The Diversity of Type Ia Supernovae from Broken Symmetries

Type Ia supernovae result when carbon-oxygen white dwarfs in binary systems accrete mass from companion stars, reach a critical mass, and explode. The near uniformity of their light curves makes these supernovae good standard candles for measuring cosmic expansion, but a correction must be applied to account for the fact that the brighter supernovae have broader light curves. One-dimensional modelling, with a certain choice of parameters, can reproduce this general trend in the width-luminosity relation, but the processes of ignition and detonation have recently been shown to be intrinsically asymmetric. Here we report on multi-dimensional modelling of the explosion physics and radiative transfer that reveals that the breaking of spherical symmetry is a critical factor in determining both the width luminosity relation and the observed scatter about it. The deviation from sphericity can also explain the finite polarization detected in the light from some supernovae. The slope and normalization of the width-luminosity relation has a weak dependence on certain properties of the white dwarf progenitor, in particular the trace abundances of elements other than carbon and oxygen. Failing to correct for this effect could lead to systematic overestimates of up to 2% in the distance to remote supernovae.Comment: Accepted to Natur

Investigations with satellite data temperature retrievals

A method is presented for using satellite measurements to interpolate vertical temperature soundings between radiosonde stations. The method finds a set of coefficients, which when multiplied by corresponding measured radiance quantities, yield zero temperature error at a radiosonde station. This derived set of coefficients is then applied to satellite radiance measurements at places between radiosonde stations. The computations show, for example, that the average absolute error in the layer 1000-800 mbs is only 0.3K when the corresponding 'minimum-information' method error was 2.9K. The method may be most applicable to measurements from geostationary satellites, but should also be applicable to measurements from polar orbiting satellites under certain conditions

Hubble Space Telescope Fine Guidance Sensor Parallaxes For Four Classical Novae

We have used data obtained with the Fine Guidance Sensors on the Hubble Space Telescope to derive precise astrometric parallaxes for four classical novae: V603 Aql, DQ Her, GK Per, and RR Pic. All four objects exceeded the Eddington limit at visual maximum. Re-examination of the original light curve data for V603 Aql and GK Per has led us to conclude that their visual maxima were slightly brighter than commonly assumed. With known distances, we examine the various maximum magnitude-rate of decline relationships that have been established for classical novae. We find that these four objects show a similar level of scatter about these relationships as seen in larger samples of novae whose distances were determined using indirect techniques. We also examine the nebular expansion parallax method and find that it fails for three of the four objects. In each case it was possible to find an explanation for the failure of that technique to give precise distance estimates. DQ Her appears to suffer from an anomalously high extinction when compared to field stars on its sight line. We suggest that this is likely due to local material, which may also be the source of the IRAS detections of this object.NASA from the Space Telescope Science Institute AR12617NASA NAS 5-26555McDonald Observator

The Internal Proper Motions Of Stars In The Open Cluster M35

Relative proper motions, based on 108 orbits of Hubble Space Telescope Fine Guidance Sensor data extending from 1992 to 2006, are reported for 74 stars in the open cluster M35 (NGC 2168). A subset of 22 of these objects are then used to compute the cluster's internal proper motion dispersions in both right ascension and declination. We find that these dispersions are equal to within their measurement errors. The average one-dimensional dispersion is 0.018 +/- 0.002 arcsec century(-1). When combined with the M35 radial velocity dispersion of 0.65 +/- 0.10 km s(-1) found by Geller et al., this produces a cluster distance of 762 +/- 145 pc. Using isochrone fits to the cluster main sequence, this distance suggests that M35 has an age of about 133 Myr. Although this age is consistent with that typically found for M35, the formal error in the dynamical distance of +/- 19% can accommodate ages between 65 Myr and 201 Myr.McDonald Observator

Manufacturing Mechatronics Using Thermal Spray Shape Deposition

A new technology for manufacturing mechatronics is described. The technique is based on recursive masking and deposition of thermally sprayed materials. Using these methods, mechanical structures can be created that embed and interconnect electronic components. This results in highly integrated mechatronic devices. A simple, electromechanical artifact was designed and produced to assess the feasibility of these techniques. The details and limitations of this project will be discussed. Areas of future research are identified which are aimed at realizing the full potential of this emerging manufacturing process.Mechanical Engineerin

X-Ray Microanalysis of Diffusible Elements in Plant Cells After Freeze-Drying, Pressure-Infiltration with Ether and Embedding in Plastic

The technique of vacuum-pressure infiltration of freeze-dried plant tissues with diethyl ether and plastic, originally developed for the cellular localization of water-soluble 14C-assimilates, proved to be suitable for X-ray microanalysis of diffusible elements at the sub-cellular level. Apart from movements of elements caused by ice crystal formation and collapse of eutectic structures several lines of evidence suggest that additional dislocations of elements during the preparation were minimal: (1) Soluble Ca remained evenly distributed in vacuoles, (2) the contents of K relative to Ca were the same at different sites within a vacuole, (3) the relative vacuolar Ca-contents of different leaves, determined by X-ray microanalysis, corresponded to the relative Ca-contents of pressed saps of the same leaves as analyzed by atomic absorption spectrometry