Challenges Modeling the Low-Luminosity Type Iax Supernovae

Numerical models allow the investigation of phenomena that cannot exist in a laboratory. Computational simulations are therefore essential for advancing our knowledge of astrophysics, however, the very nature of simulation requires making assumptions that can substantially affect their outcome. Here, we present the challenges faced when simulating dim thermonuclear explosions, Type Iax supernovae. This class of dim events produce a slow moving, sparse ejecta that presents challenges for simulation. We investigate the limitations of the equation of state and its applicability to the expanding, cooling ejecta. We also discuss how the "fluff", i.e. the low-density gas on the grid in lieu of vacuum, inhibits the ejecta as it expands. We explore how the final state of the simulation changes as we vary the character of the burning, which influences the outcome of the explosion. These challenges are applicable to a wide range of astrophysical simulations, and are important to discuss and overcome as a community.Comment: 10 pages, 7 figures, submitted to the Proceedings of 15th International Conference on Numerical Modeling of Space Plasma Flows (AstroNum

A transitional disk around an intermediate mass star in the sparse population of the Orion OB1 Association

We present a detailed study of the disk around the intermediate mass star SO 411, aiming to explain the spectral energy distribution of this star. We show that this is a transitional disk truncated at $\sim$11 au, with $\sim$0.03 lunar masses of optically thin dust inside the cavity. Gas also flows through the cavity, since we find that the disk is still accreting mass onto the star, at a rate of $\sim 5x10^{-9}$ Msun/yr. Until now, SO 411 has been thought to belong to the $\sim$3 Myr old {$\sigma$} Orionis cluster. However, we analyzed the second Gaia Data Release in combination with kinematic data previously reported, and found that SO 411 can be associated with an sparse stellar population located in front of the {$\sigma$} Orionis cluster. If this is the case, then SO 411 is older and even more peculiar, since primordial disks in this stellar mass range are scarce for ages $>$5 Myr. Analysis of the silicate 10$\mu$m feature of SO 411 indicates that the observed feature arises at the edge of the outer disk, and displays a very high crystallinity ratio of $\sim$0.5, with forsterite the most abundant silicate crystal. The high forsterite abundance points to crystal formation in non-equilibrium conditions. The PAH spectrum of SO 411 is consistent with this intermediate state between the hot and luminous Herbig Ae and the less massive and cooler T Tauri stars. Analysis of the 7.7$\mu$m PAH feature indicates that small PAHs still remain in the SO 411 disk.Comment: Accepted in the Astrophysical Journal (17 pages, 9 Figures

Dimming the Lights: 2D Simulations of Deflagrations of Hybrid C/O/Ne White Dwarfs using FLASH

The dimmest and most numerous outlier of the Type Ia supernova population, Type Iax events, is increasingly being found in the results of observational campaigns. There is currently no single accepted model to describe these events. This 2D study explores the viability of modeling Type Iax events as a hybrid C/O/Ne white dwarf progenitor undergoing a deflagration using the multi-physics software FLASH. This hybrid was created using the stellar evolution code MESA, and its C-depleted core and mixed structure have demonstrated lower yields than traditional C/O progenitors in previous deflagration-to-detonation studies. To generate a sample, 30 "realizations" of this simulation were performed, the only difference being the shape of the initial matchhead used to start the deflagration. As consistent with earlier work, these realizations produce the familiar hot dense bound remnant surrounded by sparse ejecta. Our results indicate the majority of the star remains unburned (~70%) and bound (>90%). Our realizations produce total ejecta yields on the order of 10$^{-2}$ - 10$^{-1}$ solar masses, ejected $^{56}$Ni yields on the order of 10$^{-4}$ - 10$^{-2}$ solar masses, and ejecta kinetic energies on the order of 10$^{48}$ - 10$^{49}$ ergs. Compared to yields inferred from recent observations of the dimmest Type Iax events - SN 2007qd, SN 2008ha, SN 2010ae, SN 2019gsc, SN 2019muj, SN 2020kyg, and SN 2021fcg - our simulation produces comparable $^{56}$Ni yields, but too-small total yields and kinetic energies. Reignition of the remnant is also seen in some realizations.Comment: 43 pages, 15 figures, 4 tables. To be published in Ap

A Further Study of Linux Kernel Hugepages on A64FX with FLASH, an Astrophysical Simulation Code

We present an expanded study of the performance of FLASH when using Linux Kernel Hugepages on Ookami, an HPE Apollo 80 A64FX platform. FLASH is a multi-scale, multi-physics simulation code written principally in modern Fortran and makes use of the PARAMESH library to manage a block-structured adaptive mesh. Our initial study used only the Fujitsu compiler to utilize standard hugepages (hp), but further investigation allowed us to utilize hp for multiple compilers by linking to the Fujitsu library libmpg and transparent hugepages (thp) by enabling it at the node level. By comparing the results of hardware counters and in-code timers, we found that hp and thp do not significantly impact the runtime performance of FLASH. Interestingly, there is a significant reduction in the TLB misses, differences in cache and memory access counters, and strange behavior is observed when using thp.Comment: 10 pages, 2 figures, 7 tables. Proceedings for Practice and Experience in Advanced Research Computing (PEARC '23), July 23--27, 2023, Portland, OR, US

Fluticasone furoate/vilanterol (100/25; 200/25 μg) improves lung function in COPD: a randomised trial.

SummaryBackgroundOnce-daily combination treatment is an attractive maintenance therapy for COPD. However, the dose of inhaled corticosteroid to use in a once-daily combination is unknown. We compared two strengths of fluticasone furoate (FF) plus vilanterol (VI), the same strengths of the individual components, and placebo.MethodsMulticentre, randomised, 24-week, double-blind, placebo-controlled, parallel-group study in stable, moderate-to-severe COPD subjects (N = 1224). Subjects were randomised to FF/VI (200/25 μg; 100/25 μg), FF (200 μg; 100 μg), VI 25 μg, or placebo, once daily in the morning. Co-primary efficacy endpoints; 0–4 h weighted mean (wm) FEV1 on day 168, and change from baseline in trough (23–24 h post-dose) FEV1 on day 169. The primary safety objective was adverse events (AEs).ResultsThere was a statistically significant (p < 0.001) increase in wm FEV1 (209 ml) and trough FEV1 (131 ml) for FF/VI 200/25 μg vs. placebo; similar changes were seen for FF/VI 100/25 μg vs. placebo. Whereas the difference between FF/VI 200/25 μg and VI 25 μg in change from baseline trough FEV1 (32 ml) was not statistically significant (p = 0.224), the difference between FF/VI 200/25 μg and FF 200 μg for wm FEV1 (168 ml) was significantly different (p < 0.001). VI 25 μg significantly improved wm and trough FEV1 vs. placebo (209 ml and 131 ml, respectively). No increase was seen in on-treatment AEs or serious AEs (SAEs), with active therapy vs. placebo.ConclusionsFF/VI provides rapid and significant sustained improvement in FEV1 in subjects with moderate-to-severe COPD, which was not influenced by the dose of FF. These data suggest that FF/VI may offer clinical efficacy in COPD and warrants additional study.GSK study number: HZC112207.ClinicalTrials.gov: NCT01054885

Direct Renin Inhibition With Aliskiren Normalizes Blood Pressure in Cyp1a1-Ren2 Transgenic Rats With Inducible Angiotensin II-Dependent Malignant Hypertension

BACKGROUND: Cyp1a1-Ren2 transgenic rats [strain name: TGR(Cyp1a1Ren2)], administered indole-3-carbinol (I3C) develop angiotensin (ANG) II-dependent hypertension due to hepatic expression of the Ren2 renin gene. Although AT(1) receptor blockade prevents the development of hypertension and normalizes the elevated arterial blood pressure of Cyp1-Ren2 rats, little information is available regarding the blood pressure and renal functional responses to direct inhibition of renin in this high circulating renin model of ANG II-dependent hypertension. The present study was performed to determine the effects of acute direct renin inhibition with aliskiren on blood pressure and renal hemodynamics in Cyp1a1-Ren2 rats with ANG II-dependent malignant hypertension. METHODS: Mean arterial pressure (MAP) and renal hemodynamics were measured in pentobarbital-anesthetized male Cyp1a1-Ren2 rats during control conditions and following administration of the renin inhibitor, aliskiren (10 mg/kg, iv). RESULTS: Rats induced with I3C had higher MAP (194±7 vs. 141±2 mmHg, P<0.001), lower renal plasma flow (RPF; 2.47±0.23 vs. 4.17±0.35 ml/min.g, P<0.001), and lower glomerular filtration rate (GFR; 1.01±0.07 vs. 1.34±0.06 ml/min.g, P=0.01) than noninduced Cyp1a1-Ren2 rats (n=5). Aliskiren administration decreased MAP (194±7 to 136±2 mmHg, P<0.001) and increased RPF (2.47±0.23 vs. 4.31±0.20 ml/min.g, P<0.001) in hypertensive but not in normotensive rats, without altering GFR. CONCLUSIONS: Acute renin inhibition with aliskiren normalizes MAP and RPF in Cyp1a1-Ren2 rats with malignant hypertension. The normalization of MAP and RPF following acute renin inhibition indicates that renin generated by expression of the Ren2 gene is responsible for the maintenance of malignant hypertension and the associated reduction in renal hemodynamic function in Cyp1a1-Ren2 rats