The Orbital Period of the Be/Neutron Star Binary RX J0812.4-3114

We present the results of Rossi X-ray Timing Explorer observations of the Be star X-ray binary system RX J0812.4-3114. A light curve obtained with the RXTE All-Sky Monitor shows that the source is currently in an active state with outbursts occurring at approximately 80 day intervals. The source underwent a transition from an inactive state to this regular outburst state early in 1998. An observation of RX J0812.4-3114 was obtained with the RXTE Proportional Counter Array close to the time of a predicted maximum in March 1999 and strong pulsations were detected at a period of 31.88 seconds. This confirms the result of an earlier PCA observation by Reig & Roche which was serendipitously also obtained near the predicted maximum flux of the 80 day period and also near the start of the current active state. We interpret the periodicity in the ASM light curve as indicating the orbital period of RX J0812.4-3114 with outbursts occurring around periastron passage

Phase vortices from a Young's three-pinhole interferometer

An analysis is presented of the phase vortices generated in the far field, by an arbitrary arrangement of three monochromatic point sources of complex spherical waves. In contrast with the case of three interfering plane waves, in which an infinitely-extended vortex lattice is generated, the spherical sources generate a finite number of phase vortices. Analytical expressions for the vortex core locations are developed and shown to have a convenient representation in a discrete parameter space. Our analysis may be mapped onto the case of a coherently-illuminated Young's interferometer, in which the screen is punctured by three rather than two pinholes.Comment: 10 pages, 8 figures, REVTeX4, Submitted to Phys. Rev.

Iterative image reconstruction algorithms using wave-front intensity and phase variation,”

Iterative algorithms that reconstruct images from far-field x-ray diffraction data are plagued with convergence difficulties. An iterative image reconstruction algorithm is described that ameliorates these convergence difficulties through the use of diffraction data obtained with illumination modulated in both intensity and phase

4U2206+54 - an Unusual High Mass X-ray Binary with a 9.6 Day Orbital Period but No Strong Pulsations

Rossi X-ray Timing Explorer All-Sky Monitor observations of the X-ray source 4U2206+54, previously proposed to be a Be star system, show the X-ray flux to be modulated with a period of approximately 9.6 days. If the modulation is due to orbital variability then this would be one of the shortest orbital periods known for a Be star X-ray source. However, the X-ray luminosity is relatively modest whereas a high luminosity would be predicted if the system contains a neutron star accreting from the denser inner regions of a Be star envelope. Although a 392s pulse period was previously reported from EXOSAT observations, a reexamination of the EXOSAT light curves does not show this or any other periodicity. An analysis of archival RXTE Proportional Counter Array observations also fails to show any X-ray pulsations. We consider possible models that may explain the properties of this source including a neutron star with accretion halted at the magnetosphere and an accreting white dwarf.Comment: Accepted for publication in the Astrophysical Journa

Evidence for a very slow X-ray pulsar in 2S0114+650 from RXTE All-Sky Monitor Observations

Rossi X-ray Timing Explorer (RXTE) All-Sky Monitor (ASM) observations of the X-ray binary 2S0114+650 show modulations at periods close to both the optically derived orbital period (11.591 days) and proposed pulse period (~ 2.7 hr). The pulse period shows frequency and intensity variability during the more than 2 years of ASM observations analyzed. The pulse properties are consistent with this arising from accretion onto a rotating neutron star and this would be the slowest such period known. The shape of the orbital light curve shows modulation over the course of the entire orbit and a comparison is made with the orbital light curve of Vela X-1. However, the expected phase of eclipse, based on an extrapolation of the optical ephemeris, does not correspond with the observed orbital minimum. The orbital period derived from the ASM light curve is also slightly longer than the optical period.Comment: To be published in the Astrophysical Journal, 1999, volume 511. 9 figure

Unique phase recovery for nonperiodic objects

It is well known that the loss of phase information at detection means that a diffraction pattern may be consistent with a multitude of physically different structures. This Letter shows that it is possible to perform unique structural determination in the absence of a priori information using x-ray fields with phase curvature. We argue that significant phase curvature is already available using modern x-ray optics and we demonstrate an algorithm that allows the phase to be recovered uniquely and reliably. DOI: 10.1103/PhysRevLett.91.203902 PACS numbers: 42.30.Rx, 41.50.+h, 61.10.Nz, 87.10.+e Since the discovery of the laws describing the diffraction of x rays by crystals, x-ray diffraction has played a pivotal role in developing an understanding of the physics of materials and is a central technique of modern structural biology. The development of very high-brightness x-ray sources, such as third-generation synchrotron sources, enables diffraction data to be acquired from ever-smaller samples. The loss of phase information at measurement may be compensated by introducing additional information via, for example, atomicity assumptions in direct methods The diffraction imaging work of Miao et al. [5], following on from the ideas of Sayre and colleagues Recent work has shown that noninterferometric phase recovery is possible in real space for x rays [10], along with other forms of waves Suppose a coherent x-ray wave, inc r r; z, wherer r is a two-dimensional vector, strikes a finite sample and produces a diffracted wave diff . The sample is assumed to be sufficiently small so that the diffracted field is detected in the far field and its diffracting properties are contained in its 3D scattering potential, Vr r; z. In the far field, diff r r; z ! diff r , where r is the distance of the observation point from the detector point, x ; y ; 1 ÿ 2 x ÿ 2 y q is the unit vector in the direction of propagation, and we define x ; y . As a very small sample will only diffract x rays weakly, we adopt the Born approximation so that the diffracted wave is described by diff r inc r f r ; where where k 0 2=, and is the wavelength. In the P H Y S I C A

Impact mass flow sensor for monitoring peanut harvest yields

Yield monitoring systems for harvesting machines and methods that can provide yield monitoring of crops are described. Machines include those that pneumatically convey crop through the machine such as peanut harvesting machines. The yield monitoring system includes a force sensor that can be located in conjunction with a duct of the harvesting machine such that impact of the crop materials on an impact plate within the duct will be registered by the force sensor. This registration can be used to determine a mass flow rate for the crop, which can be correlated to yield of the crop. The systems can include additional components such as optical monitors, moisture sensors, and pressure sensors

Partnerships to Address School Safety through a Student Support Lens

School safety is a primary concern of school leaders, employees, parents, and a variety of community stakeholders. Attempts to mitigate and prevent school safety concerns often focus on strategies around school climate assessment, emergency communication, school safety plan development, and school resource officer employment (U.S. DHS et al., 2018). Involvement of key stakeholders, such as school social workers, school counselors, and school-based mental health professionals is emphasized in creating and assessing school safety in a wholistic manner. This article provides an overview of a Trainings to Increase School Safety grant program that was implemented with public school stakeholders through partnerships between a university and five public school districts in the Southeastern North Carolina region