Kavli Affiliate: Deepto Chakrabarty
| First 5 Authors: Mason Ng, Andrew K. Hughes, Jeroen Homan, Jon M. Miller, Sean N. Pike
| Summary:
We report on X-ray (NICER/NuSTAR/MAXI/Swift) and radio (MeerKAT) timing and
spectroscopic analysis from a three-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 suggests 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 sources in the atoll state. A timing analysis with NICER
data revealed several instances of an $approx8$ Hz quasi-periodic 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 (NBOs) 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 K$alpha$, and K$beta$ X-ray
absorption lines, whose origins likely lie in an accretion disk atmosphere.
| Search Query: ArXiv Query: search_query=au:”Deepto Chakrabarty”&id_list=&start=0&max_results=3