A Space-Based Physics Lab: the Search for Very High-Mass Neutron Stars via Shapiro Delay
Abstract
Millisecond pulsar (MSP) timing — the rotation-counting technique by which the ephemeris of a pulsar is determined with great precision — serves as a unique astrophysical probe of general relativity. When an MSP passes behind its stellar companion along an observer’s line of sight, the pulsar’s signal is delayed as it traverses the gravitational potential well of its partner. Measurements of this so-called Shapiro delay, in addition to standard parameters gleaned from pulsar timing, yield the binary system’s inclination angle and the masses of both the companion star and pulsar. These mass determinations are vital for understanding the neutron star equation of state and mass-radius relationship; in fact, recent Shapiro delay measurements have already begun to constrain neutron star physics at hyper-nuclear densities. We present a status report on a campaign to observe two intriguing MSPs, J0721-2038 and J1400-1431, and determine whether they show significant Shapiro delay in their timing residuals. While the primary goal of this study is to precisely measure very high neutron star masses, the observations will also help characterize the poorly understood distribution of neutron star masses on the whole.
- Publication:
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American Astronomical Society Meeting Abstracts #231
- Pub Date:
- January 2018
- Bibcode:
- 2018AAS...23124315T