David D. Allred received Alumni Professorship Award

As part of its Quesst mission, NASA will fly the supersonic X-59 aircraft over communities to assess human annoyance to quieter sonic booms. As preparation for this flight test campaign continues, there are still many unanswered questions regarding best practices for sonic boom measurements inside and outside communities. This paper features sonic boom measurement and signal processing information including time-domain windowing, zero padding, digital pole-shift filtering, ground-based vs. elevated microphones, atmospheric turbulence, and contaminating noise mitigation. This work both summarizes previous recommendations and provides new recommendations for sonic boom measurement and signal processing. Thus, this paper serves as an overview of the research and recommendations.

We examine deep optical images of edge-on galaxies selected from the Sloan Digital Sky Survey (SDSS) Stripe 82. The entire sample consists of over 800 genuine edge-on galaxies with spectroscopic redshifts out to z similar to 0.2. To discern the faintest details around the galaxies, we use three different data sources with a photometric depth of down to 30 mag arcsec(-2) in the r band: SDSS Stripe 82, Hyper Suprime-Cam Strategic Program, and DESI Legacy Imaging Surveys. Our analysis of the deep images reveals a variety of low surface brightness features. 49 galaxies exhibit prominent tidal structures, including tidal tails, stellar streams, bridges, and diffuse shells. Additionally, 56 galaxies demonstrate peculiar structural features such as lopsided discs, faint warps, and dim polar rings. Overall, we detect low surface brightness structures in 94 galaxies out of 838, accounting for 11 per cent of the sample. Notably, the fraction of tidal structures is only 5.8 per cent, which is significantly lower than that obtained in modern cosmological simulations and observations. Previous studies have shown that strongly interacting galaxies have stellar discs about 1.5-2 times thicker than those without apparent interactions. In an analysis where tidal features are carefully masked for precise disc axis ratio measurements, we show that discs of galaxies with tidal features are 1.33 times thicker, on average, than control galaxies that do not have visible tidal features. Furthermore, we find that edge-on galaxies with tidal structures tend to have a higher fraction of oval and boxy discs than galaxies without tidal features.

The model manifold, an information geometry tool, is a geometric representation of a model that can quantify the expected information content of modeling parameters. For a normal-mode sound propagation model in a shallow ocean environment, transmission loss (TL) is calculated for a vertical line array and model manifolds are constructed for both absolute and relative TL. For the example presented in this paper, relative TL yields more compact model manifolds with seabed environments that are less statistically distinguishable than manifolds of absolute TL. This example illustrates how model manifolds can be used to improve experimental design for inverse problems.

Windows for vacuum ultraviolet (VUV) sources are valuable for many applications but difficult to fabricate due to most materials being too absorptive at VUV wavelengths. We have designed, fabricated, and characterized a carbon nanotube (CNT) collimator as a window with high (VUV) transmission and significant differential pumping. The CNT collimators are arrays of square channels of various dimensions and height with sidewalls composed of vertically aligned CNT forests. The CNT collimators in this work exhibited peak intensity transmissions for VUV light (58.4 nm) of 18%–37% of that reported for the same system without a collimator present [S. Olsen, D. Allred, and R. Vanfleet, J. Vac. Sci. Technol. A (2024)]. Further analysis found that the peak intensity transmissions were lowered due to carbon deposition on the phosphor viewing screen from contaminants. The CNT collimator also had significant sidewall reflection in the VUV range (⁠R = 0.21 +/- 0.08) in the VUV range for angles 15.6 degrees and below). Pressure ratios (low pressure over high pressure) in the VUV transmission experiment were dominated by leaks in the alignment mechanism. Additional experiments demonstrated the CNT collimator’s reflection and superior differential pumping with pressure ratios less than 0.001.

Hollow cathodes are a common type of vacuum ultraviolet (VUV) light source with a wide range of design and application. We determined the VUV (58.4 nm) intensity distribution of a hollow cathode as a function of current and pressure. Our model describes the intensity distribution of a McPherson 629-like hollow cathode helium plasma within the range of 0.50–1.00 A and 0.50–1.00 Torr as a ring with a center peak. We found that for all pressures and currents considered, the ring emits more VUV light than the center peak. We also found that the center peak has a minimum VUV light emission near 0.9 Torr.

We present a new catalog of Kepler planet candidates that prioritizes accuracy of planetary dispositions and properties over uniformity. This catalog contains 4376 transiting planet candidates, including 1791 residing within 709 multiplanet systems, and provides the best parameters available for a large sample of Kepler planet candidates. We also provide a second set of stellar and planetary properties for transiting candidates that are uniformly derived for use in occurrence rate studies. Estimates of orbital periods have been improved, but as in previous catalogs, our tabulated values for period uncertainties do not fully account for transit timing variations (TTVs). We show that many planets are likely to have TTVs with long periodicities caused by various processes, including orbital precession, and that such TTVs imply that ephemerides of Kepler planets are not as accurate on multidecadal timescales as predicted by the small formal errors (typically 1 part in 10(6) and rarely >10(-5)) in the planets' measured mean orbital periods during the Kepler epoch. Analysis of normalized transit durations implies that eccentricities of planets are anticorrelated with the number of companion transiting planets. Our primary catalog lists all known Kepler planet candidates that orbit and transit only one star; for completeness, we also provide an abbreviated listing of the properties of the two dozen nontransiting planets that have been identified around stars that host transiting planets discovered by Kepler.