Anticorrelated Hard X‐Ray Time Lag in GRS 1915+105: Evidence for a Truncated Accretion Disk

Choudhury, Manojendu; Rao, A. R.; Dasgupta, Surajit; Pendharkar, Jayant; Sriram, K.; Agrawal, Vivek

doi:10.1086/432675

Cited by 20 publications

(50 citation statements)

References 23 publications

(34 reference statements)

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“…Examination of the model independent spectra showed that there were minute changes indicating pivoting and marginal pivoting. Similar kind of pivoting features were observed in Cyg X-3, XTE J1550-564 and GRS 1915+105 (Choudhury & Rao 2004, Choudhury et al 2005, Sriram et al 2007). …”

Section: Analysis and Resultssupporting

confidence: 77%

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A truncated accretion disk in the galactic black hole candidate source H1743–322

Sriram

Agrawal

Rao

2009

Res. Astron. Astrophys.

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To investigate the geometry of the accretion disk in the source H1743-322, we have carried out a detailed X-ray temporal and spectral study using RXTE pointed observations. We have selected all data pertaining to the Steep Power Law (SPL) state during the 2003 outburst of this source. We find anti-correlated hard X-ray lags in three of the observations and the changes in the spectral and timing parameters (like the QPO frequency) confirm the idea of a truncated accretion disk in this source. Compiling data from similar observations from other sources, we find a correlation between the fractional change in the QPO frequency and the observed delay. We suggest that these observations indicate a definite size scale in the inner accretion disk (the radius of the truncated disk) and we explain the observed correlation using various disk parameters like Compton cooling time scale, viscous time scale etc..

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Section: Analysis and Resultssupporting

confidence: 77%

“…Both the sources show a pivoting feature and changes in the spectral parameters during the lags (Choudhury et al 2005, Sriram et al 2007. The lags obtained between soft and hard flux in SPL/VHS state clearly suggest that the accretion disk structure changes, may be because of relative changes in the mass accretion rate.…”

Section: Discussionmentioning

confidence: 82%

A truncated accretion disk in the galactic black hole candidate source H1743–322

Sriram

Agrawal

Rao

2009

Res. Astron. Astrophys.

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“…For Cyg X-3, the anti-correlated hard lags are detected in the hard state, which range from ∼ 620 to ∼ 950 seconds (Choudhury & Rao 2004). The anti-correlated hard lags are detected in the IMS of GRS 1915+105 (Choudhury et al 2005), XTE 1550-564 (Sriram et al 2007) and H1743-322 (Sriram, Agrawal, & Raghurama Rao 2009), which range from ∼ 128 to ∼ 1600 seconds, ∼ 132 to ∼ 376 seconds and ∼ 442 to ∼ 1591 seconds, respectively. From the above results, it is easy to note that the ranges of anti-correlated hard lags detected in different BHXBs are similar.…”

Section: Comparison With Other Xrbsmentioning

confidence: 90%

“…Since then cross-correlation analysis has been widely used for study of the timing properties of XRBs. Tens of seconds to over 1500 seconds anti-correlated time lags were detected in the IMS of other BHXBs that are GRS 1915+105 (Choudhury et al 2005), XTE J1550-564, 4U 1630-47 (Sriram et al 2007), H1743-322 Raghurama Rao 2009) andGX 339-4 (Sriram, Rao, &Choi 2010). Similar kinds of anti-correlated time lags were observed in six other NS LMXBs, including four Z-sources (Cyg X-2 (Lei et al 2008), GX 5-1 (Sriram, Choi, & Rao 2012), XTE J1701-462 (Wang et al 2014) and GX 349+2 (Ding et al 2016)) and two atoll sources (4U 1735-44 (Lei et al 2013) and 4U 1608-52 ), and positive correlated time lags were also observed in them.…”

Section: Introductionmentioning

confidence: 99%

A study of the cross-correlation and time lag in black hole X-ray binary XTE J1859+226

Pei

Ding

et al. 2017

Astrophys Space Sci

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With Rossi X-ray Timing Explorer (RXTE) data,we systematically study the cross-correlation and time lag in all spectral states of black hole X-ray binary (BHXB) XTE J1859+226 in detail during its entire 1999−2000 outburst that lasted for 166 days. Anti-correlations and positive correlations and their respective soft and hard X-ray lags are only detected in the first 100 days of the outburst when the luminosity is high. This suggests that the cross-correlations may be related to high luminosity. Positive correlations are detected in every state of XTE J1859+226, viz., hard state, hard-intermediate state (HIMS), soft-intermediate state (SIMS) and soft state. However, anti-correlations are only detected in HIMS and SIMS, anti-correlated hard lags are only detected in SIMS, while anti-correlated soft lags are detected in both HIMS and SIMS. Moreover, the ratio of the observations with anti-correlated soft lags to hard lags detected in XTE J1859+226 is significantly different from that in neutron star low-mass X-ray binaries (NS LMXBs). So far, anti-correlations are never de- tected in the soft state of BHXBs but detected in every branch or state of NS LMXBs. This may be due to the origin of soft seed photons in BHXBs is confined to the accretion disk and, for NS LMXBs, from both accretion disk and the surface of the NS. We notice that the timescale of anti-correlated time lags detected in XTE J1859+226 is similar with that of other BHXBs and NS LMXBs. We suggest that anti-correlated soft lag detected in BHXB may result from fluctuation in the accretion disk as well as NS LMXB.

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“…The study of the cross correlation function (CCF) gives an insight into the correlation strength of the energy dependence of light curves, which would unhttp://pkas.kas.org veil the various mechanisms involved in the accretion disk. Earlier studies of CCFs between soft and hard energy bands in a few black hole and neutron star sources showed anti-correlated hard/soft delays of a few tens to hundreds of seconds, though most of them were found to be correlated (Choudhury et al, 2005;Sriram et al, 2007;Lei et al, 2008;Sriram et al, 2009;Sriram et al, 2010;Sriram et al, 2012). These studies of CCFs were performed at a high Fourier time scale or correlation time scale of the order of a few hundreds to thousands seconds.…”

Section: Introductionmentioning

confidence: 98%

A Study of the Dynamical Cross Correlation Function in a Black Hole Source Xte J1550-564

Sriram¹,

Choi²,

Rao³

2015

Publications of The Korean Astronomical Society

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The short time scale X-ray variability associated with the accretion disk around compact objects is complex and is vaguely understood. The study of the cross correlation function gives an insight into the energy dependent behavior of the variations and hence connected processes. Using high resolution RXTE data, we investigate the dynamical cross correlation function of an observation of a black hole source XTE J1550-564 in the steep power law state. The cross correlation between soft and hard X-ray energy bands revealed both correlated and anti-correlated delays (≤ ±15 s) on a correlation time scale of 50 s. It was noticed that the observed delays were similar to the delays between X-ray and optical/IR bands in other black hole and neutron star sources. We discuss the possible mechanisms/processes to explain the observed delays in the dynamical CCF.

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Anticorrelated Hard X‐Ray Time Lag in GRS 1915+105: Evidence for a Truncated Accretion Disk

Cited by 20 publications

References 23 publications

A truncated accretion disk in the galactic black hole candidate source H1743–322

A truncated accretion disk in the galactic black hole candidate source H1743–322

A study of the cross-correlation and time lag in black hole X-ray binary XTE J1859+226

A Study of the Dynamical Cross Correlation Function in a Black Hole Source Xte J1550-564

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