439 research outputs found
On the Ninth Circuit\u27s New Definition of Piracy: Japanese Whalers v. the Sea Shepherd-Who are the Real Pirates (i.e. Plunderers)?
On The Problem of Utilizing Unilateral Action To Prevent Acts Of Sea Piracy and Terrorism: A Proactive Approach To The Evolution Of International Law
The goal of this article is to determine how the international community can prevent piracy and terrorism. The irony is that perhaps piracy may subside at last, but only as a result of the increased efforts of the international community to prevent terrorism. The purpose of this article, therefore, is to explore the parameters of the problems and trends toward serious destruction connected to these acts and to suggest that if regional approaches fail, certain unilateral actions against the perpetrators may be necessary in order to avoid massive human and environmental destruction. The core question is whether unilateral action growing out of treaty obligations should be permitted
The Dilemma of Piratical Ransoms: Should They Be Paid Or Not: On the Human Rights of Kidnapped Seamen and Their Families
The Supernova Remnant W44: confirmations and challenges for cosmic-ray acceleration
The middle-aged supernova remnant (SNR) W44 has recently attracted attention
because of its relevance regarding the origin of Galactic cosmic-rays. The
gamma-ray missions AGILE and Fermi have established, for the first time for a
SNR, the spectral continuum below 200 MeV which can be attributed to neutral
pion emission. Confirming the hadronic origin of the gamma-ray emission near
100 MeV is then of the greatest importance. Our paper is focused on a global
re-assessment of all available data and models of particle acceleration in W44,
with the goal of determining on a firm ground the hadronic and leptonic
contributions to the overall spectrum. We also present new gamma-ray and CO
NANTEN2 data on W44, and compare them with recently published AGILE and Fermi
data. Our analysis strengthens previous studies and observations of the W44
complex environment and provides new information for a more detailed modeling.
In particular, we determine that the average gas density of the regions
emitting 100 MeV - 10 GeV gamma-rays is relatively high (n= 250 - 300 cm^-3).
The hadronic interpretation of the gamma-ray spectrum of W44 is viable, and
supported by strong evidence. It implies a relatively large value for the
average magnetic field (B > 10^2 microG) in the SNR surroundings, sign of field
amplification by shock-driven turbulence. Our new analysis establishes that the
spectral index of the proton energy distribution function is p1 = 2.2 +/- 0.1
at low energies and p2 = 3.2 +/- 0.1 at high energies. We critically discuss
hadronic versus leptonic-only models of emission taking into account
simultaneously radio and gamma-ray data. We find that the leptonic models are
disfavored by the combination of radio and gamma-ray data. Having determined
the hadronic nature of the gamma-ray emission on firm ground, a number of
theoretical challenges remains to be addressed.Comment: 13 pages, 11 figures, accepted by A&
A molecular shell with star formation toward the supernova remnant G349.7+0.2
A field of ~38'x38' around the supernova remnant (SNR) G349.7+0.2 has been
surveyed in the CO J=1-0 transition with the 12 Meter Telescope of the NRAO,
using the On-The-Fly technique. The resolution of the observations is 54". We
have found that this remnant is interacting with a small CO cloud which, in
turn, is part of a much larger molecular complex, which we call the ``Large CO
Shell''. The Large CO Shell has a diameter of about 100 pc, an H_2 mass of
930,000 solar masses, and a density of 35 cm-3. We investigate the origin of
this structure and suggest that an old supernova explosion ocurred about 4
million years ago, as a suitable hypothesis. Analyzing the interaction between
G349.7+0.2 and the Large CO Shell, it is possible to determine that the shock
front currently driven into the molecular gas is a non-dissociative shock
(C-type), in agreement with the presence of OH 1720 MHz masers. The positional
and kinematical coincidence among one of the CO clouds that constitute the
Large CO Shell, an IRAS point-like source and an ultracompact H II region,
indicate the presence of a recently formed star. We suggest that the formation
of this star was triggered during the expansion of the Large CO Shell, and
suggest the possibility that the same expansion also created the progenitor
star of G349.7+0.2. The Large CO Shell would then be one of the few
observational examples of supernova-induced star formation.Comment: accepted in Astronomical Journal, corrected typo in the abstract (in
first line, 38' instead of 38"
Isolated X-ray -- infrared sources in the region of interaction of the supernova remnant IC 443 with a molecular cloud
The nature of the extended hard X-ray source XMMU J061804.3+222732 and its
surroundings is investigated using XMM-Newton, Chandra, and Spitzer
observations. This source is located in an interaction region of the IC 443
supernova remnant with a neighboring molecular cloud. The X-ray emission
consists of a number of bright clumps embedded in an extended structured
non-thermal X-ray nebula larger than 30" in size. Some clumps show evidence for
line emission at ~1.9 keV and ~3.7 keV at the 99% confidence level. Large-scale
diffuse radio emission of IC 443 passes over the source region, with an
enhancement near the source. An IR source of about 14" x 7" size is prominent
in the 24 um, 70 um, and 2.2 um bands, adjacent to a putative Si K-shell X-ray
line emission region. The observed IR/X-ray morphology and spectra are
consistent with those expected for J/C-type shocks of different velocities
driven by fragmented supernova ejecta colliding with the dense medium of a
molecular cloud. The IR emission of the source detected by Spitzer can be
attributed to both continuum emission from an HII region created by the ejecta
fragment and line emission excited by shocks. This source region in IC 443 may
be an example of a rather numerous population of hard X-ray/IR sources created
by supernova explosions in the dense environment of star-forming regions.
Alternative Galactic and extragalactic interpretations of the observed source
are also discussed.Comment: The Astrophysical Journal, v. 677 (April 2008), in pres
On the nature of the hard X-ray source IGR J2018+4043
We found a very likely counterpart to the recently discovered hard X-ray
source IGR J2018+4043 in the multi-wavelength observations of the source field.
The source, originally discovered in the 20-40 keV band, is now confidently
detected also in the 40-80 keV band, with a flux of (1.4 +/- 0.4) x 10(-11) erg
cm(-2) s(-1). A 5 ks Swift observation of the IGR J2018+4043 field revealed a
hard point-like source with the observed 0.5-10 keV flux of 3.4(+0.7)(-0.8) x
10(-12) erg cm(-2) s(-1) (90% confidence level) at alpha = 20h18m38.55s, delta
= +40d41m00.4s (with a 4.2" uncertainty). The combined Swift-INTEGRAL spectrum
can be described by an absorbed power-law model with photon index gamma = 1.3
+/- 0.2 and N_H = 6.1(+3.2)(-2.2) x 10(22) cm(-2). In archival optical and
infrared data we found a slightly extended and highly absorbed object at the
Swift source position. There is also an extended VLA 1.4 GHz source peaked at a
beam-width distance from the optical and X-ray positions. The observed
morphology and multiwavelength spectra of IGR J2018+4043 are consistent with
those expected for an obscured accreting object, i.e. an AGN or a Galactic
X-ray binary. The identification suggests possible connection of IGR J2018+4043
to the bright gamma-ray source GEV J2020+4023 (3EG J2020+4017) detected by COS
B and CGRO EGRET in the gamma-Cygni SNR field.Comment: 5 pages, 3 figures, uses emulateapj styl
Structure and Magnetic Fields in the Precessing Jet System SS433 III. Evolution of the Intrinsic Brightness of the Jets from a Deep Multi-Epoch VLA Campaign
We present a sequence of five deep observations of SS433 made over the summer
of 2007 using the VLA in the A configuration at 5 and 8 GHz. In this paper we
study the brightness profiles of the jets and their time evolution. We also
examine the spectral index distribution in the source. We find (as previously
reported from the analysis of a single earlier image) that the profiles of the
east and west jets are remarkably similar if projection and Doppler beaming are
taken into account. The sequence of five images allows us to disentangle the
evolution of brightness of individual pieces of jet from the variations of jet
power originating at the core. We find that the brightness of each piece of the
jet fades as an exponential function of age (or distance from the core),
exp(-tau/tau'), where tau is the age at emission and tau' = 55.9 +- 1.7 days.
This evolutionary model describes both the east and west jets equally well.
There is also significant variation (by a factor of at least five) in jet power
with birth epoch, with the east and west jets varying in synchrony. The lack of
deceleration between the scale of the optical Balmer line emission (10^15 cm)
and that of the radio emission (10^17 cm) requires that the jet material is
much denser than its surroundings. We find that the density ratio must exceed
300:1.Comment: 26 pages, 13 Figures, Accepted for publication in the Astrophysical
Journa
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