The Binary Nature of PSR J2032+4127

TL;DR

This paper presents evidence that PSR J2032+4127 is part of a highly-eccentric binary system with a Be star, explaining its increased spin-down rate and predicting an upcoming periastron in 2018 for observing high-energy emissions.

Contribution

It provides the first binary model for PSR J2032+4127, linking its spin-down behavior to binary motion and predicting observable phenomena during the next periastron.

Findings

PSR J2032+4127 is in a binary system with a Be star.

The binary orbit has a period of 20-30 years.

Upcoming periastron in early 2018 offers observational opportunities.

Abstract

PSR J2032+4127 is a gamma-ray and radio-emitting pulsar which has been regarded as a young luminous isolated neutron star. However, its recent spin-down rate has extraordinarily increased by a factor of two. We present evidence that this is due to its motion as a member of a highly-eccentric binary system with a 15-solar-mass Be star, MT91~213. Timing observations show that, not only are the positions of the two stars coincident within 0.4 arcsec, but timing models of binary motion of the pulsar fit the data much better than a model of a young isolated pulsar. MT91~213, and hence the pulsar, lie in the Cyg~OB2 stellar association, which is at a distance of only 1.4-1.7 kpc. The pulsar is currently on the near side of, and accelerating towards, the Be star, with an orbital period of 20-30 years. The next periastron is well-constrained to occur in early 2018, providing an opportunity to observe enhanced high-energy emission as seen in other Be-star binary systems.