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Discovery Of The Millisecond Pulsar PSR J2043+1711

03/04/2012

It is with great pleasure that I am able to report the discovery of a new member of the millisecond pulsar (MSP) family by Guillemot et al. 2012. This new MSP, confirmed with the Green Bank Telescope, has a spin period of 2.38 ms, is relatively nearby (d <~2 kpc) and is in a 1.48 day orbit around a low mass companion, probably a He-type (Helium) white dwarf. MSPs are a sub-class of neutron stars,  highly-magnetic and rapidly rotating; with typical rotational periods in the range of about 1-30 milliseconds ( Chakrabarty et al. 2003). PSR J2043+1711 is the third MSP to be discovered at Nançay in a Fermi source, after PSRs J2017+0603 and J2302+4442 (Cognard et al. 2011).

MSPs are thought to be re-cycled, in the sense that they were once slowly rotating and thus old neutron stars which have been spun-up to millisecond periods by the accretion of matter and thus transfer of angular momentum from a binary companion (Bisnovatyi-Kogan & Komberg 1974; Alpar et al. 1982) with the exception of perhaps just a handful, e.g. PSR B1937+21 (Kızıltan & Thorsett 2009). In this sense, MSPs are closely related to low-mass X-ray binary (LMXB) systems. The transfer of angular momentum by accreted matter from a low-mass companion acts to increased to rotation rate of the pulsar companion, performing up to hundred revolutions every second.

Despite the numerous discoveries, 30 per cent of the sources in the 2FGL catalogue remain unassociated and could potentially hide unknown gamma-ray pulsars. However, the discovery by Guillemot et al. 2012 is the first such 2FGL MSP association, linking PSR J2043+1711 to 2FGL J2043.2+1711.

Before this study, the Fermi LAT catalogue source 2FGL J2043.2+1711 was already listed in the 1FGL as 1FGL J2043.2+1709, and it had no known counterpart. It’s one saving grace was that it had spectral and variability properties that made it a plausible gamma-ray pulsar. After two unscuccessful observations of 2FGL J2043.2+1711, on December 12th of 2009, Guillemot et al. managed to capture statistically healthy 19σ candidate with a rotational period of 2.379 ms. was observed in the third observation. The 2.379-ms candidate was finally confirmed with observations made at the Green Bank Telescope at 350MHz during a survey of Fermi LAT unassociated sources (see Hessels et al. 2011) and at the Arecibo telescope at 327MHz with the .Wide-band Arecibo Pulsar Processors. Furthermore, substantial accelerations of the rotational period across the confirmation observations were measured, indicating that the pulsar is in a binary system, linking the MSP spin-up paradigm.

Of the pulsars discovered in Fermi unassociated sources that have been published to date (Cognard et al. 2011; Ransom et al. 2011; Keith et al. 2011), PSRs J2043+1711 and J2017+0603 are the two systems with the best timing precision. This happens because they have very sharp features in their pulse profiles (Guillemot et al. 2012). Given this high timing precision, Guillemot et al. stated that continued Arecibo timing might provide a precise distance measurement which, given the observed gamma-ray energy flux, and could provide a lower limit for the moment of inertia of this MSP.

Continued timing of PSR J2043+1711 will also improve the measurement of the Shapiro delay, providing precise estimates of the masses of the components of the system. Combining this precise mass with a lower limit on the moment of inertia could provide a stringent constraint of the equation of state (EoS) for neutron stars, an important theoretical step in compact object physics.

Journal References:

  • Kızıltan, B.; Thorsett, S. E. (2009) Constraints On Pulsar Evolution: The Joint Period-Spin-Down Distribution Of Millisecond PulsarsThe Astrophysical Journal: Letters, 693 (2): pp.L109–L112.
  • Ransom, S.M. et al. (2011) Three Millisecond Pulsars In Fermi LAT Unassociated Bright SourcesThe Astrophysical Journal: Letters, 727 (1), Article I.D.: L16.
  • Guillemot, L. et al. (2012) Discovery Of The Millisecond Pulsar PSR J2043+1711 In A Fermi Source With The Nançay Radio TelescopeMonthly Notices Royal Astronomical Society421 (3): pp. 1610-1627.
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