70,177 research outputs found
A 2 h periodic variation in the low-mass X-ray binary Ser X-1
No full textSpectroscopy of the low-mass X-ray binary Ser X-1 using the Gran Telescopio Canarias have revealed a ?2 h periodic variability that is present in the three strongest emission lines. We tentatively interpret this variability as due to orbital motion, making it the first indication of the orbital period of Ser X-1. Together with the fact that the emission lines are remarkably narrow, but still resolved, we show that a main-sequence K dwarf together with a canonical 1.4 M? neutron star gives a good description of the system. In this scenario, the most likely place for the emission lines to arise is the accretion disc, instead of a localized region in the binary (such as the irradiated surface or the stream-impact point), and their narrowness is due instead to the low inclination (?10°) of Ser X-1
[Report to W. P. Gannaway by P. M. Parks, February 10, 1964 #2]
No full textIntelligence report addressed to W. P. Gannaway of the Dallas Police Department's Special Service Bureau. The report, which was submitted by detective P. M. Parks, states that Brenda Ray is married to W. G. Abbotts, who is the step-son of Gerald Ray. Brenda Ray and her husband travel with a carnival
New insights on accretion in supergiant fast X-ray transients from XMM-Newton and INTEGRAL observations of IGR J17544-2619
No full textXMM–Newton observations of the supergiant fast X-ray transient IGR J17544?2619 are reported and placed in the context of an analysis of archival INTEGRAL/IBIS data that provide a refined estimate of the orbital period at 4.9272?±?0.0004?d. A complete outburst history across the INTEGRAL mission is reported. Although the new XMM–Newton observations (each lasting ?15 ks) targeted the peak flux in the phase-folded hard X-ray light curve of IGR J17544?2619, no bright outbursts were observed, the source spending the majority of the exposure at intermediate luminosities of the order of several 1033?erg?s?1 (0.5–10 keV) and displaying only low level flickering activity. For the final portion of the exposure, the luminosity of IGR J17544?2619 dropped to ?4?×?1032?erg?s?1 (0.5–10 keV), comparable with the lowest luminosities ever detected from this source, despite the observations being taken near to periastron. We consider the possible orbital geometry of IGR J17544?2619 and the implications for the nature of the mass transfer and accretion mechanisms for both IGR J17544?2619 and the supergiant fast X-ray transients (SFXTs) population. We conclude that accretion under the ‘quasi-spherical accretion’ model provides a good description of the behaviour of IGR J17544?2619 and suggests an additional mechanism for generating outbursts based upon the mass accumulation rate in the hot shell (atmosphere) that forms around the neutron star under the quasi-spherical formulation. Hence, we hope to aid in explaining the varied outburst behaviours observed across the SFXT population with a consistent underlying physical model
Frank (Fred?) McDonald, M. W. and T. T at Foret, Romare
No full textThis record was harvested from a previous catalogue system and will be withdrawn in 2025. Information in this record may be superseded or incomplete. Visit this record in UMA's new catalogue at: https://archives.library.unimelb.edu.au/nodes/view/247626170909
Item: [1981.0081.00021] "Frank (Fred?) McDonald, M. W. and T. T at Foret, Romare
Ray W. Hamilton
No full textThe Oklahoma A&M College World War I Veterans collection captures the memories and experiences of the men and women of Oklahoma Agricultural and Mechanical College who served in World War I. In 1919, a project headed by Maude Cass, the editor of the 1919 Redskin; Professor Maroney of the Department of History; Margaret Walters, Librarian; and J.W. Cantwell, the College President, was undertaken to survey these veterans. The surveys were returned along with photographs, letters, and newspaper clippings documenting these veterans’ experiences during World War I
Novel spectral-timing methods for X-ray binary variability studies
No full textThis work explores the connection between the spectral properties of the X-ray emission produced by black hole X-ray binaries (BHXRBs) and the variability properties of these sources that are embedded in light curves. While BHXRBs are mostly studied using ‘static observables‘ such as the average energy spectrum, a variability timescale-resolved study (in terms of Fourier-frequencies) provides a much stronger and more reliable tool for understanding the intricate physics and geometrical properties of accretion flows around stellar-mass black holes.In the present Thesis, we first show how the geometrical properties of the accretion disc can be mapped by combining spectra and frequency-resolved time-lags. A time-scale-dependent reflection model is developed in terms of Fourier-frequencies and compared to observational hard-state data of GX 339–4 obtained with XMM-Newton. Secondly, we explore the variability properties of the accretion disc in SWIFT J1753.5–0127 using a combination of novel spectral timing methods and the soft X-ray coverage of XMM-Newton. Finally, we show the development of a novel technique for fitting correlated signals in the Fourier domain as a function of energy and Fourier-frequency that can prove particularly useful with high signal-to-noise datasets from future X-ray missions
Time Resolved Two Dimensional X-Ray Densitometry of a Two Phase Flow Downstream of a Ventilated Cavity
No full textTo measure the void fraction distribution in gas-liquid flows, a two-dimensional x-ray densitometry system was developed. This system is capable of acquiring a two-dimensional projection with a 225 cm2 area of measurement through 21 cm of water. The images can be acquired at rates on the order of 1 kHz. Common sources of error in x-ray imaging, such as x-ray scatter, image distortion, veiling glare, and beam hardening were considered, and mitigated. The measured average void fraction was compared success fully to that of a phantom target and found to be within 1%. To evaluate the performance of the new system, the flow in and downstream of a ventilated nominally two-dimensional partial cavity was investigated and compared to measurements from dual tip fiber optical probes and high speed video. The measurements were found to have satisfactory agreement for void fractions above 5% of the selected void fraction measurement range.Office of Naval Research under grant N00014-10-1-097
Development and optimisation of supercritical fluid deposition of semiconductor films
No full textThis thesis is concerned with the deposition, and characterisation, of semiconductor thin films and microstructures deposited from a supercritical fluid. Thin films of CdS, GaP, InP, InAs, and Ge were deposited using supercritical CO2 and CO2-solvent mixtures. Ge was deposited into macropores etched into crystalline silicon substrates. A variety of reactors were designed in order to achieve the successful deposition of the materials. The surface morphology and crystallinity of the films were characterised by scanning electron microscopy and X-ray diffraction. The chemical composition of the films was analysed by energy or wavelength dispersive X-ray spectroscopy, secondary ion mass spectroscopy, Auger electron spectroscopy, and X-ray photoelectron spectroscopy. The optoelectronic quality of the CdS and InP films was analysed by photoluminescence spectroscopy and mapping. The CdS films deposited were confirmed to be of hexagonal phase by X-ray diffraction and exhibited band edge luminescence. The InP and InAs films were determined to be of cubic structure and the InP films were found to exhibit weak band edge luminescence. The fabrication of macroporous silicon templates by photoelectrochemical etching is also discussed. Pores with diameters of between 60 nm and 2 µm were fabricated, having aspect ratios of up to 100:1. Ge was successfully deposited into macropores etched into these crystalline silicon templates with near conformal coverage
Letter to Cyrus S. Avery (and W. M. Trotter) from W. S. Key (by Ray Lindsey) dated November 27, 1935
No full textLetter to Cyrus S. Avery (and W. M. Trotter) from W. S. Key (by Ray Lindsey) dated November 27, 1935The Cyrus S. Avery Collection chronicles the life and times of Cyrus Stevens Avery. Known as the 'Father of Route 66', Avery served in government positions and elected offices as well as in highway associations that led him to have an influential impact on the planning and development of the initial American highway system. Through Avery's involvement with the City of Tulsa, Oklahoma and his own agricultural interests, the collection also documents a growing city and its' rural life in the early twentieth century
Relations between x-ray timing features and spectral parameters of galactic black hole x-ray binaries
No full textWe present a study of correlations between spectral and timing parameters for a sample of black hole X-ray binary candidates. Data are taken from GX
339-4, H 1743-322, and XTE J1650-500, as the Rossi X-ray Timing Explorer
(RXTE) observed complete outbursts of these sources. In our study we investigate outbursts that happened before the end of 2009 to make use of the high-energy coverage of the HEXTE detector and select observations that
show a certain type of quasi-periodic oscillations (type-C QPOs). The spectral parameters are derived using the empirical convolution model simpl to model the Comptonized component of the emission together with a disc blackbody for the emission of the accretion disc. Additional spectral features, namely a reflection component, a high-energy cut-off, and excess emission at 6.4 keV, are taken into account. Our investigations confirm the known positive
correlation between photon index and centroid frequency of the QPOs and reveal an anti-correlation between the fraction of up-scattered photons and the QPO frequency. We show that both correlations behave as expected in the “sombrero”
geometry. Furthermore, we find that during outburst decay the correlation between photon index and QPO frequency follow a general track, independent of individual outbursts
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