2,798 research outputs found
Magnetar-like Emission from the Young Pulsar in Kes 75
We report detection of magnetar-like X-ray bursts from the young pulsar PSR
J1846-0258, at the center of the supernova remnant Kes 75. This pulsar, long
thought to be rotation-powered, has an inferred surface dipolar magnetic field
of 4.9x10^13 G, higher than those of the vast majority of rotation-powered
pulsars, but lower than those of the ~12 previously identified magnetars. The
bursts were accompanied by a sudden flux increase and an unprecedented change
in timing behavior. These phenomena lower the magnetic and rotational
thresholds associated with magnetar-like behavior, and suggest that in neutron
stars there exists a continuum of magnetic activity that increases with
inferred magnetic field strength.Comment: 17 pages, 2 figures, accepted for publication in Science. Note: The
content of this paper is embargoed until February 21, 200
¿Qué tecnologías están siendo aplicadas en La Guajira (Colombia) para la recolección y distribución de agua?
Within this article we take a brief look at the water situation in Guajira (Colombia). We talk about the available water resource and its rationing for the support of the community. We also present a small historical review to know the origin of the inconveniences related to water in the territory. The technologies used to obtain drinking water are then discussed. First, we describe the drinking water wells that are not an applied technology, but they are one of the main sources of supply, and are still being installed throughout the region. Secondly we will see the water desalination system, its application in this territory and its different methods and techniques developed, and as the latest technology is the Warka wáter, an ambitious project but little applied due to the climatic and geographical conditions of the territory.Dentro de este artículo damos un breve vistazo a la situación del agua en la Guajira (Colombia). Se habla del recurso hídrico disponible y su racionamiento para el sostenimiento de la comunidad. También se presenta una pequeña reseña histórica para conocer el origen de los inconvenientes relacionados con el agua en el territorio. Luego se habla de las tecnologías usadas para la obtención de agua potable. Primero se describen los pozos de agua potable que no son una tecnología aplicada, pero son una de las principales fuentes de abastecimiento, y aun en la actualidad están siendo instalados por toda la región. En segundo lugar veremos el sistema de desalinización de agua, su aplicación en este territorio y sus diferentes métodos y técnicas desarrolladas, y como última tecnología está el Warka wáter un proyecto ambicioso pero poco aplicado por las condiciones climáticas y geográficas del territorio
PSR J2229+6114: Discovery of an Energetic Young Pulsar in the Error Box of the EGRET Source 3EG J2227+6122
We report the detection of radio and X-ray pulsations at a period of 51.6 ms
from the X-ray source RX/AX J2229.0+6114 in the error box of the EGRET source
3EG J2227+6122. An ephemeris derived from a single ASCA observation and
multiple epochs at 1412 MHz from Jodrell Bank indicates steady spin-down with
P-dot = 7.83 x 10^(-14) s/s. From the measured P and P-dot we derive spin-down
power E-dot = 2.2 x 10^(37) erg/s, magnetic field B = 2.0 x 10^(12) G, and
characteristic age P/2P-dot = 10,460 yr. An image from the Chandra X-ray
Observatory reveals a point source surrounded by centrally peaked diffuse
emission that is contained within an incomplete radio shell. We assign the name
G106.6+2.9 to this new supernova remnant, which is evidently a pulsar wind
nebula. For a distance of 3 kpc estimated from X-ray absorption, the ratio of
X-ray luminosity to spin-down power is ~8 x 10^(-5), smaller than that of most
pulsars, but similar to the Vela pulsar. If PSR J2229+6114 is the counterpart
of 3EG J2227+6122 then its efficiency of gamma-ray production, if isotropic, is
0.016 (d/3 kpc)^2. It obeys an established trend of gamma-ray efficiency among
known gamma-ray pulsars which, in combination with the demonstrated absence of
any other plausible counterpart for 3EG J2227+6122, makes the identification
compelling. If confirmed, this identification bolsters the pulsar model for
unidentified Galactic EGRET sources.Comment: 5 pages, 4 figures, accepted by The Astrophysical Journal Letter
The Parkes multibeam pulsar survey: IV. Discovery of 180 pulsars and parameters for 281 previously known pulsars
The Parkes multibeam pulsar survey has led to the discovery of more than 700
pulsars. In this paper, we provide timing solutions, flux densities and pulse
profiles for 180 of these new discoveries. Two pulsars, PSRs J1736-2843 and
J1847-0130 have rotational periods P > 6s and are therefore among the slowest
rotating radio pulsars known. Conversely, with P = 1.8ms, PSR J1843-1113 has
the third shortest period of pulsars currently known. This pulsar and PSR
J1905+0400 (P = 3.8ms) are both solitary. We also provide orbital parameters
for a new binary system, PSR J1420-5625, which has P = 34ms, an orbital period
of 40 days and a minimum companion mass of 0.4 solar masses. The 10 degree-wide
strip along the Galactic plane that was surveyed is known to contain 264 radio
pulsars that were discovered prior to the multibeam pulsar survey. We have
redetected almost all of these pulsars and provide new dispersion measure
values and flux densities at 20cm for the redetected pulsars.Comment: 35 pages, accepted for publication in MNRAS, a high quality image of
the figure on page 32 is available from
http://www.atnf.csiro.au/research/pulsar/images/pmsurvey_fig.p
On the Possibility of the Detection of Extinct Radio Pulsars
We explore the possibilities for detecting pulsars that have ceased to
radiate in the radio band. We consider two models: the model with hindered
particle escape from the pulsar surface (first suggested by Ruderman and
Sutherland 1975) and the model with free particle escape (Arons 1981; Mestel
1999). In the model with hindered particle escape, the number of particles that
leave the pulsar magnetosphere is small and their radiation cannot be detected
with currently available instruments. At the same time, for the free particle
escape model, both the number of particles and the radiation intensity are high
enough for such pulsars to be detectable with the presently available receivers
such as GLAST and AGILE spacecrafts. It is also possible that extinct radio
pulsars can be among the unidentified EGRET sources.Comment: 5 pages, 1 figure corrected version of the paper that was published
in Astronomy Letter
CoRoT measures solar-like oscillations and granulation in stars hotter than the Sun
Oscillations of the Sun have been used to understand its interior structure.
The extension of similar studies to more distant stars has raised many
difficulties despite the strong efforts of the international community over the
past decades. The CoRoT (Convection Rotation and Planetary Transits) satellite,
launched in December 2006, has now measured oscillations and the stellar
granulation signature in three main sequence stars that are noticeably hotter
than the sun. The oscillation amplitudes are about 1.5 times as large as those
in the Sun; the stellar granulation is up to three times as high. The stellar
amplitudes are about 25% below the theoretic values, providing a measurement of
the nonadiabaticity of the process ruling the oscillations in the outer layers
of the stars.Comment: 7 pages, 4 figure
Polarized radio emission from the magnetar XTE J1810-197
We have used the Parkes radio telescope to study the polarized emission from
the anomalous X-ray pulsar XTE J1810-197 at frequencies of 1.4, 3.2, and 8.4
GHz. We find that the pulsed emission is nearly 100% linearly polarized. The
position angle of linear polarization varies gently across the observed pulse
profiles, varying little with observing frequency or time, even as the pulse
profiles have changed dramatically over a period of 7 months. In the context of
the standard pulsar "rotating vector model," there are two possible
interpretations of the observed position angle swing coupled with the wide
profile. In the first, the magnetic and rotation axes are substantially
misaligned and the emission originates high in the magnetosphere, as seen for
other young radio pulsars, and the beaming fraction is large. In the second
interpretation, the magnetic and rotation axes are nearly aligned and the line
of sight remains in the emission zone over almost the entire pulse phase. We
deprecate this possibility because of the observed large modulation of thermal
X-ray flux. We have also measured the Faraday rotation caused by the Galactic
magnetic field, RM = +77 rad/m^2, implying an average magnetic field component
along the line of sight of 0.5 microG.Comment: Accepted for publication in ApJ Letters. Six pages with 4 figure
Densidade e tamanho de grupos de Callicebus cf pallescens (Primates: Pitheciidae) na Fazenda Santa Teresa, Pantanal.
Os primatas da infraordem Platyrrhini são divididos em quatro famílias, dentre elas a Pitheciidae. Um gênero bastante representativo nesta família é Callicebus, com 29 espécies reconhecidas, sendo que 22 ocorrem no Brasil e apenas uma destas, Callicebus pallescens, ocorre na região do Pantanal. Esta espécie, conhecida popularmente na região como boca-d’água, é encontrada nas regiões não inundáveis da borda oeste do Pantanal, especialmente no Maciço do Urucum, Morrarias do Castelo e de Santa Teresa, além da Serra do Amolar. Dados existentes para Callicebus no Pantanal foram coletados utilizando métodos limitados. Este trabalho buscou estimar a densidade e o tamanho dos grupos de Callicebus cf pallescens, na fazenda Santa Teresa, localizada na Morraria de Santa Teresa e baía Vermelha, Corumbá, MS. The Primates of the Platyrrhini infraorder are divided in four families, being Pitheciidae one of them. A very representative genus in this family is Callicebus with 29 known species, 22 of them occurring in Brazil and only one of them, Callicebus pallescens, occurring in the Pantanal Wetland region. This titi monkey species, which is known as “boca-d´água” in the region, is found in the not flooded areas of Pantanal west border, mainly at Urucum Mountain range, Castelo e Santa Teresa mountains, besides the Serra do Amolar ridge. Existing data on Callicebus pallescens at the Pantanal were collected using limited methods. This research aimed to estimate density and group size of Callicebus cf pallescens at the Santa Teresa Ranch (18°18’ S; 57°30’ W), located in the mountains Santa Tereza and Baía Vermelha, Corumbá, MS
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