Millisecond pulsars’ age reassessed

UC Santa Cruz : Astronomers Bülent Kiziltan and Stephen Thorsett of the University of California, Santa Cruz , have come up with a more accurate way to peg the ages of millisecond pulsars.The standard method for estimating pulsar ages is known to yield unreliable results, especially for the fast-spinning millisecond pulsars, says Kiziltan."An accurate determination of pulsar ages is of fundamental importance, because it has ramifications for understanding the formation and evolution of pulsars, the physics of neutron stars, and other areas,” he adds.The standard approach to determine the “characteristic” or “spin-down” age of a pulsar is based on two parameters: the period between pulses and the rate at which they slow down. Kiziltan and Thorsett showed that this method may over- or under-estimate the age of a pulsar by a factor of 10 when applied to millisecond pulsars.To improve the accuracy of the standard technique, they incorporated additional constraints that arise from the spin-up process and physical limits on the maximum spin period. “We modified the age calculations to be consistent with these constraints and showed that this approach can achieve estimates closer to the true age of the pulsar,” Kiziltan says.By including in their model previously ignored features such as the maximum possible rate of rotation and subtle shifts in the observed radio frequency due to a pulsar’s motion across the sky, the team finds that some millisecond pulsars are up to 10 times younger or 10 times older than earlier estimates suggest.