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Multiwavelength behaviour of Cygnus X-3 and related objects
I present a detailed study of the behaviour of the exotic X-ray binary Cygnus X-3 at radio, (sub)mm, infrared, red-optical and X-ray wavelengths. Further unusual properties of the system are unearthed and previously expounded models are refined by new observations. In order to address the broader picture, a multiwavelength comparison of Cygnus X-3 with other ‘radio-jet’ X-ray binaries is also undertaken.
Infrared observations of Cyg X-3 at high time resolution reveal many rapid flare events superimposed upon the 4.8 hr (presumed) orbital motion. Photometry simultaneously in the H & K-bands allows strong constraints to be placed upon T & Nε for the flaring component. Dereddening of RI- J-H-K-L-L’ photometry places limits on the likely extinction to Cyg X-3 of 4.5 ≤ AJ ≤ 7.5 mag. Further infrared study, simultaneous with radio monitoring and observations with OSSE/GRO and the INT shed greater light on the source, including possible orbital colour changes and a longterm correlation between radio and infrared flux levels. Deep imaging of the field reveals many previously undiscovered infrared sources within a few arcsec of Cyg X-3.
Simultaneous millimetre and radio observations of Cyg X-3 reveal anomalously strong mm fluxes. Interpreting this in terms of significant absorption of the cm fluxes during the passage outwards of the radio-emitting plasmons, strengthens the case for a dense stellar wind in the Cyg X-3 system. Further radio and sub(mm) observations of Cyg X-3 during outburst confirm previously observed phenomena such as quenched radio emission prior to outburst, and establish the importance of radiation loss mechanisms in the decay of radio plasmons ejected from the source. A model describing the qualitative behaviour of the source during outburst is presented
Simultaneous radio and X-ray observations of Galactic Centre low mass X-ray binaries
We have performed simultaneous X-ray and radio observations of thirteen
Galactic centre low-mass X-ray binaries in 1998 April using the Wide-Field
Cameras onboard BeppoSAX and the Australia Telescope Compact Array, the latter
simultaneously at 4.8 and 8.64 GHz. We detect two Z sources, GX 17+2 and GX
5-1, and the unusual `hybrid' source GX 13+1. Upper limits, which are
significantly deeper than previous non-detections, are placed on the radio
emission from two more Z sources and seven atoll sources. Hardness-Intensity
diagrams constructed from the Wide-Field Camera data reveal GX 17+2 and GX 5-1
to have been on the lower part of the horizontal branch and/or the upper part
of the normal branch, at the time of the observations, and the two non-detected
Z sources, GX 340+0 and GX 349+2, to have been on the lower part of the normal
branch. This is consistent with the previous empirically-determined relation
between radio and X-ray emission from Z sources, in which radio emission is
strongest on the Horizontal branch and weakest on the Flaring branch. For the
first time we have information on the X-ray state of atoll sources, which are
clearly radio-quiet relative to the Z sources, during periods of observed radio
upper limits. We place limits on the linear polarisation from the three
detected sources, and use accurate radio astrometry of GX 17+2 to confirm that
it is probably not associated with the optical star NP Ser. Additionally we
place strong upper limits on the radio emission from the X-ray binary 2S
0921-630, disagreeing with suggestions that it is a Z-source viewed edge-on.Comment: Accepted for publication in MNRA
Low Luminosity States of the Black Hole Candidate GX 339-4. I. ASCA and Simultaneous Radio/RXTE Observations
We discuss a series of observations of the black hole candidate GX 339-4 in
low luminosity, spectrally hard states. We present spectral analysis of three
separate archival Advanced Satellite for Cosmology and Astrophysics (ASCA) data
sets and eight separate Rossi X-ray Timing Explorer (RXTE) data sets. Three of
the RXTE observations were strictly simultaneous with 843 MHz and 8.3-9.1 GHz
radio observations. All of these observations have (3-9 keV) flux approximately
< 10^{-9} ergs s^{-1} cm^{-2}. The ASCA data show evidence for an 6.4 keV Fe
line with equivalent width 40 eV, as well as evidence for a soft excess that is
well-modeled by a power law plus a multicolor blackbody spectrum with peak
temperature 150-200 eV. The RXTE data sets also show evidence of an Fe line
with equivalent widths 20-140 eV. Reflection models show a hardening of the
RXTE spectra with decreasing X-ray flux; however, these models do not exhibit
evidence of a correlation between the photon index of the incident power law
flux and the solid angle subtended by the reflector. `Sphere+disk'
Comptonization models and Advection Dominated Accretion Flow (ADAF) models also
provide reasonable descriptions of the RXTE data. The former models yield
coronal temperatures in the range 20-50 keV and optical depths of \tau ~ 3. The
model fits to the X-ray data, however, do not simultaneously explain the
observed radio properties. The most likely source of the radio flux is
synchrotron emission from an extended outflow of size greater than O(10^7
GM/c^2).Comment: 18 pages in latex emulateapj.sty. Accepted for publication in the
Astrophysical Journa
An asymmetric arcsecond radio jet from Circinus X-1
In observations with the Australia Telescope Compact Array we have resolved
the radio counterpart of the unusual X-ray binary Cir X-1 into an asymmetric
extended structure on arcsecond scales. In order to quantify the asymmetry we
have redetermined as accurately as possible both the optical and radio
coordinates of the source. The extended emission can be understood as a
compact, absorbed core at the location of the X-ray binary, and extended
emission up to 2 arcsec to the southeast of the core. The arcsec-scale extended
emission aligns with the larger, more symmetric arcmin-scale collimated
structures in the surrounding synchrotron nebula. This suggests that the
transport of mass and/or energy from the X-ray binary to the synchroton nebula
is occurring via the arcsec-scale structures. The ratio of extended flux from
the southeast to that from the northwest of the core is at least 2:1.
Interpreted as relativistic aberration of an intrinsically symmetric jet from
the source, this implies a minimum outflow velocity of 0.1 c. Alternatively,
the emission may be intrinsically asymmetric, perhaps as a result of the high
space velocity of the system.Comment: Accepted for publication in ApJ Letters. Three figure
Quenching of the radio jet during the X-ray high state of GX 339-4
We have observed the black hole candidate X-ray binary GX 339-4 at radio
wavelengths before, during and after the 1998 high/soft X-ray state transition.
We find that the radio emission from the system is strongly correlated with the
hard X-ray emission and is reduced by a factor > 25 during the high/soft state
compared to the more usual low/hard state. At the points of state transition we
note brief periods of unusually optically-thin radio emission which may
correspond to discrete ejection events. We propose that in the low/hard state
black hole X-ray binaries produce a quasi-continuous outflow, in the high/soft
state this outflow is suppressed, and that state transitions often result in
one or more discrete ejection events. Future models for low/hard states, such
as ADAF/ADIOS solutions, need to take into account strong outflow of
relativistic electrons from the system. We propose that the inferred
Comptonising corona and the base of the jet-like outflow are the same thing,
based upon the strong correlation between radio and hard X-ray emission in GX
339-4 and other X-ray binaries, and the similarity in inferred location and
composition of these two components.Comment: Accepted for publication in ApJ Letter
Peak Luminosities of the Hard States of GX 339-4: Implications for the Accretion Geometry, Disk Mass, and Black Hole Mass
We have analyzed observations of the black hole transient {GX 3394} made
with the {\it Rossi} X-ray Timing Explorer (RXTE) and the Burst and Transient
Source Experiment (BATSE) on board the Compton Gamma-ray Observatory (CGRO). We
have found a nearly linear relation between the peak flux during the low/hard
(LH) state that occurs at the beginning of an outburst and the time since the
flux peak of the latest LH state identified in the previous outburst. Assuming
that the rate at which mass accumulates in the accretion disk between these
peaks is constant and that any mass that remains in the disk after an outburst
has a negligible effect on the next outburst, this nearly linear relation
suggests that the peak flux during the LH state that occurs at the beginning of
an outburst is related to the mass in the disk, and thus that the entire disk
is probably involved in powering these LH states. We have also found a positive
correlation between the peak luminosities of the LH state in the three recent
outbursts of {GX 3394} and the peak luminosities of the following HS state.
This correlation is similar to the correlations reported previously for {Aql
X1}, {4U 170544}, and {XTE J1550564}, providing further support that
the accretion flow that powers the LH state is related to the accretion flow
that powers the following HS state. Although the luminosity of the LH-to-HS
transition varies by up to an order of magnitude, the neutron stars and the
black holes are distinguishable in the state transition luminosity. We discuss
the implications for the mass determination of the compact stars in the
ultraluminous X-ray sources (ULXs).Comment: to appear in Ap
Lord of the Rings: A Kinematic Distance to Circinus X-1 from a Giant X-Ray Light Echo
Circinus X-1 exhibited a bright X-ray flare in late 2013. Follow-up
observations with Chandra and XMM-Newton from 40 to 80 days after the flare
reveal a bright X-ray light echo in the form of four well-defined rings with
radii from 5 to 13 arcminutes, growing in radius with time. The large fluence
of the flare and the large column density of interstellar dust towards Circinus
X-1 make this the largest and brightest set of rings from an X-ray light echo
observed to date. By deconvolving the radial intensity profile of the echo with
the MAXI X-ray lightcurve of the flare we reconstruct the dust distribution
towards Circinus X-1 into four distinct dust concentrations. By comparing the
peak in scattering intensity with the peak intensity in CO maps of molecular
clouds from the Mopra Southern Galactic Plane CO Survey we identify the two
innermost rings with clouds at radial velocity ~ -74 km/s and ~ -81 km/s,
respectively. We identify a prominent band of foreground photoelectric
absorption with a lane of CO gas at ~ -32 km/s. From the association of the
rings with individual CO clouds we determine the kinematic distance to Circinus
X-1 to be kpc. This distance rules out
earlier claims of a distance around 4 kpc, implies that Circinus X-1 is a
frequent super-Eddington source, and places a lower limit of on the Lorentz factor and an upper limit of on the jet viewing angle.Comment: 20 pages, 21 figures, Astrophysical Journal, in prin
Identification of a Likely Radio Counterpart of the Rapid Burster
We have identified a likely radio counterpart to the low-mass X-ray binary
MXB 1730-335 (the Rapid Burster). The counterpart has shown 8.4 GHz radio
on/off behavior correlated with the X-ray on/off behavior as observed by the
RXTE/ASM during six VLA observations. The probability of an unrelated, randomly
varying background source duplicating this behavior is 1-3% depending on the
correlation time scale. The location of the radio source is RA 17h 33m 24.61s;
Dec -33d 23' 19.8" (J2000), +/- 0.1". We do not detect 8.4 GHz radio emission
coincident with type II (accretion-driven) X-ray bursts. The ratio of radio to
X-ray emission during such bursts is constrained to be below the ratio observed
during X-ray persistent emission at the 2.9-sigma level. Synchrotron bubble
models of the radio emission can provide a reasonable fit to the full data set,
collected over several outbursts, assuming that the radio evolution is the same
from outburst to outburst, but given the physical constraints the emission is
more likely to be due to ~hour-long radio flares such as have been observed
from the X-ray binary GRS 1915+105.Comment: 28 pages, 4 figures; accepted for publication in ApJ (no changes
The Impact of a Material’s Inherent and Process Stress on Meeting Specification and Tolerances: A Six Sigma Case Study
This Six-Sigma Case Study was conducted in a local aerospace company that produces high quality precision-machined jet engine components. These complex turbine components have thin walls that must meet tight tolerances. Disks, shafts, rotating seals, plates, and cases range in size from 3" to 80" in diameter. This case focused on a 16” (diameter) rear cooling plate whose production required 18 machining processes. The objective was to determine if it was possible to eliminate the final manual lathing process. Manual lathing was used as the last step because the material characteristics of the plate and the stress induced by the previous processes caused the final product to expand. Stress can cause unsatisfactory changes in the plate’s dimensions. Stress is not only inherent in the material’s internal properties but is also induced during machining. It is critical that the operator’s cut is precise and does not remove too much material. During the two most critical steps of 18, measurements were taken. It was theorized that relaxing the first process tolerances could allow later processes to be numerically machine controlled to conform closer to the prescribed tolerance of the final product. Plates were tested using these revised tolerances. After the plate was shot peened (a stress redistribution process) measurements confirmed that non-conformance had been eliminated and the final machining process could be discontinued. Cost savings for eliminating the last machining and inspection process was $268 per plate or an annual saving of approximately 11% of total cost for the item studied
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