ner_tags: O O O O O O O O O O O O O O O O O O B-Wavelength O O B-CelestialObject I-CelestialObject O O O O O O O O O O O O O O O O O O O O O O O O O O O B-CelestialObject I-CelestialObject O O O O O O O O O O O O O O O O O O O O O O O B-Citation I-Citation I-Citation I-Citation O O O O O O O O O O O O O O O O B-Wavelength O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O B-CelestialObject I-CelestialObject O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O B-Citation I-Citation I-Citation I-Citation I-Citation I-Citation B-CelestialObject I-CelestialObject O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O B-CelestialObject I-CelestialObject O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O B-Citation I-Citation I-Citation I-Citation I-Citation I-Citation O O O O O O O O O B-CelestialObject I-CelestialObject O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O B-Citation I-Citation I-Citation I-Citation O O O
tokens: are very restrictive, as η is likely to be less than unity. These limits can also accommodate the gamma-ray luminosity of 3FGL J1417.5–4402, 3 × 10 34 erg s −1 at a distance of 4.4 kpc (see Section 4 ). 3.5. Evolutionary Track With a binary period of 5.4 days, PSR J1417–4402 is on the evolutionary track of low-to-intermediate mass companions that started mass transfer onto a neutron star after they left the main sequence (Podsiadlowski et al. 2002 ), and have increasing periods. This distinguishes them from the black widows, redbacks, and other low-mass X-ray binaries that have binary periods day, began mass transfer on the main sequence, and evolve toward shorter periods. For 1 M secondaries, these classes are separated by a bifurcation period of hr at the onset of mass transfer. With M , the companion of PSR J1417–4402 must have already lost most of its initial mass, only a fraction of which, accreting onto the neutron star, is sufficient to spin it up to 2.66 ms. In the models of Podsiadlowski et al. ( 2002 ), PSR J1417–4402 is not far from the ends of the tracks that terminate when the binary period is in the range 6–20 days, and the companion is a He white dwarf of 0.2–0.3 M . The neutron stars in these calculations, assumed to begin with 1.4 M , end in the range 1.8–2.2 M . Exactly how far PSR J1417–4402 is along this evolution is difficult to determine, since its companion may or may not be filling its Roche lobe, may or may not be finished accreting onto the neutron star, and may be losing mass mostly through ablation by the pulsar wind, a process that is difficult to model. 4. CONCLUSIONS We have discovered a 2.66 ms pulsar in orbit around the 5.4 day optical variable discovered by Strader et al. ( 2015 ) in the error ellipse of the high-energy gamma-ray source 3FGL J1417.5–4402. The orbital dynamics require that the companion mass is M . The presence of radio pulsations suggests that the neutron star is not currently accreting (see Section 3.2 ). The pulsar is only detected a fraction of the time it is observed (although few observations exist at orbital phases Figure 2 ), and is likely eclipsed for more than half the orbit by outflowing material from the companion; this has so far prevented us from obtaining a phase-connected timing solution. The DM distance of 1.6 kpc is in conflict with the original estimate of , which was based on the assumption that the companion fills its Roche lobe. This ambiguity then affects most of the remaining interpretation, including the precise evolutionary state of the system, whether it currently has an accretion disk, and the masses, which depend on the modeled inclination angle. The current estimate of M should really be regarded as an upper limit. There are several claims of massive neutron stars in redbacks and black widows. Modeling these systems, however, is difficult, especially in the presence of significant heating of the secondary by the pulsar (see, e.g., Romani et al. 2015 ). So far