AstroSat View of Transient Low-mass X-ray Binary XTE J1701-462: Spectral and Temporal Evolution along the Z-track

Abstract

AstroSat observed transient neutron star low-mass X-ray binary XTE J1701-462 for a total duration of $\sim$ 135 ks during its 2022 outburst. The source traced a complete `Z' shaped structure in the hardness intensity diagram (HID). The source exhibited an extended horizontal branch and a short-dipping flaring branch in the HID. We find that most suitable spectral model comprises emission from a standard multi-color accretion disk (diskbb in XSPEC) and Comptonized radiation from a hot central corona, described by Comptb model of XSPEC. The observed disk component is cool, having a temperature in the range of 0.28-0.42 keV and truncated far (250 - 1600 km) from the compact object. The Compton corona has an optical depth in the range of 3.4-5.1 and a temperature in the range of 3.3-4.5 keV. The disk and corona flux as well as truncation radius vary significantly along the HID. The temperature $k{T}_{in}$ depends on both luminosity and inner disk radius and hence shows marginal variation as compared to the truncation radius. The timing analysis revealed horizontal branch oscillations in the frequency range $\sim 34-40$ Hz. The frequency and rms strength of HBO vary systematically as the source moves along the horizontal branch. The observed correlation of the HBO properties with the position on the HB is similar to that previously reported in this source using RXTE data during the 2006 outburst of the source. The source also showed normal branch oscillations with frequency $\sim$ 6.7 Hz in the middle and the lower normal branch. The energy-dependent study of the HBO properties suggests that the HBO is stronger in the higher energy band. We also observed very-low frequency noise and band-limited noise components in the power density spectra. The break frequency of BLN component was found to be tightly correlated with the HBO frequency.

Accepted for Publication in Publications of the Astronomical Society of Australia, 9 figures, 9 tables

References in corpus (13)

• Evaluating Spectral Models and the X-ray States of Neutron-Star X-ray Transients
• RXTE observations of the first transient Z source XTE J1701-462: shedding new light on mass accretion in luminous neutron star LMXBs
• A new Comptonization model for low-magnetized accreting neutron stars in low mass X-ray binaries
• Radius Constraints from Reflection Modeling of Cygnus X-2 with NuSTAR and NICER
• Type I X-ray Bursts from the Neutron-star Transient XTE J1701-462
• Correlations in Horizontal Branch Oscillations and Break Components in XTE J1701-462 and GX 17+2
• Wide-band view of High Frequency QPOs of GRS 1915+105 in 'softer' variability classes observed with AstroSat
• NuSTAR view of the Z-type neutron star low-mass X-ray binary Cygnus~X--2
• Detection of significant X-ray polarization from transient NS-LMXB XTE J1701-462 with IXPE and its implication on the coronal geometry
• AstroSat view of LMC X-2: Evolution of broadband X-ray spectral properties along a complete Z-track
• AstroSat view of the neutron star low-mass X-ray binary GX 340+0
• AstroSat view of `Clocked` burster GS 1826-238:broad-band spectral nature of persistent and burst emission during soft state
• The accretion rate independence of horizontal branch oscillation in XTE J1701-462

Cited by in corpus (1)

• Tracing the outburst decay of soft X-ray transients Aql X-1 and 4U 1608-52 with XSPECT