Two New roAp Stars Discovered with TESS

We present two new rapidly oscillating Ap (roAp) stars, TIC 198781841 and TIC 229960986, discovered in TESS photometric data. The periodogram of TIC 198781841 has a large peak at 166.506 day−1 (1.93 mHz), with two nearby peaks at 163.412 day−1 (1.89 mHz) and 169.600 day−1 (1.96 mHz). These correspond to three independent high-overtone pressure modes, with alternating even and odd ℓ values. TIC 229960986 has a high-frequency triplet centered at 191.641 day−1 (2.218 mHz), with sidebands at 191.164 day−1 (2.213 mHz) and 192.119 day−1 (2.224 mHz). This pulsation appears to be a rotationally split dipole mode, with sideband amplitudes significantly larger than that of the central peak; hence, both pulsation poles are seen over the rotation cycle. Our photometric identification of two new roAp stars underscores the remarkable ability of TESS to identify high-frequency pulsators without spectroscopic observations.

A two-fluid model for the formation of clusters close to a continuous or almost continuous transition

Experiments have shown that spatial heterogeneities can arise when the glass transition in polymers as well as in a number of low molecular weight compounds is approached by lowering the temperature. This formation of “clusters” has been detected predominantly by small angle light scattering and ultrasmall angle x-ray scattering from the central peak on length scales up to about 200 nm and by mechanical measurements including, in particular, piezorheometry for length scales up to several microns. Here we use a macroscopic two-fluid model to study the formation of clusters observed by the various experimental techniques. As additional macroscopic variables, when compared to simple fluids, we use a transient strain field to incorporate transient positional order, along with the velocity difference and a relaxing concentration field for the two subsystems. We show that an external homogeneous shear, as it is applied in piezorheometry, can lead to the onset of spatial pattern formation. To address the issue of additional spectral weight under the central peak we investigate the coupling to all macroscopic variables. We find that there are additional static as well as dissipative contributions from both, transient positional order, as well as from concentration variations due to cluster formation, and additional reversible couplings from the velocity difference. We also briefly discuss the influence of transient orientational order. Finally, we point out that our description is more general, and could be applied above continuous or almost continuous transitions

Geology of the Eminescu (H-09) quadrangle: Mapping status

<p><strong>Abstract</strong></p> <p>The coordinated Mercury’s global mapping project (Galluzzi et al. (2021), aims at delivering quadrangle geological maps for the entire surface of Mercury by using the available basemaps derived from the NASA MESSENGER Mercury Dual Imaging Systems (MDIS) images. The NASA MESSENGER mission was able to cover the surface of Mercury with an average resolution of 200 m/px globally. This allows to produce a series of 1:3M regional geologic maps to be used in support to the ESA/JAXA BepiColombo mission. Here we present the status of the geologic mapping of the Eminescu (H-09) quadrangle, which covers the area between latitudes 22.5°N, -22.5°S and longitudes 72°E, 144°E. The selection of this quadrangle was based on its wealth of many interesting features (e.g., Beagle Rupes, hollow deposits on Eminescu crater, pyroclastic deposits at the margin of the Caloris basin) and on the color variability between the different terrain types that allows to reconstruct the geological history of H-09.</p> <p><strong>Methods</strong></p> <p>In this work, we used the available basemaps derived from the MESSENGER MDIS instrument images, such as the monochrome morphology image mosaics at high- and low-incidence angle (BDR, HIE, HIW and LOI) with a resolution of 166 m/px, together with the enhanced-color and 3-color global mosaics, having a resolution of 665 m/px.</p> <p>The chosen 1:3M output scale is achieved by mapping at an average scale of 1:400k, which is appropriate for the used basemaps. For the symbology, we applied, and in some cases revisited, the Federal Geographic Data Committee (FGDC) and the United Stated Geographic System (USGS) recommendations. The classification of the crater types was based on their diameter, degradation degree and superposition order. The crater's ejecta, central peak, and floor morphology (hummocky or smooth) were distinguished and mapped only for craters larger than 20 km, to avoid the saturation of map features. The terrain units were identified by means of morphology and crater-density, by distinguishing between smooth, intermediate and intercrater plains. We used different symbologies for geological contacts and linear features by distinguishing between certain and approximate contacts, or certain and uncertain/hidden structures, respectively. In particular, the linear features layer encompasses morphologies such as crater rims (up to 5 km in diameter), fault scarps, wrinkle ridges and volcanic vents. The variability in color and albedo was digitized within a surface features polygon layer (e.g., dark material, bright material, and hollow clusters). We did not consider details smaller than 4 km, nor linear features whose distance was smaller than this same threshold to avoid map readability issues.</p> <p><strong>Results</strong></p> <p>The mapping of H-09 is still in progress. The preliminary analysis shows an intriguing morphology related to endogenic and exogenic processes, where intensive tectonic and cratering structures constitute together the main geological events that provided the heterogeneity of terrains in the quadrangle. The tectonic events were probably driven by global cooling, however, we found both compressive and tensional tectonic features on the surface. Hollow clusters are spread all over the quadrangle in different sizes and locations (e.g., crater floors, central peaks). The Eminescu crater located in H-09, between latitudes 12.3°N, 8.8°N  and longitudes 115.9°E, 112.2°E in H-09, is a relatively young crater on Mercury's surface and is characterized by extensive ejecta for one radius from the crater's rim and a recently hollowed central peak. These features and its enhanced color variability will probably require a higher-resolution study of this crater by integrating the geomorphological map with spectral data.</p> <p>This map will be the first geological product for this region with such a scale. Once the mapping is completed, we will be able to determine the absolute ages of the units to classify the terrains in chronological order and provide a complete geological and morphological analysis to understand the geological evolution of the quadrangle. Therefore, through the mapping of H-09 we aim at supporting the ESA/JAXA BepiColombo mission to Mercury by targeting all interesting features and contributing to the investigation and the understanding of Mercury.</p> <p><strong>Keywords: </strong>Mercury (planet), Eminescu Quadrangle, Geological Mapping, MESSENGER, MDIS.</p> <p><strong>Acknowledgements</strong></p> <p>This research has been supported by European Union’s Horizon 2020 under grant agreement N° 776276-PLANMAP.</p> <p><strong>References</strong></p> <p>Galluzzi et al. (2021), PGM Meeting 2021, LPI Contrib. No. 2610.</p>

Distinguishing friction- from shock-generated melt products in hypervelocity impact structures

ABSTRACT Field, microtextural, and geochemical evidence from impact-related melt rocks at the Manicouagan structure, Québec, Canada, allows the distinction to be made between friction-generated (pseudotachylite) and shock-generated melts. Making this distinction is aided by the observation that a significant portion of the impact structure’s central peak is composed of anorthosite that was not substantially involved in the production of impact melt. The anorthosite contrasts with the ultrabasic, basic, intermediate, and acidic gneisses that were consumed by decompression melting of the >60 GPa portion of the target volume to form the main impact melt body. The anorthosite was located below this melted volume at the time of shock loading and decompression, and it was subsequently brought to the surface from 7–10 km depth during the modification stage. Slip systems (faults) within the anorthosite that facilitated its elevation and collapse are occupied by pseudotachylites possessing anorthositic compositions. The Manicouagan pseudotachylites were not shock generated; however, precursor fracture-fault systems may have been initiated or reactivated by shock wave passage, with subsequent tectonic displacement and associated frictional melting occurring after shock loading and rarefaction. Pseudotachylites may inject off their generation planes to form complex intrusive systems that are connected to, but are spatially separated from, their source horizons. Comparisons are made between friction and shock melts from Manicouagan with those developed in the Vredefort and Sudbury impact structures, both of which show similar characteristics. Overall, pseudotachylite has compositions that are more locally derived. Impact melts have compositions reflective of a much larger source volume (and typically more varied source lithology inputs). For the Manicouagan, Vredefort, and Sudbury impact structures, multiple target lithologies were involved in generating their respective main impact melt bodies. Consequently, impact melt and pseudotachylite can be discriminated on compositional grounds, with assistance from field and textural observations. Pseudotachylite and shock-generated impact melt are not the same products, and it is important not to conflate them; each provides valuable insight into different stages of the hypervelocity impact process.

Effects of Turbulent Atmosphere on the Propagation Properties of Vortex Hermite-cosine-hyperbolic-Gaussian Beams

The propagation properties of a vortex Hermite-cosh-Gaussian beam (vHChGB) in atmospheric turbulence are investigated based on the extended Huygens–Fresnel diffraction integral and Rytov method. The analytical formula for the average intensity of a vHChGB propagating in turbulent atmosphere is derived in detail. The influence of the turbulence strength on the intensity distribution under the change of beam parameters conditions is illustrated numerically and discussed. Results show the profile of the initial vHChGB remains unchanged within small propagation distance range, and at certain propagation distance a central peak intensity appears, and finally the beam evolves into Gaussian profile–like in far-field. The rising speed of the central peak intensity is faster when the turbulence strength is larger or the beam parameters such as the beam order, the vortex charge and the Gaussian waist width are smaller. With a small decentered parameter b, the beam profile changes faster as the wavelength is larger, whereas the reverse behavior occurs when b is large. The obtained results may be useful for the practical applications of vHChGB in optical communications and remote sensing.

Computer Support of Analysis of Optical Spectra Measurements

The verification of measurement errors has a big impact on the assessment of the accuracy of conducted measurements and obtained results. In many cases, computer simulation results are compared with measurement results in order to evaluate measurement errors. The purpose of our research was to check the accuracy of measurements made with a Fabry–Perot interferometer working in the transmission mode. In the measurement setup, a 1310 nm superluminescent diode light source, single-mode optical fibers and an optical spectrum analyzer were used. The influence of the length of the resonating cavity and refractive index on the envelope of the optical spectrum was investigated. A program was created that models the envelope of the optical spectrum on the basis of the length of the resonating cavity, the refractive index and the light source output spectral characteristic, which in simulation was assumed to have the shape of Gaussian distribution. After the simulation the program compares the simulated and measured optical spectrum. The comparison of simulated and measured optical spectra proved to be challenging due to the shift in the position of the central peak between the simulated and measured optical spectrum. There are two ways to perform model fitting: by adjusting the position of central peaks or minimums next to the central peak. It was observed that the second solution was more optimal and was implemented in the program.

Propagation of Vortex Cosine-hyperbolic-gaussian Beams in Atmospheric Turbulence

In this paper, the propagation properties of a vortex cosh-Gaussian beam (vChGB) in turbulent atmosphere are investigated. Based on the extended Huygens–Fresnel diffraction integral and the Rytov method, the analytical expression for the average intensity of the vChGB propagating in the atmospheric turbulence is derived. The effects of the turbulent strength and the beam parameters on the intensity distribution and the beam spreading are illustrated numerically and analyzed in detail. It is shown that upon propagating, the incident vChGB keeps its initial hollow dark profile within a certain propagation distance, then the field loses gradually its central hole-intensity and transformed into a Gaussian–like beam for large propagation distance. The rising speed of the central peak is demonstrated to be faster when the constant strength turbulence or the wavelength are larger and the Gaussian width is smaller. The obtained results can be beneficial for applications in optical communications and remote sensing.

Fiber Optic Sensor for Detecting Neoplastic Lesions in Biological Tissues—A Preliminary Study

Tissues affected by neoplastic lesions differ from healthy tissues in terms of functionality and anatomy. These changes affect light’s propagation in tissue by modifying the refractive index, and scattering and absorption coefficients. The primary purpose of this research was to create a system to detect local changes in the refractive index using a fiber optic sensor. A prototype of a micromachine for biomedical applications has been developed. The measurements were performed using the low-coherence interferometry method, i.e., a measurement technique based on the interference of light waves from a broadband light source. The constructed optical system uses a light source with a central wavelength of 1550 nm, a spectrum analyzer, a fiber optic sensor operating on the basis of a Fabry–Perot interferometer and a silver mirror acting as a reflective layer. Measurements of the interference spectrum of reference oils, used for calibration due to the high stability of their parameters, were performed. It has been shown that the developed fiber optic sensor is able to detect changes in the refractive index based on a shift in the position of the central peak in the interference spectrum. It is also sensitive to changes of the absorption coefficient.

Anomalous Dielectric Variability in the central peak of Tycho crater on the Moon: New insights from Mini-RF S-band Observations

<p>One of the unique candidates to explore the evolution of physical surface processes on the Moon is Tycho, a dark haloed impact crater representing well-preserved bright ray pattern and intact crater morphology. Sampling of the central peak in such complex crater formation proves significant in terms of unraveling intriguing science of the lunar interior. With the current state-of-the-art radar technology, it is possible to evaluate the response of the geologic features constrained in the near surface and subsurface regolith environments. This can be achieved by modelling the dielectric constant of media, which is a physical parameter crucial for furthering our knowledge about the distribution of materials within different stratigraphic layers at multiple depths. Here, we used the applicability of Mini-RF S-band data augmented with a deep learning based inversion model to retrieve the dielectric variations over the central peak of the Tycho crater. A striking observation is made in certain regions of the central peak, wherein we observe anomalously high dielectric constant, not at all differentiated in the hyperspectral image and first Stokes parameter image, which usually is a representation of retrieved backscatter of the target. The results are also supported by comparing the variations in the scattering mechanisms. We found those particular regions to be associated with high degree of depolarization, thereby attributing to the presence of cm- to m- scale scatterers buried within a low dielectric layer that are not big enough to produce even-bounce geometry for the radar wave. Moreover, we also observe high rock concentration in the central peak slopes from DIVINER data and NAC images, indicating the exposure of clasts ranging in size from 10 meter to 100s of meter. Furthermore, from surface temperature data, these distinctive outcrops sense warmer temperature at night than the surrounding, which suggests the existence of thermal skin depth in such vicinities. Interestingly, we are able to quantify the pessimistic dielectric constant limit of the large boulder in the middle of the central peak, observable at the Mini-RF radar wavelength, as 4.54 + j0.077. Compared to the expected dielectric constant of rocks, this value is lowered significantly. One probable reason could be the emergence of small radar shadows due to the rugged surface of the boulder on the radar illuminated portion. From our analysis, we showcase the anomalous dielectric variability of Tycho central peak, thereby providing new insights into the evolution of the impact cratering process that could be important for both science and necessary for framing human or robotic exploration strategies.  </p>