A Search for Candidate Light Echoes: Photometry of Supernova Environments

Supernova (SN) light echoes could be a powerful tool for determining distances to galaxies geometrically, Sparks 1994. In this paper we present CCD photometry of the environments of 64 historical supernovae, the first results of a program designed to search for light echoes from these SNe. We commonly find patches of optical emission at, or close to, the sites of the supernovae. The color distribution of these patches is broad, and generally consistent with stellar population colors, possibly with some reddening. However there are in addition patches with both unusually red and unusually blue colors. We expect light echoes to be blue, and while none of the objects are quite as blue in V-R as the known light echo of SN1991T, there are features that are unusually blue and we identify these as candidate light echoes for follow-on observations.Comment: 13 pages, Latex, 5 Postscript Tables, 42 Postscript figures, accepted for publication in the A&AS. Figures 1 through 36 are available at the web address: http://www.stsci.edu/~boffi

Cryogenic thermocouple calibration tables

Thermocouple calibration standards are developed for low-temperature thermocouple materials. Thermovoltage, thermopower, and the thermopower derivative are presented in tabular and graphical form

The Effects of Changes in Reaction Rates on Simulations of Nova Explosions

Classical novae participate in the cycle of Galactic chemical evolution in which grains and metal enriched gas in their ejecta, supplementing those of supernovae, AGB stars, and Wolf-Rayet stars, are a source of heavy elements for the ISM. Once in the diffuse gas, this material is mixed with the existing gases and then incorporated into young stars and planetary systems during star formation. Infrared observations have confirmed the presence of carbon, SiC, hydrocarbons, and oxygen-rich silicate grains in nova ejecta, suggesting that some fraction of the pre-solar grains identified in meteoritic material come from novae. The mean mass returned by a nova outburst to the ISM probably exceeds ~2 x 10^{-4} Solar Masses. Using the observed nova rate of 35 per year in our Galaxy, it follows that novae introduce more than ~7 x 10^{-3} Solar Masses per year of processed matter into the ISM. Novae are expected to be the major source of 15N and 17O in the Galaxy and to contribute to the abundances of other isotopes in this atomic mass range. Here, we report on how changes in the nuclear reaction rates affect the properties of the outburst and alter the predictions of the contributions of novae to Galactic chemical evolution. We also discuss the necessity of including the pep reaction in studies of thermonuclear runaways in material accreted onto white dwarfs.Comment: 9 pages, 2 figures, as it appeared in the Proceedings of the Tours 2006 Symposium on Nuclear Physic

Cryogenic thermocouple tables

Cryogenic standardized thermocouple materials table

Theoretical Studies of Accretion of Matter onto White Dwarfs and the Single Degenerate Scenario for Supernovae of Type Ia

We present a brief summary of the Single Degenerate Scenario for the progenitors of Type Ia Supernovae in which it is assumed that a low mass carbon-oxygen white dwarf is growing in mass as a result of accretion from a secondary star in a close binary system. Recent hydrodynamic simulations of accretion of solar material onto white dwarfs without mixing always produce a thermonuclear runaway and steady burning does not occur. For a broad range in WD mass (0.4 Solar masses to 1.35 Solar Masses), the maximum ejected material occurs for the 1.25 Solar Mass sequences and then decreases as the white dwarf mass decreases. Therefore, the white dwarfs are growing in mass as a consequence of the accretion of solar material and as long as there is no mixing of accreted material with core material. In contrast, a thermonuclear runaway in the accreted hydrogen-rich layers on the low luminosity WDs in close binary systems where mixing of core matter with accreted material has occurred is the outburst mechanism for Classical, Recurrent, and Symbiotic novae. The differences in characteristics of these systems is likely the WD mass and mass accretion rate. The high levels of enrichment of CN ejecta in elements ranging from carbon to sulfur confirm that there is dredge-up of matter from the core of the WD and enable them to contribute to the chemical enrichment of the interstellar medium. Therefore, studies of CNe can lead to an improved understanding of Galactic nucleosynthesis, some sources of pre-solar grains, and the Extragalactic distance scale. The characteristics of the outburst depend on the white dwarf mass, luminosity, mass accretion rate, and the chemical composition of both the accreting material and WD material. The properties of the outburst also depends on when, how, and if the accreted layers are mixed with the WD core and the mixing mechanism is still unknown.Comment: 25 Pages, Bulletin of the Astronomical Society of India (BASI) in pres

The Palaeoecology of the Interglacial Deposits at Histon Road, Cambridge

Von den interglazialen Schichten in Histon Road, Cambridge, ist ein 8-m-Kern gewonnen worden. Er gestattete eine genaue Untersuchung der Pflanzen- und der Land- und Süßwasser-Molluskenreste. Die betreffenden Schichten gehören der Zone g der letzten Interglazialzeit und der Zone h-i an: letzteres Symbol soll andeuten, daß, obwohl die Kontinuität der Schichten nicht unterbrochen ist, die Picea-Zone, h, in diesem einzigen in Großbritannien bekannten Ausschnitt aus diesem Teil der letzten Interglazialzeit fehlt. Von Zone f ist keine Spur gefunden worden. Um ein Bild von der Paläoökologie zu bekommen, wurden die makroskopischen Pflanzenreste und Mollusken aus 41 Teilstücken inventarisiert, von denen jedes durchschnittlich 15 cm Länge hätte. Etwa 3000 Früchte und Samen und 16000 Mollusken wurden gefunden. Diese sind in ökologische und klimatische Verteilungsgruppen eingeteilt worden. Die Bedeutung der Variationen innerhalb dieser Gruppen wird behandelt. Die Pflanzenreste und Mollusken scheinen ein einheitliches Bild von einem Zustand zu bieten, der vom Sumpf bis zum fließenden Gewässer variiert, wie es von einem aufschüttend mäandrierenden Flusse zu erwarten ist.researc

Polarization Diagnostics for Cool Core Cluster Emission Lines

The nature of the interaction between low-excitation gas filaments at ~104 K, seen in optical line emission, and diffuse X-ray emitting coronal gas at ~107 K in the centers of galaxy clusters remains a puzzle. The presence of a strong, empirical correlation between the two gas phases is indicative of a fundamental relationship between them, though as yet of undetermined cause. The cooler filaments, originally thought to have condensed from the hot gas, could also arise from a merger or the disturbance of cool circumnuclear gas by nuclear activity. Here, we have searched for intrinsic line emission polarization in cool core galaxy clusters as a diagnostic of fundamental transport processes. Drawing on developments in solar astrophysics, direct energetic particle impact induced polarization holds the promise to definitively determine the role of collisional processes such as thermal conduction in the ISM physics of galaxy clusters, while providing insight into other highly anisotropic excitation mechanisms such as shocks, intense radiation fields, and suprathermal particles. Under certain physical conditions, theoretical calculations predict of the order of 10% polarization. Our observations of the filaments in four nearby cool core clusters place stringent upper limits ( 0.1%) on the presence of emission line polarization, requiring that if thermal conduction is operative, the thermal gradients are not in the saturated regime. This limit is consistent with theoretical models of the thermal structure of filament interfacesPeer reviewe

Bats of Kansas

In memory of Curtis J. Schmidt (1977-2022) Invariably, our most feared neighbors on planet earth are the animals that we know the least about. Almost as frequently, when people are exposed to these animals, the fear turns quickly to fascination. Unfortunately, many of these animals are accessible only to the professional scientist. Though science has made great strides in understanding the basic biology and behaviors of many of our least-known animals, this information is generally kept locked away from the general public by the dry, technical language of science. In this publication, it is our hope to open your eyes to the world of perhaps the last great, misunderstood group of animals-the bats. Further, it is our hope, by dispensing (as much as possible) with technical language, to bring across the intense fascination that we share for these animals and to infect you with that same fascination. In order to accomplish our task we have prepared the book in five sections. Because our main goal is to open your eyes to the fascinating world of bats, we have designed the first section to answer the most often asked questions about bats. The second provides a key to the bats of Kansas so that you can identify any bat you discover. In the third section we introduce you to the sixteen species that are known to occur in Kansas. As is the case for human neighbors, there may be bats in Kansas that we haven\u27t met yet. The fourth section describes these species of possible occurrence and tells you where to look for them. Unfortunately, we have only a limited amount of space, so the fifth section tells you how to find additional information

Current problems in Stellar Pulsation Instabilities

Instabilities of pulsating variable stars, such as Cepheid variables, Cepheid masses, early-type variable stars, White Dwarfs, and Mira variables, are discussed

Two Clusters with Radio-quiet Cooling Cores

Radio lobes inflated by active galactic nuclei at the centers of clusters are a promising candidate for halting condensation in clusters with short central cooling times because they are common in such clusters. In order to test the AGN-heating hypothesis, we obtained Chandra observations of two clusters with short central cooling times yet no evidence for AGN activity: Abell 1650 and Abell 2244. The cores of these clusters indeed appear systematically different from cores with more prominent radio emission. They do not have significant central temperature gradients, and their central entropy levels are markedly higher than in clusters with stronger radio emission, corresponding to central cooling times ~ 1 Gigayear. Also, there is no evidence for fossil X-ray cavities produced by an earlier episode of AGN heating. We suggest that either (1) the central gas has not yet cooled to the point at which feedback is necessary to prevent it from condensing, possibly because it is conductively stabilized, or (2) the gas experienced a major heating event $\gtrsim 1$ Gyr in the past and has not required feedback since then. The fact that these clusters with no evident feedback have higher central entropy and therefore longer central cooling times than clusters with obvious AGN feedback strongly suggests that AGNs supply the feedback necessary to suppress condensation in clusters with short central cooling times.Comment: ApJ Letter, in pres