807 research outputs found
HI gas in rejuvenated radio galaxies: GMRT observations of the DDRG J1247+6723
We report the detection of HI absorption towards the inner double of the
double-double radio galaxy (DDRG) J1247+6723 with the Giant Metrewave Radio
Telescope (GMRT). The inner double is a Giga-hertz peaked spectrum (GPS) source
with a linear size of 14 pc while the overall size defined by the outer double
is 1195 kpc, making it a giant radio source. The absorption profile is well
resolved and consists of a number of components on either side of the optical
systemic velocity. The neutral hydrogen column density is estimated to be
N(HI)=6.73*10^{20}(T_s/100)(f_c/1.0) cm^{-2}, where T_s and f_c are the spin
temperature and covering factor of the background source respectively. We
explore any correlation between the occurrence of HI absorption and
rejuvenation of radio activity and suggest that there could be a strong
relationship between them.Comment: 5 pages, 2 figures, accepted for publication in MNRAS Letter
J0041+3224: a new double-double radio galaxy
We report the discovery of a double-double radio galaxy (DDRG), J0041+3224,
with the Giant Metrewave Radio Telescope (GMRT) and subsequent high-frequency
observations with the Very Large Array (VLA). The inner and outer doubles are
aligned within about 4 deg and are reasonably collinear with the parent optical
galaxy. The outer double has a steeper radio spectrum compared with the inner
one. Using an estimated redshift of 0.45, the projected linear sizes of the
outer and inner doubles are 969 and 171 kpc respectively. The time scale of
interruption of jet activity has been estimated to be about 20 Myr, similar to
other known DDRGs. We have compiled a sample of known DDRGs, and have
re-examined the inverse correlation between the ratio of the luminosities of
the outer to the inner double and the size of the inner double, l_{in}. Unlike
the other DDRGs with l_{in} larger than about 50 kpc, the inner double of
J0041+3224 is marginally more luminous than the outer one. The two DDRGs with
l_{in} less than about a few kpc have a more luminous inner double than the
outer one, possibly due to a higher efficiency of conversion of beam energy as
the jets propagate through the dense interstellar medium. We have examined the
symmetry parameters and find that the inner doubles appear to be more
asymmetric in both its armlength and flux density ratios compared with the
outer doubles, although they appear marginally more collinear with the core
than the outer double. We discuss briefly possible implications of these
trends.Comment: Accepted for publication in MNRAS, 9 pages, 10 figure
Gauge boson fusion as a probe of inverted hierarchies in supersymmetry
Supersymmetric scenarios with inverted mass hierarchy can be hard to observe
at a hadron collider, particularly for the non-strongly interacting sector. We
show how the production of stau-pairs via gauge boson fusion, along with hard
jets in the high rapidity region, can be instrumental in uncovering the
signatures of such scenarios. We demonstrate this both in a model-independent
way and with reference to some specific, well-motivated models.Comment: RevTeX4, 4 pages, 2 figures. Final version to appear in Phys.Rev.D
Changes in context, figures modified. References added. Conclusions unchange
Interactive flight control system analysis program
A summary of the development, use, and documentation of the interactive software (DIGIKON IV) for flight control system analyses is presented. A list of recommendations for future development is also included
Charged basal stacking fault (BSF) scattering in nitride semiconductors
A theory of charge transport in semiconductors in the presence of basal
stacking faults is developed. It is shown that the presence of basal stacking
faults leads to anisotropy in carrier transport. The theory is applied to
carrier transport in non-polar GaN films consisting of a large number BSFs, and
the result is compared with experimental data.Comment: 4 pages, 3 figure
Evolution of Multipolar Magnetic Fields in Isolated Neutron Stars and its effect on Pulsar Radio Emission
The evolution of the multipolar structure of the magnetic field of isolated
neutron stars is studied assuming the currents to be confined to the crust.
Lower orders () of multipole are seen to evolve in a manner similar to
the dipole suggesting little or no evolution of the expected pulse shape. We
also study the multifrequency polarization position angle traverse of PSR
B0329+54 and find a significant frequency dependence above 2.7 GHz. We
interpret this as an evidence of strong multipolar magnetic field present in
the radio emission region.Comment: 2 pages, 2 figures, uses newpasp.sty, to appear in ASP Conf. Series,
IAU Coll. 177 on Pulsar Astronomy-2000 and Beyond, ed. M. Kramer, N. Wex, R.
Wielebinsk
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