Effects of Spin on High-Energy Radiation from Accreting Black Holes

Observations of jets in X-ray binaries show a correlation between radio power and black hole spin. This correlation, if confirmed, points towards the idea that relativistic jets may be powered by the rotational energy of black holes. In order to examine this further, we perform general-relativistic radiative transport calculations on magnetically arrested accretion flows, which are known to produce powerful jets via the Blandford-Znajek (BZ) mechanism. We find that the X-ray and gamma-ray emission strongly depend on spin and inclination angle. Surprisingly, the high-energy power does not show the same dependence on spin as the BZ jet power, but instead can be understood as a redshift effect. In particular, photons observed perpendicular to the spin axis suffer little net redshift until originating from close to the horizon. Such observers see deeper into the hot, dense, highly-magnetized inner disk region. This effect is largest for rapidly rotating black holes due to a combination of frame dragging and decreasing horizon radius. While the X-ray emission is dominated by the near horizon region, the near-infrared radiation originates at larger radii. Therefore, the ratio of X-ray to near-infrared power is an observational signature of black hole spin.Comment: 15 pages, 13 figures, added panel in Figure 4 showing viewing angle dependence and extended the discussion in Section 4, accepted for publication in Ap

Early Childhood Overweight and Obesity in Multigenerational Households

This study investigates grandmothers’ role in the health of their grandchildren. The relationship between child weight status from ages three to nine and grandmothers’ coresidence up to age nine is examined using data from The Fragile Families and Wellbeing Study, a large nationally representative dataset of urban low-income families in the United States. Logistic regression estimates the association between grandmother coresidence and child unhealthy weight status. Analyses adjust for child and mother characteristics, culture, race/ethnicity, SES, parenting practices, and built environment. Children who have ever lived with a grandmother by age three are at increased odds of unhealthy weight at age three, even after controlling for contributing factors. Grandmothers’ influence on weight gain in three year olds appears to fade by age nine. Findings indicate that grandmothers’ presence may present risks for three year olds’ health in situations of coresidence and should be further explored in future research. Explanations for this association are pursued

Summary of drag clean-up tests in NASA Langley full-scale tunnel

This summary of drag results presents tabulations on fighter aircraft and light twin general aviation aircraft wind tunnel tests. The figures show that the friction drag for light twins is larger than that for the fighters because of the greater wetted area and the smaller wing area used for reference. Full scale tunnel tests developed the following design features contributing to excessive drag: cooling flow system, engine exhaust stacks, landing gears, control surface gaps, and wing irregularities and leakages

Analysis of means of improving the uncontrolled lateral motions of personal airplanes

A theoretical analysis has been made of means of improving the uncontrolled motions of personal airplanes. The purpose of this investigation was to determine whether such airplanes could be made to fly uncontrolled for an indefinite period of time without getting into dangerous attitudes and for a reasonable period of time (1 to 3 min) without deviating excessively from their original course. The results of this analysis indicated that the uncontrolled motions of a personal airplane could be made safe as regards spiral tendencies and could be greatly improved as regards maintenance of course without resort to an autopilot. The only way to make the uncontrolled motions completely satisfactory as regards continuous maintenance of course, however, is to use a conventional type of autopilot