The cross-correlation analysis in Z source GX 349+2

Abstract

Using all the observations from Rossi X-ray Timing Explorer for Z source GX 349+2, we systematically carry out cross-correlation analysis between its soft and hard X-ray light curves. During the observations from January 9 to January 29, 1998, GX 349+2 traced out the most extensive Z track on its hardness-intensity diagram, making a comprehensive study of cross-correlation on the track. The positive correlations and positively correlated time lags are detected throughout the Z track. Outside the Z track, anti-correlations and anti-correlated time lags are found, but the anti-correlated time lags are much longer than the positively correlated time lags, which might indicate different mechanisms for producing the two types of time lags. We argue that neither the short-term time lag models nor the truncated accretion disk model can account for the long-term time lags in neutron star low mass X-ray binaries (NS-LMXBs). We suggest that the extended accretion disk corona model could be an alternative model to explain the long-term time lags detected in NS-LMXBs.

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

“…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. Furthermore, the evolution of the crosscorrelation along the branches in the CCD or hardness intensity diagram (HID) was studied for the six NS LMXBs.…”

“…8). This phenomenon is also detected in atoll source 4U 1608-52 ) and Z-source GX 349+2 (Ding et al 2016). However, for atoll source 4U 1735-44 (Lei et al 2013) and Z-source XTE J1701-462 (Wang et al 2014), the length of time lags in positive correlation observations does not show obvious difference from that in anti-correlation observations.…”

“…10. GX 349+2 (Z-source) shows the same phenomenon (Ding et al 2016), while the opposite is detected in Z-source Cyg X-2 (Lei et al 2008), Z-source GX 5-1 (Sriram, Choi, & Rao 2012), Z-source XTE J1701-462 (Wang et al 2014), atoll source 4U 1735-44 (Lei et al 2013) and atoll source 4U 1608-52 ).…”

“…Lei et al (2008), (2) Sriram, Choi, & Rao (2012), (3) Wang et al (2014), (4) Ding et al (2016), (5) Lei et al (2013), (6) Lei et al (2014), (7) Choudhury & Rao (2004), (8) Choudhury et al (2005), (9) 5-1 (Z-source) (Sriram, Choi, & Rao 2012), 4U 1735-44 (atoll source) (Lei et al 2013), 4U 1608-52 (atoll source) , XTE J1701-462 (Z-source) (Wang et al 2014)). Spectral analysis shows that the inner disk radius (∝ N 1/2 bb ) is changing, and this could be the evidence of the movement of accretion disk front (see Table 5).…”

Test the growth models of black hole by jointing LIGO and Insight-HXMT observations

“…Insight-HXMT can also quickly implement a Target of Opportunity observation to scan the GW localization area for potential X-ray emission from the GW source. So far, Insight-HXMT has made many interesting and important discoveries (see for example [18][19][20][21][22]). Although Insight-HXMT did not detect any significant high energy (0.2-5 MeV) radiation from GW events, it provides most stringent constraints ( 10 −7 to 10 −6 erg/cm 2 /s) for these GW events and any other possible precursor or extended emissions in 0.2-5 MeV [1,17,23].…”