X-Ray and Radio Monitoring of the Neutron Star Low-mass X-Ray Binary 1A 1744-361: Quasiperiodic Oscillations, Transient Ejections, and a Disk Atmosphere

Ng, M; Hughes, AK; Homan, J; Miller, JM; Pike, SN; Altamirano, D; Bult, P; Chakrabarty, D; Buisson, DJK; Coughenour, BM; Fender, R; Guillot, S; Güver, T; Jaisawal, GK; Jaodand, AD; Malacaria, C; Miller-Jones, JCA; Sanna, A; Sivakoff, GR; Strohmayer, TE; Tomsick, JA; van den Eijnden, J

Journal article

X-Ray and Radio Monitoring of the Neutron Star Low-mass X-Ray Binary 1A 1744-361: Quasiperiodic Oscillations, Transient Ejections, and a Disk Atmosphere

Abstract:: We report on X-ray (NICER/NuSTAR/MAXI/Swift) and radio (MeerKAT) timing and spectroscopic analysis from a 3 month monitoring campaign in 2022 of a high-intensity outburst of the dipping neutron star low-mass X-ray binary 1A 1744−361. The 0.5–6.8 keV NICER X-ray hardness–intensity and color–color diagrams of the observations throughout the outburst suggest that 1A 1744−361 spent most of its outburst in an atoll-state, but we show that the source exhibited Z-state-like properties at the peak of the outburst, similar to a small sample of other atoll-state sources. A timing analysis with NICER data revealed several instances of an ≈8 Hz quasiperiodic oscillation (QPO; fractional rms amplitudes of ∼5%) around the peak of the outburst, the first from this source, which we connect to the normal branch QPOs seen in the Z-state. Our observations of 1A 1744−361 are fully consistent with the idea of the mass accretion rate being the main distinguishing parameter between atoll- and Z-states. Radio monitoring data by MeerKAT suggests that the source was at its radio-brightest during the outburst peak, and that the source transitioned from the “island” spectral state to the “banana” state within ∼3 days of the outburst onset, launching transient jet ejecta. The observations present the strongest evidence for radio flaring, including jet ejecta, during the island-to-banana spectral state transition at low accretion rates (atoll-state). The source also exhibited Fe xxv, Fe xxvi Kα, and Kβ X-ray absorption lines, whose origins likely lie in an accretion disk atmosphere.

Publication status:: Published

Peer review status:: Peer reviewed

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APA Style

Ng, M., Hughes, A. K., Homan, J., Miller, J. M., Pike, S. N., Altamirano, D., Bult, P., Chakrabarty, D., Buisson, D. J. K., Coughenour, B. M., Fender, R., Guillot, S., Güver, T., Jaisawal, G. K., Jaodand, A. D., Malacaria, C., Miller-Jones, J. C. A., Sanna, A., Sivakoff, G. R., … van den Eijnden, J. (2024). X-Ray and Radio Monitoring of the Neutron Star Low-mass X-Ray Binary 1A 1744-361: Quasiperiodic Oscillations, Transient Ejections, and a Disk Atmosphere. The Astrophysical Journal, 966(2).

MLA Style

Ng, M., et al. “X-Ray and Radio Monitoring of the Neutron Star Low-Mass X-Ray Binary 1A 1744-361: Quasiperiodic Oscillations, Transient Ejections, and a Disk Atmosphere.” The Astrophysical Journal, vol. 966, no. 2, American Astronomical Society, 2024.

Chicago Style

Ng, M, AK Hughes, J Homan, JM Miller, SN Pike, D Altamirano, P Bult, et al. 2024. “X-Ray and Radio Monitoring of the Neutron Star Low-Mass X-Ray Binary 1A 1744-361: Quasiperiodic Oscillations, Transient Ejections, and a Disk Atmosphere.” The Astrophysical Journal 966 (2).
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