arXiv subjects

M. J. Keith

Publications and source records attributed to M. J. Keith.

113 records · Page 7Linked to original sources

arXiv2010

Selection of radio pulsar candidates using artificial neural networks

Radio pulsar surveys are producing many more pulsar candidates than can be inspected by human experts in a practical length of time. Here we present a technique to automatically identify credible pulsar candidates from pulsar surveys using an artificial neural network. The technique has been applied to candidates from a recent re-analysis of the Parkes multi-beam pulsar survey resulting in the discovery of a previously unidentified pulsar.

astro-ph.IM↗

arXiv2009

Polarisation measurements of five pulsars with interpulses

We present polarisation observations of five pulsars whose profiles exhibit two distinct emission regions separated by close to 180 degrees of longitude. We fitted the position angle of the linear polarisation using the rotating vector model and convincingly show that all the pulsars have the angle between their magnetic and rotation axes close to 90 degrees. The simplest interpretation of the results is that we see `main pulse' emission from one pole and `interpulse' emission from the opposite pole. We have attempted to produce emission maps of the magnetosphere above the polar caps for each pulsar and find that the maps support the view that the emission region in pulsars is complex, even when the profile appears simple. For three pulsars, we can derive emission heights and polar maps which are consistent with emission regions located symmetrically about the magnetic axis and confined to the open field lines. For two pulsars, we find that either the emission arises from `closed' field lines or that the profiles are highly asymmetric with respect to the magnetic axis.

astro-ph.SR↗

arXiv2009

Discovery of 28 pulsars using new techniques for sorting pulsar candidates

Modern pulsar surveys produce many millions of candidate pulsars, far more than can be individually inspected. Traditional methods for filtering these candidates, based upon the signal-to-noise ratio of the detection, cannot easily distinguish between interference signals and pulsars. We have developed a new method of scoring candidates using a series of heuristics which test for pulsar-like properties of the signal. This significantly increases the sensitivity to weak pulsars and pulsars with periods close to interference signals. By applying this and other techniques for ranking candidates from a previous processing of the Parkes Multi-beam Pulsar Survey, 28 previously unknown pulsars have been discovered. These include an eccentric binary system and a young pulsar which is spatially coincident with a known supernova remnant.

astro-ph.SR↗

arXiv2008

PSR J1753-2240: A mildly recycled pulsar in an eccentric binary system

We report the discovery of PSR J1753-2240 in the Parkes Multibeam Pulsar Survey database. This 95-ms pulsar is in an eccentric binary system with a 13.6-day orbital period. Period derivative measurements imply a characteristic age in excess of 1 Gyr, suggesting that the pulsar has undergone an episode of accretion-induced spin-up. The eccentricity and spin period are indicative of the companion being a second neutron star, so that the system is similar to that of PSR J1811-1736, although other companion types cannot be ruled out at this time. The companion mass is constrained by geometry to lie above 0.48 solar masses, although long-term timing observations will give additional constraints. If the companion is a white dwarf or main sequence star, optical observations may yield a direct detection of the companion. If the system is indeed one of the few known double neutron star systems, it would lie significantly far from the recently proposed spin-period/eccentricity relationship.

astro-ph↗

arXiv2008

A high frequency search for radio pulsars in EGRET error boxes

We present a new survey for pulsars in the error boxes of the low-latitude EGRET sources 3EG J1027-5817, 3EG J1800-2338 and 3EG J1810-1032. Although all of these sources have been covered by previous pulsar surveys, the recent discovery of the young, energetic pulsar PSR J1410-6132 at 6.7 GHz has shown that pulsars of this type can be hidden from low frequency surveys. Using an observing frequency of 3.1 GHz we discovered a 91-ms pulsar, PSR J1028-5819, which observations made at the Parkes telescope and the Australia Telescope Compact Array have shown to be young and energetic. We believe this pulsar is likely to be powering the unidentified EGRET source 3EG J1027-5817. Like other energetic pulsars, PSR J1028-5819 is highly linearly polarised, but astonishingly has a pulse duty cycle of only 0.4%, one of the smallest in the entire pulsar catalogue.

astro-ph↗