21-year timing of the black-widow pulsar J2051-0827
  Timing results for the black-widow pulsar J2051-0827 are presented, using a 21-year dataset from four European Pulsar Timing Array telescopes and the Parkes radio telescope. This dataset, which is the longest published to date for a black-widow system, allows for an improved analysis that addresses previously unknown biases. While secular variations, as identified in previous analyses, are recovered, short-term variations are detected for the first time. Concurrently, a significant decrease of approx. 2.5x10-3 cm-3 pc in the dispersion measure associated with PSR J2051-0827 is measured for the first time and improvements are also made to estimates of the proper motion. Finally, PSR J2051-0827 is shown to have entered a relatively stable state suggesting the possibility of its eventual inclusion in pulsar timing arrays. 
G. Shaifullah, J. P. W. Verbiest, P. C. C. Freire, T. M. Tauris, N.   Wex, S. Os{\l}owski, B. W. Stappers, C. G. Bassa, R. N...
astro-ph.HE astro-ph.GA astro-ph.SR