143 research outputs found
No Pulsar Left Behind. I. Timing, Pulse-sequence Polarimetry, and Emission Morphology for 12 pulsars
In this paper we study a set of twelve pulsars that previously had not been
characterized. Our timing shows that eleven of them are "normal" isolated
pulsars, with rotation periods between 0.22 and 2.65 s, characteristic ages
between 0.25 Myr and 0.63 Gyr, and estimated magnetic fields ranging from 0.05
to 3.8x 10^{12} G. The youngest pulsar in our sample, PSR~J0627+0706, is
located near the Monoceros supernova remnant (SNR G205.5+0.5), but it is not
the pulsar most likely to be associated with it. We also confirmed the
existence of a candidate from an early Arecibo survey, PSR~J2053+1718, its
subsequent timing and polarimetry are also presented here. It is an isolated
pulsar with a spin period of 119 ms, a relatively small magnetic field of
5.8x10^9 G and a characteristic age of 6.7 Gyr; this suggests the pulsar was
mildly recycled by accretion from a companion star which became unbound when
that companion became a supernova. We report the results of single-pulse and
average Arecibo polarimetry at both 327 and 1400 MHz aimed at understanding the
basic emission properties and beaming geometry of these pulsars. Three of them
(PSRs~J0943+2253, J1935+1159 and J2050+1259) have strong nulls and sporadic
radio emission, several others exhibit interpulses (PSRs J0627+0706 and
J0927+2345) and one shows regular drifting subpulses (J1404+1159).Comment: 17 pages, 14 figure
The Long Wavelength Array Software Library
The Long Wavelength Array Software Library (LSL) is a Python module that
provides a collection of utilities to analyze and export data collected at the
first station of the Long Wavelength Array, LWA1. Due to the nature of the data
format and large-N (100 inputs) challenges faced by the LWA, currently
available software packages are not suited to process the data. Using tools
provided by LSL, observers can read in the raw LWA1 data, synthesize a filter
bank, and apply incoherent de-dispersion to the data. The extensible nature of
LSL also makes it an ideal tool for building data analysis pipelines and
applying the methods to other low frequency arrays.Comment: accepted to the Journal of Astronomical Instrumentation; 24 pages, 4
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The Impact of Spatial Heterogeneity in Land Use Practices and Aquifer Characteristics on Groundwater Conservation Policy Cost
Estimation of agricultural policy cost for a given level of groundwater conservation requires the establishment of an accurate baseline condition. This is especially critical when the benefits and cost of any conservation program are generally estimated relative to the status quo policy or baseline situation. An inaccurate baseline estimate will lead to poor estimates of potential water conservation savings and agricultural policy cost. Over a 60-year planning horizon per acre net present value is as much as 29.8% higher for a study area when aquifer characteristics are assumed to be homogenous and set to their average area value than when the heterogeneity in aquifer characteristics is explicitly modeled.Aquifer Modeling, Economics, Resource /Energy Economics and Policy,
Observability of pulsar beam bending by the Sgr~A* black hole
According to some models, there may be a significant population of radio
pulsars in the Galactic center. In principle, a beam from one of these pulsars
could pass close to the supermassive black hole (SMBH) at the center, be
deflected, and be detected by Earth telescopes. Such a configuration would be
an unprecedented probe of the properties of spacetime in the moderate- to
strong-field regime of the SMBH. We present here background on the problem, and
approximations for the probability of detection of such beams. We conclude that
detection is marginally probable with current telescopes, but that telescopes
that will be operating in the near future, with an appropriate multiyear
observational program, will have a good chance of detecting a beam deflected by
the SMBH.Comment: 18 pages, 16 figure
AN ECCENTRIC BINARY MILLISECOND PULSAR with A HELIUM WHITE DWARF COMPANION in the GALACTIC FIELD
Low-mass white dwarfs (LMWDs) are believed to be exclusive products of binary evolution, as the universe is not old enough to produce them from single stars. Because of the strong tidal forces operating during the binary interaction phase, the remnant systems observed today are expected to have negligible eccentricities. Here, we report on the first unambiguous identification of an LMWD in an eccentric (e = 0.13) orbit around the millisecond pulsar PSR J2234+0511, which directly contradicts this picture. We use our spectra and radio-timing solution (derived elsewhere) to infer the WD temperature (Teff = 8600 ±190 K), and peculiar systemic velocity relative to the local standard of rest ( km s-1). We also place model-independent constraints on the WD radius ( ) and surface gravity ( dex). The WD and kinematic properties are consistent with the expectations for low-mass X-ray binary evolution and disfavor a dynamic three-body formation channel. In the case of the high eccentricity being the result of a spontaneous phase transition, we infer a mass of ∼1.60 M o for the pulsar progenitor, which is too low for the quark-nova mechanism proposed by Jiang et al., and too high for the scenario of Freire & Tauris, in which a WD collapses into a neutron star via a rotationally delayed accretion-induced collapse. We find that eccentricity pumping via interaction with a circumbinary disk is consistent with our inferred parameters. Finally, we report tentative evidence for pulsations that, if confirmed, would transform the star into an unprecedented laboratory for WD physics
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