CHIME Discovery of a Binary Pulsar with a Massive Non-Degenerate Companion

Bridget Andersen ( Université McGill )

Of the more than 3,000 radio pulsars currently known, only ~300 are in binary systems, and only five of these consist of young pulsars with massive non-degenerate companions. We present the discovery and initial timing, accomplished using the Canadian Hydrogen Intensity Mapping Experiment (CHIME) telescope, of the 6th such binary pulsar, PSR J2108+4516, a radio pulsar with a 0.577-s spin period in a 269-day orbit of eccentricity 0.09 around a companion of minimum mass ~11 solar masses. Notably, the pulsar undergoes periods of substantial eclipse, disappearing from the CHIME 400-800 MHz observing band for a large fraction of its orbit, and significant dispersion measure and scattering variations throughout its orbit, pointing to the possibility of a circumstellar disk or very dense stellar wind associated with the companion star. Sub-arcsecond resolution imaging with the Karl G. Jansky Very Large Array unambiguously localized the source to an OBe-type massive companion, located at a distance of ~3 kpc. With further multi-wavelength follow-up, PSR J2108+4516 promises to serve as another rare laboratory for the exploration of companion winds, circumstellar disks, and short-term evolution through extended-body orbital dynamics.