1,224 research outputs found
On the correlation between radio and X-ray flux in Low/Hard state Black Holes
Radio emission from X-ray binary systems (XRBs) has developed in recent years
from being peculiar phenomenon to being recognised as an ubiquitous property of
several classes of XRBs. In this scenario the synchrotron emission is
interpreted as the radiative signature of jet-like outflows, some or all of
which may possess relativistic bulk motion. We have analysed a collection of
quasi-simultaneous radio/X-ray observations of Black Holes in the Low/Hard
X-ray state, finding evidence of a clear correlation between their fluxes over
many orders of magnitude in luminosity. Given that the correlation extends down
to GX 339-4 and V404 Cyg in quiescence, we can confidently assert that even at
accretion rates as low as ~ 10^{-5} dot{m}_{Edd} a powerful jet is being
formed. The normalisation of the correlation is very similar across a sample of
nine sources, implying that it is nearly independent of jet inclination angle.
Remarkably, V 404 Cyg is the second source (after GX 339-4) to show the
correlation S_{radio} proportional to S_{X}^{+0.7} from quiescent level up to
close to the High/Soft state transition. Moreover, assuming the same physics
and accretion:outflow coupling for all of these systems, the simplest
interpretation for the observed scenario is that outflows in Low/Hard state do
not have large bulk Lorentz factors.Comment: 4 pages, 3 figures, Proceedings of the 4th Microquasar Workshop, eds.
Ph Durouchoux, Y. Fuchs and J. Rodriguez, published by the Center for Space
Physics: Kolkat
Extended X-ray Emission From a Quasar-Driven Superbubble
We present observations of extended, 20-kpc scale soft X-ray gas around a
luminous obscured quasar hosted by an ultra-luminous infrared galaxy caught in
the midst of a major merger. The extended X-ray emission is well fit as a
thermal gas with a temperature of kT ~ 280 eV and a luminosity of L_X ~ 10^42
erg/s and is spatially coincident with a known ionized gas outflow. Based on
the X-ray luminosity, a factor of ~10 fainter than the [OIII] emission, we
conclude that the X-ray emission is either dominated by photoionization, or by
shocked emission from cloud surfaces in a hot quasar-driven wind.Comment: Accepted for publication in ApJ, 6 pages, 2 figure
Resilience in same-sex-parented families: The lived experience of adults with gay, lesbian, or bisexual parents
Gay, lesbian, and bisexual parents experience stress, as heterocentricism and/or homonegativity permeate the Australian context. Despite challenges faced by these parents and their families, research consistently shows children raised by same-sex parents to be as psychologically healthy, and as socially and academically well-adjusted, as their peers raised in traditional heterosexual-parented families. The ability of these children to flourish despite the challenges they face highlights the resilience of this minority group. Contrary to comparative research, the current study is framed by a phenomenological approach, and utilized narrative methodology to qualitatively explore the lived experiences of the adult children of same-sex parents. Participants (N = 8) were over 18, lived in Australia, and had at least one parent who identified as gay, lesbian, or bisexual. Thematic analysis indicated that the dissolution of their biological parents\u27 marriage and subsequent blending of two families were the most salient issues for participants. Participants did indicate fear and/or experience of homophobic reactions, parental modelling, controlling disclosure, social support, an outward perspective, and time to adjust were important in coping with challenges. Participants also indicated that their nontraditional family structure gave them unique advantages and emphasized the importance of secure, loving relationships within their family
Dynamical Formation of Millisecond Pulsars in Globular Clusters
The cumulative luminosity distribution functions (CLFs) of radio millisecond
pulsars (MSPs) in globular clusters (GCs) and in the Galactic field at a
frequency of 1.4 GHz have been examined. Assuming a functional form, where is the number of MSPs and is the luminosity at 1.4 GHz, it
is found that the CLFs significantly differ with a steeper slope, , in GCs than in the Galactic field (), suggesting a
different formation or evolutionary history of MSPs in these two regions of the
Galaxy. To probe the production mechanism of MSPs in clusters, a search of the
possible relationships between the MSP population and cluster properties was
carried out. The results of an investigation of 9 GCs indicate positive
correlations between the MSP population and the stellar encounter rate and
metallicity. This provides additional evidence suggesting that stellar
dynamical interactions are important in the formation of the MSP population in
GCs.Comment: 18 pages, 3 figures, 4 tables, accepted for publication in Ap
Cygnus X-3 in outburst : quenched radio emission, radiation losses and variable local opacity
We present multiwavelength observations of Cygnus X-3 during an extended
outburst in 1994 February - March. Intensive radio monitoring at 13.3, 3.6 &
2.0 cm is complemented by observations at (sub)millimetre and infrared
wavelengths, which find Cyg X-3 to be unusually bright and variable, and
include the first reported detection of the source at 0.45 mm. We report the
first confirmation of quenched radio emission prior to radio flaring
independent of observations at Green Bank. The observations reveal evidence for
wavelength-dependent radiation losses and gradually decreasing opacity in the
environment of the radio jet. We find that the radiation losses are likely to
be predominantly inverse Compton losses experienced by the radio-emitting
electrons in the strong radiation field of a luminous companion to the compact
object. We interpret the decreasing opacity during the flare sequence as
resulting from a decreasing proportion of thermal electrons entrained in the
jet, reflecting a decreasing density in the region of jet formation. We
present, drawing in part on the work of other authors, a model based upon
mass-transfer rate instability predicting gamma-ray, X-ray, infrared and radio
trends during a radio flaring sequence.Comment: LaTeX, 11 pages, 6 figures. Submitted to MNRA
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