Search Results (22)

Ejecta from core-collapse supernovae interact with the circumstellar medium shed by the progenitor star, producing X-ray emission. Previous studies analyzed the X-ray spectrum of the Type IIb supernova SN 2011dh up to ∼500 days after explosion. Long-term monitoring of X-ray emission provides valuable constraints on supernova evolution and progenitor systems, yet such studies remain rare for Type IIb events due to limited data. Here we present the most comprehensive X-ray light curve of SN 2011dh to date, combining all available Chandra and XMM-Newton data with previously published and newly released Swift observations, extending coverage to ∼5100 days. We measure a luminosity decline consistent with $L_X\propto t^{-0.74\pm 0.04}$ and infer a mass-loss rate of $(1.0$–$2.2)\times {10}^{-6}{M}_{\odot }{\mathrm{yr}}^{-1}$ for $v_w=10\mathrm{km}{\mathrm{s}}^{-1}$, or $(2.0$–$4.4)\times {10}^{-6}{M}_{\odot }{\mathrm{yr}}^{-1}$ for $v_w=20\mathrm{km}{\mathrm{s}}^{-1}$. These estimates agree with earlier results, supporting the interpretation that the X-ray emission has been dominated by an adiabatic reverse shock. The consistency of our late-time results with previous studies demonstrates that SN 2011dh has evolved steadily for nearly 14 years. Full article

The Western diet (WD) has been linked to various structural and functional alterations in the left ventricle (LV), but the molecular response of the right ventricle (RV) remains largely unknown. Given the RV’s distinct anatomical and functional characteristics, it is crucial to understand how long-term WD exposure affects RV gene expression, especially in a sex-specific context. Our objective was to perform gene expression profiling of the RV late responses to WD in wild-type mice. Male and female C57BL/6J mice were fed a WD for 125 days from 300 to 425 days of age, and RV tissues were collected at 530 and 640/750 (female/male) days. mRNA sequencing was performed on RV tissues to identify differentially expressed genes (DEGs) between WD-fed and normal diet (ND)-fed groups. Data processing and analysis were conducted using the STAR aligner and DESeq2. WD-induced RV transcriptomic changes were characterized by differential expression of genes associated with cardiac remodeling and transcriptional regulation in both sexes. In females, additional genes showing altered expression were associated with immune response, whereas in males, changes were more limited, primarily involving genes related to circadian rhythm and cardiac remodeling. Echocardiography revealed modest, sex-specific differences: WD-fed females showed a decrease in right-ventricular internal diameter in diastole and a trend toward increased pulmonary trunk diameter, whereas males showed no notable changes. These exploratory results suggest that WD is associated with modest transcriptomic changes in the RV in both sexes, with only minor structural differences observed in females, indicating subtle sex-specific effects after a switch to normal chow. Full article

This article presents the study of an architectural-constructive type located in Valencia: ribless brick vaults built with the “catalan” technique (one single brick plement approximately 5 cm thick). This is a very specific variant of the star-shaped vault, from the late 15th and early 16th centuries, of which we will examine a representative example: the vault that covers the entrance to the Mas Palace in Valencia. The methodology used is dual in nature: on the one hand, a historical study has been carried out to contextualize the typology, and on the other, a metric analysis of the Mas Palace vault has been carried out using laser scanning technology as a prominent tool. These two parts have finally been put into relationship, determining the formal correspondences that define the type, as well as the particularities of the built work. The main finding of the research is the consideration of this star-shaped vaults, not as a set of particular cases, but as a well-defined typology, which was widespread and successful in its context. We have also determined that its formal characteristics are not only due to aesthetic but also functional (stability and fire resistance) issues. This research, therefore, has allowed us to ponder the importance of a constructive solution that usually goes unnoticed and whose originality does not lie in the techniques used but in their original combination. Full article

The envelopes of Red Supergiants (RSGs) have a unique chemical environment not seen in other types of stars. They foster an oxygen-rich synthesis but are tempered by sporadic and chaotic mass loss, which distorts the envelope and creates complex outflow sub-structures consisting of knots, clumps, and arcs. Near the stellar photosphere, molecules and grains form under approximate LTE conditions, as predicted by chemical models. However, the complicated outflows appear to have distinct chemistries generated by shocks and dust destruction. Various RSG envelopes have been probed for their molecular content, mostly by radio and millimeter observations; however, VY Canis Majoris (VY CMa) and NML Cygni (NML Cyg) display the highest chemical complexity, and also the most complicated envelope structure. Thus far, over 29 different molecules have been identified in the envelopes of RSGs. Some molecules are common for circumstellar gas, including CO, SiO, HCN and H₂O, which have abundances of ∼10⁻⁶–10⁻⁴, relative to H₂. More exotic oxides have additionally been discovered, such as AlO, AlOH, PO, TiO₂, and VO, with abundances of ∼10⁻⁹–10⁻⁷. RSG shells support intricate maser emission in OH, H₂O and SiO, as well. Studies of isotope ratios in molecules suggest dredge-up at least into the H-burning shell, but further exploration is needed. Full article

Identifications of red supergiants (RSGs) in the Milky Way and nearby galaxies have experienced an exponential increase in recent years, driven by advancements in selection techniques, the continued expansion of archival datasets, and a steady increase in spectroscopic data. This review describes the advances in methodologies and selection criteria for identifying RSGs and presents the current census of these stars in our own Galaxy and nearby galaxies. It also describes the insights gained from resolving nearby RSGs and their complex circumstellar material in the Milky Way and from the growing samples of RSGs being discovered in the Local Group and beyond. These advances impact the Humphreys–Davidson limit in the cool part of the Hertzsprung–Russell diagram. Furthermore, they provide insight into extreme RSGs and the role of photometric variability and, in particular, of the newly discovered phenomenon of dimming events. Recent observations have enabled the determination of the binarity fraction among RSGs, offering new constraints to stellar evolution. Looking ahead, the synergy between large-scale surveys, high-resolution observations, and emerging machine-learning tools promises to further transform our understanding of the final evolutionary stages of massive stars in the coming decade. Full article

Using the atmospheric pulsation code written by George Bowen, we have performed a parameter study examining the effects of modifying various parameters of models of oxygen-rich AGB atmospheres pulsating in the fundamental and first-overtone modes. For each pulsation mode, we have examined the effects of adjusting the dust condensation temperature, dust condensation temperature range, pulsation amplitude, dust opacity, and metallicity. Our model grids are generated with the constraint that their luminosities are chosen to span the range of observed mass loss rates at a chosen mass. The dust condensation temperature, pulsation amplitude, and dust opacity have strong effects on the ultimate location and shape of the final model grids in the mass luminosity plane. The mass loss rate evolution of the fundamental and first-overtone mode models show a significant difference in behavior. While the fundamental mode models exhibit the typically assumed power–law relation with mass and luminosity, the first-overtone mode models show significant non-power law behavior at observed mass loss rates. Effectively, models in the first-overtone mode require somewhat higher luminosities to reach the same mass loss rates seen in fundamental mode models of the same mass, consistent with observed AGB stars. Full article

Flares, sometimes accompanied by coronal mass ejections (CMEs), are the result of sudden changes in the magnetic field of stars with high energy release through magnetic reconnection, which can be observed across a wide range of the electromagnetic spectrum from radio waves to the optical range to X-rays. In our observational review, we attempt to collect some fundamental new results, which can largely be linked to the Big Data era that has arrived due to the expansion of space photometric observations over the last two decades. We list the different types of stars showing flare activity and their observation strategies and discuss how their main stellar properties relate to the characteristics of the flares (or even CMEs) they emit. Our goal is to focus, without claiming to be complete, on those results that may, in one way or another, challenge the “standard” flare model based on the solar paradigm. Full article

We present photodynamical models of four eclipsing binary systems that show strong evidence of being members of higher-order multiple systems via their strong eclipse timing variations and/or via the presence of extra eclipse events. Three of these systems are from the main Kepler mission, and the other is from the K2 mission. We provide some ground-based radial velocities measurements for the three Kepler systems and make use of recent light curves from the TESS mission. Our sample consists of two 2 + 1 systems and two 2 + 2 systems. The first 2 + 1 system, KIC 7668648, consists of an eclipsing binary ($P_{\mathrm{bin}}$ = 27.8 days) with late-type stars ($M_1=0.8403\pm 0.0090$$M_{\odot }$, $R_1=1.0066\pm 0.0036R_{\odot }$ and $M_2=0.8000\pm 0.0085M_{\odot }$, $R_2=0.8779\pm 0.0032R_{\odot }$) with a low-mass star ($M_3=0.2750\pm 0.0029M_{\odot }$, $R_3=0.2874\pm 0.0010R_{\odot }$) on a roughly coplanar outer orbit ($P_3=208$ days). There are several eclipse events involving the third star that allow for the precise determination of the system parameters. The second 2 + 1 system, KIC 10319590, consists of a binary ($P_{\mathrm{bin}}=21.3$ days) with late-type stars ($M_1=1.108\pm 0.043M_{\odot }$, $R_1=1.590\pm 0.019R_{\odot }$ and $M_2=0.743\pm 0.023M_{\odot }$, $R_2=0.7180\pm 0.0086R_{\odot }$) that stopped eclipsing about a third of the way into the nominal Kepler mission. We show here that the third star in this system is a Sun-like star ($M_3=1.049\pm 0.038M_{\odot }$, $R_3=1.39\pm 0.11R_{\odot }$) on an inclined outer orbit ($P_3=456$ days). In this case, there are no extra eclipse events. We present the first comprehensive solution for KIC 5255552 and demonstrate that it is a 2 + 2 system consisting of an eclipsing binary ($P_{\mathrm{bin},1}=32.5$ days) with late-type stars ($M_1=0.950\pm 0.018M_{\odot }$, $R_1=0.9284\pm 0.0063R_{\odot }$ and $M_2=0.745\pm 0.014M_{\odot }$, $R_2=0.6891\pm 0.0051R_{\odot }$) paired with a non-eclipsing binary ($P_{\mathrm{bin},2}=33.7$ days) with somewhat lower-mass stars ($M_3=0.483\pm 0.010M_{\odot }$, $R_3=0.4640\pm 0.0036R_{\odot }$ and $M_4=0.507\pm 0.010M_{\odot }$, $R_4=0.4749\pm 0.0031R_{\odot }$). The two binaries, which have nearly coplanar orbits, orbit their common barycenter on a roughly aligned outer orbit ($P_{\mathrm{out}}=878$ days). There are extra eclipse events involving the component stars of the non-eclipsing binary, which leads to relatively small uncertainties in the system parameters. The second 2 + 2 system, EPIC 220204960, consists of a pair of eclipsing binaries ($P_{\mathrm{bin},2}=13.3$ days, $P_{\mathrm{bin},2}=14.4$ days) that both consist of two low-mass stars ($M_1=0.54M_{\odot }$, $R_1=0.46R_{\odot }$, $M_2=0.46M_{\odot }$, $R_2=0.37R_{\odot }$ and $M_3=0.38M_{\odot }$, $R_3=0.40R_{\odot }$, $M_4=0.38M_{\odot }$, $R_4=0.37R_{\odot }$) that orbit their common barycenter on a poorly determined outer orbit. Because of the relatively short time span of the observations (≈80 days for the photometry and ≈70 days for the radial velocity measurements), the masses and radii of the four stars in EPIC 220204960 can only be determined with accuracies of ≈10% and ≈5%, respectively. We show that the most likely period of the outer orbit is 957 days, with a $1\sigma$ range of 595 to 1674 days. We can only place weak constraints on the mutual inclinations of the orbital planes, and additional radial velocity measurements and/or additional eclipse observations would allow for much tighter constraints on the properties of the outer orbit. Full article

Symbiotic stars are interacting binary systems composed of an evolved star (generally a late-type red giant) and a degenerate or dwarf companion in orbit close enough for mass transfer to occur. Understanding the status of the late-type star is important for developing binary models for the symbiotic systems as it affects the transfer of matter needed to activate the hot component. Infrared observations have been very useful in probing the nature of late-type stars in symbiotic systems. This work presents a set of symbiotic stars observed with SOAR/OSIRIS (R∼3000) in the H-band. We aimed to search for possible molecular circumstellar emission, to characterize the cool companion in these systems, and to confront the new findings with those obtained from the previous K-band classifications. We detected molecular emission from just one object, BI Cru, which displays the second-overtone CO-bands. To fit the observed photospheric CO absorption bands, we used the MARCS atmosphere models. We present our results as a mini atlas of symbiotic stars in the near-infrared region to facilitate the comparison among different observed symbiotic systems. Full article

The electron impact excitation and ionization processes are crucial for modeling the spectra of different astrophysical objects, from atmospheres of late-type stars to remnants of supernovae and up to the light emission from neutron star mergers, to name just a few. Despite their significance, however, little is known quantitatively about these processes for low- and medium-impact energies of, say, $E_{\mathrm{kin}}\lesssim 5000$ eV of the free incident electron. To further explore the role of impact excitation, we here expanded Jac, the Jena Atomic Calculator, to the computation of distorted wave collision strengths for fine-structure-resolved, as well as configuration-averaged transitions. While we excluded the formation of dielectronic resonances, these tools can be readily applied for ions with a complex shell structure and by including the major relativistic contributions to these strengths. Detailed computations of the collision strengths are shown and explained for the impact excitation of lithium- and chlorine-like ions. When compared with other, well-correlated methods, good agreement was found, and hence, these tools will support studies of effective collision strengths for a wide range of electron impact energies, levels, and ionic charge states. Full article

The Kepler and TESS space missions significantly expanded our knowledge of what types of stars display flaring activity by recording a vast amount of super-flares from solar-like stars, as well as detecting flares from hotter stars of A-F spectral types. Currently, we know that flaring occurs in the stars as hot as B-type ones. However, the structures of atmospheres of hot B-A stars crucially differ from the ones of late types, and thus the occurrence of flaring in B-A type stars requires some extension of our theoretical views of flare formation and therefore a detailed study of individual objects. Here we present the results of our spectral and photometric study of HD 36030, which is a B9 V star with flares detected by the TESS satellite. The spectra we acquired suggest that the star is in a binary system with a low-mass secondary component, but the light curve lacks any signs of periodic variability related to orbital motion or surface magnetic fields. Because of that, we argue that the flares originate due to magnetic interaction between the components of the system. Full article

Palaeolake Flixton, in the eastern Vale of Pickering in northeast Yorkshire, UK, existed as open water during the Lateglacial and early to mid-Holocene, until hydroseral succession and gradual terrestrialisation changed it to an area of fen and basin peatland by the later mid-Holocene. The environs of the lake were occupied by Late Palaeolithic and Mesolithic people over thousands of years and many Early Mesolithic sites, in particular, have been found located along the ancient lake edge, including the paradigm site for the British Early Mesolithic at Star Carr, where occupation occurred over several centuries. We have analysed eleven sediment cores, distributed in most parts of the palaeolake area, for pollen and stratigraphic data with which to reconstruct lake development and vegetation history. These new diagrams augment earlier pollen studies from the western part of the lake, particularly in the Star Carr area and near other major Mesolithic sites around Seamer Carr. Especially informative are a long core from the deepest part of the lake; cores that document the Lateglacial as well as early Holocene times, and evidence for the later Mesolithic that helps to balance the high density of Late Mesolithic sites known from research in the adjacent uplands of the North York Moors. There are many records of charcoal in the deposits but, especially for the earliest examples, it is not always possible to tie them firmly to either human activity or natural causes. Overall, the new and previously existing diagrams provide evidence for the spatial reconstruction of vegetation history across this important wetland system, including (a) for the progression of natural community successions within the wetland and on the surrounding dryland (b) the influence of climate change in bringing about changes in woodland composition and (c) for discussion of the possibility of human manipulation of the vegetation in the Late Upper Palaeolithic, Early and Late Mesolithic. Results show that climate was the main driver of longer-term vegetation change. Centennial-scale, abrupt climate events caused significant vegetation reversals in the Lateglacial Interstadial. The Lateglacial vegetation was very similar throughout the lake hinterland, although some areas supported some scrubby shrub rather than being completely open. Immigration and spread of Holocene woodland taxa comprised the familiar tree succession common in northern England but the timings of the establishment and the abundance of some individual tree types varied considerably around the lake margins because of edaphic factors and the effects of fire, probably of human origin. Woodland successions away from proximity to the lake were similar to those recorded in the wider landscape of northern England and produced a dense, homogenous forest cover occasionally affected by fire. Full article

Evidence from the analysis of eclipsing binary systems revealed that late-type stars are larger and cooler than predicted by models, and that this is probably caused by stellar magnetic activity. In this work, we revisit this problem taking into account the advancements in the last decade. We provide and updated a list of 32 eclipsing binary or multiple systems, including at least one star with a mass $\lesssim 0.7$ M${}_{\odot }$ and with mass and radius measured to an accuracy better than 3%. The comparison with stellar structure and evolution theoretical models reveals an overall discrepancy of about 7% and −4% for the radius and effective temperature, respectively, and that it may be larger than previously found below the full convection boundary. Furthermore, the hypothesis of stellar activity is reinforced by the comparison of different systems with similar components. Further eclipsing binaries with accurately determined masses and radii, and with estimated activity levels, as well as the implementation of magnetic activity in theoretical models will help to improve our knowledge of low-mass stars, which are prime targets for exoplanet surveys. Full article

DNA-based screening in individuals without known risk factors potentially identifies those who may benefit from genetic counseling, early medical interventions, and/or avoidance of late or missed diagnoses. While not currently in widespread usage, technological advances in genetic analysis overcome barriers to access by enabling less labor-intensive and more cost-efficient means to discover variants of clinical importance. This study describes the technical validation of a 430-gene next-generation sequencing based assay, GeneCompass^TM, indicated for the screening of healthy individuals in the areas of actionable health risks, pharmaceutical drug response, and wellness traits. The test includes genes associated with Mendelian disorders and genetic susceptibility loci, encompassing 14 clinical areas and pharmacogenetic variants. The custom-designed target enrichment capture and bioinformatics pipelines interrogate multiple variant types, including single nucleotide variants, insertions/deletions (indels), copy number variants, and functional haplotypes (star alleles), including tandem alleles and structural variants. Validation was performed against reference DNA from three sources: 1000 Genomes Project (n = 3), Coriell biobank (n = 105), and previously molecularly characterized biological specimens: blood (n = 15) and saliva (n = 11). Analytical sensitivity and specificity for single nucleotide variants (SNVs) were 97.57% and 99.99%, respectively, and for indels were 74.57% and 97.34%, respectively. This study demonstrates the validity of an NGS assay for genetic screening and the broadening of access to preventative genomics. Full article

The placenta participates in cholesterol biosynthesis and metabolism and regulates exchange between the maternal and fetal compartments. The fetus has high cholesterol requirements, and it is taken up and synthesized at elevated rates during pregnancy. In placental cells, the major source of cholesterol is the internalization of lipoprotein particles from maternal circulation by mechanisms that are not fully understood. As in hepatocytes, syncytiotrophoblast uptake of lipoprotein cholesterol involves lipoprotein receptors such as low-density lipoprotein receptor (LDLR) and scavenger receptor class B type I (SR-BI). Efflux outside the cells requires proteins such as the ATP-binding cassette (ABC) transporters ABCA1 and ABCG1. However, mechanisms associated with intracellular traffic of cholesterol in syncytiotrophoblasts are mostly unknown. In hepatocytes, uptaken cholesterol is transported to acidic late endosomes (LE) and lysosomes (LY). Proteins such as Niemann–Pick type C 1 (NPC1), NPC2, and StAR related lipid transfer domain containing 3 (STARD3) are required for cholesterol exit from the LE/LY. These proteins transfer cholesterol from the lumen of the LE/LY into the LE/LY-limiting membrane and then export it to the endoplasmic reticulum, mitochondria, or plasma membrane. Although the production, metabolism, and transport of cholesterol in placental cells are well explored, there is little information on the role of proteins related to intracellular cholesterol traffic in placental cells during physiological or pathological pregnancies. Such studies would be relevant for understanding fetal and placental cholesterol management. Oxidative stress, induced by generating excess reactive oxygen species (ROS), plays a critical role in regulating various cellular and biological functions and has emerged as a critical common mechanism after lysosomal and mitochondrial dysfunction. This review discusses the role of cholesterol, lysosomal and mitochondrial dysfunction, and ROS in the development and progression of hypercholesterolemic pregnancies. Full article