PSR J1903+0327

PSR J1903+0327 is a millisecond pulsar in a highly eccentric binary orbit.[1]

The pulsar was discovered in an ongoing L-band (1.4 GHz) survey with the 305 m diameter Arecibo radio telescope.[2]

The pulse period is 2.15 ms, or 465.1 times per second. Analysis of the pulse timing residuals shows a binary orbit with a period of 95.17 days, and a high eccentricity, e = 0.437. The mass of the companion is ~1 solar mass (M☉), while the pulsar mass is unusually large at 1.67 ± 0.02 M☉;[3] the third largest precisely measured mass after those of PSR J1614−2230 and PSR J0348+0432. A near-infrared companion, KS = 18 (2.22µ), is observed in Gemini North images at its radio position, in 2011 radial velocity measurements made with the VLT confirmed this to be the companion to the millisecond pulsar; the first such system to be observed in the Galaxy.

Popular theories for the formation of binary millisecond pulsars require mass transfer onto the rotating neutron star from a white dwarf companion in order to spin it up to periods less than about 10 ms—a process expected to be accompanied by strong tidal forces, producing a highly circular orbit. The main-sequence companion and the eccentric orbit of PSR J1903+0327 do not conform to this expectation. The system is likely to have originated as a triple system. The remnant of the star that transferred mass to the neutron star (its original close companion) was later ejected by a gravitational interaction with the unevolved third member of the system; its present main-sequence companion.

References
  1. Champion, David J.; Ransom, S. M.; Lazarus, P.; Camilo, F.; Bassa, C.; Kaspi, V. M.; Nice, D. J.; Freire, P. C. C.; et al. (2008). "An Eccentric Binary Millisecond Pulsar in the Galactic Plane". Science. 320 (5881): 1309–1312. arXiv:0805.2396. Bibcode:2008Sci...320.1309C. doi:10.1126/science.1157580. PMID 18483399. S2CID 6070830.
  2. Cordes, J. M.; Freire, P. C. C.; Lorimer, D. R.; Camilo, F.; Champion, D. J.; Nice, D. J.; Ramachandran, R.; Hessels, J. W. T.; et al. (2006). "Arecibo Pulsar Survey Using ALFA. I. Survey Strategy and First Discoveries". Astrophys. J. 637 (1): 446–455. arXiv:astro-ph/0509732. Bibcode:2006ApJ...637..446C. doi:10.1086/498335. S2CID 55390845.
  3. Freire, P. C. C.; Bassa, C. G.; Wex, N.; Stairs, I. H.; Champion, D. J.; Ransom, S. M.; Lazarus, P.; Kaspi, V. M.; et al. (2011). "On the nature and evolution of the unique binary pulsar J1903+0327". Monthly Notices of the Royal Astronomical Society. 412 (4): 2763. arXiv:1011.5809. Bibcode:2011MNRAS.412.2763F. doi:10.1111/j.1365-2966.2010.18109.x. S2CID 67841433.


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