484 research outputs found
The Missing Link: Bayesian Detection and Measurement of Intermediate-Mass Black-Hole Binaries
We perform Bayesian analysis of gravitational-wave signals from non-spinning,
intermediate-mass black-hole binaries (IMBHBs) with observed total mass,
, from to and
mass ratio 1\mbox{--}4 using advanced LIGO and Virgo detectors. We employ
inspiral-merger-ringdown waveform models based on the effective-one-body
formalism and include subleading modes of radiation beyond the leading
mode. The presence of subleading modes increases signal power for inclined
binaries and allows for improved accuracy and precision in measurements of the
masses as well as breaking of extrinsic parameter degeneracies. For low total
masses, , the observed chirp
mass ( being the
symmetric mass ratio) is better measured. In contrast, as increasing power
comes from merger and ringdown, we find that the total mass
has better relative precision than . Indeed, at high
(), the signal resembles a
burst and the measurement thus extracts the dominant frequency of the signal
that depends on . Depending on the binary's inclination, at
signal-to-noise ratio (SNR) of , uncertainties in can be
as large as \sim 20 \mbox{--}25\% while uncertainties in are \sim 50 \mbox{--}60\% in binaries with unequal masses (those
numbers become versus in more symmetric binaries).
Although large, those uncertainties will establish the existence of IMBHs. Our
results show that gravitational-wave observations can offer a unique tool to
observe and understand the formation, evolution and demographics of IMBHs,
which are difficult to observe in the electromagnetic window. (abridged)Comment: 17 pages, 9 figures, 2 tables; updated to reflect published versio
High Energy Variability Of Synchrotron-Self Compton Emitting Sources: Why One Zone Models Do Not Work And How We Can Fix It
With the anticipated launch of GLAST, the existing X-ray telescopes, and the
enhanced capabilities of the new generation of TeV telescopes, developing tools
for modeling the variability of high energy sources such as blazars is becoming
a high priority. We point out the serious, innate problems one zone
synchrotron-self Compton models have in simulating high energy variability. We
then present the first steps toward a multi zone model where non-local, time
delayed Synchrotron-self Compton electron energy losses are taken into account.
By introducing only one additional parameter, the length of the system, our
code can simulate variability properly at Compton dominated stages, a situation
typical of flaring systems. As a first application, we were able to reproduce
variability similar to that observed in the case of the puzzling `orphan' TeV
flares that are not accompanied by a corresponding X-ray flare.Comment: to appear in the 1st GLAST symposium proceeding
An investigation into the Multiple Optimised Parameter Estimation and Data compression algorithm
We investigate the use of the Multiple Optimised Parameter Estimation and
Data compression algorithm (MOPED) for data compression and faster evaluation
of likelihood functions. Since MOPED only guarantees maintaining the Fisher
matrix of the likelihood at a chosen point, multimodal and some degenerate
distributions will present a problem. We present examples of scenarios in which
MOPED does faithfully represent the true likelihood but also cases in which it
does not. Through these examples, we aim to define a set of criteria for which
MOPED will accurately represent the likelihood and hence may be used to obtain
a significant reduction in the time needed to calculate it. These criteria may
involve the evaluation of the full likelihood function for comparison.Comment: 5 pages, 8 figures; corrections and additions to match version
published in MNRAS Letters; added reference to published versio
Inventions and patenting in Africa: Empirical trends from 1970 to 2010
Economic development is increasingly dependent upon on utilizing new knowledge to innovate and create value, even in traditional industries and in low-income countries. This analysis uses evidence on patent families to assess innovation activity throughout sub-Saharan Africa. We find patent activity in sub-Saharan Africa-both by African inventors and by foreign inventors-is comparable to similar regions around the world, when conditioned on economic size. Patent filings in Africa have grown, particularly, since the mid-1990s, but at different rates within different African jurisdictions. Types of technologies being patented in Africa have remained stable over 30 years, with most in pharmaceuticals, chemistry, biotechnology, and engineering. The majority of patent filings in Africa are from Europe, the United States, and other high income countries. Yet, in South Africa, between 15% and 20% of patent filings are by residents of South Africa, and 3% are from other developing and emerging economies. Only a small share of inventions globally are made in sub-Saharan Africa, but for those inventions that do arise in Africa, foreign filings are made widely outside of Africa
- β¦