Constraining the Envelope Structure of L1527 IRS: Infrared Scattered Light Modeling

We model Spitzer Space Telescope observations of the Taurus Class 0 protostar L1527 IRS (IRAS 04368+2557) to provide constraints on its protostellar envelope structure. The nearly edge-on inclination of L1527 IRS, coupled with the highly spatially-resolved near to mid-infrared images of this object and the detailed IRS spectrum, enable us to constrain the outflow cavity geometry quite well, reducing uncertainties in the other derived parameters. The mid-infrared scattered light image shows a bright central source within a dark lane; the aspect ratio of this dark lane is such that it appears highly unlikely to be a disk shadow. In modeling this dark lane, we conclude that L1527 IRS is probably not described by a standard TSC envelope with simple bipolar cavities. We find it necessary to model the dark lane and central source as a modified inner envelope structure. This structure may be due either to a complex wind-envelope interaction or induced by the central binary. To fit the overall SED, we require the central source to have a large near to mid-infrared excess, suggesting substantial disk accretion. Our model reproduces the overall morphology and surface brightness distribution of L1527 IRS fairly well, given the limitations of using axisymmetric models to fit the non-axisymmetric real object, and the derived envelope infall rates are in reasonable agreement with some other investigations. IRAC observations of L1527 IRS taken 12 months apart show variability in total flux and variability in the opposing bipolar cavities, suggesting asymmetric variations in accretion. We also provide model images at high resolution for comparison to future observations with current ground-based instrumentation and future space-based telescopes.Comment: 50 pages, 14 figures 2 tables, accepted by the Astrophysical Journal. The manuscript with full resolution figures can be downloaded from http://astro.lsa.umich.edu/~jjtobin/L1527.pd

Weak Coherent State Path Integrals

Weak coherent states share many properties of the usual coherent states, but do not admit a resolution of unity expressed in terms of a local integral. They arise e.g. in the case that a group acts on an inadmissible fiducial vector. Motivated by the recent Affine Quantum Gravity Program, the present article studies the path integral representation of the affine weak coherent state matrix elements of the unitary time-evolution operator. Since weak coherent states do not admit a resolution of unity, it is clear that the standard way of constructing a path integral, by time slicing, is predestined to fail. Instead a well-defined path integral with Wiener measure, based on a continuous-time regularization, is used to approach this problem. The dynamics is rigorously established for linear Hamiltonians, and the difficulties presented by more general Hamiltonians are addressed.Comment: 21 pages, no figures, accepted by J. Math. Phy

Early focus development effort, ultrasonic inspection of fixed housing metal-to-adhesive bondline

An ultrasonic technique was developed for the fixed housing metal-to-adhesive bondline that will support the Flight 15 time frame and subsequent motors. The technique has the capability to detect a 1.0 inch diameter unbond with a 90 percent probability of detection (POD) at a 95 percent confidence level. The technique and support equipment will perform within the working envelope dictated by a stacked motor configuration

The influence of agitation on a continuous counter-current liquid-liquid extraction column

This work presents operating data and correlations of agitated extraction equipment studied under continuous counter-current flow. The experimental work was carried out in at agitated column 36 inches in length with an internal diameter of 2 inches using the system toluene, benzoic acid and water. The working section of the column was 24 inches. The design of the column used for the experimental work is similar to that proposed in a patent by van Dijck (3). The column is similar only to the extent that the patent covers numerous conditions of vertical agitation. The distribution data and the equilibrium solubility curve were determined by Appel and Elgin (1). The experimental results obtained indicate that an agitated counter-current extraction column possesses a number of advantages over its stationary counterpart. Agitation increases the efficiency of a liquid liquid extraction column and by proper control of agitation the extraction coefficient can be made nearly independent of the dispersed phase flow rate. The results obtained also made possible the derivation of an empirical equation correlating H.T.U., agitation and thruput for the system benzoic acid, toluene and water. (H.T.U.)= 33.4/T (2.73 - Log10 R.P.M.

Recreation of twenty patients of the state hospital for mental diseases at Howard, Rhode Island.

Thesis (M.S.)--Boston Universit