3,482 research outputs found
Limits on the Mass, Velocity and Orbit of PSR J19336211
We present a high-precision timing analysis of PSR J19336211, a
millisecond pulsar (MSP) with a 3.5-ms spin period and a white dwarf (WD)
companion, using data from the Parkes radio telescope. Since we have accurately
measured the polarization properties of this pulsar we have applied the matrix
template matching approach in which the times of arrival are measured using
full polarimetric information. We achieved a weighted root-mean-square timing
residuals (rms) of the timing residuals of 1.23 , 15.5
improvement compared to the total intensity timing analysis. After studying the
scintillation properties of this pulsar we put constraints on the inclination
angle of the system. Based on these measurements and on mapping we put
a 2- upper limit on the companion mass (0.44 M). Since this
mass limit cannot reveal the nature of the companion we further investigate the
possibility of the companion to be a He WD. Applying the orbital period-mass
relation for such WDs, we conclude that the mass of a He WD companion would be
about 0.260.01 M which, combined with the measured mass function
and orbital inclination limits, would lead to a light pulsar mass
1.0 M. This result seems unlikely based on current neutron star
formation models and we therefore conclude that PSR J19336211 most likely
has a CO WD companion, which allows for a solution with a more massive pulsar
Can we see pulsars around Sgr A*? - The latest searches with the Effelsberg telescope
Radio pulsars in relativistic binary systems are unique tools to study the
curved space-time around massive compact objects. The discovery of a pulsar
closely orbiting the super-massive black hole at the centre of our Galaxy, Sgr
A*, would provide a superb test-bed for gravitational physics. To date, the
absence of any radio pulsar discoveries within a few arc minutes of Sgr A* has
been explained by one principal factor: extreme scattering of radio waves
caused by inhomogeneities in the ionized component of the interstellar medium
in the central 100 pc around Sgr A*. Scattering, which causes temporal
broadening of pulses, can only be mitigated by observing at higher frequencies.
Here we describe recent searches of the Galactic centre region performed at a
frequency of 18.95 GHz with the Effelsberg radio telescope.Comment: 3 pages, 2 figures, Proceedings of IAUS 291 "Neutron Stars and
Pulsars: Challenges and Opportunities after 80 years", 201
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Atmospheric rivers do not explain UK summer extreme rainfall
Extreme rainfall events continue to be one of the largest natural hazards in the UK. In winter, heavy precipitation and floods have been linked with intense moisture transport events associated with atmospheric rivers (ARs), yet no large-scale atmospheric precursors have been linked to summer flooding in the UK. This study investigates the link between ARs and extreme rainfall from two perspectives: 1) Given an extreme rainfall event, is there an associated AR? 2) Given an AR, is there an associated extreme rainfall event? We identify extreme rainfall events using the UK Met Office daily rain-gauge dataset and link these to ARs using two different horizontal resolution atmospheric datasets (ERA-Interim and 20th Century Re-analysis). The results show that less than 35% of winter ARs and less than 15% of summer ARs are associated with an extreme rainfall event. Consistent with previous studies, at least 50% of extreme winter rainfall events are associated with an AR. However, less than 20% of the identified summer extreme rainfall events are associated with an AR. The dependence of the water vapor transport intensity threshold used to define an AR on the years included in the study, and on the length of the season, is also examined. Including a longer period (1900-2012) compared to previous studies (1979-2005) reduces the water vapor transport intensity threshold used to define an AR
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Stratigraphy of a Lateglacial lake basin sediment sequence at Turret Bank, upper Glen Roy, Lochaber: implications for the age of the Turret Fan
New lithostratigraphical, pollen-stratigraphical and tephrostratigraphical data are presented
for a sediment sequence at Turret Bank, a site that lies close to the confluence of the River
Turret with the River Roy in Lochaber, the western Scottish Highlands. The site is also
adjacent to the inner margin of a major gravel fan, the Glen Turret Fan, the age of which has
been debated and has a crucial bearing on the overall sequence of events in Glen Roy,
especially concerning the maximum limit of Loch Lomond Readvance (Younger Dryas) ice.
Several lines of evidence point to the sediment sequence at Turret bank having been wholly
deposited during the Loch Lomond Stadial-early Holocene transition: (i) the pollen sequence
is typical for this transitional period; (ii) varved deposits preserved in the sequence bear a
strong resemblance to mid-Stadial varves in a regional master varve scheme for Glen Roy
and vicinity (the Lochaber Master Varve Chronology); and (iii) an early Holocene tephra –
the Askja-S Tephra – is preserved within the sequence. Some limitations with the new data
are considered, but it is concluded that the coherent integration of lithostratigraphic,
geomorphological, pollen-stratigraphical and tephrostratigraphical data point to the likelihood
that Loch Lomond Readvance ice extended to the inner margin of the Glen Turret Fan, and
that the fan was probably constructed by glacial meltwaters at this time
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