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Thu Jul 05, 2007

Two accretion-powered millisecond pulsars active in June

I'm not sorry to be wrong about HETE J1900.1-2455 returning to quiescence; Swift and RXTE observations following the nondetection last month indicate that the source is as bright as before. This is bad news for anticipated measurements of the quiescent flux with Chandra, but good news for our ongoing RXTE monitoring and pulsation searches.

Also last month the 8th accretion-powered millisecond pulsar was discovered, Swift J1756.9-2508. At 182 Hz the source is the slowest of the class (by 3 Hz); the 54-minute orbital period indicates an ultracompact (and thus likely H-poor) mass donor. The pulsar was only active for two weeks, and was undetected with Swift by June 21. A paper is in preparation by the Swift team.

Labels: 2007, /pulsars