Fe Kα Emission Line Research Articles

The properties of the X-ray corona in the distant (z= 3.91) quasar APM 08279+5255

We present new jointXMM-NewtonandNuSTARobservations of APM 08279+5255, a gravitationally-lensed, broad-absorption line quasar (z = 3.91). After showing a fairly stable flux (f2 − 10 ≃ 4 − 5.5 × 10−13erg s−1) from 2000 to 2008, APM 08279+5255 was found in a fainter state in the latest X-ray exposures (f2 − 10 ≃ 2.7 × 10−13erg s−1), which can likely be ascribed to a lower X-ray activity. Moreover, the 2019 data present a prominent Fe Kαemission line and do not show any significant absorption line. This fainter state, coupled to the first hard X-ray sampling of APM 08279+5255, allowed us to measure X-ray reflection and the high-energy cutoff in this source for the first time. From the analysis of previousXMM-NewtonandChandraobservations, X-ray reflection is demonstrated to be a long-lasting feature of this source, but less prominent prior to 2008, possibly due to a stronger primary emission. The estimated high-energy cutoff (Ecut = 99−35+91keV) sets a new redshift record for the farthest ever measured and places APM 08279+5255 in the allowed region of the compactness-temperature diagram of X-ray coronae, in agreement with previous results on high-zquasars.

Response of the Fe Kα line emission to the X-ray continuum variability in the changing-look active galactic nucleus NGC 1566

NGC 1566 is a changing look AGN known to exhibit recurrent X-ray outbursts with each lasting for several years. The most recent X-ray outburst is observed on 2018, with a substantial increase of 2–10 keV flux by a factor of ∼24 than the historical minimum. We re-analyze the XMM-Newton and NuSTAR observations covering the pre-outburst, outburst and post-outburst epochs, and confirm the discovery of the broad feature in the ∼5–7 keV band during the period of outburst that could be interpreted as a relativistic Fe Kα emission line. Our analysis suggests that its flux has increased in tandem with the 2–10 keV continuum, making it the second changing look AGN in which the broad Fe Kα line responds to the X-ray continuum variability. This behavior strongly supports the idea that X-rays originates in a corona above the accretion disk, and disk reflection produces the relativistic Fe Kα line. In addition, we find the response of narrow Fe Kα emission line to the changes in the X-ray continuum on a time-scale as short as four months, allowing to put the location of line-emitting region at <0.1 pc, comparable to the size of optical BLR. By comparing to the changing look AGN NGC 2992, the Fe Kα variation rate (the ratio of Fe Kα variation to luminosity variation) in NGC 1566 appears greater, which could be possibly explained by larger amount of gas or Fe abundance responsible for producing the Fe Kα line for the latter. The strength of variable broad Fe Kα line as well as the soft X-ray excess emission appears to be correlated with the accretion rate, which could be explained as due to the state transition associated with the changing-look phenomenon.

Are Compton-thin AGNs Globally Compton Thin?

Abstract We select eight nearby active galactic nuclei (AGNs) which, based on previous work, appear to be Compton-thin in the line of sight. We model with mytorus their broadband X-ray spectra from 20 individual observations with Suzaku, accounting self-consistently for Fe Kα line emission, as well as direct and scattered continuum from matter with finite column density and solar Fe abundance. Our model configuration allows us to measure the global, out of the line of sight, equivalent hydrogen column density separately from that in the line of sight. For 5 out of 20 observations (in 3 AGNs) we find that the global column density is in fact ≳1.5 × 1024 cm−2, consistent with the distant scattering matter being Compton-thick. For a fourth AGN, two out of five observations are also consistent with being Compton-thick, although with large errors. Some of these AGNs have been reported to host relativistically broadened Fe Kα emission. Based on our modeling, the Fe Kα emission line is not resolved in all but two Suzaku observations, and the data can be fitted well with models that only include a narrow Fe Kα emission line.

The first simultaneous X-ray broadband view of Mrk 110 with XMM-Newton and NuSTAR

Context. Soft and hard X-ray excesses, compared to the continuum power-law shape between ∼2−10 keV, are common features observed in the spectra of active galactic nuclei (AGN) and are associated with the accretion disc-corona system around the supermassive black hole. However, the dominant process at work is still highly debated and has been proposed to be either relativistic reflection or Comptonisation. Such an investigation can be problematic for AGN that have significant intrinsic absorption, either cold or warm, which can severely distort the observed continuum. Therefore, AGN with no (or very weak) intrinsic absorption along the line-of-sight, called bare AGN, are the best targets for directly probing disc-corona systems. Aims. We aim to characterise the main X-ray spectral physical components from the bright bare broad-line Seyfert 1 AGN Mrk 110, as well as the physical process(es) at work in its disc-corona system viewed almost face-on. Methods. We perform the X-ray broadband spectral analysis thanks to two simultaneous XMM-Newton and NuSTAR observations performed on November 16−17, 2019, and April 5−6, 2020. We also use a deep NuSTAR observation obtained in January 2017 for the spectral analysis above 3 keV. Results. The broadband X-ray spectra of Mrk 110 are characterised by the presence of a prominent and absorption-free smooth soft X-ray excess, moderately broad O VII and Fe Kα emission lines, and a lack of a strong Compton hump. The continuum above ∼3 keV is very similar at both epochs, while some variability (stronger when brighter) is present for the soft X-ray excess. A combination of soft and hard Comptonisation by a warm and hot corona, respectively, plus mildly relativistic disc reflection reproduce the broadband X-ray continuum very well. The inferred warm corona temperature, kTwarm ∼ 0.3 keV, is similar to the values found in other sub-Eddington AGN, whereas the hot corona temperature, kThot ∼ 21−31 keV (depending mainly on the assumed hot corona geometry), is found to be in the lower range of the values measured in AGN.

NuSTAR and Swift observations of the extragalactic black hole X-ray binaries

ABSTRACT We present the results obtained from detailed spectral and timing studies of extragalactic black hole X-ray binaries LMC X–1 and LMC X–3, using simultaneous observations with Nuclear Spectroscopic Telescope Array (NuSTAR) and Neil Gehrels Swift observatories. The combined spectra in the 0.5–30 keV energy range, obtained between 2014 and 2019, are investigated for both sources. We do not find any noticeable variability in 0.5–30 keV light curves, with 0.1–10 Hz fractional rms estimated to be &amp;lt;2 per cent. No evidence of quasi-periodic oscillations is found in the power density spectra. The sources are found to be in the high soft state during the observations with disc temperature Tin ∼ 1 keV, photon index, Γ &amp;gt; 2.5 and thermal emission fraction, fdisc &amp;gt; 80 per cent. An Fe Kα emission line is detected in the spectra of LMC X–1, though no such feature is observed in the spectra of LMC X–3. From the spectral modelling, the spins of the black holes in LMC X–1 and LMC X–3 are estimated to be in the range of 0.92–0.95 and 0.19−0.29, respectively. The accretion efficiency is found to be, η ∼ 0.13 and η ∼ 0.04 for LMC X–1 and LMC X–3, respectively.

A Weakening Compton Hump and Soft X-Ray Excess Detected in the Seyfert 1 Galaxy MCG –02–58–22

Abstract We have carried out an extensive X-ray spectral study of the bare Seyfert 1 galaxy MCG –02–58–22 to ascertain the nature of the X-ray reprocessing media using observations from Suzaku (2009) and simultaneous observations from XMM-Newton and NuSTAR (2016). The most significant results of our investigation are as follows. (1) The primary X-ray emission from the corona is constant in these observations, in terms of both the power-law slope (Γ = 1.80) and luminosity (L 2−10 keV = 2.55 × 1044 erg s−1). (2) The soft excess flux decreased by a factor of 2 in 2016, the Compton hump weakened/vanished in 2016, and the narrow FeKα emission line became marginally broad (σ = 0.35 ± 0.08 keV) and its flux doubled in 2016. (3) From physical model fits, we find that the normalization of the narrow component of the FeKα line does not change in the two epochs, although the Compton hump vanishes in the same time span. Since the primary X-ray continuum does not change, we presume that any changes in the reprocessed emission must arise due to changes in the reprocessing media. Our primary conclusions are as follows. (a) The vanishing of the Compton hump in 2016 can probably be explained by a dynamic clumpy torus that is infalling/outflowing or a polar dusty wind. (b) The torus in this active galactic nucleus possibly has two structures: an equatorial toroidal disk (producing the narrow FeKα emission) and a polar component (producing the variable Compton hump). (c) The reduction of the soft excess flux by half and increase in the FeKα flux by a factor of 2 in the same period cannot be adequately explained by an ionized disk reflection model alone.

Chandra Observations of Excess Fe Kα Line Emission in Galaxies with High Star Formation Rates: X-Ray Reflection on Galaxy Scales?

Abstract In active galactic nuclei (AGNs), fluorescent Fe Kα (iron) line emission is generally interpreted as originating from obscuring material around a supermassive black hole on the scale of a few parsecs. However, recent Chandra studies indicate the existence of iron line emission extending to kiloparsec scales in the host galaxy. The connection between iron line emission and large-scale material can be spatially resolved directly only in nearby galaxies, but could be inferred in more distant AGNs by a connection between line emission and star-forming gas and dust that is more extended than the parsec-scale torus. Here we present the results from a stacking analysis and X-ray spectral fitting performed on sources in the Chandra Deep Field South (CDFS) 7 Ms observations. From the deep stacked spectra, we select sources with stellar mass at 0.5 &lt; z &lt; 2, obtaining 25 sources with high-infrared (IR) luminosity (star formation rate, SFRFIR ≥ 17 M ☉ yr−1) and 32 sources below this threshold. We find that the equivalent width (EW) of the iron line EW(Fe) is a factor of three higher with 3σ significance for high-IR luminosity measured from Herschel observations, indicating a connection between iron line emission and star-forming material on galaxy scales. We show that there is no significant dependence of the EW(Fe) on M * or X-ray luminosity, suggesting that the reflection of AGN X-ray emission over large scales in their host galaxies may be widespread.

Accretion properties of MAXI J1813-095 during its failed outburst in 2018

We present the results obtained from detailed timing and spectral studies of a black hole candidate MAXI J1813–095 using Swift, NICER, and NuSTAR observations during its 2018 outburst. The timing behavior of the source is mainly studied by examining NICER light curves in the 0.5–10 keV range. We did not find any signature of quasi-periodic oscillations in the power density spectra of the source. We carry out spectral analysis with a combined disk blackbody & power law model, and physical two-component advective flow (TCAF) model. From the combined disk blackbody & power-law model, we extracted thermal and non-thermal fluxes, photon index and inner disk temperature. We also find evidence for weak reflection in the spectra. We have tested the physical TCAF model on a broadband spectrum from NuSTAR and Swift/XRT. The parameters like mass accretion rates, the size of Compton clouds and the shock strength are extracted. Our result affirms that the source remained in the hard state during the entire outburst which indicates a ‘failed’ outburst. We estimate the mass of the black hole as 7.4 ± 1.5 M ⊙ from the spectral study with the TCAF model. We apply the LAOR model for the Fe Kα line emission. From this, the spin parameter of the black hole is ascertained as a* > 0.76$ The inclination angle of the system is estimated to be in the range of 28° – 45° from the reflection model. We find the source distance to be ∼ 6 kpc.

Properties of Faint X-ray Activity of XTE J1908+094 in 2019

We study the properties of the faint X-ray activity of Galactic transient black hole candidate XTE J1908+094 during its 2019 outburst. Here, we report the results of detailed spectral and temporal analysis during this outburst using observations from Nuclear Spectroscopic Telescope Array (NuSTAR). We have not observed any quasi-periodic-oscillations (QPOs) in the power density spectrum (PDS). The spectral study suggests that the source remained in the softer (more precisely, in the soft–intermediate) spectral state during this short period of X-ray activity. We notice a faint but broad Fe Kα emission line at around 6.5 keV. We also estimate the probable mass of the black hole to be 6.5−0.7+0.5M⊙, with 90% confidence.

The Distance of the Narrow FeKalpha Emitting Region for a Sample of Compton-thin Type-II Active Galactic Nuclei

Abstract I have studied the variability of the FeKα emission line flux in response to changes in the 2–10 keV unabsorbed flux in a sample of Compton thin type-II active galactic nuclei. All of the 20 sources in the sample studied by Laha et al., exhibit the presence of a narrow FeKα emission line. Except for one source (NGC 2992), all other sources show no correlations between the FeKα emission line flux and 2–10 keV unabsorbed flux. This implies that although most of the sources have shown significant variations in their 2–10 keV flux, the FeKα emission line did not get enough time to respond to those changes. This helps us put lower limits on the distance of the FeKα emitters to &gt;10 lt-yr from the central engine, equivalent to ∼3 pc which is consistent with the standard torus/narrow-line-region distance. I conclude that the FeKα emission lines of these sources arise from reflection of the hard X-ray photons off neutral materials located beyond pcscale.

Spatially resolved X-ray spectroscopy of the archetype type 2 active galactic nucleus NGC 1068 with Chandra

Abstract We investigate spatial distributions of iron Kα (Fe-Kα) lines in the cental 100 pc of the Seyfert 2 galaxy NGC 1068 observed with Chandra. The spatial distributions of Fe-Kα lines, neutral and highly ionized, around the center of the galactic nucleus are not isotropic, as consistently confirmed in both image and spectral analyses. The hydrogen number density of the gas clouds responsible for the neutral Fe-Kα line emission is estimated to be 102–103 cm−3 for the sampled regions near the galactic core. The photo-ionization model, where iron is assumed to be ionized by X-rays from the galactic nucleus, yields ionization parameters lower than 19 for these clouds. The range of this ionization parameter is two or three orders of magnitude lower than the theoretically expected value to produce the observed helium-like Fe-Kα line intensities. Therefore, the photo-ionization model is excluded from the explanation of the amount of highly ionized iron that is responsible for the observed Fe-Kα lines. Also, we find anti-correlation in the spatial distributions between the molecular cloud in the area observed with ALMA and that of the Fe-Kα lines, including that from neutral iron. We suggest that X-ray iron-line and radio molecular cloud observations are complementary to probe the distribution of matters in the central regions around the cores of active galactic nuclei.

The Kiloparsec-scale Fe Ka Emission in the Compton-thin Seyfert 2 Galaxy NGC 4388 Resolved by Chandra

Abstract We present imaging and spectral analysis of the combined ∼48 ks Chandra observations of Seyfert 2 galaxy NGC 4388. Compared with previous studies, three prominent extended X-ray structures around the nucleus on a kiloparsec-scale are well imaged, allowing an in-depth spatially resolved study. Both the extended hard continuum (4–6 keV) and the Fe Kα line (6.2–6.7 keV) show similar morphology, consistent with a scenario where the ionizing emission from the nucleus is reprocessed by circumnuclear cold gas, resulting in a weak reflection continuum and an associated neutral Fe Kα line. This has been seen in other Compton-thick active galactic nuclei (AGN), but NGC 4388 is one of the rare cases with a lower column density (N H &lt; 1.25 × 1024 cm−2) along the line of sight. Significant differences in equivalent width of the Fe Kα emission line (up to a factor of 3) are found for the nuclear and extended regions. Such a difference could be ascribed to different column densities or scattering angles with respect to the line of sight, rather than variations in iron abundances. The northeast and west extended structures appear to be aligned with the larger-scale galactic disk and dust lane in the HST V − H color map, and are located at the peak of molecular gas distribution. The morphology of remaining extended features likely traces edges of a known radio jet, indicating that the outflow at the kiloparsec-scale may have compressed the interstellar gas and produced clumps working as the reflector to enhance line emission. In addition, using [O iv] emission as a proxy of the AGN intrinsic luminosity, we find that both of the extended Fe Kα emission and reflection continuum are linearly correlated with the [O iv] luminosity, which indicates a connection between the central AGN and the extended emission.

The Correlated Response of the Narrow FeKα Emission Line to the Primary Continuum Changes in the Seyfert Galaxy NGC 2992

Abstract The intensely varying Active Galactic nucleus (AGN) NGC 2992, on timescales of days to years, provides us with a unique testbed to study the response of the narrow FeKα emission line to the changes in the primary 2–10 keV AGN continuum. We find a strong correlation between the narrow FeKα line flux and the 2–10 keV flux with a Spearman correlation coefficient s = 0.70 and probability p &lt; 0.001, over a period of ∼20 yr. There is no evidence of such a correlation in &lt;1 yr, but the FeKα flux responds at ∼3 yr timescales, allowing us to put the reprocessor distance scale to 0.3 pc ≤ d ≤ 1 pc, consistent with that of torus reflection. The primary 2–10 keV continuum of NGC 2992 undergoes a high-low-high transition in ∼16 yr (2003–2019). Future long term monitoring will be crucial.

The chemical composition of the accretion disc and donor star in ultra-compact X-ray binaries: A comprehensive X-ray analysis

ABSTRACT We have analysed the X-ray spectra of all known Ultra-Compact X-ray Binaries (UCXBs), with the purpose of constraining the chemical composition of their accretion disc and donor star. Our investigation was focused on the presence (or absence) of the Fe Kα emission line, which was used as the probe of chemical composition of the disc, based on previously established theoretical predictions for the reflection of X-ray radiation off the surface of C/O-rich or He-rich accretion discs in UCXBs. We have contrasted the results of our spectral analysis to the history of type I X-ray bursts from these systems, which can also indicate donor star composition. We found that UCXBs with prominent and persistent iron Kα emission also featured repeat bursting activity. On the other hand, the UCXBs for which no iron line was detected, appear to have few or no type I X-ray bursts detected over more than a decade of monitoring. Based on Monte Carlo simulations, demonstrating a strong correlation between the Fe Kα line strength and the abundance of C and O in the accretion disc material and given the expected correlation between the H/He abundance and the recurrence rate of type I X-ray bursts, we propose that there is a considerable likelihood that UCXBs with persistent iron emission have He-rich donors, while those that do not, likely have C/O or O/Ne/Mg-rich donors. Our result strongly advocate for the development of more sophisticated simulations of X-ray reflection from hydrogen-poor accretion discs.

Probing the nuclear and circumnuclear properties of NGC 6300 using X-ray observations

ABSTRACT We present the results obtained from a detailed X-ray timing and spectral analysis of the Seyfert 2 galaxy NGC 6300 by using observations from the Suzaku observatory, theChandra X-ray Observatory and the Nuclear Spectroscopic Telescope Array(NuSTAR) mission between 2007 and 2016. We calculate the variance and the rms fractional variability of the source in different energy bands and we find variabilities in various energy bands. Spectral properties of the source are studied by using various phenomenological and physical models. The properties of the Compton clouds, reflection, Fe Kα line emission and soft X-ray excess are studied in detail. Several physical parameters of the source are extracted and investigated to establish the presence/absence of any correlation between them. We also investigate the nature of the circumnuclear ‘torus’ and we find that the torus is not uniform, but clumpy. The observed changes in the line-of-sight column density can be explained in terms of transiting clouds. The iron line-emitting region is found to be different in the different epochs of observations. We also observe that the torus and the nucleus independently evolve over the years.

Unveiling Sub-pc Supermassive Black Hole Binary Candidates in Active Galactic Nuclei

Abstract The elusive supermassive black hole binaries (SMBHBs) are thought to be the penultimate stage of galaxy mergers, preceding a final coalescence phase. SMBHBs are sources of continuous gravitational waves, possibly detectable by pulsar timing arrays; the identification of candidates could help in performing targeted gravitational wave searches. Due to SMBHBs’ origin in the innermost parts of active galactic nuclei (AGN), X-rays are a promising tool for unveiling their presence, by means of either double Fe Kα emission lines or periodicity in their light curve. Here we report on a new method for selecting SMBHBs by means of the presence of a periodic signal in their Swift Burst Alert Telescope (BAT) 105 month light curves. Our technique is based on Fisher’s exact g-test and takes into account the possible presence of colored noise. Among the 553 AGN selected for our investigation, only the Seyfert 1.5 galaxy Mrk 915 emerges as a candidate SMBHB; from subsequent analysis of its light curve we find a period P 0 = 35 ± 2 months, and the null hypothesis is rejected at the 3.7σ confidence level. We also present a detailed analysis of the BAT light curve of the only previously X-ray-selected binary candidate source in the literature, the Seyfert 2 galaxy MCG+11-11-032. We find P 0 = 26.3 ± 0.6 months, consistent with the one inferred from previously reported double Fe Kα emission lines.

Isolated AGNs NGC 5347, ESO 438‐009, MCG‐02‐04‐090, and J11366‐6002: Swift and NuSTAR joined view1

AbstractWe present the spectral analysis with the Nuclear Spectroscopic Telescope Array (NuSTAR) of four isolated galaxies with active galactic nuclei selected from the 2MIG catalogue: NGC 5347, ESO 438‐009, MCG‐02‐09‐040, and IGR J11366‐6002. We also used the Swift/Burst Alert Telescope (BAT) data up to ∼150 keV for MCG 02‐09‐040, ESO 438‐009, and IGR J11366‐6002 as well as the Swift/XRT data in 0.3–10 keV energy band for NGC 5347, ESO 438‐009, and IGR J11366‐6002. All the sources appear to have the reflected spectrum component with different reflection fractions in addition to the primary power‐law continuum. We found that power‐law indices for these sources lie between 1.6 and 1.8. The spectra of two sources, NGC 5347 and MCG‐02‐09‐040, show the Fe Kα emission line. For both of these sources, the Fe Kα lines have a significant value of EW ∼1 keV. The X‐ray spectrum of NGC 5347 is best fitted by a pure reflection model with Ecut ∼ 117 keV and without the presence of any additional primary power‐law component. We also found that the X‐ray spectrum of MCG‐02‐09‐040 shows the presence of heavy neutral obscuration of NH ∼ 1024 cm−2. However, this provides a non‐physical value of reflection in the case with fitting by a simple reflection model. A more appropriate fit is obtained with adopting the physical Monte Carlo‐based model as BNTorus. It allowed us to determine the absorption value of NH ∼ 1.04 × 1024 cm−2 and reasonable power‐law index of Γ ≈ 1.63. Results for MCG‐02‐09‐040 are presented for the first time.

Probing cosmic rays with Fe Kα line structures generated by multiple ionization process

Abstract Supernova remnants (SNRs) have been regarded as major acceleration sites of Galactic cosmic rays. Recent X-ray studies revealed neutral Fe Kα line emission from dense gas in the vicinity of some SNRs, which can be best interpreted as K-shell ionization of Fe atoms in the gas by sub-relativistic particles accelerated in the SNRs. In this Letter, we propose a novel method of constraining the composition of particles accelerated in SNRs, which is currently unknown. When energetic heavy ions collide with target atoms, their strong Coulomb field can easily cause simultaneous ejection of multiple inner-shell electrons of the target. This results in shifts in characteristic X-ray line energies, forming distinctive spectral structures. Detection of such structures in the neutral Fe Kα line strongly supports the particle ionization scenario, and furthermore provides direct evidence of heavy ions in the accelerated particles. We construct a model for the Fe Kα line structures by various projectile ions utilizing atomic-collision data.

X-ray spectral and image spatial models of NGC 3081 with Chandra data

AbstractThe physical properties of AGN such as accretion rate, column density, temperature of hot corona and other characteristics can be found from X-ray spectral data. We present the results of spatial and spectral analysis for Sy2 type galaxy NGC 3081 obtained with different mathematical tools of the Chandra Interactive Analysis of Observations software. We found evidence of extended emission in 0.5-3.0 keV as well as derived parameters for model A: photon index , column density , warm component and hot component . We detected the presence of a component of the reflection spectrum, Fe Kα emission line with and .

X-raying winds in distant quasars: The first high-redshift wind duty cycle

Aims. Theoretical models of wind-driven feedback from active galactic nuclei (AGN) often identify ultra-fast outflows as being the main agent in the generation of galaxy-sized outflows, which are possibly the main actors in establishing so-called AGN-galaxy co-evolution. Ultra-fast outflows are well characterized in local AGN but much less is known in quasars at the cosmic time when star formation and AGN activity peaked (z ≃ 1–3). It is therefore necessary to search for evidence of ultra-fast outflows in high-z sources to test wind-driven AGN feedback models. Methods. Here we present a study of Q2237+030, the Einstein Cross, a quadruply-imaged radio-quiet lensed quasar located at z = 1.695. We performed a systematic and comprehensive temporally and spatially resolved X-ray spectral analysis of all the available Chandra and XMM-Newton data (as of September 2019). Results. We find clear evidence for spectral variability, possibly due to absorption column density (or covering fraction) variability intrinsic to the source. For the first time in this quasar, we detect a fast X-ray wind outflowing at vout ≃ 0.1c that would be powerful enough (Ėkin ≃ 0.1 Lbol) to significantly affect the evolution of the host galaxy. We report also on the possible presence of an even faster component of the wind (vout ∼ 0.5c). For the first time in a high-z quasar, given the large sample and long time interval spanned by the analyzed X-ray data, we are able to roughly estimate the wind duty cycle as ≃0.46 (0.31) at 90% (95%) confidence level. Finally, we also confirm the presence of a Fe Kα emission line with variable energy, which we discuss in the light of microlensing effects as well as considering our findings on the source.