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Originally published in Science Express on 15 May 2008
Science 6 June 2008:
Vol. 320. no. 5881, pp. 1309 - 1312
DOI: 10.1126/science.1157580
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Research Articles

An Eccentric Binary Millisecond Pulsar in the Galactic Plane

David J. Champion1,2*, Scott M. Ransom3, Patrick Lazarus1, Fernando Camilo4, Cees Bassa1, Victoria M. Kaspi1, David J. Nice5, Paulo C. C. Freire6, Ingrid H. Stairs7, Joeri van Leeuwen8, Ben W. Stappers9, James M. Cordes10, Jason W. T. Hessels11, Duncan R. Lorimer12, Zaven Arzoumanian13, Don C. Backer8, N. D. Ramesh Bhat14, Shami Chatterjee15, Ismaël Cognard16, Julia S. Deneva10, Claude-André Faucher-Giguère17, Bryan M. Gaensler15, JinLin Han18, Fredrick A. Jenet19, Laura Kasian7, Vlad I. Kondratiev12, Michael Kramer9, Joseph Lazio20, Maura A. McLaughlin12, Arun Venkataraman6 and Wouter Vlemmings21

1 Department of Physics, McGill University, Montreal, QC H3A 2T8, Canada.
2 Australia Telescope National Facility (ATNF), Commonwealth Scientific and Industrial Research Organisation, Post Office Box 76, Epping NSW 1710, Australia.
3 National Radio Astronomy Observatory, 520 Edgemont Road, Charlottesville, VA 22903, USA.
4 Columbia Astrophysics Laboratory, Columbia University, 550 West 120th Street, New York, NY 10027, USA.
5 Physics Department, Bryn Mawr College, Bryn Mawr, PA 19010, USA.
6 National Astronomy and Ionosphere Center (NAIC), Arecibo Observatory, HC03 Box 53995, Arecibo, PR 00612, USA.
7 Department of Physics and Astronomy, University of British Columbia, 6224 Agricultural Road, Vancouver, BC V6T 1Z1, Canada.
8 Astronomy Department, 441 Campbell Hall, University of California at Berkeley, Berkeley, CA 94720, USA.
9 Jodrell Bank Observatory, Manchester University, Macclesfield, Cheshire SK11 9DL, UK.
10 Astronomy Department, Cornell University, Ithaca, NY 14853, USA.
11 Astronomical Institute "Anton Pannekoek," University of Amsterdam, Kruislaan 403, 1098 SJ Amsterdam, The Netherlands.
12 Department of Physics, West Virginia University, Morgantown, WV 26506, USA.
13 Center for Research and Exploration in Space Science and Technology, and X-ray Astrophysics Laboratory, NASA Goddard Space Flight Center, Code 662, Greenbelt, MD 20771, USA.
14 Swinburne University of Technology, Post Office Box 218, Hawthorn, Victoria 3122, Australia.
15 School of Physics, The University of Sydney, NSW 2006 Australia.
16 LaboratoiredePhysiqueet Chimiedel'Environnement, Centre National de la Recherche Scientifique, UMR 6115 3A, Avenue de la Recherche Scientifique, F-45071 Orleans Cedex 2, France.
17 Harvard-Smithsonian Center for Astrophysics, 60 Garden Street, MS-10, Cambridge, MA 02138, USA.
18 National Astronomical Observatories, Chinese Academy of Sciences, Jia-20 DaTun Road, Chaoyang District, Beijing 100012, China.
19 Center for Gravitational Wave Astronomy, University of Texas, Brownsville, TX 78520, USA.
20 Naval Research Laboratory (NRL), 4555 Overlook Avenue, SW, Washington, DC 20375, USA.
21 Argelander-Institut für Astronomie, University of Bonn, Auf dem Hügel 71, 53121 Bonn, Germany.


Figure 1 Fig. 1. Residual pulse arrival times as a function of orbital phase (mean anomaly) for PSR J1903+0327 after subtraction of the best-fit timing model. The timing residuals are from observations made with the Arecibo telescope (blue circles), the Westerbork Synthesis Radio Telescope (red triangles), and the Green Bank Telescope (green crosses) and are defined as observed minus model. (Top) The measured timing residuals if no orbit is accounted for. The resulting curve is the Roemer delay (i.e., the light-travel time across the orbit), and its nonsinusoidal shape shows the large eccentricity (e = 0.44) of PSR J1903+0327. The uncertainties on the data points would be the same as in the lower panels, but the scale is different by a factor of 106. (Middle) The same residuals as in the top panel but with the Roemer delay and all general relativistic delays except for Shapiro delay from the timing solution in Table 1 removed. (Bottom) The timing residuals for the full Damour and Deruelle General Relativistic (DDGR) timing model described in Table 1, which assumes that general relativity fully describes the parameters of the binary system (32). The weighted root-mean-square timing residual shown here is 1.9 µs. [View Larger Version of this Image (30K GIF file)]
 

Figure 2 Fig. 2. Rotation periods, period derivatives, and orbital eccentricities (for binary pulsars) of pulsars in the disk of the Galaxy. The bottom face of the cube shows a plot of rotation period versus rotation period derivative for all Galactic pulsars. Colored points show the binary pulsars, projected upward from the bottom face in proportion to their orbital eccentricities. Square blue points are double neutron star systems, triangular green points are pulsars with MS or massive companions, circular yellow points are pulsars with white dwarf or sub-dwarf companions, and the red star is PSR J1903+0327, which occupies a unique place in the diagram. [View Larger Version of this Image (34K GIF file)]
 

Figure 3 Fig. 3. AKS-band image of the PSR J1903+0327 field taken during excellent seeing conditions (0.3 to 0.4'') with the Gemini North telescope. The red circle shows the 2-{sigma} error circle, with radius 0.32'' (produced by the frame-tie uncertainties in right ascension and declination), for the position of the pulsar based on astrometric calibrations made with the 2MASS catalog. The star within the error circle is the possible MS companion to the pulsar. [View Larger Version of this Image (128K GIF file)]
 

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