Improved asteroseismic inversions for red-giant surface rotation rates

Asteroseismic observations of internal stellar rotation have indicated a substantial lack of angular momentum transport in theoretical models of subgiant and red-giant stars. Accurate core and surface rotation rate measurements are therefore needed to constrain internal transport processes included in the models. We eliminate substantial systematic errors of asteroseismic surface rotation rates found in previous studies. We propose a new objective function for the Optimally Localized Averages method of rotational inversions for red-giant stars, which results in more accurate envelope rotation rate estimates obtained from the same data. We use synthetic observations from stellar models across a range of evolutionary stages and masses to demonstrate the improvement. We find that our new inversion technique allows us to obtain estimates of the surface rotation rate that are independent of the core rotation. For a star at the base of the red-giant branch, we reduce the systematic error from about 20% to a value close to 0, assuming constant envelope rotation. We also show the equivalence between this method and the method of linearised rotational splittings. Our new rotational inversion method substantially reduces the systematic errors of red-giant surface rotation rates. In combination with independent measures of the surface rotation rate, this will allow better constraints to be set on the internal rotation profile. This will be a very important probe to further constrain the internal angular momentum transport along the lower part of the red-giant branch.Comment: 17 pages, 22 figures, accepted for publication in Astronomy and Astrophysic

Asteroseismic sensitivity to internal rotation along the red-giant branch

Transport of angular momentum in stellar interiors is currently not well understood. Asteroseismology can provide us with estimates of internal rotation of stars and thereby advances our understanding of angular momentum transport. We can measure core-rotation rates in red-giant stars and we can place upper bounds on surface-rotation rates using measurements of dipole ($l=1$) modes. Here, we aim to determine the theoretical sensitivity of modes of different spherical degree towards the surface rotation. Additionally, we aim to identify modes that can potentially add sensitivity at intermediate radii. We used asteroseismic rotational inversions to probe the internal stellar rotation profiles in red-giant models from the base of the red-giant branch up to the luminosity bump. We used the inversion method of multiplicative optimally localised averages (MOLA) to assess how well internal and surface rotation rates can be recovered from different mode sets and different synthetic rotation profiles. We confirm that dipole mixed modes are sufficient to set constraints on the average core-rotation rates in red giants. However, surface-rotation rates estimated with only dipole mixed modes are contaminated by the core rotation. We show that the sensitivity to the surface rotation decreases from the base of the red-giant branch until it reaches a minimum at 0.6-0.8$L_\text{bump}$ due to a glitch in the buoyancy frequency. Thereafter a narrow range of increased surface sensitivity just below the bump luminosity exists. Quadrupole and octopole modes have more sensitivity in the outer parts of the star. If observed, quadrupole and octopole modes enable us to distinguish between differential and solid body rotation in the convection zone. To obtain accurate estimates of rotation rates at intermediate radii, acoustic oscillation modes with a spherical degree of $l\approx10$ are needed.Comment: accepted for publication in Astronomy and Astrophysics, revised manuscript after language editin

Inverse analysis of asteroseismic data: a review

Asteroseismology has emerged as the best way to characterize the global and internal properties of nearby stars. Often, this characterization is achieved by fitting stellar evolution models to asteroseismic observations. The star under investigation is then assumed to have the properties of the best-fitting model, such as its age. However, the models do not fit the observations perfectly. This is due to incorrect or missing physics in stellar evolution calculations, resulting in predicted stellar structures that are discrepant with reality. Through an inverse analysis of the asteroseismic data, it is possible to go further than fitting stellar models, and instead infer details about the actual internal structure of the star at some locations in its interior. Comparing theoretical and observed stellar structures then enables the determination of the locations where the stellar models have discrepant structure, and illuminates a path for improvements to our understanding of stellar evolution. In this invited review, we describe the methods of asteroseismic inversions, and outline the progress that is being made towards measuring the interiors of stars.Comment: 12 pages, 1 figure. Invited review, Dynamics of the Sun and Star

Observational predictions for Thorne-\.Zytkow objects

Thorne-$\.Z$ytkow objects (T$\.Z$O) are potential end products of the merger of a neutron star with a non-degenerate star. In this work, we have computed the first grid of evolutionary models of T$\.Z$Os with the MESA stellar evolution code. With these models, we predict several observational properties of T$\.Z$Os, including their surface temperatures and luminosities, pulsation periods, and nucleosynthetic products. We expand the range of possible T$\.Z$O solutions to cover $3.45 \lesssim \log \left(T/K\right) \lesssim 3.65$ and $4.85 \lesssim \log \left(L/L_{\odot}\right) \lesssim 5.5$. Due to the much higher densities our T$\.Z$Os reach compared to previous models, if T$\.Z$Os form we expect them to be stable over a larger mass range than previously predicted, without exhibiting a gap in their mass distribution. Using the GYRE stellar pulsation code we show that T$\.Z$Os should have fundamental pulsation periods of 1000--2000 days, and period ratios of $\approx$0.2--0.3. Models computed with a large 399 isotope fully-coupled nuclear network show a nucleosynthetic signal that is different to previously predicted. We propose a new nucleosynthetic signal to determine a star's status as a T$\.Z$O: the isotopologues $^{44}\rm{Ti} \rm{O}_2$ and $^{44}\rm{Ti} \rm{O}$, which will have a shift in their spectral features as compared to stable titanium-containing molecules. We find that in the local Universe (~SMC metallicities and above) T$\.Z$Os show little heavy metal enrichment, potentially explaining the difficulty in finding T$\.Z$Os to-date.Comment: 17 pages, 16 figures, 3 Tables, Sumbitedd to MNRAS, Zenodo data available https://doi.org/10.5281/zenodo.453442

Perspectives on the Restatement (Fourth) Project

Good morning, everyone, and thank you all for coming. It is great to have this conversation, particularly with so many people who are already helpfully contributing to this project. As Bill said, I just wanted to say a little bit about the treaty prong of the project that was approved for consideration by the ALI a couple of years ago. First of all, I should note we get a lot of questions about whether or not we are addressing executive agreements and congressional executive agreements, in addition to Article II treaties. And the current answer is that we are not. We were originally tasked by the ALI to take up the status of Article II treaties in U.S. domestic law, and that is the current character of the project

Fetal Lead Exposure at Each Stage of Pregnancy as a Predictor of Infant Mental Development

BACKGROUND: The impact of prenatal lead exposure on neurodevelopment remains unclear in terms of consistency, the trimester of greatest vulnerability, and the best method for estimating fetal lead exposure. OBJECTIVE: We studied prenatal lead exposure’s impact on neurodevelopment using repeated measures of fetal dose as reflected by maternal whole blood and plasma lead levels. METHODS: We measured lead in maternal plasma and whole blood during each trimester in 146 pregnant women in Mexico City. We then measured umbilical cord blood lead at delivery and, when offspring were 12 and 24 months of age, measured blood lead and administered the Bayley Scales of Infant Development. We used multivariate regression, adjusting for covariates and 24-month blood lead, to compare the impacts of our pregnancy measures of fetal lead dose. RESULTS: Maternal lead levels were moderately high with a first-trimester blood lead mean (± SD) value of 7.1 ± 5.1 μg/dL and 14% of values ≥10 μg/dL. Both maternal plasma and whole blood lead during the first trimester (but not in the second or third trimester) were significant predictors (p < 0.05) of poorer Mental Development Index (MDI) scores. In models combining all three trimester measures and using standardized coefficients, the effect of first-trimester maternal plasma lead was somewhat greater than the effect of first-trimester maternal whole blood lead and substantially greater than the effects of second- or third-trimester plasma lead, and values averaged over all three trimesters. A 1-SD change in first-trimester plasma lead was associated with a reduction in MDI score of 3.5 points. Postnatal blood lead levels in the offspring were less strongly correlated with MDI scores. CONCLUSIONS: Fetal lead exposure has an adverse effect on neurodevelopment, with an effect that may be most pronounced during the first trimester and best captured by measuring lead in either maternal plasma or whole blood

Inhibition of Pyruvate Kinase M2 by Reactive Oxygen Species Contributes to Cellular Antioxidant Responses

Control of intracellular reactive oxygen species (ROS) concentrations is critical for cancer cell survival. We show that, in human lung cancer cells, acute increases in intracellular concentrations of ROS caused inhibition of the glycolytic enzyme pyruvate kinase M2 (PKM2) through oxidation of Cys[superscript 358]. This inhibition of PKM2 is required to divert glucose flux into the pentose phosphate pathway and thereby generate sufficient reducing potential for detoxification of ROS. Lung cancer cells in which endogenous PKM2 was replaced with the Cys[superscript 358] to Ser[superscript 358] oxidation-resistant mutant exhibited increased sensitivity to oxidative stress and impaired tumor formation in a xenograft model. Besides promoting metabolic changes required for proliferation, the regulatory properties of PKM2 may confer an additional advantage to cancer cells by allowing them to withstand oxidative stress.National Institutes of Health (U.S.) (R03MH085679)National Institutes of Health (U.S.) (1P30CA147882)Burroughs Wellcome FundDamon Runyon Cancer Research FoundationSmith Family FoundationStarr Cancer Consortiu

An approach to assessment of endocrine disruption in the National Children's Study.

In this article we consider the importance of assessing endocrine disruption in a large new cohort that has been proposed, the National Children's Study (NCS). We briefly review evidence that endocrine disruption is a potentially important hypothesis for human studies and weigh the need to assess endocrine disruption in the NCS. We note the salient features of earlier, similar cohort studies that serve as reference points for the design of the NCS. Finally, we discuss features of the NCS that would allow or enhance assessment of endocrine disruption, even if endocrine disruption were not a primary hypothesis motivating the study. At this time, the evidence supporting endocrine disruption in humans with background-level exposures is not strong. Thus, a compelling rationale for the NCS will probably need to be based on core hypotheses that focus on other issues. Nonetheless, if properly designed, the NCS could serve as an excellent resource for investigating future hypotheses regarding endocrine disruption