The discovery of the 528.6 Hz accreting millisecond X-ray pulsar MAXI J1816-195

Abstract

We present the discovery of 528.6 Hz pulsations in the new X-ray transient MAXI J1816-195. Using NICER, we observed the first recorded transient outburst from the neutron star low-mass X-ray binary MAXI J1816-195 over a period of 28 days. From a timing analysis of the 528.6 Hz pulsations, we find that the binary system is well described as a circular orbit with an orbital period of 4.8 hours and a projected semi-major axis of 0.26 light-seconds for the pulsar, which constrains the mass of the donor star to $0.10-0.55M_{\odot }$. Additionally, we observed 15 thermonuclear X-ray bursts showing a gradual evolution in morphology over time, and a recurrence time as short as 1.4 hours. We did not detect evidence for photospheric radius expansion, placing an upper limit on the source distance of 8.6 kpc.

8 pages, 3 figures, 2 tables. Accepted for publication in ApJ Letters

References in corpus (5)

• TEMPO2, a new pulsar timing package. I: Overview
• Order in the Chaos: Spin-up and Spin-down during the 2002 Outburst of SAX J1808.4-3658
• Timing an Accreting Millisecond Pulsar: Measuring the Accretion Torque in IGR J00291+5934
• Puzzling thermonuclear burst behaviour from the transient low-mass X-ray binary IGR J17473-2721
• The efficiency of nuclear burning during thermonuclear (Type I) bursts as a function of accretion rate

Cited by in corpus (1)

• Detection of a strong ~2.5 Hz modulation in the Newly Discovered Millisecond Pulsar MAXI J1816-195