arXiv subjects

Abderahmen Zoghbi

Publications and source records attributed to Abderahmen Zoghbi.

38 records · Page 3Linked to original sources

arXiv2013

Calculating Time Lags From Unevenly-Sampled Light Curves

Timing techniques offer powerful tools to study dynamical astrophysical phenomena. In the X-ray band, they offer the potential of probing accretion physics down to the event horizon. Recent work has used frequency and energy-dependent time lags as a tool for studying relativistic reverberation around the black holes in several Seyfert galaxies. This was achieved thanks to the evenly-sampled light curves obtained using XMM-Newton. Continuous-sampled data is however not always available and standard Fourier techniques are not applicable. Here, building on the work of Miller et al. (2010), we discuss and use a maximum likelihood method to obtain frequency-dependent lags that takes into account light curve gaps. Instead of calculating the lag directly, the method estimates the most likely lag values at a particular frequency given two observed light curves. We use Monte Carlo simulations to assess the method's applicability, and use it to obtain lag-energy spectra from Suzaku data for two objects, NGC 4151 and MCG-5-23-16, that had previously shown signatures of iron K reverberation. The lags obtained are consistent with those calculated using standard methods using XMM-Newton data.

astro-ph.HE↗

arXiv2011

X-ray Reverberation close to the black hole in RE J1034+396

In previous work, we discussed the detection of reverberation delays in the NLS1 1H0707-495. The delays originate close to the black hole. Here, we show that RE J1034+396 shows very similar lag properties. At low frequencies (< 1 \times 10-4 Hz), the time lag between energy bands increases with energy separation, similar to that commonly seen in Galactic black holes and other AGN. At higher frequencies (~ 3.5 \times 10-4 Hz), the soft (< 1 keV) and hard (> 3 keV) bands lag behind the intermediate band (1-3 keV). The simplest interpretation is that the intermediate band is dominated by the direct power-law continuum, while the soft and hard bands are dominated by the relativistically-smeared reflected emission. The low frequency delays are present in both available observations. The high frequency lags are only seen in one observation. In the observation where high frequency reverberation delays are observed, the spectrum contains a power-law component and there is a QPO in the light curve. In the other observation, no power-law component is required and no QPO is seen. The lags originate a few gravitational radii from the black hole, and the QPO is associated with the power-law emitting corona.

astro-ph.HE↗