The X-ray Counterpart Of The High-B Pulsar PSR J0726-2612
Abstract
Middle-aged, cooling neutron stars are observed both as relatively rapidly spinning radio pulsars and as more slowly spinning, strongly magnetized isolated neutron stars (INSs), which stand out by their thermal X-ray spectra. The difference between the two classes may be that the INSs initially had much strong magnetic fields that have decayed. In order to test this, we used the Chandra X-ray Observatory to observe 1RXS J072559.8-261229, a possible X-ray counterpart to PSR J0726-2612, the nearest and least extincted among the possible slowly-spinning, strong-field INS progenitors with a 3.44 s period and an inferred magnetic field of 3×1013 G (it is likely in the Gould belt, at 1 kpc). We confirm the identification and find that the pulsar has a spectrum consistent with being purely thermal, with a blackbody temperature kT = 87±5 eV and radius R 5.7 km kpc-1. We also detect sinusoidal pulsations at twice the radio period with a semi-amplitude of 27±5%. The properties of PSR J0726-2612 strongly resemble those of the INSs, except for its much shorter characteristic age of 200 kyr (rather than several Myr). We conclude that PSR J0726-2612 is indeed an example of a young INS - one that started with a magnetic field strength on the low end of those inferred for the INSs and, therefore, has decayed by a relatively small amount. Our results suggest that long-period, strong-field pulsars and INSs are members of the same class. Our identification also opens up new opportunities to understand the puzzling X-ray and optical emission of the INSs, since radio timing, polarimetry, and astrometry can all better constrain the distance, age, phase stability, and emitting geometry of PSR J0726-2612 than would be possible with X-ray data alone.
- Publication:
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American Astronomical Society Meeting Abstracts #219
- Pub Date:
- January 2012
- Bibcode:
- 2012AAS...21923702S