2,309 research outputs found
Emission from Bow Shocks of Beamed Gamma-Ray Bursts
Beamed gamma-ray burst (GRB) sources produce a bow shock in their gaseous
environment. The emitted flux from this bow shock may dominate over the direct
emission from the jet for lines of sight which are outside the angular radius
of the jet emission, theta. The event rate for these lines of sight is
increased by a factor of 260*(theta/5_degrees)^{-2}. For typical GRB
parameters, we find that the bow shock emission from a jet with half-angle of
about 5 degrees is visible out to tens of Mpc in the radio and hundreds of Mpc
in the X-rays. If GRBs are linked to supernovae, studies of peculiar supernovae
in the local universe should reveal this non-thermal bow shock emission for
weeks to months following the explosion.Comment: ApJ, submitted, 15 pages, 3 figure
CCD photometric and mass function study of 9 young Large Magellanic Cloud star clusters
We present CCD photometric and mass function study of 9 young Large
Magellanic Cloud star clusters namely NGC 1767, NGC 1994, NGC 2002, NGC 2003,
NGC 2006, SL 538, NGC 2011, NGC 2098 and NGC 2136. The BVRI data reaching down
to V ~ 21 mag, are collected from 3.5-meter NTT/EFOSC2 in sub-arcsec seeing
conditions. For NGC 1767, NGC 1994, NGC 2002, NGC 2003, NGC 2011 and NGC 2136,
broad band photometric CCD data are presented for the first time. Seven of the
9 clusters have ages between 16 to 25 Myr while remaining two clusters have
ages Myr (NGC 2098) and Myr (NGC 2136). For 7 younger
clusters, the age estimates based on a recent model and the integrated spectra
are found to be systematically lower ( 10 Myr) from the present estimate.
In the mass range of , the MF slopes for 8 out of nine
clusters were found to be similar with the value of ranging from
to . For NGC 1767 it is flatter with . Mass segregation effects are observed for NGC 2002, NGC 2006,
NGC 2136 and NGC 2098. This is consistent with the findings of Kontizas et al.
for NGC 2098. Presence of mass segregation in these clusters could be an
imprint of star formation process as their ages are significantly smaller than
their dynamical evolution time. Mean MF slope of
derived for a sample of 25 young ( Myr) dynamically unevolved LMC
stellar systems provide support for the universality of IMF in the intermediate
mass range .Comment: To appear in MNRA
Work probability distribution and tossing a biased coin
We show that the rare events present in dissipated work that enters Jarzynski
equality, when mapped appropriately to the phenomenon of large deviations found
in a biased coin toss, are enough to yield a quantitative work probability
distribution for Jarzynski equality. This allows us to propose a recipe for
constructing work probability distribution independent of the details of any
relevant system. The underlying framework, developed herein, is expected to be
of use in modelling other physical phenomena where rare events play an
important role.Comment: 6 pages, 4 figures
Purification, crystallization and preliminary X-ray studies of Mycobacterium tuberculosis RRF
The ribosome recycling factor from Mycobacterium tuberculosis has been crystallized. The monoclinic crystals, with 52.5% solvent content, contain one protein molecule in the asymmetric unit
Jet break time -- flux density relationship and constraints on physical parameters of GRB afterglows
We derive a relation between the flux density at the light-curve
break of a gamma-ray burst (GRB) afterglow and the break time . The
break is due to the transition from the spherical-like to jet-like evolution of
the afterglow, when the Lorentz factor of the jet equals the inverse of the
initial half-opening angle, i.e., . We show that this
relation indeed behaves as among GRBs for the
slow-cooling case, where is the power-law index of electron distribution. A
statistical analysis of the optical jet breaks of nine GRBs gives , which is consistent with the shock acceleration theory. The value of
derived in this way is different from the observed temporal index
() of the late-time light curve after ,
which suffers several uncertainties from the unclear hydrodynamics of the
sideways expansion and exhibits a large dispersion. Our results not only
confirm that the remnants of GRBs are standard candles, but also provide the
first evidence that the physical parameters of relativistic shocks are
universal, with the favored values and .Comment: 11 pages including 3 color figure
Death-feigning behavior in the Common Sand Boa, Eryx conicus (Schneider 1801) (Erycidae), and the Common Wolfsnake, Lycodon aulicus (Linnaeus 1758) (Colubridae)
Signatures of two-dimensionalisation of 3D turbulence in presence of rotation
A reason has been given for the inverse energy cascade in the
two-dimensionalised rapidly rotating 3D incompressible turbulence. For such
system, literature shows a possibility of the exponent of wavenumber in the
energy spectrum's relation to lie between -2 and -3. We argue the existence of
a more strict range of -2 to -7/3 for the exponent in the case of rapidly
rotating turbulence which is in accordance with the recent experiments. Also, a
rigorous derivation for the two point third order structure function has been
provided helping one to argue that even with slow rotation one gets, though
dominated, a spectrum with the exponent -2.87, thereby hinting at the
initiation of the two-dimensionalisation effect with rotation.Comment: An extended and typos-corrected version of the earlier submissio
Performance Analysis of Two Receiver Arrangements for Wireless Battery Charging System
Two different arrangements for Wireless Battery Charging Systems (WBCSs) with a series-parallel resonant topology have been analyzed in this paper. The first arrangement charges the battery by controlling the receiver-side rectifier current and voltage without a chopper, while the second arrangement charges it with a chopper while keeping the chopper input voltage constant. The comparison of these two arrangements is made based on their performance on various figures of merit, such as the sizing factor of both the supply voltage source and receiver coil, overall system efficiency, power-transfer ratio, receiver efficiency, and cost estimation. Later, the simulated study is verified by the experimental setup designed to charge the electric vehicle
Coherent amplitudon generation in K_0.3MoO_3 through ultrafast inter-band quasi particle decay
The charge density wave system K_0.3MoO_3 has been studied using variable
energy pump-probe spectroscopy, ellipsometry, and inelastic light scattering.
The observed transient reflectivity response exhibits quite a complex behavior,
containing contributions due to quasi particle excitations, coherent
amplitudons and phonons, and heating effects. The generation of coherent
amplitudons is discussed in terms of relaxation of photo-excited quasi
particles, and is found to be resonant with the interband plasmon frequency.
Two additional coherent excitations observed in the transients are assigned to
zone-folding modes of the charge density wave state
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