The Reverberation Lag in the Low-Mass X-Ray Binary H1743-322

Abstract

The evolution of the inner accretion flow of a black hole X-ray binary (BHXRB) during the outburst is still a matter of active research. X-ray reverberation lags are powerful tools to constrain the disk-corona geometry. We present a study of X-ray lags in the black hole transient H1743-322. We compared results obtained from the analysis of all the publicly available XMM-Newton observations. These observations were carried out during two different outbursts, happened in 2008 and 2014. During all the observations the source is caught in the hard state and at similar luminosities (L 3−10 keV /L Edd ∼ 0.004). We detected a soft X-ray lag of ∼60 ms, most likely due to thermal reverberation. We did not detect any significant change of the lag amplitude among the different observations, indicating a similar disk-corona geometry at the same luminosity in the hard state. On the other hand, we observe significant differences between the reverberation lag detected in H1743-322 and in GX 339-4 (at similar luminosities in the hard state), which might indicate variations of the geometry from source to source.

Evolution of the reverberation lag in GX 339–4 at the end of an outburst

“…The analogies with the soft lag detected in archival data of GX 339-4 and H1743-322 in the hard state (Uttley et al 2011;De Marco et al 2015;De Marco & Ponti 2016) and ascribed to disc thermal reverberation suggest a common origin. Here we test this hypothesis by investigating variations of the lag amplitude as a function of the accretion regime.…”

“…The lag, detected in the soft X-ray band, was interpreted as thermal reprocessing of the hard X-ray photons in the disc. Extending this analysis to a larger sample, we found evidence of a trend of decreasing thermal reverberation lag amplitude as a function of luminosity throughout the hard state at the beginning of the outburst in GX 339-4 and H1743-322 (De Marco et al 2015;De Marco & Ponti 2016). This trend is in agreement with predictions of truncated disc models (e.g.…”

“…Assuming a color temperature correction factor of ∼ 1.9− 2.2 (equation A13 in Davis, Done, & Blaes 2006) these values are close to those obtained from our spectral fits (Table 2 and De Marco et al 2015 for the archival XMM observations). Of course these must be taken as back-of-the-envelope estimates, since more precise estimates of the disc inner radius require accounting for several observational aspects (as discussed in De Marco & Ponti 2016) and the use of selfconsistent spectral timing models.…”

A physical model for the spectral-timing properties of accreting black holes

“…Nonetheless, there are much simpler PSDs seen in the lower luminosity low/hard states which presumably imply a simpler source structure, and there are now detections of reverberation lags from the central source illuminating the accretion disc which give independent-size-scale information in GX339-4 (De Marco & Ponti 2016;De Marco et al 2017). We will extend our method to fit these data in future work.…”

Accretion Disks and Coronae in the X-Ray Flashlight

“…Studies of these time delays in BH LMXBs indicate that there is a significant change when moving from the soft to the hard state, which may indicate that the inner disk moves outwards in the hard state (e.g. De Marco et al 2015;De Marco and Ponti 2016;De Marco et al 2017). Reverberation can possibly be observed in NS LMXBs as well (Barret 2013;Cackett 2016), but needs to be further developed.…”