Accretion Onto the Supermassive Black Hole in the High-Redshift Radio-Loud Agn 0957+561

Abstract

We present the results of our X-ray, UV and optical monitoring campaign of the first gravitationally lensed AGN from late 2009 to mid 2010. The trailing (B) image of the AGN 0957+561 shows the intrinsic continuum variations that were predicted in advance based on observations of the leading (A) image in the gr optical bands. This multiwavelength variability of the B image allows us to carry out a reverberation mapping analysis in the radio-loud AGN 0957+561 at redshift z = 1.41. We find that the U -band and r-band light curves are highly correlated with the g-band record, leading and trailing it by 3 ± 1 days (U band) and 4 ± 1 days (r band). These 1σ measurements are consistent with a scenario in which flares originated in the immediate vicinity of the supermassive black hole are thermally reprocessed in a standard accretion disk at ∼ 10-20 Schwarzschild radii from the central dark object. We also report that the light curve for the X-ray emission with power-law spectrum is delayed with respect to those in the U gr bands by ∼ 32 days. Hence, the central driving source can not be a standard corona emitting the observed power-law X-rays. This result is also supported by X-ray reprocessing simulations and the absence of X-ray reflection features in the spectrum of 0957+561. We plausibly interpret the lack of reflection and the 32-day delay as evidence for a power-law X-ray source in the base of the jet at a typical height of ∼ 200 Schwarzschild radii. A central EUV source would drive the variability of 0957+561.

A 5.5-year robotic optical monitoring of Q0957+561: substructure in a non-local cD galaxy

“…From the LRT main fluctuations in the g-band and r-band fluxes of Q0957+561B, we infer Δt rg > 2.5 d at the 97% confidence level (α = 9 d). A very accurate, 1σ delay Δt rg = 4 ± 1 d was also obtained from these data (Gil-Merino et al 2012). However, Δt rg < 2.5 d at the 98% confidence level (α = 9 d) for Q0957+561A data.…”

Time-Domain Studies of Gravitationally Lensed Quasars

“…In addition, the optical flux ratio A/B changed little in the first 10 years of observations, i.e., between the identification as a quasar pair in 1996 and our LQLM I campaign (see Dai & Kochanek 2009 and references therein). For example, the r-band light curve of the A image and the properly shifted r-band light curve of B were consistent with each other throughout the LQLM I period, so the variability over this time segment was basically intrinsic to the distant quasar (Goicoechea et al 2008a). However, the LQLM III light curves indicate that the r-band flux ratio had evolved in 2010-2011.…”

“…SBS 0909+532. The LQLM I light curves in the r band led to a robust time-delay between its two images of ∆t AB = −49 ± 6 days and ∆t ij = t j −t i , B leading (Goicoechea et al 2008a). In addition, the optical flux ratio A/B changed little in the first 10 years of observations, i.e., between the identification as a quasar pair in 1996 and our LQLM I campaign (see Dai & Kochanek 2009 and references therein).…”

“…These initial brightness records were used to measure time delays between images and optical bands (Shalyapin et al 2008), and to analyse the structure function of the rest-frame UV variability (Goicoechea et al 2008b;. Later, LQLM II fluxes in the griz bands, together with concurrent spacebased observations from Swift/UVOT and Chandra, unveiled details of the accretion flow and its jet connection in a distant radio-loud quasar for the first time (see Gil-Merino et al 2011). Our global database in the gr bands is also providing surprising results on the chromaticity in ∆t AB and the long-term evolution of B/A, which are probably related to the presence of a dense cloud within the cD lensing galaxy along the line of sight to the A image.…”

Exploration of quasars with theGaiamission

“…Furthermore, a hot corona above the SMBH produces X-ray photons. Reprocessing of these X-ray photons into UV-optical continuum radiation by the accretion disk could induce variability of short or medium timescale (Collin-Souffrin 1991;George & Fabian 1991;Gil-Merino et al 2012).…”