AstroSat view of the neutron star low-mass X-ray binary GX 340+0

Abstract

Understanding the spectral evolution along the `Z'-shaped track in the hardness-intensity diagram of Z-sources, which are a class of luminous neutron star low-mass X-ray binaries, is crucial to probe accretion processes close to the neutron star. Here, we study the horizontal branch (HB) and the normal branch (NB) of the Z source GX 340+0 using $AstroSat$ data. We find that the HB and the NB appear as two different types of X-ray intensity dips, which can appear in any sequence and with various depths. Our $0.8-25$ ~keV spectra of dips and the hard apex can be modeled by the emissions from an accretion disk, a Comptonizing corona covering the inner disk, and the neutron star surface. We find, as the source moves onto the HB the corona is replenished and energized by the disk and a reduced amount of disk matter reaches the neutron star surface. We also conclude that quasi-periodic oscillations during HB/NB are strongly associated with the corona, and explain the evolution of strength and hard-lag of this timing feature using the estimated coronal optical depth evolution.

Updating to the published version

References in corpus (15)

• The corona contracts in a black-hole transient
• 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
• Coupling between the accreting corona and the relativistic jet in the micro quasar GRS 1915+105
• vKompth: A variable Comptonisation model for low-frequency quasi-periodic oscillations in black-hole X-ray binaries
• Large Area X-ray Proportional Counter (LAXPC) in Orbit Performance : Calibration, background, analysis software
• Disk reflection signatures in the spectrum of the bright Z-source GX 340+0
• An explanation of the Z-track sources
• Broadband reflection spectroscopy of MAXI J1535-571 using AstroSat: Estimation of black hole mass and spin
• Spectro-timing analysis of MAXI J1535-571 using AstroSat
• The comptonizing medium of the black-hole X-ray binary MAXI~J1535$-$571 through type-C quasi-periodic oscillations
• A spectral study of the black hole X-ray binary MAXI J1820+070 with AstroSat and NuSTAR
• A model for the Z-track phenomenon in GX 5-1 and observational evidence for the physical origins of the kHz QPO
• An alternative scheme to estimate AstroSat/LAXPC background for faint sources
• Timing and spectral study of XB 1254-690 using new RXTE PCA data

Cited by in corpus (1)

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