Unveiling Su Aurigae in the near Infrared: New high spatial resolution results using Adaptive Optics

We present here new results on circumstellar nebulosity around SU Aurigae, a T-Tauri star of about 2 solar mass and 5 Myrs old at 152 pc in the J, H and K bands using high resolution adaptive optics imaging (0\farcs30) with the Penn state IR Imaging Spectrograph (PIRIS) at the 100 inch Mt. Wilson telescope. A comparison with HST STIS optical (0.2 to 1.1 micron) images shows that the orientation of the circumstellar nebulosity in the near-IR extends from PAs 210 to 270 degrees in H and K bands and up to 300 degrees in the J band. We call the circumstellar nebulosity seen between 210 to 270 degrees as 'IR nebulosity'. We find that the IR nebulosity (which extends up to 3.5 arcsecs in J band and 2.5 arcsecs in the K band) is due to scattered light from the central star. The IR nebulosity is either a cavity formed by the stellar outflows or part of the circumstellar disk. We present a schematic 3-dimensional geometrical model of the disk and jet of SU Aur based on STIS and our near-IR observations. According to this model the IR nebulosity is a part of the circumstellar disk seen at high inclination angles. The extension of the IR nebulosity is consistent with estimates of the disk diameter of 50 to 400 AU in radius, from earlier mm, K band interferometric observations and SED fittings.Comment: Accepted for publications in the Astronomical Journal, to appear in the May issue of the Journa

Cryptoendolith colonization of diverse substrates (1): cultivation and characterization

We are investigating whether cryptoendolithic microorganisms are able to colonize diverse substrates through biogenic weathering. This first part of the study involves the cultivation and characterization of microbial consortia from Antarctic sandstone habitats

Alteration of the Nakhlite Lava Pile: was water on the surface, seeping down, or at depth, percolating up? Evidence (such as it is) from carbonates

We present carbon and oxygen isotope data on carbonates in five nakhlites and use the results to interpret the martian weathering processes

LkHα\alpha 330: Evidence for dust clearing through resolved submillimeter imaging

Mid-infrared spectrophotometric observations have revealed a small sub-class of circumstellar disks with spectral energy distributions (SEDs) suggestive of large inner gaps with low dust content. However, such data provide only an indirect and model dependent method of finding central holes. We present here the direct characterization of a 40 AU radius inner gap in the disk around LkHa 330 through 340 GHz (880 micron) dust continuum imaging with the Submillimeter Array (SMA). This large gap is fully resolved by the SMA observations and mostly empty of dust with less than 1.3 x 10^-6 M_solar of solid particles inside of 40 AU. Gas (as traced by accretion markers and CO M-band emission) is still present in the inner disk and the outer edge of the gap rises steeply -- features in better agreement with the underlying cause being gravitational perturbation than a more gradual process such as grain growth. Importantly, the good agreement of the spatially resolved data and spectrophometry-based model lends confidence to current interpretations of SEDs with significant dust emission deficits as arising from disks with inner gaps or holes. Further SED-based searches can therefore be expected to yield numerous additional candidates that can be examined at high spatial resolution.Comment: 11 pages, 3 figures, accepted to ApJ

Can a Logarithmically Running Coupling Mimic a String Tension?

It is shown that a Coulomb potential using a running coupling slightly modified from the perturbative form can produce an interquark potential that appears nearly linear over a large distance range. Recent high-statistics SU(2) lattice gauge theory data fit well to this potential without the need for a linear string-tension term. This calls into question the accuracy of string tension measurements which are based on the assumption of a constant coefficient for the Coulomb term. It also opens up the possibility of obtaining an effectively confining potential from gluon exchange alone.Comment: 13 pages, LaTeX, two figures not included, available from author. revision - Line lengths fixed so it will tex properl

Were Presolar Grains Destroyed by the Nebular Process Responsible for the Volatile Element Fractionation?

We present SiC abundances from a number of CM and CR chondrites using NanoSIMS raster ion imaging of acid residues. We find higher SiC abundances for CRs than previously estimated based on noble gases

A Partition of Unity Method for Divergence-Free or Curl-Free Radial Basis Function Approximation

Divergence-free (div-free) and curl-free vector fields are pervasive in many areas of science and engineering, from fluid dynamics to electromagnetism. A common problem that arises in applications is that of constructing smooth approximants to these vector fields and/or their potentials based only on discrete samples. Additionally, it is often necessary that the vector approximants preserve the div-free or curl-free properties of the field to maintain certain physical constraints. Div/curl-free radial basis functions (RBFs) are a particularly good choice for this application as they are meshfree and analytically satisfy the div-free or curl-free property. However, this method can be computationally expensive due to its global nature. In this paper, we develop a technique for bypassing this issue that combines div/curl-free RBFs in a partition of unity framework, where one solves for local approximants over subsets of the global samples and then blends them together to form a div-free or curl-free global approximant. The method is applicable to div/curl-free vector fields in ℝ2 and tangential fields on two-dimensional surfaces, such as the sphere, and the curl-free method can be generalized to vector fields in ℝd. The method also produces an approximant for the scalar potential of the underlying sampled field. We present error estimates and demonstrate the effectiveness of the method on several test problems

Recent Trends in Heat-Related Mortality in the United States: An Update Through 2018

Much research has shown a general decrease in the negative health response to extreme heat events in recent decades. With a society that is growing older, and a climate that is warming, whether this trend can continue is an open question. Using eight additional years of mortality data, we extend our previous research to explore trends in heat-related mortality across the United States. For the period 1975–2018, we examined the mortality associated with extreme-heat-event days across the 107 largest metropolitan areas. Mortality response was assessed over a cumulative 10-day lag period following events that were defined using thresholds of the excess heat factor, using a distributed-lag nonlinear model. We analyzed total mortality and subsets of age and sex. Our results show that in the past decade there is heterogeneity in the trends of heat-related human mortality. The decrease in heat vulnerability continues among those 65 and older across most of the country, which may be associated with improved messaging and increased awareness. These decreases are offset in many locations by an increase in mortality among men 45–64 (+1.3 deaths per year), particularly across parts of the southern and southwestern United States. As heat-warning messaging broadly identifies the elderly as the most vulnerable group, the results here suggest that differences in risk perception may play a role. Further, an increase in the number of heat events over the past decade across the United States may have contributed to the end of a decades-long downward trend in the estimated number of heat-related fatalities