The Cross Spectral Time lags evolution along branches in XTE J1701-462

Abstract

We investigate the cross spectrum of XTE J1701-462 in various types of Neutron Star-Low Mass X-ray Binary subclasses, during its 2006-2007 outburst. We analyze the relation between the time lags and temporal variabilities. We find that the hard time lags accompany with the horizontal branch oscillations (HBOs) and the soft time lags dominate the noise in the low frequency range 0.1-10 Hz on HB. In the Cyg-like phase, the time lags decrease on the middle normal branch (NB) from HB/NB vertex to NB/FB vertex, whereas the time lags are roughly invariant in the Sco-like source. We discuss that the Compton upscattering by the corona introduces the soft lag in low frequency noise. We interpret that the variation of the Comptonization component from the disk emission lead to the HBOs' time lags evolution along the Z tracks. We also report the rms amplitude spectrum and phase lag spectrum for the NBO. The $\sim$ $160^{\circ }$ phase lag is found. We present that the rms amplitude of both the Cyg-like and the Sco-like NBO linearly increase with the photon energy in low energy bands, and it will drop in the highest energy band.

Accepted for publication in The Astrophysical Journal

References in corpus (4)

• RXTE observations of the first transient Z source XTE J1701-462: shedding new light on mass accretion in luminous neutron star LMXBs
• The Spectral Evolution along the Z track of the Bright Neutron Star X-ray Binary GX 17+2
• Evolution of cross-correlation and time lag of Cyg X-2 along the branches
• Energy dependence of Normal Branch Oscillation in Scorpius X-1

Cited by in corpus (4)

• Correlations in Horizontal Branch Oscillations and Break Components in XTE J1701-462 and GX 17+2
• Constraining the Coronal Heights and Readjustment Velocities Based on the Detection of a Few Hundred Seconds Delays in the Z Source GX 17+2
• Cross-correlations between soft and hard light curves depending on luminosity in the transient neutron star XTE J1701-462
• The accretion rate independence of horizontal branch oscillation in XTE J1701-462