An Apparent Precessing Helical Outflow from a Massive Evolved Star: Evidence for Binary Interaction


Ryan M. Lau$^{1,2}$, Matthew J. Hankins$^{1}$, Terry L. Herter$^{1}$, Mark R. Morris$^{3}$, Elisabeth A. C. Mills$^{4}$, Michael E. Ressler$^{2}$

1 - Cornell Astronomy Department; 2 - Caltech/JPL; 3 - Department of Physics and Astronomy, UCLA; 4 - National Radio Astronomy Observatory

Massive, evolved stars play a crucial role in the metal-enrichment, dust budget, and energetics of the interstellar medium; however, the details of their evolution are uncertain because of their rarity and short lifetimes before exploding as supernovae. Discrepancies between theoretical predictions from single-star evolutionary models and observations of massive stars have evoked a shifting paradigm that implicates the importance of binary interaction. We present mid- to far-infrared observations from the Stratospheric Observatory for Infrared Astronomy (SOFIA) of a conical ``helix'' of warm dust ($\sim180$ K) that appears to extend from the Wolf-Rayet star WR102c. Our interpretation of the helix is a precessing, collimated outflow that emerged from WR102c during a previous evolutionary phase as a rapidly rotating luminous blue variable. We attribute the precession of WR102c to gravitational interactions with an unseen compact binary companion whose orbital period can be constrained to $800\,\mathrm{d} < P < 1400$ d from the inferred precession period, $\tau_p \sim 1.4\times 10^4$ yr, and limits imposed on the stellar and orbital parameters of the system. Our results concur with the range of orbital periods ($P\lesssim 1500$ d) where spin-up via mass exchange is expected to occur for massive binary systems.

Reference: arXiv:1512.07639
Status: Manuscript has been accepted

Weblink: http://arxiv.org/abs/1512.07639

Comments: Revised version to be updated Tuesday 1/19/2016

Email: ryanlau@caltech.edu