A 1.05 M{sub ☉} companion to PSR J2222–0137: The coolest known white dwarf?
- Department of Physics, University of Wisconsin-Milwaukee, 1900 East Kenwood Boulevard, Milwaukee, WI 53211 (United States)
- Department of Physics and Astronomy, West Virginia University, White Hall, Box 6315, Morgantown, WV 26506-6315 (United States)
- Department of Physics and Astronomy, University of North Carolina, Chapel Hill, NC 27599-3255 (United States)
- Space Radiation Laboratory, California Institute of Technology, 1200 East California Boulevard, MC 249-17, Pasadena, CA 91125 (United States)
- ASTRON, P.O. Box 2, 7990 AA Dwingeloo (Netherlands)
- National Radio Astronomy Observatory, 520 Edgemont Road, Charlottesville, VA 22903-2475 (United States)
The recycled pulsar PSR J2222–0137 is one of the closest known neutron stars (NSs) with a parallax distance of 267{sub −0.9}{sup +1.2} pc 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 M{sub ☉}) and a high companion mass (1.05 ± 0.06 M{sub ☉}) consistent with either a low-mass NS or a high-mass white dwarf. We can largely reject the NS hypothesis on the basis of the system's extremely low eccentricity (3 × 10{sup –4})—too low to have been the product of two supernovae under normal circumstances. However, despite deep optical and near-infrared searches with Southern Astrophysical Research 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 crystallized and entered the faster Debye-cooling regime.
- OSTI ID:
- 22365697
- Journal Information:
- Astrophysical Journal, Vol. 789, Issue 2; Other Information: Country of input: International Atomic Energy Agency (IAEA); ISSN 0004-637X
- Country of Publication:
- United States
- Language:
- English
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