Probing spectral and temporal evolution of the neutron star low-mass X-ray binary 4U 1724-30 with AstroSat

Abstract

We report the broadband spectro-temporal study of the poorly studied accreting neutron star (NS) low mass X-ray binary (LMXB) 4U 1724-30 using data from Soft X-ray Telescope (SXT) and Large Area X-ray Proportional Counters (LAXPC) instruments on board AstroSat. The dim persistent LMXB source was observed with AstroSat over 4 epochs in 2017, all of which corresponded to a low-luminosity non-thermal emission dominated (hard/island) emission state with modest spectral evolution. All the X-ray broadband spectra can be modelled by a combination of thermal emission from the NS boundary layer (BL) or NS surface and a non-thermal emission component possibly originating from the inverse Comptonization of the disc seed photons. We investigate the presence of frequency and energy-dependent variabilities to probe the origin of the disc/coronal fluctuations. We also report the detection of a Type-I X-ray burst displaying a photospheric radius expansion (PRE). During the burst, a hard X-ray shortage in the 30-80 keV energy band and the enhancement of the persistent emission reveal the burst feedback on the overall accretion process. Using the touch-down burst flux $\sim$ $4.25\times 10^{-8}$ erg s${}^{-1}$ cm${}^{-2}$, the distance of the source is estimated as $\sim$ 8.4 kpc.

arXiv comment12 pages, 9 figures, 6 tables. Accepted for publication in MNRAS

References in corpus (40)

• On the Absorption of X-rays in the Interstellar Medium
• Masses, Radii, and Equation of State of Neutron Stars
• Modelling the behaviour of accretion flows in X-ray binaries
• Thermonuclear (type-I) X-ray bursts observed by the Rossi X-ray Timing Explorer
• RXTE Observation of Cygnus X-1: II. Timing Analysis
• Photospheric radius expansion X-ray bursts as standard candles
• Correlation between Compton reflection and X-ray slope in Seyferts and X-ray binaries
• The causal connection between disc and power-law variability in hard state black hole X-ray binaries
• Neutron star stiff equation of state derived from cooling phases of the X-ray burster 4U 1724-307
• Evaluating Spectral Models and the X-ray States of Neutron-Star X-ray Transients
• Evidence for accretion rate change during type I X-ray bursts
• The Discovery of a State Dependent Hard Tail in the X-ray Spectrum of the Luminous Z-source GX 17+2
• An exact analytic treatment of propagating mass accretion rate fluctuations in X-ray binaries
• The Multi-INstrument Burst ARchive (MINBAR)
• X-ray bursts at extreme mass accretion rates from GX 17+2
• The broad band X-ray/hard X-ray spectra of accreting neutron stars
• Patterns of energy-dependent variability from Comptonization
• Spectral Fits to the 1999 Aql X-1 Outburst Data
• Evidence of heavy-element ashes in thermonuclear X-ray bursts with photospheric superexpansion
• AstroSat view of MAXI J1535-571: broadband spectro-temporal features
• Measurement of neutron star parameters: a review of methods for low-mass X-ray binaries
• Detection of Low-Hard State Spectral and Timing Signatures from the Black Hole X-Ray Transient XTE J1650-500 at Low X-Ray Luminosities
• Eddington-limited X-ray Bursts as Distance Indicators. I. Systematic Trends and Spherical Symmetry in Bursts from 4U 1728-34
• The hard X-ray shortages prompted by the clock bursts in GS 1826--238
• Type-I X-ray bursts reveal a fast co-evolving behavior of the corona in an X-ray binary
• Spectro-timing analysis of MAXI J1535-571 using AstroSat
• Accretion flow diagnostics with X-ray spectral-timing: the hard state of SWIFT J1753.5-0127
• New insights on the puzzling LMXB 1RXS J180408.9-342058: the intermediate state, the clocked type-I X-ray bursts and much more
• Large Area X-ray Proportional Counter (LAXPC) Instrument on AstroSat
• Burst-induced coronal cooling in GS 1826-24 The clock wagging its tail
• A NuSTAR observation of the reflection spectrum of the low mass X-ray binary 4U 1728-34
• Diagnosing the burst influence upon accretion in the clocked burster GS 1826--238
• Effects of thermonuclear X-ray bursts on non-burst emissions in the soft state of 4U 1728--34
• Discovery of kilohertz quasi-periodic oscillations and state transitions in the low-mass X-ray binary 1E~1724-3045 (Terzan 2)
• Cooling of Accretion Disc Coronae by Type I X-ray Bursts
• Evolution of accretion disc reflection spectra due to a Type I X-ray burst
• Aperiodic variability of low-mass X-ray binaries at very low frequencies
• Bright X-ray bursts from 1E 1724-3045 in Terzan 2
• Timing and spectral study of XB 1254-690 using new RXTE PCA data
• The failed state transition of the ATOLL source GRS 1724-308

Cited by in corpus (3)

• UltraCompCAT: a comprehensive Catalogue of Ultra-Compact and Short Orbital Period X-ray Binaries
• Insight-HXMT observations on thermonuclear X-ray bursts from 4U~1608--52 in 2022: the accretion rate dependent anisotropy of burst emission
• AstroSat observation of rapid Type-I thermonuclear burst from the low mass X-ray binary GX 3+1