United States Naval Research Laboratory

Lunar mare basalts are often rich in titanium, hosted predominantly within the mineral ilmenite (Fe2+Ti4+O3). Here, we examine ilmenite in a ~ 3.8 billion-year-old mare basalt (Apollo rock 75035) using high-resolution electron microscopy and electron energy loss spectroscopy. A key finding is that 75035 ilmenite is itself enriched in Ti, beyond the end member of the conventional solid solution series. Using energy loss near-edge spectroscopy, we determine that the excess Ti is trivalent, with Ti3+ accounting for 13% of the total Ti content. This discovery confirms the presence of trivalent Ti in lunar ilmenite, long hypothesized based on the Moon’s reducing environment. Accounting for the change in implied stoichiometry, a review of literature data suggests that Ti3+ may be present in ilmenite across a wide range of lunar samples. We extrapolate known relationships from the literature to connect Ti3+ to redox conditions, estimating the oxygen fugacity during crystallization of 75035 to be below the iron-wüstite buffer, ΔIW≤ − 1.6. Further quantifying the relationship between Ti valence state and oxygen fugacity would allow Ti3+-bearing ilmenite to serve as an oxybarometer able to access the reducing conditions found on many planetary bodies.

Abstract JWST imagery of the approaching Kreutz sungrazer C/2026 A1 (MAPS) appears sufficient to distinguish the comet’s nucleus from the surrounding dust. Coma model fitting indicates the morphology is compatible with a ∼0.4 km diameter nucleus—likely larger than those of the minor Kreutz fragments routinely discovered with coronagraphs, and comparable to or slightly smaller than that of C/2011 W3 (Lovejoy). However, since C/2026 A1 is the only Kreutz sungrazer whose nucleus has been directly observed, these comparisons should be treated with caution.

The Negative Attitude toward Robots Scale (NARS) was designed to measure people’s general attitudes toward robots. Originally developed and validated in Japanese, the NARS was translated into English without revalidation and has become widely used in human-robot interaction research. This study aims to validate the translated NARS factor structure via confirmatory factor analysis using existing datasets. Results (N = 2154) indicated a moderate support for the three-factor structure with some problematic items. Additionally, many papers modified the NARS in some way, including changing wording or rating scale. Not only is this not recommended, but it suggests that there may be a disconnect between the scale and how researchers would like to use it. Together, we suggest that researchers consider the consequences of modification and emphasize the importance of validating scales to ensure their adequate measurement ability and the quality of research results.

Epsilon near zero (ENZ) materials have potential in various applications such as all-optical switching and quantum information. Materials that support ENZ modes include metamaterials, semiconductors, and transparent conducting oxides (TCOs) like indium tin oxide (ITO). ITO supports an ENZ mode in the near-infrared (IR), giving rise to large nonlinearities and enabling strong optically induced changes in its refractive index. Recently, a perovskite TCO, La-doped BaSnO3 (LBSO) has demonstrated wide tunability of the ENZ wavelength ranging from the near IR to mid-IR regions. In this work, we use a reflective gold layer to access the Ferrell-Berreman (FB) mode of LBSO, a special class of leaky optical mode that occurs at the material’s ENZ wavelength. The FB mode has strong extinction, making it an ideal candidate for reflection modulation. Here, we interrogate the charge carrier dynamics of multiple Au-coated LBSO samples with varying ENZ wavelengths, paying special attention to the tuning behavior of the FB mode. We find that, upon UV excitation, injected charge carriers are long-lived compared to other transparent conducting oxides and that the photoexcited carriers induce strong modulation of the FB mode. This Au-coated LBSO shows promise for infrared optical switching applications, especially those requiring high thermal stability.

Abstract The electron density of the solar corona is a fundamental parameter in many areas of solar physics. Traditionally, routine estimates of coronal density have relied exclusively on white-light observations. However, these density estimates, obtained by inverting the white-light data, require simplifying assumptions, which may affect the robustness of the measurements. Hence, to improve the reliability of coronal density measurements, it is highly desirable to explore other complementary methods. In this study, we estimate the coronal electron densities in the middle corona, between approximately 1.7 and 3.5 R ⊙ , using low-frequency radio observations from the recently commissioned Long Wavelength Array at the Owens Valley Radio Observatory (OVRO-LWA). The results demonstrate consistency with those derived from white-light coronagraph data and predictions from theoretical models. We also derive a density model valid between 1.7 and 3.5 r ⊙ , given by <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:mi>ρ</mml:mi> <mml:mo stretchy="false">(</mml:mo> <mml:msup> <mml:mrow> <mml:mi>r</mml:mi> </mml:mrow> <mml:mrow> <mml:mo accent="true">′</mml:mo> </mml:mrow> </mml:msup> <mml:mo stretchy="false">)</mml:mo> <mml:mo>=</mml:mo> <mml:mn>1.27</mml:mn> <mml:msup> <mml:mrow> <mml:mi>r</mml:mi> <mml:msup> <mml:mrow/> <mml:mrow> <mml:mo accent="true">′</mml:mo> </mml:mrow> </mml:msup> </mml:mrow> <mml:mrow> <mml:mo>−</mml:mo> <mml:mn>2</mml:mn> </mml:mrow> </mml:msup> <mml:mo>+</mml:mo> <mml:mn>29.02</mml:mn> <mml:msup> <mml:mrow> <mml:mi>r</mml:mi> <mml:msup> <mml:mrow/> <mml:mrow> <mml:mo accent="true">′</mml:mo> </mml:mrow> </mml:msup> </mml:mrow> <mml:mrow> <mml:mo>−</mml:mo> <mml:mn>4</mml:mn> </mml:mrow> </mml:msup> <mml:mo>+</mml:mo> <mml:mn>71.18</mml:mn> <mml:msup> <mml:mrow> <mml:mi>r</mml:mi> <mml:msup> <mml:mrow/> <mml:mrow> <mml:mo accent="true">′</mml:mo> </mml:mrow> </mml:msup> </mml:mrow> <mml:mrow> <mml:mo>−</mml:mo> <mml:mn>6</mml:mn> </mml:mrow> </mml:msup> </mml:math> , where <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:msup> <mml:mrow> <mml:mi>r</mml:mi> </mml:mrow> <mml:mrow> <mml:mo accent="true">′</mml:mo> </mml:mrow> </mml:msup> <mml:mo>=</mml:mo> <mml:mi>r</mml:mi> <mml:mo>/</mml:mo> <mml:msub> <mml:mrow> <mml:mi>R</mml:mi> </mml:mrow> <mml:mrow> <mml:mo>⊙</mml:mo> </mml:mrow> </mml:msub> </mml:math> , with r the heliocentric distance. OVRO-LWA is a solar-dedicated radio interferometer that provides science-ready images with low latency, making it well suited for generating regular and independent estimates of coronal densities to complement existing white-light techniques.

Abstract Our survey of the fourth Fermi Large Area Telescope catalog (4FGL) unassociated gamma-ray source regions using the X-Ray Telescope (XRT) and Ultraviolet/Optical Telescope (UVOT) on board the Neil Gehrels Swift Observatory (Swift) provides new XRT and UVOT source detections and localizations to help identify potential low-energy counterparts to unassociated Fermi gamma-ray sources. We present a catalog of 218 singlet and 70 multiplet Swift X-ray sources detected within the positional uncertainty ellipses of 244 unassociated Fermi gamma-ray sources from the 4FGL-DR4 catalog, 144 of which are not previously cataloged by S. Kerby et al. For each X-ray source, we derive its X-ray flux and photon index, then use simultaneous UVOT observations with optical survey data to estimate its V -band magnitude. We use these parameters as inputs for a multilayer perceptron neural network classifier (NNC) trained to classify sources as blazars, pulsars, or ambiguous gamma-ray sources. For the 213 singlet sources with X-ray and optical data, we classify 173 as likely blazars ( P bzr &gt; 0.99) and six as likely pulsars ( P bzr &lt; 0.01), with 34 sources yielding ambiguous results. Including 70 multiplet X-ray sources, we increase the number of P bzr &gt; 0.99 sources to 227 and P bzr &lt; 0.01 sources to 16. For the subset of these classifications that have been previously studied, a large majority agree with prior classifications, supporting the validity of using this NNC to classify the unknown and newly detected gamma-ray sources.

We report on progress in fabrication of cladded rare earth doped single crystal fiber. Crystalline core fabrication, cladding compositions and cladding fabrication are discussed with the end goal of facilitating of splicing and integration into laser systems. Progress in splicing single crystal fiber to silica fiber with low loss will be reported.

Recent in situ measurements of electric fields from missions such as Polar, DEMETER, and the Van Allen Probes have reported anomalies in double-probe electric field measurements, attributed to unintended coupling between the sensor and nearby driven stub surfaces through the ambient plasma. The Van Allen Probes Electric Field and Waves (EFW) instrument observed anomalous gain and phase responses under specific plasma conditions, with densities between 30 and 2000 cm⁻³ and frequencies up to a few kHz. Although commonly observed in on-orbit measurements, the physical cause of these anomalies remains poorly understood. Here we present a model of the feedback interaction between the EFW sensor and driven stub surface mediated by the surrounding plasma. We use a numerical simulation of conductive surfaces immersed in a warm, magnetized plasma to calculate the mutual impedance between the sensor and stub across a range of plasma environments. By incorporating a simplified model of the stub-biasing electronics, we directly compare model predictions with the anomalous gain and phase responses observed on orbit. The modeled feedback response agrees well with EFW observations. We suggest that feedback involving kinetic H⁺ lower-hybrid modes explains the observed anomalies. This effect is strongest in dense plasmas where electrons become partially demagnetized and the Debye length approaches the stub length. These results inform the interpretation and design of future spaceborne electric field measurements.

Early-type galaxies host low-luminosity active galactic nuclei, as indicated by radio emission spanning up to several orders of magnitude in terms of the physical scale, ranging from compact parsec-scale to extended kiloparsec-scale radio morphology. We investigate the Eddington-scaled radio luminosity distribution of nearby early-type galaxies in a large sample of 117 sources to confirm whether this distribution is bimodal, as previously inferred for a smaller sample of 62 galaxies. We also consider whether the bimodality can be attributed to specific host galaxy properties. We compiled a sample of early-type galaxies with black hole masses measured using direct methods, as well as the radio flux densities at 1.4,GHz and 3,GHz. We used statistical tests to confirm whether the Eddington-scaled radio luminosities are bimodal. We investigated the properties of radio-dim and -bright sources, assessed the presence of extended jets with VLASS imaging, and examined host galaxy kinematics and central stellar structure. We confirm, using a twice larger sample of all known 1.4,GHz-detected early-type galaxies with directly measured black hole masses (117 galaxies), that the distribution of ̊m 1.4,GHz /L_ Edd is bimodal, with a characteristic antimode at L_ ̊m 1.4,GHz /L_ Edd ≈ -8.6, which disappears when considering the subset of sources with black hole masses obtained using the M_ ̊m BH -σ_⋆ relation. The radio-bright peak is dominated by galaxies hosting resolved jets, while radio-dim systems show compact nuclear emission with many showing excess radio emission relative to that expected from star formation as indicated by the well-known far-infrared and radio (FIR-radio) correlation. Moreover, we find that radio-bright galaxies are primarily slow rotators with depleted stellar cores, whereas radio-dim galaxies are predominantly fast rotators. We show that nearby early-type galaxies with direct black hole mass measurements exhibit a clear bimodality in Eddington-scaled radio luminosity, separating radio-dim nuclei with compact emission from radio-bright systems hosting extended jets. The dichotomy correlates strongly with host-galaxy kinematics and central structure, suggesting that the ability to sustain jet production is governed primarily by galaxy assembly history and feeding mode, rather than by black hole mass or accretion rate alone. In this term, the radio output of radio-dim sources likely reflects modest, intermittent supplies of magnetized gas delivered to the accretion flow through stochastic processes and, most plausibly, the tidal disruption of giant-branch stars passing through the immediate vicinity of the supermassive black hole (SMBH).

Abstract Accurate pulsar astrometric estimates are essential to almost all high-precision pulsar timing experiments. Traditional pulsar timing techniques refine these estimates by including them as free parameters when fitting a model to observed pulse time-of-arrival measurements. However, reliable submilliarcsecond astrometric estimations require years of observations. Even then, power from red noise can be inadvertently absorbed into astrometric parameter fits. This effect biases the resulting estimates and reduces the sensitivity to red noise processes, including gravitational waves (GWs). In this work, we seek to mitigate these shortcomings by using pulsar astrometric estimates derived from very long baseline interferometry (VLBI) as priors for the timing fit. First, we used VLBI and timing astrometric estimates of 18 millisecond pulsars to calibrate a rotation between the reference frames used in timing and VLBI, with a precision of ∼0.7 mas. Through this frame tie, we combined timing- and VLBI-based probabilities to obtain a maximum-posterior astrometric solution. We found offsets between our results and the timing-based astrometric solutions, which, if real, would lead to the absorption of spectral power at the frequencies of interest for single-source GW searches. However, we do not find significant power absorption due to astrometric fitting at the low-frequency domain of the GW background.