On Carbon Burning in Super Asymptotic Giant Branch Stars

We explore the detailed and broad properties of carbon burning in Super Asymptotic Giant Branch (SAGB) stars with 2755 MESA stellar evolution models. The location of first carbon ignition, quenching location of the carbon burning flames and flashes, angular frequency of the carbon core, and carbon core mass are studied as a function of the ZAMS mass, initial rotation rate, and mixing parameters such as convective overshoot, semiconvection, thermohaline and angular momentum transport. In general terms, we find these properties of carbon burning in SAGB models are not a strong function of the initial rotation profile, but are a sensitive function of the overshoot parameter. We quasi-analytically derive an approximate ignition density, $\rho_{ign} \approx 2.1 \times 10^6$ g cm$^{-3}$, to predict the location of first carbon ignition in models that ignite carbon off-center. We also find that overshoot moves the ZAMS mass boundaries where off-center carbon ignition occurs at a nearly uniform rate of $\Delta M_{\rm ZAMS}$/$\Delta f_{\rm{ov}}\approx$ 1.6 $M_{\odot}$. For zero overshoot, $f_{\rm{ov}}$=0.0, our models in the ZAMS mass range $\approx$ 8.9 to 11 $M_{\odot}$ show off-center carbon ignition. For canonical amounts of overshooting, $f_{\rm{ov}}$=0.016, the off-center carbon ignition range shifts to $\approx$ 7.2 to 8.8 $M_{\odot}$. Only systems with $f_{\rm{ov}}$ $\geq 0.01$ and ZAMS mass $\approx$ 7.2-8.0 $M_{\odot}$ show carbon burning is quenched a significant distance from the center. These results suggest a careful assessment of overshoot modeling approximations on claims that carbon burning quenches an appreciable distance from the center of the carbon core.Comment: Accepted ApJ; 23 pages, 21 figures, 5 table

Bell's Theorem from Moore's Theorem

It is shown that the restrictions of what can be inferred from classically-recorded observational outcomes that are imposed by the no-cloning theorem, the Kochen-Specker theorem and Bell's theorem also follow from restrictions on inferences from observations formulated within classical automata theory. Similarities between the assumptions underlying classical automata theory and those underlying universally-unitary quantum theory are discussed.Comment: 12 pages; to appear in Int. J. General System

Properties of Carbon-Oxygen White Dwarfs From Monte Carlo Stellar Models

We investigate properties of carbon-oxygen white dwarfs with respect to the composite uncertainties in the reaction rates using the stellar evolution toolkit, Modules for Experiments in Stellar Astrophysics (MESA) and the probability density functions in the reaction rate library STARLIB. These are the first Monte Carlo stellar evolution studies that use complete stellar models. Focusing on 3 M$_{\odot}$ models evolved from the pre main-sequence to the first thermal pulse, we survey the remnant core mass, composition, and structure properties as a function of 26 STARLIB reaction rates covering hydrogen and helium burning using a Principal Component Analysis and Spearman Rank-Order Correlation. Relative to the arithmetic mean value, we find the width of the 95\% confidence interval to be $\Delta M_{{\rm 1TP}}$ $\approx$ 0.019 M$_{\odot}$ for the core mass at the first thermal pulse, $\Delta$$t_{\rm{1TP}}$ $\approx$ 12.50 Myr for the age, $\Delta \log(T_{{\rm c}}/{\rm K}) \approx$ 0.013 for the central temperature, $\Delta \log(\rho_{{\rm c}}/{\rm g \ cm}^{-3}) \approx$ 0.060 for the central density, $\Delta Y_{\rm{e,c}} \approx$ 2.6$\times$10$^{-5}$ for the central electron fraction, $\Delta X_{\rm c}(^{22}\rm{Ne}) \approx$ 5.8$\times$10$^{-4}$, $\Delta X_{\rm c}(^{12}\rm{C}) \approx$ 0.392, and $\Delta X_{\rm c}(^{16}\rm{O}) \approx$ 0.392. Uncertainties in the experimental $^{12}$C($\alpha,\gamma)^{16}\rm{O}$, triple-$\alpha$, and $^{14}$N($p,\gamma)^{15}\rm{O}$ reaction rates dominate these variations. We also consider a grid of 1 to 6 M$_{\odot}$ models evolved from the pre main-sequence to the final white dwarf to probe the sensitivity of the initial-final mass relation to experimental uncertainties in the hydrogen and helium reaction rates.Comment: Accepted for publication in The Astrophysical Journal; 19 Pages, 23 Figures, 5 Table

XMM-Newton observations of SDSS J143030.22−-001115.1: an unusually flat spectrum AGN

We present XMM observations of the AGN SDSS 1430-0011. The low S/N spectrum of this source obtained in a snap shot Chandra observation showed an unusually flat continuum. With the follow up XMM observations we find that the source spectrum is complex; it either has an ionized absorber or a partially covering absorber. The underlying power-law is in the normal range observed for AGNs. The low luminosity of the source during Chandra observations can be understood in terms of variations in the absorber properties. The X-ray and optical properties of this source are such that it cannot be securely classified as either a narrow line Seyfert 1 or a broad line Seyfert 1 galaxy.Comment: Submitted to A

Current Research in the Sabine Mine’s Rusk Permit, Rusk County, Texas

In 2014–2015, Prewitt and Associates, Inc., conducted test excavations at seven Native American sites—41RK674, 41RK680, 41RK693, 41RK695, 41RK703, 41RK704, and 41RK729—in northeast Rusk County, Texas. These sites are in Area W of the South Hallsville No. 1 Mine’s Rusk Permit, which is operated by North American Coal Corporation–Sabine Mine. The excavations consisted of 92 m2 (80.7 m3) of hand-dug test units and 63 backhoe trenches (702 m2). Testing determined that the sites have components dating as early as the Middle Archaic period (ca. 3500 B.C.) and as late as the Late Caddo period (late A.D. 1400s), with Late Archaic, Woodland, Early Caddo, and Middle Caddo components represented as well. Four sites have moderate to high densities of cultural materials representing substantial Native American occupations, although none have middens indicating especially prolonged use. Sites 41RK674 and 41RK693 are interpreted as Late Caddo and Middle Caddo farmsteads, respectively, albeit briefly occupied ones. Site 41RK703 has prominent Middle Archaic and probably Late Archaic components representing repeated use as a campsite, with lesser Woodland and Early Caddo components indicating non-residential use. The primary component at 41RK704 represents repeated use during the Woodland period as a special-purpose campsite, and a secondary Early Caddo component reflects less-intensive use as a procurement/processing location or short-term campsite. The other three sites were used less intensively, with 41RK680 having a Woodland component, 41RK695 having a Late Caddo component, and 41RK729 having an unidentified Caddo component; these sites likely were used as procurement or processing locations or short-term campsites

Can Galactic Cosmic Rays Account for Solar 6Li Without Overproducing Gamma Rays?

Cosmic-ray interactions with interstellar gas produces both 6Li, which accumulates in the interstellar medium (ISM), and $\pi^0$ mesons, which decay to gamma-rays which propagate throughout the cosmos. Local 6Li abundances and extragalactic gamma-rays thus have a common origin which tightly links them. We exploit this connection to use gamma-ray observations to infer the contribution to 6Li nucleosynthesis by standard Galactic cosmic-ray (GCR) interactions with the ISM. Our calculation uses a carefully propagated cosmic-ray spectrum and accounts for 6Li production from both fusion reactions ($\alpha \alpha \to ^6Li$) as well as from spallation channels ({p,\alpha+CNO \to ^6Li). We find that although extreme assumptions yield a consistent picture, more realistic ones indicate that solar 6Li cannot be produced by standard GCRs alone without overproducing the hadronic gamma rays. Implications for the primordial 6Li production by decaying dark matter and cosmic rays from cosmological structure formation are discussed. Upcoming gamma-ray observations by GLAST will be crucial for determining the resolution of this problem.Comment: 4 pages, 1 figure To be published in ApJ

Superluminous supernovae: No threat from Eta Carinae

Recently Supernova 2006gy was noted as the most luminous ever recorded, with a total radiated energy of ~10^44 Joules. It was proposed that the progenitor may have been a massive evolved star similar to eta Carinae, which resides in our own galaxy at a distance of about 2.3 kpc. eta Carinae appears ready to detonate. Although it is too distant to pose a serious threat as a normal supernova, and given its rotation axis is unlikely to produce a Gamma-Ray Burst oriented toward the Earth, eta Carinae is about 30,000 times nearer than 2006gy, and we re-evaluate it as a potential superluminous supernova. We find that given the large ratio of emission in the optical to the X-ray, atmospheric effects are negligible. Ionization of the atmosphere and concomitant ozone depletion are unlikely to be important. Any cosmic ray effects should be spread out over ~10^4 y, and similarly unlikely to produce any serious perturbation to the biosphere. We also discuss a new possible effect of supernovae, endocrine disruption induced by blue light near the peak of the optical spectrum. This is a possibility for nearby supernovae at distances too large to be considered "dangerous" for other reasons. However, due to reddening and extinction by the interstellar medium, eta Carinae is unlikely to trigger such effects to any significant degree.Comment: 19 pages, 2 figures; Revised version as accepted for publication in Astrobiolog

Data Recovery Excavations at the J. B. White Site (41MM341), Milam County, Texas

In summer and fall 2002, personnel with Prewitt and Associates, Inc., undertook data recovery excavations at prehistoric site 41MM341 for the Texas Department of Transportation, Environmental Affairs Division, to address the requirements of Section 106 of the National Historic Preservation Act and the Texas Antiquities Code. Site 41MM341 is in central Milam County, Texas, just southeast of the town of Cameron, on a low rise in the modern floodplain of the Little River. The excavations were necessitated by the planned replacement of the State Highway 36 bridge spanning the Little River floodplain, which will directly affect the archeological deposits at 41MM341. The site, which was tested in 2001 and determined eligible for listing in the National Register of Historic Places and designation as a State Archeological Landmark, is well preserved and contains stratified, multicomponent prehistoric materials encased in late Holocene alluvium. The data recovery excavations focused on broad exposure of the remains of a series of Late Prehistoric occupations dating from A.D. 800 or 900 to 1300, with more-limited sampling of a component dating to the A.D. 600– 700s. The excavations consisted of 4 backhoe trenches, 11 initial 1x1-m units, and 3 hand-excavated blocks covering 208 m2. The excavations identified a variety of cultural features and recovered the following: 303 shaped chipped stone tools; 494 expedient stone tools; 168 cores; 39,872 pieces of unmodified debitage; 30 stone tools modified by grinding or battering; 30 bone tools or modified bones; 4 ceramic sherds; 6,540 pieces of vertebrate faunal remains; more than 58.2 kg of invertebrate faunal remains; 1.6 kg of macrobotanical remains; 163.0 kg of burned and unburned rocks; and 30.0 kg of burned clay. The records generated by the excavations and later analyses and the artifacts and other materials retained for curation are housed at the Center for Archaeological Research, The University of Texas at San Antonio. Analysis of the data recovered indicates that 41MM341 was a campsite occupied perhaps mostly during the summer months by hunter-gatherers who took mussels and fish from the river and hunted a variety of game, especially deer, on the Little River floodplain and the surrounding uplands. They may have used botanical resources less, although they did consume hardwood nuts and wild onion and false garlic bulbs. One important activity performed at the site was manufacture of stone tools—mostly arrow points, knives, and expedient flake tools—using chert collected from gravel bars in the river. Many of these tools were used in the wide variety of procurement, processing, and manufacturing activities that typified daily life at 41MM341, but some appear to have been made because they would be needed later in the year after people left the site. One anticipated need was for trade with the Caddo Indians of east Texas. The people who lived at 41MM341 and other sites in the Little River valley interacted regularly with the Caddo, perhaps in trade relationships that helped cement cooperative alliances aimed at regulating competition among groups. Site 41MM341 contributes important information on this topic, which remains an interesting research issue for Native American groups who used the Blackland Prairie between central and east Texas during the Late Prehistoric period

Archeological Investigation at Yanaguana Garden in Hemisfair Park, San Antonio, Bexar County, Texas

This report describes archeological efforts done under six work orders for the development of Yanaguana Garden at HemisFair Park in downtown San Antonio, Texas. All of the projects were done by Prewitt and Associates, Inc. (PAI), for Adams Environmental, Inc. (AEI), and the City of San Antonio, Transportation and Capital Improvements (CoSA-TCI), under Texas Antiquities Permit No. 6846 (issued April 14, 2014). As described below, the Yanaguana Garden project is the first phase of a planned redevelopment of HemisFair Park for mixed-use purposes. Planning for how to deal with cultural resources during this redevelopment began in 2012 when PAI prepared two reports summarizing known archeological and historical resources and providing recommendations for future work (Dase 2013; Fields and McWilliams 2012). Almost all of the subsequent work reported here dealt strictly with the permitted archeological investigations, with limited effort going toward historical resources under a single work order