4,732 research outputs found
Out of the frying pan: a young pulsar with a long radio trail emerging from SNR G315.9-0.0
The faint radio supernova remnant SNR G315.9-0.0 is notable for a long and
thin trail that extends outward perpendicular from the edge of its
approximately circular shell. In a search with the Parkes telescope we have
found a young and energetic pulsar that is located at the tip of this
collimated linear structure. PSR J1437-5959 has period P = 61 ms,
characteristic age tau_c = 114 kyr, and spin-down luminosity dE/dt = 1.4e36
erg/s. It is very faint, with a flux density at 1.4 GHz of about 75 uJy. From
its dispersion measure of 549 pc/cc, we infer d ~ 8 kpc. At this distance and
for an age comparable to tau_c, the implied pulsar velocity in the plane of the
sky is V_t = 300 km/s for a birth at the center of the SNR, although it is
possible that the SNR/pulsar system is younger than tau_c and that V_t > 300
km/s. The highly collimated linear feature is evidently the pulsar wind trail
left from the supersonic passage of PSR J1437-5959 through the interstellar
medium surrounding SNR G315.9-0.0.Comment: accepted for publication in ApJ Letter
Factors that affect the negotiation process of SMES in trade shows
The objective of this research is to identify the factors that affect the negotiation process of SMEs in trade shows, which represent one of the most important export promotion instruments. Semi-structured interviews were carried out with Peruvians who participated in negotiations. A conceptual model was developed, which integrates the various factors identified in the literature such as (1) background factors, (2) strategic factors, (3) cultural factors, (4) negotiator factors, and (5) psychological factors, in order to confirm their impact on the negotiation process. The results revealed factors that had not been previously considered in the literature, providing a valuable insight for a future study. This research seeks to maximize the effectiveness of negotiations at trade shows, which impact the performance and export activity of exhibiting firms, allowing better export promotion policies to be developed
A Proper Motion for the Pulsar Wind Nebula G359.23-0.82, "the Mouse," Associated with the Energetic Radio Pulsar J1747-2958
The "Mouse" (PWN G359.23-0.82) is a spectacular bow shock pulsar wind nebula,
powered by the radio pulsar J1747-2958. The pulsar and its nebula are presumed
to have a high space velocity, but their proper motions have not been directly
measured. Here we present 8.5 GHz interferometric observations of the Mouse
nebula with the Very Large Array, spanning a time baseline of 12 yr. We measure
eastward proper motion for PWN G359.23-0.82 (and hence indirectly for PSR
J1747-2958) of 12.9+/-1.8 mas/yr, which at an assumed distance of 5 kpc
corresponds to a transverse space velocity of 306+/-43 km/s. Considering
pressure balance at the apex of the bow shock, we calculate an in situ hydrogen
number density of approximately 1.0(-0.2)(+0.4) cm^(-3) for the interstellar
medium through which the system is traveling. A lower age limit for PSR
J1747-2958 of 163(-20)(+28) kyr is calculated by considering its potential
birth site. The large discrepancy with the pulsar's spin-down age of 25 kyr is
possibly explained by surface dipole magnetic field growth on a timescale ~15
kyr, suggesting possible future evolution of PSR J1747-2958 to a different
class of neutron star. We also argue that the adjacent supernova remnant
G359.1-0.5 is not physically associated with the Mouse system but is rather an
unrelated object along the line of sight.Comment: 8 pages, 4 figures, emulateapj format. Accepted for publication in
The Astrophysical Journa
Using CO line ratios to trace the physical properties of molecular clouds
The carbon monoxide (CO) rotational transition lines are the most common
tracers of molecular gas within giant molecular clouds (MCs). We study the
ratio () between CO's first two emission lines and examine what
information it provides about the physical properties of the cloud. To study
we perform smooth particle hydrodynamic simulations with time
dependent chemistry (using GADGET-2), along with post-process radiative
transfer calculations on an adaptive grid (using RADMC-3D) to create synthetic
emission maps of a MC. has a bimodal distribution that is a
consequence of the excitation properties of each line, given that reaches
local thermal equilibrium (LTE) while is still sub-thermally excited in
the considered clouds. The bimodality of serves as a tracer of
the physical properties of different regions of the cloud and it helps
constrain local temperatures, densities and opacities. Additionally this
bimodal structure shows an important portion of the CO emission comes from
diffuse regions of the cloud, suggesting that the commonly used conversion
factor of between both lines may need to be studied
further.Comment: 10 pages, 8 figures, accepted to MNRA
Chandra X-Ray Observations of Nineteen Millisecond Pulsars in the Globular Cluster 47 Tucanae
We present spectral and long-timescale variability analyses of
\textit{Chandra} ACIS-S observations of the 19 millisecond pulsars (MSPs) with
precisely known positions in the globular cluster 47 Tucanae. The X-ray
emission of the majority of these MSPs is well described by a thermal
(blackbody or neutron star hydrogen atmosphere) spectrum with a temperature
K, emission radius km,
and luminosity ergs s. For several MSPs, there is
indication that a second thermal component is required, similar to what is seen
in some nearby field MSPs. The radio-eclipsing binary MSPs 47 Tuc J, O, and W
show a significant non-thermal component, with photon index ,
which may originate in an shock formed due to interaction between the
relativistic pulsar wind and matter from the stellar companion. We re-examine
the X-ray--spindown luminosity relation () and find that due to
the large uncertainties in both parameters the result is consistent with both
the linear relation and the flatter
predicted by polar cap heating models. In terms of X-ray properties, we find no
clear systematic differences between MSPs in globular clusters and in the field
of the Galaxy.Comment: 13 pages, 6 figures, accepted for publication in the Astrophysical
Journa
A new test of conservation laws and Lorentz invariance in relativistic gravity
General relativity predicts that energy and momentum conservation laws hold
and that preferred frames do not exist. The parametrised post-Newtonian
formalism (PPN) phenomenologically quantifies possible deviations from general
relativity. The PPN parameter alpha_3 (which identically vanishes in general
relativity) plays a dual role in that it is associated both with a violation of
the momentum conservation law, and with the existence of a preferred frame. By
considering the effects of alpha_3 neq 0 in certain binary pulsar systems, it
is shown that alpha_3 < 2.2 x 10^-20 (90% CL). This limit improves on previous
results by several orders of magnitude, and shows that pulsar tests of alpha_3
rank (together with Hughes-Drever-type tests of local Lorentz invariance) among
the most precise null experiments of physics.Comment: Submitted to Classical Quantum Gravity, LaTeX, requires ioplppt.sty,
no figure
1E 1547.0-5408: a radio-emitting magnetar with a rotation period of 2 seconds
The variable X-ray source 1E 1547.0-5408 was identified by Gelfand & Gaensler
(2007) as a likely magnetar in G327.24-0.13, an apparent supernova remnant. No
X-ray pulsations have been detected from it. Using the Parkes radio telescope,
we discovered pulsations with period P = 2.069 s. Using the Australia Telescope
Compact Array, we localized these to 1E 1547.0-5408. We measure dP/dt =
(2.318+-0.005)e-11, which for a magnetic dipole rotating in vacuo gives a
surface field strength of 2.2e14 G, a characteristic age of 1.4 kyr, and a
spin-down luminosity of 1.0e35 ergs/s. Together with its X-ray characteristics,
these rotational parameters of 1E 1547.0-5408 prove that it is a magnetar, only
the second known to emit radio waves. The distance is ~9 kpc, derived from the
dispersion measure of 830 pc/cc. The pulse profile at a frequency of 1.4 GHz is
extremely broad and asymmetric due to multipath propagation in the ISM, as a
result of which only approximately 75% of the total flux at 1.4 GHz is pulsed.
At higher frequencies the profile is more symmetric and has FWHM = 0.12P.
Unlike in normal radio pulsars, but in common with the other known
radio-emitting magnetar, XTE J1810-197, the spectrum over 1.4-6.6 GHz is flat
or rising, and we observe large, sudden changes in the pulse shape. In a
contemporaneous Swift X-ray observation, 1E 1547.0-5408 was detected with
record high flux, f_X(1-8 keV) ~ 5e-12 ergs/cm^2/s, 16 times the historic
minimum. The pulsar was undetected in archival radio observations from 1998,
implying a flux < 0.2 times the present level. Together with the transient
behavior of XTE J1810-197, these results suggest that radio emission is
triggered by X-ray outbursts of usually quiescent magnetars.Comment: Accepted for publication in ApJ Letter
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