FUSE Measurements of Far Ultraviolet Extinction. I. Galactic Sight Lines

We present extinction curves that include data down to far ultraviolet wavelengths (FUV; 1050 - 1200 A) for nine Galactic sight lines. The FUV extinction was measured using data from the Far Ultraviolet Spectroscopic Explorer. The sight lines were chosen for their unusual extinction properties in the infrared through the ultraviolet; that they probe a wide range of dust environments is evidenced by the large spread in their measured ratios of total-to-selective extinction, R_V = 2.43 - 3.81. We find that extrapolation of the Fitzpatrick & Massa relationship from the ultraviolet appears to be a good predictor of the FUV extinction behavior. We find that predictions of the FUV extinction based upon the Cardelli, Clayton & Mathis (CCM) dependence on R_V give mixed results. For the seven extinction curves well represented by CCM in the infrared through ultraviolet, the FUV extinction is well predicted in three sight lines, over-predicted in two sight lines, and under-predicted in 2 sight lines. A Maximum Entropy Method analysis using a simple three component grain model shows that seven of the nine sight lines in the study require a larger fraction of grain materials to be in dust when FUV extinction is included in the models. Most of the added grain material is in the form of small (radii < 200 A) grains.Comment: Accepted for publication in the Astrophysical Journal. 31 pages with 7 figure

Infrared Photometry of Red Supergiants in Young Clusters in the Magellanic Clouds

We present broad-band infrared photometry for 52 late-type supergiants in the young Magellanic Clouds clusters NGC 330, NGC 1818, NGC 2004 and NGC 2100. Standard models are seen to differ in the temperature they predict for the red supergiant population on the order of 300K. It appears that these differences most probably due to the calibration of the mixing-length parameter, $\alpha_{P}$, in the outermost layers of the stellar envelope. Due to the apparent model dependent nature of $\alpha_{P}$ we do not quantitatively compare $\alpha_{P}$ between models. Qualitatively, we find that $\alpha_{P}$ decreases with increased stellar mass within standard models. We do not find evidence for a metallicity dependence of $\alpha_{P}$.Comment: 11 pages, 4 figures. AJ accepte

Gauge Invariant Effective Lagrangian for Kaluza-Klein Modes

We construct a manifestly gauge invariant Lagrangian in 3+1 dimensions for N Kaluza-Klein modes of an SU(m) gauge theory in the bulk. For example, if the bulk is 4+1, the effective theory is \Pi_{i=1}^{N+1} SU(m)_i with N chiral (\bar{m},m) fields connecting the groups sequentially. This can be viewed as a Wilson action for a transverse lattice in x^5, and is shown explicitly to match the continuum 4+1 compactifed Lagrangian truncated in momentum space. Scale dependence of the gauge couplings is described by the standard renormalization group technique with threshold matching, leading to effective power law running. We also discuss the unitarity constraints, and chiral fermions.Comment: 21 pages, 4 figure

Radial Velocity Studies of Close Binary Stars. XI

Radial-velocity measurements and sine-curve fits to the orbital radial velocity variations are presented for ten close binary systems: DU Boo, ET Boo, TX Cnc, V1073 Cyg, HL Dra, AK Her, VW LMi, V566 Oph, TV UMi and AG Vir. By this contribution, the DDO program has reached the point of 100 published radial velocity orbits. The radial velocities have been determined using an improved fitting technique which uses rotational profiles to approximate individual peaks in broadening functions. Three systems, ET Boo, VW LMi and TV UMi, were found to be quadruple while AG Vir appears to be a spectroscopic triple. ET Boo, a member of a close visual binary with $P_{vis} = 113$ years, was previously known to be a multiple system, but we show that the second component is actually a close, non-eclipsing binary. The new observations enabled us to determine the spectroscopic orbits of the companion, non-eclipsing pairs in ET Boo and VW LMi. The particularly interesting case is VW LMi, where the period of the mutual revolution of the two spectroscopic binaries is only 355 days. While most of the studied eclipsing pairs are contact binaries, ET Boo is composed of two double-lined detached binaries and HL Dra is single-lined detached or semi-detached system. Five systems of this group were observed spectroscopically before: TX Cnc, V1073 Cyg, AK Her (as a single-lined binary), V566 Oph, AG Vir, but our new data are of much higher quality than the previous studies.Comment: Accepted by AJ, August 2006, 10 figures, 3 table

Young Clusters in the Magellanic Clouds II

We present the results of a quantitative study of the degree of extension to the boundary of the classical convective core within intermediate mass stars. The basis of our empirical study is the stellar population of four young populous clusters in the Magellanic Clouds which has been detailed in Keller, Bessell & Da Costa (2000). The sample affords a meaningful comparison with theoretical scenarios with varying degrees of convective core overshoot and binary star fraction. Two critical properties of the population, the main-sequence luminosity function and the number of evolved stars, form the basis of our comparison between the observed data set and that simulated from the stellar evolutionary models. On the basis of this comparison we conclude that the case of no convective core overshoot is excluded at a 2 sigma level.Comment: 27 pages, 12 figures, AJ accepte

Extent of hypoattenuation on CT angiography source images in Basilar Artery occlusion: prognostic value in the Basilar Artery International Cooperation Study

&lt;p&gt;&lt;b&gt;Background and Purpose:&lt;/b&gt; The posterior circulation Acute Stroke Prognosis Early CT Score (pc-ASPECTS) quantifies the extent of early ischemic changes in the posterior circulation with a 10-point grading system. We hypothesized that pc-ASPECTS applied to CT angiography source images predicts functional outcome of patients in the Basilar Artery International Cooperation Study (BASICS).&lt;/p&gt; &lt;p&gt;&lt;b&gt;Methods:&lt;/b&gt; BASICS was a prospective, observational registry of consecutive patients with acute symptomatic basilar artery occlusion. Functional outcome was assessed at 1 month. We applied pc-ASPECTS to CT angiography source images of patients with CT angiography for confirmation of basilar artery occlusion. We calculated unadjusted and adjusted risk ratios (RRs) of pc-ASPECTS dichotomized at &#8805;8 versus &#60;8. Primary outcome measure was favorable outcome (modified Rankin Scale scores 0–3). Secondary outcome measures were mortality and functional independence (modified Rankin Scale scores 0–2).&lt;/p&gt; &lt;p&gt;&lt;b&gt;Results:&lt;/b&gt; Of 158 patients included, 78 patients had a CT angiography source images pc-ASPECTS ≥8. Patients with a pc-ASPECTS ≥8 more often had a favorable outcome than patients with a pc-ASPECTS &#60;8 (crude RR, 1.7; 95% CI, 0.98–3.0). After adjustment for age, baseline National Institutes of Health Stroke Scale score, and thrombolysis, pc-ASPECTS &#8805;8 was not related to favorable outcome (RR, 1.3; 95% CI, 0.8–2.2), but it was related to reduced mortality (RR, 0.7; 95% CI, 0.5–0.98) and functional independence (RR, 2.0; 95% CI, 1.1–3.8). In post hoc analysis, pc-ASPECTS dichotomized at &#8805;6 versus &#60;6 predicted a favorable outcome (adjusted RR, 3.1; 95% CI, 1.2–7.5).&lt;/p&gt; &lt;p&gt;&lt;b&gt;Conclusions:&lt;/b&gt; pc-ASPECTS on CT angiography source images independently predicted death and functional independence at 1 month in the CT angiography subgroup of patients in the BASICS registry.&lt;/p&gt

Constraining the Unitarity Triangle with B -> V gamma

We discuss the exclusive radiative decays $B\to K^{*}\gamma$, $B \to\rho\gamma$, and $B\to\omega\gamma$ in QCD factorization within the Standard Model. The analysis is based on the heavy-quark limit of QCD. Our results for these decays are complete to next-to-leading order in QCD and to leading order in the heavy-quark limit. Special emphasis is placed on constraining the CKM-unitarity triangle from these observables. We propose a theoretically clean method to determine CKM parameters from the ratio of the $B\to\rho l\nu$ decay spectrum to the branching fraction of $B\to\rho\gamma$. The method is based on the cancellation of soft hadronic form factors in the large energy limit, which occurs in a suitable region of phase space. The ratio of the $B\to\rho\gamma$ and $B\to K^{*}\gamma$ branching fractions determines the side $R_{t}$ of the standard unitarity triangle with reduced hadronic uncertainties. The recent Babar bound on $B(B^0\to\rho^0\gamma)$ implies $R_t < 0.81 (\xi/1.3)$, with the limiting uncertainty coming only from the SU(3) breaking form factor ratio $\xi$. This constraint is already getting competitive with the constraint from $B_{s}$-$\bar B_{s}$ mixing. Phenomenological implications from isospin-breaking effects are briefly discussed.Comment: 23 pages, 8 figure