| Description |
We have discovered the most highly eccentric binary millisecond pulsar known to date, PSR J1835-3259A in the globular cluster NGC 6652. Timing with the Green Bank Telescope between 2010-2011 and 2014-2015 has resulted in the following measurements of the spin and orbital parameters: Pspin = 3.888 ms, Porb = 9.25 d, e = 0.91, asini = 19, and omegadot = 0.06 deg/yr, yielding a minimum companion mass of 0.7 solar masses and a total system mass of 3.3 solar masses. This timing solution is orbital-phase-connected but not spin-phase-connected, meaning that degeneracies exist in the solution (especially between position, spindown rate, and omegadot), and therefore our solution is not unique. The MSP is very faint (mean flux density of about 17 microJy at 2 GHz). We propose to observe NGC6652A up to three times with Parkes and the H-OH receiver (1.5 GHz central frequency), to determine if Parkes can be used to time this faint southern-sky MSP. Long-term timing of NGC6652A will yield the pulsar and companion masses. Given the total mass of the system, the companion may also be a neutron star; or, the companion is a massive white dwarf, and the pulsar may be an unusually massive neutron star, with the potential to further constrain the neutron star equation of state.
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