PSR J1311-3430: A Heavyweight Neutron Star with a Flyweight Helium Companion

TL;DR

This study presents spectroscopic and photometric observations of the PSR J1311-3430 system, revealing a heavy neutron star with a mass exceeding 2.1 solar masses, which constrains the physics of dense matter.

Contribution

The paper provides the first detailed spectroscopic and photometric analysis of PSR J1311-3430, estimating its neutron star mass to be over 2.1 solar masses, informing neutron star equation of state models.

Findings

Neutron star mass estimated >2.1 solar masses

Companion shows helium-dominated, nearly hydrogen-free atmosphere

Infrared excess indicates flaring activity

Abstract

We have obtained initial spectroscopic observations and additional photometry of the newly discovered Pb=94min gamma-ray black-widow pulsar PSR J1311-3430. The Keck spectra show a He-dominated, nearly H-free photosphere and a large radial-velocity amplitude of 609.5+/-7.5km/s. Simultaneous seven-color GROND photometry further probes the heating of this companion, and shows the presence of a flaring infrared excess. We have modeled the quiescent light curve, constraining the orbital inclination and masses. Simple heated light-curve fits give M_NS=2.7Msun, but show systematic light-curve differences. Adding extra components allows a larger mass range to be fit, but all viable solutions have M_NS>2.1Msun. If confirmed, such a large M_NS substantially constrains the equation of state of matter at supernuclear densities.