OGLE observations of four X-ray binary pulsars in the SMC

This paper presents analysis and interpretation of OGLE photometric data of four X-ray binary pulsar systems in the Small Magellanic Cloud: 1WGA J0054.9-7226, RX J0050.7-7316, RX J0049.1-7250, and 1SAX J0103.2-7209. In each case, the probable optical counterpart is identified on the basis of its optical colours. In the case of RX J0050.7-7316 the regular modulation of its optical light curve appears to reveal an ellipsoidal modulation with a period of 1.416 days. Using reasonable masses for the neutron star and the B star, we show that the amplitude and relative depths of the minima of the I-band light curve of RX J0050.7-7316 can be matched with an ellipsoidal model where the B star nearly fills its Roche lobe. For mass ratios in the range of 0.12 to 0.20, the corresponding best-fitting inclinations are about 55 degrees or larger. The neutron star would be eclipsed by the B star at inclinations larger than 60 degrees for this particular mass ratio range. Thus RX J0050.7-7316 is a good candidate system for further study. In particular, we would need additional photometry in several colours, and most importantly, radial velocity data for the B star before we could draw more quantitative conclusions about the component masses

SXP 323 - an unusual X-ray binary system in the Small Magellanic Cloud

Spectroscopic observations taken with the VLT/UVES telescope/instrument are presented of the unusual Small Magellanic Cloud (SMC) X-ray binary system SXP 323 = AX J0051-733. This system shows a clear modulation at 0.71d in long term optical photometry which has been proposed as the binary period of this system. The high resolution optical spectra, taken at a range of phases during the 0.71d cycle, rule out this possibility. Instead it is suggested that this long-term effect is due to Non Radial Pulsations (NRP) in the Be star companion to SXP 323. In addition, the spectra show clear evidence for major changes in the (V/R) ratio of the double peaks of the Balmer lines indicative of asymmetries in the circumstellar disk. The complex structure of the interstellar lines are also discussed in the context of the SMC structure.Comment: Accepted in MNRA

A Hedonic Model for Housing Prices in Wilsonville, Oregon

We estimate a hedonic model for housing prices in Wilsonville, Oregon. Our data for 197 houses is drawn from Zillow for 2014 to 2017. We find that the number of bedrooms, the square footage of the house, and whether the house is single level are statistically significant factors affecting housing prices. Location variables are also found to be statistically significant. As an example, the price of a house on the Charbonneau Golf Course is estimated to be 15% higher than the price of a house located elsewhere in Wilsonville

A major outburst from the X-ray binary RX J0520.5-6932

We report on the analysis of 8 years of MAssive Compact Halo Objects (MACHO) data for the source RX J0520.5-6932. A regular period of 24.4 days has been confirmed, however this is manifest almost entirely in the red part of the spectrum. A major outburst, lasting approximately 200 days, was observed which increased the apparent brightness of the object by approximately 0.15 magnitudes without significantly altering its V-R colour index. This outburst was also seen in X-ray data. The evidence from this analysis points to the identification of this object as a Be/X-ray binary with a periodically variable circumstellar disk and a very early optical counterpart.Comment: Paper has been accepted by MNRA

Results of recent NASA research on low-speed aerodynamic characteristics of supersonic cruise aircraft

The relatively low values of lift-curve slope produced by highly swept arrow wings, coupled with the low scrape angle of the fuselage, resulted in relatively low values of take-off and approach lift coefficients. Through the use of more efficient high-lift systems and the application of propulsive-lift concepts, it is possible to optimize the engine-airframe design for maximum range potential and also to provide good low-speed performance. Nose strakes provide significant improvements in directional stability characteristics and the use of a propulsive lateral control system provides a solution to problems associated with inherently low levels of lateral control

The X-ray Transient XTE J2012+381

We present optical and infrared observations of the soft X-ray transient (SXT) XTE J2012+381 and identify the optical counterpart with a faint red star heavily blended with a brighter foreground star. The fainter star is coincident with the radio counterpart and appears to show weak H alpha emission and to have faded between observations. The RXTE/ASM lightcurve of XTE J2012+381 is unusual for an SXT in that after an extended linear decay, it settled into a plateau state for about 40 days before undergoing a weak mini-outburst. We discuss the nature of the object and suggest similarities to long orbital period SXTs.Comment: 5 pages, 7 postscript figures included, uses mn.sty. Accepted for publication in MNRA

Long-term Properties of Accretion Disks in X-ray Binaries: II. Stability of Radiation-Driven Warping

A significant number of X-ray binaries are now known to exhibit long-term ``superorbital'' periodicities on timescales of $\sim$ 10 - 100 days. Several physical mechanisms have been proposed that give rise to such periodicities, in particular warping and/or precession of the accretion disk. Recent theoretical work predicts the stability to disk warping of X-ray binaries as a function of the mass ratio, binary radius, viscosity and accretion efficiency, and here we examine the constraints that can be placed on such models by current observations. In paper I we used a dynamic power spectrum (DPS) analysis of long-term X-ray datasets (CGRO, RXTE), focusing on the remarkable, smooth variations in the superorbital period exhibited by SMC X-1. Here we use a similar DPS analysis to investigate the stability of the superorbital periodicities in the neutron star X-ray binaries Cyg X-2, LMC X-4 and Her X-1, and thereby confront stability predictions with observation. We find that the period and nature of superorbital variations in these sources is consistent with the predictions of warping theory. We also use a dynamic lightcurve analysis to examine the behaviour of Her X-1 as it enters and leaves the 1999 Anomalous Low State (ALS). This reveals a significant phase shift some 15 cycles before the ALS, which indicates a change in the disk structure or profile leading into the ALS.Comment: 12 pages, 14 figures, Re-submitted to MNRAS after referee's comment

JeffHEALTH: Helping East Africa Link to Health

JeffHEALTH-Helping East Africa Link to Health is a student-run organization at Thomas Jefferson University dedicated to improving basic medical education and quality of life in Rwanda, which was devastated in 1994 by civil war and genocide. Working in partnership with the Rwanda Village Concept Project, a student organization at the National University of Rwanda, JeffHEALTH seeks to implement sustainable health initiatives in our partner villages. Graduate students from Thomas Jefferson University travel to Rwanda where we taught Community Health Workers from the Villages of Akarambi and Ruli the following topics: Nutrition and Vitamin Deficiencies, Family Planning, Prenatal care, HIV, Sexually Transmitted Illnesses and Hepatitis, Breast and Cervical Cancer, Diabetes, and Fistulas. We also taught two programs to children of the villages (Oral Hygiene and Soil Transmitted Helminths) and talked with young adults about Circumcision and HIV Prevention and Sex Education.https://jdc.jefferson.edu/cwicposters/1018/thumbnail.jp