1,551 research outputs found
Pro-cyclical Solow Residuals without Technology Shocks
Most Real Business Cycle models have a hard time jointly explaining the twin facts of strongly pro-cyclical Solow residuals and extremely low correlations between wages and hours. We present a model that delivers both these results without using exogenous variation in total factor productivity (technology shocks). The key innovation of the paper is to add learning-by-doing to firms technology. As a result firms optimally vary their prices to control the amount of learning which in turn influences future productivity. We show that exogenous variation in labour wedges (preference shocks) measured from aggregate data deliver around fifty percent of the standard deviation in the efficiency wedge (Solow residual) as well as realistic second moments for key aggregate variables which is in sharp contrast to the model without learning-by-doing.Business cycles, Learning-by-Doing, Productivity
X-ray Intraday Variability of Five TeV Blazars with NuSTAR
We have examined 40 NuSTAR light curves (LCs) of five TeV emitting high
synchrotron peaked blazars: 1ES 0229+200, Mrk 421, Mrk 501, 1ES 1959+650 and
PKS 2155-304. Four of the blazars showed intraday variability in the NuSTAR
energy range of 3-79 keV. Using an auto correlation function analysis we
searched for intraday variability timescales in these LCs and found indications
of several between 2.5 and 32.8 ks in eight LCs of Mrk 421, a timescale around
8.0 ks for one LC of Mrk 501, and timescales of 29.6 ks and 57.4 ks in two LCs
of PKS 2155-304. The other two blazars' LCs do not show any evidence for
intraday variability timescales shorter than the lengths of those observations,
however, the data was both sparser and noisier, for them. We found positive
correlations with zero lag between soft (3-10 keV) and hard (10-79 keV) bands
for most of the LCs, indicating that their emissions originate from the same
electron population. We examined spectral variability using a hardness ratio
analysis and noticed a general "harder-when-brighter" behavior. The 22 LCs of
Mrk 421 observed between July 2012 and April 2013 show that this source was in
a quiescent state for an extended period of time and then underwent an
unprecedented double peaked outburst while monitored on a daily basis during 10
- 16 April 2013. We briefly discuss models capable of explaining these blazar
emissions.Comment: 21 pages, 4 figures, 4 tables, Accepted for Publication in Ap
Statistical analysis of variability properties of the Kepler blazar W2R 1926+42
We analyzed Kepler light curves of the blazar W2R 1926+42 that provided
nearly continuous coverage from quarter 11 through quarter 17 (589 days between
2011 and 2013) and examined some of their flux variability properties. We
investigate the possibility that the light curve is dominated by a large number
of individual flares and adopt exponential rise and decay models to investigate
the symmetry properties of flares. We found that those variations of W2R
1926+42 are predominantly asymmetric with weak tendencies toward positive
asymmetry (rapid rise and slow decay). The durations (D) and the amplitudes
(F0) of flares can be fit with log-normal distributions. The energy (E) of each
flare is also estimated for the first time. There are positive correlations
between logD and logE with a slope of 1.36, and between logF0 and logE with a
slope of 1.12. Lomb-Scargle periodograms are used to estimate the power
spectral density (PSD) shape. It is well described by a power law with an index
ranging between -1.1 and -1.5. The sizes of the emission regions, R, are
estimated to be in the range of 1.1*10^15 cm - 6.6*10^16 cm. The flare
asymmetry is difficult to explain by a light travel time effect but may be
caused by differences between the timescales for acceleration and dissipation
of high-energy particles in the relativistic jet. A jet-in-jet model also could
produce the observed log-normal distributions
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