ArXiv:1401.2966 Discovery of a young
asteroid cluster associated with P/2012~F5 (Gibbs) http://arxiv.org/abs/1401.2966
This is a truly remarkable paper.
P/2012~F5 (Gibbs) is an active asteroid. It may be a main-belt comet
or have suffered a recent impact. It is of interest to look for
collisional families associated with active asteroids for two
reasons. First, if such an object is in fact a bona fide main-belt
comet, one possible explanation for the presence of volatiles on its
surface is a recent (few Myr-ago) collisional fragmentation that
exposed previously shielded volatiles in its interior. Second, if
instead an asteroid is active due to a very recent collisional
ejection of dust (months or less before the first observation of
activity), there is still reason to think it might be a member of a
young collisional family, because mutual collisions will (for a
while) be much more common in such families than in the asteroid belt
at large. These authors identify a collisional family of 9 asteroids associated with the active asteroid P/2012~F5 (Gibbs), which has an
orbital semimajor axis of 3 AU and a diameter of about 2 km. They
perform carefully back-integrations of the asteroids' orbits and
arrive at an age of about 1.5 Myr for the cluster – very young in
the context of the main asteroid belt. The largest asteroid in this cluster is considerably larger than the 2 km size of P/2012~F5 (Gibbs) itself, and the minimum diameter for the parent body that was shattered to make the collisional family is 10 km.
arXiv 1401.4000 A new cold
sub-Saturnian candidate planet orbiting GJ 221 http://arxiv.org/abs/1401.4000
This detection was based on a
re-analysis on radial velocity data previously indicating two
shorter-period planets. The shorter period planets are confirmed and
a new sub-Saturn mass planet with period about 500 days is
tentatively detected. This observations would be interesting if
confirmed, but with 99% confidence intervals spanning almost a factor
of three in mass and RV amplitude, it seems very tentative indeed at
present.
arXiv 1401.4388 HESS J1640-465 - an
exceptionally luminous TeV gamma-ray SNR http://arxiv.org/abs/1401.4388
HESS is an array of atmospheric
Cherenkov telescopes in Namibia, for the detection of extremely
high-energy gamma-rays. Of 70 HESS sources found so far (most
seemingly associated with star-forming regions), given its estimated
distance of 8-13 kpc, HESS J1640-465 may be the most luminous source
of TeV gamma-rays in the MWG. The source is intrinsically extended,
and the spectrum from lower-energy experiments connects smoothly with
that of HESS. Previously the X-ray through gamma-ray emission from
this source was attributed to a pulsar-wind nebula (PWN) in which the
high-energy photons would be produced by inverse Compton scattering
from highly relativistic electrons in the pulsar wind. The current
results suggest instead the acceleration of hadrons across a shock in
the supernova remnant G338.3-0.0. The main evidence for this appears
to be the absence of a break in the gamma-ray spectrum that should
appear at the point where the inverse compton/synchrotron loss time
of the parent electron population is similar to the age of the
source. Instead of this, “the featureless gamma-ray spectrum over
almost six decades in energy is challenging for any leptonic model”.
Also the emission is coincident with the shell of G338.3-0.0, and
more extended than a pulsar-wind nebula would be expected to be: it
is a much better match for a supernova remnant shell.
Other papers that I thought looked interesting, but didn't have time to read or discuss:
ArXiv 1401.2931Distribution of Electric
Currents in Solar Active Regions
arXiv 1401.2901 A high resolution
spectroscopic atlas of M subdwarfs - Effective temperature and
metallicity
arXiv 1401.3199 High frequency A-type
pulsators discovered using SuperWASP
arXiv 1401.3692 The GTC exoplanet
transit spectroscopy survey I: OSIRIS transmission spectroscopy of
the short period planet WASP-43b
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