* Astronomy

Title: 1FGL J1417.7-4407: A gamma-ray bright binary with a massive neutron star and a giant secondary
Author: Jay Strader (Michigan St.), Laura Chomiuk (Michigan St.), C. C. Cheung (NRL), David J. Sand (Texas Tech), Davide Donato (CRESST/Maryland), Robin Corbet (CRESST), Dana Koeppe (Michigan St.), Philip G. Edwards (CSIRO), Jamie Stevens (CSIRO), Leonid Petrov (Astrogeo), Ricardo Salinas (Michigan St.), Mark Peacóck (Michigan St.), Thomas Finzell (Michigan St.), Daniel Reichart (UNC), Joshua Haislip (UNC)

We present multiwavelength observations of the persistent Fermi-LAT unidentified gamma-ray source 1FGL J1417.7-4407, showing it is likely to be associated with a newly discovered X-ray binary containing a massive neutron star (nearly 2 M_sun) and a ~ 0.4 M_sun giant secondary with a 5.4 day period. SOAR optical spectroscopy at a range of orbital phases reveals variable double-peaked H-alpha emission, consistent with the presence of an accretion disk. The lack of radio emission and evidence for a disk suggests the gamma-ray emission is unlikely to originate in a pulsar magnetosphere, but could instead be associated with a pulsar wind, relativistic jet, or could be due to synchrotron self-Compton at the disk/magnetosphere boundary. Assuming a wind or jet, the high ratio of gamma-ray to X-ray luminosity (~ 20) suggests efficient production of gamma-rays, perhaps due to the giant companion. The system appears to be a low-mass X-ray binary that has not yet completed the pulsar recycling process. This system is a good candidate to monitor for a future transition between accretion-powered and rotational-powered states, but in the context of a giant secondary.

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