Discovery of thermonuclear (Type I) X-ray bursts in the X-ray binary Swift J1858.6-0814 observed with NICER and NuSTAR

Abstract

Swift J1858.6-0814 is a recently discovered X-ray binary notable for extremely strong variability (by factors $>100$ in soft X-rays) in its discovery state. We present the detection of five thermonuclear (Type I) X-ray bursts from Swift J1858.6-0814, implying that the compact object in the system is a neutron star. Some of the bursts show photospheric radius expansion, so their peak flux can be used to estimate the distance to the system. The peak luminosity, and hence distance, can depend on several system parameters; for the most likely values, a high inclination and a helium atmosphere, $D=12.8_{-0.6}^{+0.8}$ kpc, although systematic effects allow a conservative range of $9-18$ kpc. Before one burst, we detect a QPO at $9.6\pm 0.5$ mHz with a fractional rms amplitude of $2.2\pm 0.2$% ($0.5-10$ keV), likely due to marginally stable burning of helium; similar oscillations may be present before the other bursts but the light curves are not long enough to allow their detection. We also search for burst oscillations but do not detect any, with an upper limit in the best case of 15% fractional amplitude (over $1-8$ keV). Finally, we discuss the implications of the neutron star accretor and this distance on other inferences which have been made about the system. In particular, we find that Swift J1858.6-0814 was observed at super-Eddington luminosities at least during bright flares during the variable stage of its outburst.

14 pages, 8 figures, 2 tables, MNRAS accepted

References in corpus (15)

• HI4PI: A full-sky HI survey based on EBHIS and GASS
• Thermonuclear (type-I) X-ray bursts observed by the Rossi X-ray Timing Explorer
• Identification of the High-Energy Gamma-Ray Source 3FGL J1544.6-1125 as a Transitional Millisecond Pulsar Binary in an Accreting State
• The influence of accretion geometry on the spectral evolution during thermonuclear (type-I) X-ray bursts
• Superburst Models for Neutron Stars with Hydrogen and Helium-Rich Atmospheres
• A strongly heated neutron star in the transient Z source MAXI J0556-332
• Millihertz Oscillation Frequency Drift Predicts the Occurrence of Type I X-ray Bursts
• Biases for neutron-star mass, radius and distance measurements from Eddington-limited X-ray bursts
• A dichotomy between the hard state spectral properties of black hole and neutron star X-ray~binaries
• Predicting Coronal Mass Ejections Using SDO/HMI Vector Magnetic Data Products and Recurrent Neural Networks
• The variable radio counterpart of Swift J1858.6-0814
• Millihertz quasi-periodic oscillations in 4U 1636-53 associated with bursts with positive convexity only
• Discovery of a correlation between the frequency of the mHz quasi-periodic oscillations and the neutron-star temperature in the low-mass X-ray binary 4U 1636-53
• Soft X-ray emission lines in the X-ray binary Swift J1858.6-0814 observed with XMM-Newton-RGS: disc atmosphere or wind?
• Understanding superbursts

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• Dips and eclipses in the X-ray binary Swift J1858.6-0814 observed with NICER
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• Catalog of outbursts of neutron star LMXBs
• Broadband time-resolved spectroscopy of thermonuclear X-ray bursts from 4U 1636-536 using AstroSat
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• The $\text{False Widow}$ Link Between Neutron Star X-ray Binaries and Spider Pulsars
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• X-ray Eclipse Mapping Constrains the Binary Inclination and Mass Ratio of Swift J1858.6-0814
• The thermonuclear X-ray bursts of 4U 1730-22
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• Connecting the m-dots: accretion rates and thermonuclear burst recurrence times on neutron stars and white dwarfs
• X-ray Iron absorption line in Swift J1858.6-0814
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