522,803 research outputs found
Letter from Paul M. Roca on behalf of Carl Hayden to Ray E. Carr, Associated Civic Clubs of Southern Utah
No full textLetter from Paul M. Roca to Ray E. Carr on behalf of Carl Hayden politely declining his invitation
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
Sammy M. Ray Oral History
No full textAn oral history interview of military veteran Sammy M. Ray originally conducted under the auspices of the Library of Congress Veterans History Project
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
Ray M. Cline Letter
No full textA letter sent by Private First Class Ray M. Cline on April 16, 1943 to the First Christian Church of Morehead, Kentucky.https://scholarworks.moreheadstate.edu/mfcc_ww2_letters/1013/thumbnail.jp
XMM observation of 1RXS J180431.1-273932: a new M-type X-ray binary with a 494s period
No full textLow-mass X-ray binaries are peculiar binary systems composed of a compact object and a low-
mass star. Recently, a new class of these systems, known as symbiotic X-ray binaries (with a
neutron star with a M-type giant companion), has been discovered. Here, we present long-duration
XMM observations of the source 1RXS J180431.1-273932. Temporal and spectral analysis of the
source was performed along with a search for an optical counterpart. We used a Lomb-Scargle
periodogram analysis for the period search and evaluated the confidence level using Monte-Carlo
simulations. The source is characterized by regular pulses so that it is most likely a neutron star.
A modulation of 494.1 ± 0.2 s (3σ error) was found with a confidence level of >99%. Evidence
of variability is also present, since the data show a rate of change in the signal of ∼ −7.7 × 10 −4
counts s−1 hr−1 . A longer observation will be necessary in order to determine if the source shows
any periodic behavior. The spectrum can be described by a power law with photon index Γ ∼ 1
and a Gaussian line at 6.6 keV. The X-ray flux in the 0.2–10 keV energy band is 5.4 × 10 −12 erg
s−1 cm−2 . The identification of an optical counterpart (possibly an M6III red-giant star with an
apparent visual magnitude of 17.6) allows a conservative distance of ∼ 10 kpc to be estimated.
Other possibilities are also discussed. Once the distance was estimated, we got an X-ray luminosity
of LX < 6 × 1034 erg s−1 , which is consistent with the typical X-ray luminosity of a symbiotic
LMXB system
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
Robert B. Ray, M. D. Letterhead, undated
No full textThis blank sheet of letterhead for Robert. B. Ray, M. D.\u27s office includes the office phone number and the location, Kosciusko, Mississippi beneath Dr. Ray\u27s name.https://scholarsjunction.msstate.edu/mss-webb-collection/1360/thumbnail.jp
Double axis X-Ray rocking curves simulation
No full textDouble axis X-ray diffraction has been in use since 1920. Recently the layer structures of optoelectronic devices have been characterised to control the optical properties, for the purpose of optical communication. By the advent of modern fast computers it is now possible to simulate experimental data. Here various techniques used for calculating double axis x-ray rocking curves are described. Mismatch, tilt, and composition of layers, can be quickly deduced by simulation. This approach has been widely used in the electronics industry. Recently it has been observed that a peak shift in the active layer of a double heterostructure could lead to a miscalculation of mismatch. An investigation in this direction was made to check this effect in the active layer of a double heterostructure laser. By comparing experimental and simulated data it has been observed that a shift occurs in the active layer peak and it appears that the calculated thickness is 0.018 µ m instead of 0.016 µ m of active layer of the laser. It is suggested that this peak shift could be studied in graded and multiple layer structures. The interactive part of SARCA programme which is a modification of CURVES programme needed changes to accept data for reflection (h,k,l) and accept data of material for entry of mixed mode of letters, to avoid unnecessary consumption of time. For this purpose two programmes in Pascal have been written. There is also much possibility of modelling double axis x-ray diffraction rocking curve profile
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