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Post Info TOPIC: PSR J2222-0137
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RE: PSR J2222-0137
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Title: A Massive-born Neutron Star with a Massive White Dwarf Companion
Author: Ismael Cognard, Paulo C. C. Freire, Lucas Guillemot, Gilles Theureau, Thomas M. Tauris, Norbert Wex, Eleni Graikou, Michael Kramer, Ben Stappers, Andrew G. Lyne, Cees Bassa, Gregory Desvignes, Patrick Lazarus

We report on the results of a 4-year timing campaign of PSR J2222-0137, a 2.44-day binary pulsar with a massive white dwarf (WD) companion, with the Nancay, Effelsberg and Lovell radio telescopes. Using the Shapiro delay for this system, we find a pulsar mass m_{p}=1.76±0.06 solar masses and a WD mass m_{c},=,1.293 ±0.025 solar mass. We also measure the rate of advance of periastron for this system, which is marginally consistent with the GR prediction for these masses. The short lifetime of the massive WD progenitor star led to a rapid X-ray binary phase with little (< 10^{-2} solar masses) mass accretion onto the neutron star (NS); hence, the current pulsar mass is, within uncertainties, its birth mass; the largest measured to date. We discuss the discrepancy with previous mass measurements for this system; we conclude that the measurements presented here are likely to be more accurate. Finally, we highlight the usefulness of this system for testing alternative theories of gravity by tightly constraining the presence of dipolar radiation. This is of particular importance for certain aspects of strong-field gravity, like spontaneous scalarization, since the mass of PSR J2222-0137 puts that system into a poorly tested parameter range.

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RA: 22 22 05.96345, Dec -01 37 15.6270



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Title: A 1.05 Solar Mass Companion to PSR J2222-0137: The Coolest Known White Dwarf?
Author: David L. Kaplan, Jason Boyles, Bart H. Dunlap, Shriharsh P. Tendulkar, Adam T. Deller, Scott M. Ransom, Maura A. McLaughlin, Duncan R. Lorimer

The recycled pulsar PSR J2222-0137 is one of the closest known neutron stars, with a parallax distance of 267+1.2-0.9pc and an edge-on orbit. We measure the Shapiro delay in the system through pulsar timing with the Green Bank Telescope, deriving a low pulsar mass (1.20±0.14 solar masses) and a high companion mass (1.05±0.06 solar masses) consistent with either a low-mass neutron star or a high-mass white dwarf. We can largely reject the neutron star hypothesis on the basis of the system's extremely low eccentricity (3e-4) - too low to have been the product of two supernovae under normal circumstances. However, despite deep optical and near-infrared searches with SOAR and the Keck telescopes we have not discovered the optical counterpart of the system. This is consistent with the white dwarf hypothesis only if the effective temperature is <3000 K, a limit that is robust to distance, mass, and atmosphere uncertainties. This would make the companion to PSR J2222-0137 one of the coolest white dwarfs ever observed. For the implied age to be consistent with the age of the Milky Way requires the white dwarf to have already crystallised and entered the faster Debye-cooling regime.

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