mass brown dwarf transiting a hot subgiant star on a moderately eccentric orbit. TOI-1994 has an effective temperature of 7700−410+720 K, V magnitude of 10.51 mag and log(g) of 3.982−0.065+0.067 . The brown dwarf has a mass of 22.1−2.5+2.6 M J, a period of 4.034 days, an eccentricity of 0.341−0.059+0.054 , and a radius of 1.220−0.071+0.082 R J. TOI-1994b is more eccentric than other transiting brown dwarfs with similar masses and periods. The population of low-mass brown dwarfs may have properties similar to planetary systems if they were formed in the same way, but the short orbital period and high eccentricity of TOI-1994b may contrast this theory. An evolved host provides a valuable opportunity to understand the influence stellar evolution has on the substellar companion’s fundamental properties. With precise age, mass, and radius, the global analysis and characterization of TOI-1994b augments the small number of transiting brown dwarfs and allows the testing of substellar evolution models.