4,314 research outputs found
AX J0049.4-7323 - a close look at a neutron star interacting with a circumstellar disk
Detailed evidence on the system AX J0049.4-7323 is presented here to show how
the passage of the neutron star in the binary system disrupts the circumstellar
disk of the mass donor Be star. A similar effect is noted in three other
Be/X-ray binary systems. Together the observational data should provide
valuable tools for modelling these complex interactions.Comment: 4 pages, accepted for publication in MNRA
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
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 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
Performance of 75-millimeter-bore bearings using electron-beam-welded hollow balls with a diameter ratio of 1.26
An experimental investigation was performed to determine the rolling element fatigue life of electron beam-welded hollow balls with a diameter ratio (o.d./i.d.) of 1.26 and to determine the operating characteristics of bearings using these hollow balls. Similar bearings with solid balls were also tested and the data compared. The bearings were operated at shaft speeds up to 28,000 rpm with a thrust load of 2200 N (500 lb). Ball failures during the bearing tests were due to flexure fatigue. The solid and hollow ball bearings tested showed little difference in outer race temperatures and indicated the same bearing torque. The 17.5-mm (0.6875-in.) diameter balls were also tested in the five-ball fatigue tester and showed no significant difference in life when compared with the life of a solid ball
Series-hybrid bearing - An approach to extending bearing fatigue life at high speeds
Fluid film bearing of hybrid device consists of orifice compensated annular thrust bearing and self-acting journal bearing. In series hybrid bearing, both ball bearing and annular thrust bearing carry full system thrust load, but two bearings share speed. Operation of system is stable and automatically fail-safe
Leading-edge deflection optimization for a highly swept arrow wing configuration
Tests were also conducted to determine the sensitivity of the lateral stability derivative C sub l sub beta to geometric anhedral. The optimized leading edge deflection was developed by aligning the leading edge with the incoming flow along the entire span. Owing to the spanwise variation of upwash, the resulting optimized leading edge was a smooth, continuously warped surface. For the particular configuration studied, levels of leading edge suction on the order of 90 percent were achieved with the smooth, continuously warped leading edge contour. The results of tests conducted to determine the sensitivity of C sub l sub beta to geometric anhedral indicate values of delta C sub l sub beta/delta T which are in reasonable agreement with estimates provided by simple vortex lattice theories
Swift J053041.9-665426, a new Be/X-ray binary pulsar in the Large Magellanic Cloud
We observed the newly discovered X-ray source Swift J053041.9-665426 in the
X-ray and optical regime to confirm its proposed nature as a high mass X-ray
binary. We obtained XMM-Newton and Swift X-ray data, along with optical
observations with the ESO Faint Object Spectrograph, to investigate the
spectral and temporal characteristics of Swift J053041.9-665426. The XMM-Newton
data show coherent X-ray pulsations with a period of 28.77521(10) s (1 sigma).
The X-ray spectrum can be modelled by an absorbed power law with photon index
within the range 0.76 to 0.87. The addition of a black body component increases
the quality of the fit but also leads to strong dependences of the photon
index, black-body temperature and absorption column density. We identified the
only optical counterpart within the error circle of XMM-Newton at an angular
distance of ~0.8 arcsec, which is 2MASS J05304215-6654303. We performed optical
spectroscopy from which we classify the companion as a B0-1.5Ve star. The X-ray
pulsations and long-term variability, as well as the properties of the optical
counterpart, confirm that Swift J053041.9-665426 is a new Be/X-ray binary
pulsar in the Large Magellanic Cloud.Comment: 10 pages, 8 figures, accepted for publication in A&
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