The X-ray bursts of XTE J1739-285: a NICER sample

Abstract

In this work we report on observations with the Neutron Star Interior Composition Explorer of the known neutron star X-ray transient XTE J1739-285. We observed the source in 2020 February and March, finding it in a highly active bursting state. Across a 20-day period, we detected 32 thermonuclear X-ray bursts, with an average burst recurrence time of $2.0_{-0.3}^{+0.4}$ hr. A timing and spectral analysis of the ensemble of X-ray bursts reveals homogeneous burst properties, evidence for short-recurrence time bursts, and the detection of a 386.5 Hz burst oscillation candidate. The latter is especially notable, given that a previous study of this source claimed a 1122 Hz burst oscillation candidate. We did not find any evidence of variability near 1122 Hz, and instead find that the 386.5 Hz oscillation is the more prominent signal of the two burst oscillation candidates. Hence, we conclude it is unlikely that XTE J1739-285 has a sub-millisecond rotation period.

15 pages, 9 figures, 2 tables. Accepted for publication in ApJ

References in corpus (7)

• Thermonuclear (type-I) X-ray bursts observed by the Rossi X-ray Timing Explorer
• X-ray bursting neutron star atmosphere models using an exact relativistic kinetic equation for Compton scattering
• Evidence for 1122 Hz X-Ray Burst Oscillations from the Neutron-Star X-Ray Transient XTE J1739-285
• The influence of accretion geometry on the spectral evolution during thermonuclear (type-I) X-ray bursts
• Thermonuclear Bursts with Short Recurrence Times from Neutron Stars Explained by Opacity-Driven Convection
• Ignition latitude and the shape of Type I X-ray bursts
• The accretion rate dependence of burst oscillation amplitude

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