Hard Band Research Articles

BASS-XL: X-ray variability properties of unobscured active galactic nuclei

ABSTRACT We investigate the X-ray variability properties of Seyfert 1 Galaxies belonging to the BAT AGN Spectroscopic Survey (BASS). The sample includes 151 unobscured (NH < 1022 cm−2) AGNs observed with XMM–Newton for a total exposure time of ∼27 ms, representing the deepest variability study done so far with high signal-to-noise XMM–Newton observations, almost doubling the number of observations analysed in previous works. We constrain the relation between the normalized excess variance and the 2–10 keV AGN luminosities, black hole masses, and Eddington ratios. We find a highly significant correlation between $\sigma _{\rm NXS}^2$ and MBH , with a scatter of ∼0.85 dex. For sources with high L2–10 this correlation has a lower normalization, confirming that more luminous (higher mass) AGNs show less variability. We explored the $\sigma _{\rm NXS}^2$ versus MBH relation for the sub-sample of sources with MBH estimated via the ‘reverberation mapping’ technique, finding a tighter anticorrelation, with a scatter of ∼0.65 dex. We examine how the $\sigma _{\rm NXS}^2$ changes with energy by studying the relation between the variability in the hard (3–10 keV) and the soft (0.2–1 keV)/medium (1–3 keV) energy bands, finding that the spectral components dominating the hard energy band are more variable than the spectral components dominating in softer energy bands, on time-scales shorter than 10 ks.

Colliding winds in WR21 and WR31 – I. The X-ray view

ABSTRACT WR21 and WR31 are two WR + O binaries with short periods, quite similar to the case of V444 Cyg. The XMM-Newton observatory has monitored these two objects and clearly revealed phase-locked variations as expected from colliding winds. The changes are maximum in the soft band (0.5–2.0 keV, variations by a factor 3–4) where they are intrinsically linked to absorption effects. The increase in absorption due to the dense WR wind is confirmed by the spectral analysis. The flux maximum is however not detected exactly at conjunction with the O star in front but slightly afterwards, suggesting Coriolis deflection of the collision zone as in V444 Cyg. In the hard band (2–10 keV), the variations (by a factor of 1.5–2.0) are much more limited. Because of the lower orbital inclinations, eclipses as observed for V444 Cyg are not detected in these systems.

The MUSE Ultra Deep Field (MUDF). IV. A pair of X-ray weak quasars at the heart of two extended Lyα nebulae

ABSTRACT We present the results obtained from follow-up observations of the MUSE Ultra Deep Field (MUDF) at X-ray energies with XMM–Newton. The MUDF is centred on a unique field with two bright, physically associated quasars at z ≃ 3.23, separated by ∼500 kpc in projection. Both quasars are embedded within extended Lyα nebulae (${\gtrsim}100\,{\rm kpc}$ at a surface brightness flux level of ≈6 × 10−19 ${\rm erg\,s^{-1}\,cm^{-2}\,arcsec^{-2}}$), whose elongated morphology is suggestive of an extended filament connecting the quasar haloes. The new X-ray observations presented here allow us to characterize the physical properties (e.g. X-ray slope, luminosities, gas column densities) in the innermost region of the MUDF quasars. We find that both quasars are X-ray underluminous compared to objects at similar ultraviolet luminosities. Based on our X-ray spectral analysis, absorbing columns of NH(z) ≳ 1023 cm−2 appear unlikely therefore such a weakness is possibly intrinsic. When also including literature data, we do not observe any detectable trend between the area of the nebulae and nuclear luminosities at both the rest-frame 2 keV and 2500 Å. The area is also not correlated with the X-ray photon index nor with the integrated band flux in the hard band (2–10 keV). We also do not find any trend between the extended Lyα emission of the nebulae and the nuclear X-ray luminosity. Finally, the properties of the MUDF quasars’ nebulae are consistent with the observed relation between the Lyα integrated luminosity of the nebulae and their area. Our results suggest that the quasar ionization power is not a strong driver of the morphology and size of the nebulae.

Investigating the energy-dependent temporal nature of black hole binary system H 1743-322

ABSTRACT Black hole X-ray binaries routinely exhibit quasi-periodic oscillations (QPOs) in their power density spectrum. Studies of QPOs have demonstrated immense ability to understand these dynamical systems although their unambiguous origin still remains a challenge. We investigate the energy-dependent properties of the Type-C QPOs detected for H 1743-322 as observed with AstroSat in its two X-ray outbursts of 2016 and 2017. The combined broad-band LAXPC and SXT spectrum is well modelled with a soft thermal and a hard Comptonization component. The QPO exhibits soft/negative lags i.e. variation in soft-band lags the variation in hard band, although the upper harmonic shows opposite behaviour i.e. hard/positive lags. Here, we model energy-dependent properties (fractional root mean square and time-lag variation with energy) of the QPO and its upper harmonic individually with a general scheme that fits these properties by utilizing the spectral information and consequently allows to identify the radiative component responsible for producing the variability. Considering the truncated disc picture of accretion flow, a simple model with variation in inner disc temperature, heating rate, and fractional scattering with time delays is able to describe the fractional rms and time-lag spectra. In this work, we show that this technique can successfully describe the energy-dependent features and identify the spectral parameters generating the variability.

Investigation of the Electronic Structure of the Mg<sub>99.2</sub>Zn<sub>0.2</sub>Y<sub>0.6</sub> Alloy Using X-ray Photoelectron Spectroscopy

We investigated the electronic structure of the Mg99.2Zn0.2Y0.6 alloy using hard and soft X-ray photoemission spectroscopy and electronic band structure calculations to understand the mechanism of the phase stability of this material. Electronic structure of the Mg99.2Zn0.2Y0.6 alloy showed a semi-metallic electronic structure with a pseudo-gap at the Fermi level. The observed electronic structure of the Mg99.2Zn0.2Y0.6 alloy suggests that the presence of a pseudogap structure is responsible for phase stability.

Revealing the intrinsic X-ray reverberation lags in IRAS 13224−3809 through the Granger causality test

ABSTRACT The Granger causality is an econometric test for determining whether one time series is useful for forecasting another one with a certain Granger lag. Here, the light curves in the 0.3–1 keV (reflection dominated, soft) and 1.2–5 keV (continuum dominated, hard) bands of active galactic nuclei are produced, and the Granger lags are estimated and compared to the traditional lag–frequency spectra. We find that the light curves in the hard band Granger-cause (lead) those in the soft band, whereas the obtained Granger lags could be interpreted as the intrinsic reverberation lags. Then, we extract the Granger-lag profiles from 14 XMM–Newton observations of IRAS 13224−3809, and find that the lags are significant in 12 observations. The majority of the obtained Granger (intrinsic) lags are ∼200–500 s. With the IRAS 13224−3809 mass of 2 × 106 M⊙, these lags correspond to the true light travel distance of ∼20–50 rg. Hence, by assuming a lamp-post geometry and a face-on disc, this places the corona at ∼10–25 rg above the central black hole. Moreover, multiple Granger lags consisting of the small and large lags of <500 s and >1000 s are detected in four observations. This means that the corona height can significantly evolve from ∼10–25 rg to ∼55rg, or vice versa, towards the end of the observation. Granger lags are a promising way to measure the intrinsic lags, and provide evidence of coronal height variability within each individual observation.

Extended Hard X-Ray Emission in Highly Obscured AGNs

Kiloparsec-scale hard (>3 keV) X-ray continuum and fluorescent Fe Kα line emission has been recently discovered in nearby Compton-thick (CT) active galactic nuclei (AGNs), which opens new opportunities to improve AGN torus modeling and investigate how the central supermassive black hole interacts with and impacts the host galaxy. Following a pilot Chandra survey of nearby CT AGNs, we present in this paper the results of Chandra spatial analysis of five uniformly selected non-CT but still heavily obscured AGNs to investigate the extended hard X-ray emission by measuring the excess emission counts, excess fractions, and physical scales. Three of these AGNs show extended emission in the 3.0–7.0 keV band detected at >3σ above the Chandra point-spread function with total excess fractions ranging from ∼8% to 20%. The extent of the hard emission ranges from at least ∼250 pc to 1.1 kpc in radius. We compare these new sources with CT AGNs and find that CT AGNs appear to be more extended in the hard band than the non-CT AGNs. Similar to CT AGNs, the amounts of extended hard X-ray emission relative to the total emission of these obscured AGNs are not negligible. Together with other AGNs detected with extended hard X-ray emission in the literature, we further explore potential correlations between the extended hard X-ray component and AGN parameters. We also discuss the implications for torus modeling and AGN feedback. Considering potential contributions from X-ray binaries (XRBs) to the extended emission, we do not see strong XRB contamination in the overall sample.

Unravelling optical and X-ray properties of the disc-dominated intermediate polar IGR J15094-6649

ABSTRACT We present analyses of an Intermediate Polar, IGR J15094-6649, based on the archival optical data obtained from the Transiting Exoplanet Survey Satellite (TESS) and X-ray data obtained from the Suzaku, NuSTAR, and Neil Gehrels Swift Observatory (Swift). Present analysis confirms and refines the previously reported spin period of IGR J15094-6649 as 809.49584 ± 0.00075 s. Clear evidence of a beat period of 841.67376 ± 0.00082 s is found during the long-term TESS optical observations, which was not evident in the earlier studies. The dominance of X-ray and optical spin pulse unveils the disc-fed dominance accretion, however, the presence of an additional beat frequency indicates that part of the accreting material also flows along the magnetic field lines. The energy-dependent spin pulsations in the low (<10 keV) energy band are due to the photoelectric absorption in the accretion flow. However, the complex absorbers may be responsible to produce low amplitude spin modulations via Compton scattering in the hard (>10 keV) energy band and indicate that the height of the X-ray emitting region may be negligible. The observed double-humped X-ray profiles with a pronounced dip are indicative of the photoelectric absorption in the intervening accretion stream. Analysis of the X-ray spectra reveals the complexity of the X-ray emission, being composed of multitemperature plasma components with a soft excess, reflection, and suffers from strong absorption.

Metal Ballads as Low Pop? An Approach to Sentimentality and Gendered Performances in Popular Hard Rock and Metal Songs

Ballads are often among the bestselling songs of heavy metal and hard rock bands. Within these genres, ballads represent a way to address emotions such as love that are not part of the primary self-understanding of those genres. Still, “genre ideals and style” often seem to be at odds with the sentimental aesthetics of the ballad and its emotional expression and experience. In this article, we take a close look at the sonic, textual, performative, visual, and emotional-somatic articulation of love and the generation of sentimentality in three selected metal ballads. Even if the term “power ballad,” which is often used in reference to hard rock and metal ballads, refers to the simultaneity of “heaviness” in the sound and the thematization of love in the lyrics, sentimental ballads in the stereotypically more masculine-connotated genres nevertheless create friction and skepticism in their discursive evaluation, as they generate aesthetic discrepancies between concrete songs and genre conventions. Their quantitative popularity contrasts with their qualitative evaluation. Therefore, in a second step, we analyze the reception of the selected ballads, in particular their discursive evaluations in music reviews, in order to point out the ways of argumentation through which frictions are established. As a result, we show that evaluations are related to how love is addressed in the songs and to the extent of proximity of the ballads to genre rules.

The Extragalactic Serendipitous Swift Survey (ExSeSS) – I. Survey definition and measurements of the X-ray number counts

ABSTRACT We present the Extragalactic Serendipitous Swift Survey (ExSeSS), providing a new well-defined sample constructed from the observations performed using the Swift X-ray Telescope. The ExSeSS sample consists of 79 342 sources detected in the medium (1–2 keV), hard (2–10 keV), or total (0.3–10 keV) energy bands, covering 2086.6 deg2 of sky across a flux range of f0.3–10 keV ∼ 10−15 − 10−10 erg s−1 cm−2. Using the new ExSeSS sample we present measurements of the differential number counts of X-ray sources as a function of 2–10 keV flux that trace the population of Active Galactic Nuclei (AGNs) in a previously unexplored regime. We find that taking the line-of-sight absorption column density into account has an effect on the differential number count measurements and is vital to obtain agreement with previous results. In the hard band, we obtain a good agreement between the ExSeSS measurements and previous, higher energy data from NuSTAR and Swift/BAT when taking into account the varying column density of the ExSeSS sample as well as the X-ray spectral parameters of each of the samples we are comparing to. We also find discrepancies between the ExSeSS measurements and AGN population synthesis models, indicating a change in the properties of the AGN population over this flux range that is not fully described by current models at these energies, hinting at a larger, moderately obscured population at low redshifts (z ≲ 0.2) that the models are not currently taking into account.

An electronic panoptic society: Hierarchical surveillance, normalizing judgment, and examination in American hard rock band Starset

In the early 21st century, the whole society finished the transformation from a panopticon to an electronic super panopticon. With the development of intellectual technology, the view of surveillance increases. People in a technological society are monitored in every movement they make. In Starset’s post-apocalyptic society of the future, people are controlled by technology and become docile and prolific labor machines. This essay will analyze three songs by American hard rock band Starset, Breach, Where the skies end and Icarus, using three of Foucault’s theories of discipline and punishment, hierarchical surveillance, normalizing judgment and examination. Under the disciplinary surveillance, people from Starset’s post-apocalyptic society have been tamed by the power of technology and are constantly disciplining themselves and checking themselves, becoming a single efficient producer. It also shows that society is becoming a transparent high-speed panopticon prison.

A systematic comparison of galaxy cluster temperatures measured with NuSTAR and Chandra

ABSTRACT Temperature measurements of galaxy clusters are used to determine their masses, which in turn are used to determine cosmological parameters. However, systematic differences between the temperatures measured by different telescopes imply a significant source of systematic uncertainty on such mass estimates. We perform the first systematic comparison between cluster temperatures measured with Chandra and NuSTAR. This provides a useful contribution to the effort of cross-calibrating cluster temperatures due to the harder response of NuSTAR compared with most other observatories. We measure average temperatures for eight clusters observed with NuSTAR and Chandra. We fit the NuSTAR spectra in a hard (3–10 keV) energy band, and the Chandra spectra in both the hard and a broad (0.6–9 keV) band. We fit a power-law cross-calibration model to the resulting temperatures. At a Chandra temperature of 10 keV, the average NuSTAR temperature was $(10.5\pm 3.7)$ and $(15.7\pm 4.6){{\ \rm per\ cent}}$, lower than Chandra for the broad- and hard-band fits, respectively. We explored the impact of systematics from background modelling and multiphase temperature structure of the clusters, and found that these did not affect our results. Our sample are primarily merging clusters with complex thermal structures so are not ideal calibration targets. However, given the harder response of NuSTAR, it would be expected to measure a higher average temperature than Chandra for a non-isothermal cluster, so we interpret our measurement as a lower limit on the difference in temperatures between NuSTAR and Chandra.

Study of X-Ray Intraday Variability of HBL Blazars Based on Observations Obtained with XMM-Newton

We present an extensive study on the X-ray intraday variability of 10 teraelectronvolt-emitting high synchrotron peaked blazars (HBLs): 1ES 0229+200, 1ES 0414+009, PKS 0548-322, 1ES 1101-232, 1H 1219+301, H 1426+428, Mrk 501, 1ES 1959+650, PKS 2005-489, and 1ES 2344+514 made with 25 XMM-Newton pointed observations during its operational period. Intraday variability has been estimated in three energy bands: soft (0.3–2 keV), hard (2–10 keV), and total (0.3–10 keV). Although seven out of 10 teraelectronvolt HBLs exhibited some intraday variability at 3σ levels, no major variations exceeding 6% were detected. We explored the spectral properties of the sample by extracting the hardness ratio from the soft and hard bands; no significant variations in the hardness ratio were observed in any source. We performed power spectral density analyses on the variable light curves by fitting power laws, yielding slopes lying in the range of 1.11–2.93 for different HBLs. We briefly discuss possible emission mechanisms and carry out rough estimates for magnetic fields, electron Lorentz factors, and emission region sizes for seven of these HBLs.

Search for Nonthermal X-ray Emission in the Ophiuchus Galaxy Cluster

We present the results of our study of the X-ray emission from the Ophiuchus galaxy cluster based on INTEGRAL/IBIS data in the energy range 20–120 keV. Our goal is the search for a nonthermal emission component from the cluster. Using the INTEGRAL data over the period of observations 2003–2009, we have constructed the images of the Ophiuchus galaxy cluster in different energy bands from 20 to 120 keV with the extraction of spectral information. We show that in the hard X-ray energy band the source is an extended one with an angular size of $$4.9^{\prime}\pm 0.1^{\prime}$$ . Assuming a fixed intracluster gas temperature of 8.5 keV, a power-law component of the possible nonthermal X-ray emission is observed at a 5.5 $$\sigma$$ significance level, the flux from which is consistent with previous studies. However, in view of the uncertainty in constraining the thermal emission component in the X-ray spectrum at energies above 20 keV, we cannot make the assertion about a significant detection of nonthermal emission from the cluster. Based on the fact of a confident detection of the cluster up to 70 keV, we can draw the conclusion only about the possible presence of a nonthermal excess at energies above 60 keV.

X-ray spectral and timing analysis of the Compton Thick Seyfert 2 galaxy NGC 1068

ABSTRACT We present the timing and spectral analysis of the Compton Thick Seyfert 2 active galactic nuclei NGC 1068 observed using NuSTAR and XMM–Newton. In this work for the first time we calculated the coronal temperature ($\rm {kT_{e}}$) of the source and checked for its variation between the epochs if any. The data analysed in this work comprised of (a) eight epochs of observations with NuSTAR carried out during the period 2012 December to 2017 November, and, (b) six epochs of observations with XMM–fNewton carried out during 2000 July to 2015 February. From timing analysis of the NuSTAR observations, we found tfhe source not to show any variations in the soft band. However, on examination of the flux at energies beyond 20 keV, during 2014 August and 2017 August the source was brighter by about 20 and 30 per cent, respectively, compared to the mean flux of the three 2012 NuSTAR observations as in agreement with earlier results in literature. From an analysis of XMM–Newton data we found no variation in the hard band (2–4 keV) between epochs as well as within epochs. In the soft band (0.2–2 keV), while the source was found to be not variable within epochs, it was found to be brighter in epoch B relative to epoch A. By fitting physical models we determined $\rm {kT_{e}}$ to range between 8.46$^{+0.39}_{-0.66}$ and 9.13$^{+0.63}_{-0.98}$ keV. From our analysis, we conclude that we found no variation of $\rm {kT_{e}}$ in the source.

Possible non-thermal origin of the hard X-ray emission in the merging galaxy cluster SPT-CL J2031−4037

ABSTRACT Non-thermal emission from clusters of galaxies at the high-energy X-ray regime has been searched with various instruments, but the detection significance of this emission has yet been found to be either marginal or controversial. Taking advantage of NuSTAR’s unique capability to focus X-rays in the hard energy band, we present a detailed analysis of 238 ks NuSTAR observations of the merging galaxy cluster SPT-CL J2031−4037, searching for non-thermal inverse Compton emission. Our spectral analysis of SPT-CL J2031−4037 shows a possibility that the hard X-ray emission of the cluster can be described by a non-thermal component, though we cannot completely rule out a purely thermal origin for this hard emission. Including the statistical and systematic uncertainties, our best model fit yields a 20–80 keV non-thermal flux of $3.93_{-1.10}^{+1.24} \times 10^{-12}$ erg s−1 cm−2. The estimated non-thermal flux is comparable to those found in other galaxy clusters using NuSTAR and other X-ray instruments. Using this non-thermal flux with the existing radio data of the cluster, we estimate a volume-averaged magnetic field strength in the range of around 0.1–0.2 µG.

Anticorrelated lags in a neutron star Z source GX 5-1: AstroSat’s View

ABSTRACT We report the cross-correlation function studies of a neutron star low-mass X-ray binary, a Z source GX 5-1, using Soft X-ray Telescope (SXT) and Large Area X-ray Proportional Counter (LAXPC) energy bands onboard AstroSat. For the first time, we report the lag between soft (0.8–2.0 keV, SXT) and hard X-ray energy bands (10–20 and 16–40 keV, LAXPC) in GX 5-1 and detected lags of the order of a few tens to hundreds of seconds in the horizontal branch. We interpreted them as the readjustment time-scale of the inner region of the accretion disc. We used various two components and three-component spectral models to unfold the spectra and observed the changes in soft and hard component fluxes that were exhibiting horizontal branch oscillation variations. It was observed that the bbody component assumed to be originating from the boundary layer over the NS and was also found to vary along with the HBO variation where lags were detected. We constrained the size of the comptonizing region of the order 15–55 km, assuming that lags were due to variation in the size of the corona. We noticed a similar size of the comptonizing region after employing other models and suggest that the overall size of corona must be of the order of a few tens of km to explain the lags, HBO variation, and respective spectral variations. In a case study, it was noted that the BL size increases as GX 5-1 vary from the top of the HB to the upper vertex.

Extreme heavy metal and blasphemy in Iran: the case of Confess

Since the revolution in 1979, the Islamic Republic of Iran has imprisoned musicians, especially punk, hip-hop, and hard rock bands, as well as those playing heavy metal subgenres. Extreme heavy metal artists and fans emerged in the 1990s. The government soon targeted them as Satanists and began a systematic crackdown on metalheads. The metalcore band Confess is the most well-known case. The band was arrested in 2015 on counts of blasphemy, disturbing public opinion through the production of music, participating in interviews with the opposition media and propaganda against the Islamic Republic of Iran, among other charges. The majority of secular countries today do not consider extreme heavy metal to be transgressive. This is not the case in contexts where religious traditions have a significant influence on society. By analysing the narrative of the band Confess, the purpose of this paper is to provide an understanding of how Iranian extreme metal musicians resist religious oppression, challenge their government, religious precepts, and social values through their music.

An Analytical Fourier Transformation Model for the Production of Hard and Soft X-Ray Time Lags in Active Galactic Nuclei: Application to 1H 0707-495

The variability of the X-ray emission from active galactic nuclei is often characterized using time lags observed between soft and hard energy bands in the detector. The time lags are usually computed using the complex cross-spectrum, which is based on the Fourier transforms of the hard and soft time series data. It has been noted that some active galactic nuclei display soft X-ray time lags, in addition to the more ubiquitous hard lags. Hard time lags are thought to be produced via propagating fluctuations, spatial reverberation, or via the thermal Comptonization of soft seed photons injected into a hot electron cloud. The physical origin of the soft lags has been a subject of debate over the last decade. Currently, the reverberation interpretation is recognized as a leading theory. In this paper, we explore the alternative possibility that the soft X-ray time lags result partially from the thermal and bulk Comptonization of monochromatic seed photons which, in the case of the narrow-line Seyfert 1 galaxy 1H 0707-495, may correlate with fluorescence of iron L-line emission. In our model, the seed photons are injected into a hot, quasi-spherical corona in the inner region of the accretion flow. We develop an exact, time-dependent analytical model for the thermal and bulk Comptonization of the seed photons based on a Fourier-transformed radiation transport equation, and we demonstrate that the model successfully reproduces both the hard and soft time lags observed from 1H 0707-495.

The 700 ks Chandra Spiderweb Field

Aims. We present an analysis of the 700 ks Chandra ACIS-S observation of the field around the radio galaxy J1140-2629 (the Spiderweb Galaxy) at z = 2.156, focusing on the nuclear activity in the associated large-scale environment. Methods. We identified unresolved X-ray sources in the field down to flux limits of 1.3 × 10−16 and 3.9 × 10−16 erg s−1 cm−2 in the soft (0.5–2.0 keV) and hard (2–10 keV) band, respectively. We searched for counterparts in the optical, near-infrared, and submillimeter catalogs available in the literature to identify X-ray sources belonging to the protocluster and derived their X-ray properties. Results. We detect 107 X-ray unresolved sources within 5 arcmin (corresponding to 2.5 Mpc) of J1140-2629, among which 13 have optical counterparts with spectroscopic redshift 2.11 < z < 2.20, and 1 source has a photometric redshift consistent with this range. The X-ray-emitting protocluster members are distributed approximately over a ∼3.2 × 1.3 Mpc2 rectangular region. An X-ray spectral analysis for all the sources within the protocluster shows that their intrinsic spectral slope is consistent with an average ⟨Γ⟩∼1.84 ± 0.04. Excluding the Spiderweb Galaxy, the best-fit intrinsic absorption for five protocluster X-ray members is NH > 1023 cm−2, while another six have upper limits of the order of a few times 1022 cm−2. Two sources can only be fitted with very flat Γ ≤ 1, and are therefore considered Compton-thick candidates. The 0.5–10 keV rest-frame luminosities of the 11 Compton-thin protocluster members corrected for intrinsic absorption are greater than 2 × 1043 erg s−1. These values are typical for the bright end of a Seyfert-like distribution and significantly greater than X-ray luminosities expected from star formation activity. The X-ray luminosity function of the AGN in the volume associated to the Spiderweb protocluster in the range 1043 < LX < 1044.5 erg s−1 is at least ten times higher than that in the field at the same redshift and significantly flatter, implying an increasing excess at the bright end. The X-ray AGN fraction is measured to be 25.5 ± 4.5% of the spectroscopically confirmed members in the stellar mass range log(M*/M⊙) > 10.5. This value corresponds to an enhancement factor of 6.0−3.0+9.0 for the nuclear activity with L0.5 − 10 keV > 4 × 1043 erg s−1 with respect to the COSMOS field at comparable redshifts and stellar mass range. Conclusions. We conclude that the galaxy population in the Spiderweb protocluster is characterized by enhanced X-ray nuclear activity triggered by environmental effects on megaparsec scales.