Abstract Recent photometric surveys with JWST have revealed a significant population of mysterious objects with red colours, compact morphologies, frequent signs of active galactic nucleus (AGN) activity, and negligible X-ray emission. These ‘Little Red Dots’ (LRDs) have been explored through spectral and photometric studies, but their nature is still under debate. As part of the BlackTHUNDER survey, we have observed UNCOVER_20466, one of the most distant LRDs known (z = 8.5), with the JWST/NIRSpec IFU. Previous JWST/NIRCam and JWST/NIRSpec MSA observations of this source revealed its LRD nature, as well as the presence of an AGN. Using our NIRSpec IFU data, we confirm that UNCOVER_20466 is an LRD (based on spectral slopes and compactness) that contains an overmassive black hole. However, our observed Balmer decrements do not suggest strong dust attenuation, resulting in a lower $\rm H\beta$-based bolometric luminosity and λEdd ($\sim 10~{{\ \rm per\ cent}}$) than previously found. This source lies on local relations between MBH − σ* and MBH − Mdyn, suggesting that this could be a progenitor of the core of a lower-redshift galaxy. We explore the possible evolution of this source, finding evidence for substantial black hole accretion in the past and a likely origin as a heavy seed at high redshift (∼103 M⊙). $\rm Ly\alpha$ emission is strongly detected, implying $f_{\rm esc}^{\rm Ly\alpha }\sim 30~{{\ \rm per\ cent}}$. The extremely high $\rm [OIII]\lambda 4363$/$\rm H\gamma$ ratio is indicative of not only AGN photoionization and heating, but also extremely high densities ($n_{\rm e}\sim 10^7\, \rm cm^{-3}$), suggesting that this black hole at such high redshift may be forming in an ultra-dense protogalaxy.

Abstract Changing-look active galactic nuclei (CLAGNs) are a unique population of AGNs that exhibit the appearance (turn-on) or disappearance (turn-off) of broad emission lines. This study aims to explore the intrinsic mechanisms of CLAGNs by investigating their photometric variability using data from the Zwicky Transient Facility (ZTF), which has provided high-cadence observations over the past 6 yr. By visual inspections, we construct a sample of 152 CLAGNs from the literature, all of which show spectral transitions and large optical variability in their ZTF light curves. By analyzing 90 of these CLAGNs and the control samples of Type 1 AGNs, Type 2 AGNs, and extremely variable quasars (EVQs), matched in redshift (0.2 < z < 0.8) and supermassive black hole mass, we compare the color variability, structure function (SF), and variability metric σ QSO , which quantifies how closely the light curves resemble a damped random walk model. We find that while CLAGNs and EVQs differ from typical Type 1 and Type 2 AGNs in bolometric luminosity and Eddington ratio, the on- and off-state CLAGNs share similar variability patterns with the overall CLAGN population, and distinct from EVQs and Type 1 and Type 2 AGNs. This suggests that “on” and “off” CLAGNs are not simply equivalent to Type 1 and Type 2 AGNs, respectively. Instead of undergoing genuine transitions between two AGN types, CLAGNs may inhabit a critical state where moderate fluctuations in the accretion rate lead to temporary spectral changes.

Abstract We present new Chandra observations of seven luminous quasars at z > 6.5. Combined with archival Chandra observations of all other known quasars, they form nearly complete X-ray observations of all currently known z ∼ 7 quasars with M 1450 < –26.5, except for J0313−1806 at z = 7.642 and J0910−0414 at z = 6.636. Together with existing ground-based near-infrared spectroscopy and Atacama Large Millimeter Array observations, we investigate the correlations between X-ray emission (the X-ray luminosity L X and the optical/UV-to-X-ray spectral slope α OX ) and various quasar properties (rest-UV luminosity L 2500 Å , bolometric luminosity L bol , C iv blueshift, and infrared luminosity L IR ). We find most z > 6.5 quasars follow a similar α OX – L 2500 Å relation as z ∼ 1–6 quasars, but also display a large scatter. We find a potential correlation between α OX and the C iv blueshift, suggesting a soft optical/UV-to-X-ray spectral energy distribution shape is frequently associated with fast disk winds. Furthermore, we analyze the X-ray spectrum of 11 quasars at z > 6.5 with Chandra detection, and find that the best-fit photon index, Γ, is 2.41 ± 0.27, which is likely driven by high accretion rates of z > 6.5 quasars. In addition, we find there are no significant correlations between either L X and L IR , nor L bol and L IR , suggesting no strong correlations between quasar luminosity and star formation luminosity for the most luminous quasars at z > 6.5.

We present the first broadband spectral and timing study of the Be/X-ray pulsar XTE J0111.2−7317 (SXP31.0) during the first major outburst since its discovery in 1998. This giant type II outburst, observed between April and September 2025, marks the source’s return to activity after nearly three decades of quiescence. Using NuSTAR observations together with data from Swift /XRT and SRG /ART-XC, we followed the outburst’s evolution, with the source reaching a bolometric luminosity of L bol = 3.6 × 10 38 erg s −1 . The broadband spectra are well described by an absorbed cutoff power law, two blackbody components (hot and soft), and a narrow Fe K α line. No cyclotron absorption features were detected in either the phase-averaged or phase-resolved spectra in the 5–50 keV band. Most notably, we report the discovery of a previously undetected quasiperiodic oscillation (QPO) at 0.8 ± 0.1 mHz, characterized by a fractional root-mean-square (rms) amplitude of 14% at a super-Eddington bolometric luminosity of L bol = 2.5 × 10 38 erg s −1 . In contrast, the previously reported 1.27 Hz QPO was not detected. While the 0.8 mHz QPO is present, the pulsed fraction (PF) is low in soft X-rays, which is consistent with other super-Eddington pulsars exhibiting mHz QPOs; however, it rises above 20 keV to reach 35%. The QPO vanishes in subsequent observations coinciding with a sharp increase in the PF and a distinct change in pulse profile morphology. It was not observed in any follow-up observations at luminosities above or below its initial detection, suggesting it is a transient phenomenon.

Abstract We have observed the low-mass molecular cloud core G204.4-11.3A2-NE (G204NE) in the direction of Orion B giant molecular cloud with the Atacama Large Millimeter/submillimeter Array in Band 6. The 1.3 mm continuum images and visibilities unveil a compact central structure with a radius of ∼12 au, while showing no signature of binarity down to 18 au. The bolometric temperature and luminosity of this source are derived to be ∼33 K and ∼1.15 L ⊙ , respectively. Chemical stratification is observed in dense gas tracers, with C 18 O emission peaking at the continuum position surrounded by the spatially extended emission of N 2 D + and DCO + . This implies that the core is in a very early evolutionary stage in which CO depletion occurs in most regions except for a small area heated by the central source. The envelope kinematics indicate a rotating and infalling structure with a central protostar mass of 0.08–0.1 M ⊙ . The protostar drives a collimated outflow traced by CO, SiO, SO, and H 2 CO, with misaligned blueshifted and redshifted lobes exhibiting a pair of bow-like patterns. High-velocity jets, extending up to 720 au, are detected in CO, SiO, and SO lines. The jet launching region is likely within twice of the dust sublimation zone. The absence of a binary signature suggests the outflows and jets are driven by a single protostar, although a close binary cannot be ruled out. The observed deflection of the outflows and jet is likely due to turbulent accretion in a moderately magnetized core.

We examine the connection between galaxy mergers and the triggering of active galactic nuclei (AGNs) using a sample of 614 type 1 AGNs at z < 0.07, along with a control sample of inactive galaxies matched to the AGNs for comparison. We used tidal features, detected in deep images from the DESI Legacy Imaging Survey, as direct evidence of recent mergers. We find that the fraction of type 1 AGN hosts with tidal features ( f T ) is higher for AGNs with higher luminosities and (to a lesser extent) more massive black holes. Specifically, f T rapidly increases from 0.05 ± 0.03 to 0.75 ± 0.13 as the luminosity of the [O III ] λ 5007 emission line ( L [O III ] ), an indicator for bolometric AGN luminosity, increases in the range 10 39.5 ≲ L [O III ] /(erg s −1 ) ≲ 10 42.5 . In addition, f T increases from 0.13 ± 0.03 to 0.43 ± 0.09 as black hole mass ( M BH ) increases in the range 10 6.0 ≲ M BH / M ⊙ ≲ 10 8.5 . The fraction f T also increases with the Eddington ratio, although the trend is less significant compared to that with L [O III ] and M BH . The excess of f T , defined as the ratio of f T for AGNs to that of their matched inactive counterparts, exhibits similar trends, primarily increasing with L [O III ] and weakly with M BH . Our results indicate that, in the local Universe, galaxy mergers are the predominant triggering mechanism for high-luminosity AGNs, whereas they play a lesser role in triggering lower-luminosity AGNs. Additionally, strong events, such as galaxy mergers, may be more necessary to activate massive black holes in more massive galaxies due to their lower gas fractions.

Context. Protostellar multiplicity is a common outcome of the star formation process. To fully understand the formation and evolution of these systems, the physical parameters of the molecular gas together with the dust must be systematically characterized. Aims. Using observations of molecular gas tracers, we characterize the physical properties of cloud cores in the Perseus molecular cloud (average distance of 295 pc) at envelope scales (5000-8000 AU). Methods. We used Atacama Pathfinder EXperiment (APEX) and Nobeyama 45m Radio Observatory (NRO) observations of DCO + , H 2 CO, and c-C 3 H 2 in several transitions to derive the physical parameters of the gas toward 31 protostellar systems in Perseus. The angular resolutions ranged from 18" to 28.7", equivalent to 5000-8000 AU scales at the distance of each subregion in Perseus. The gas kinetic temperature was obtained from DCO + , H 2 CO, and c-C 3 H 2 line ratios. Column densities and gas masses were then calculated for each species and transition. Gas kinetic temperature and gas masses were compared with bolometric luminosity, envelope dust mass, and multiplicity to search for statistically significant correlations. Results. Gas kinetic temperature derived from H 2 CO, DCO + , and c-C 3 H 2 line ratios have average values of 26 K, 14, and 16 K, respectively, with a range of 10-26 K for DCO + and c-C 3 H 2 . The gas kinetic temperature obtained from H 2 CO line ratios have a range of 13-82 K. Column densities of all three molecular species are on the order of 10 11 to 10 14 cm −2 , resulting in gas masses of 10 −11 to 10 −9 M ⊙ . Statistical analysis of the physical parameters finds: i) similar envelope gas and dust masses for single and binary protostellar systems; ii) multiple protostellar systems (>2 components) tend to have slightly higher gas and dust masses than binaries and single protostars; iii) a continuous distribution of gas and dust masses is observed regardless of separation between components in protostellar systems.

Abstract We present a comprehensive long-term multiwavelength study of the active galactic nucleus NGC 3822, based on 17 yr (2008–2025) of X-ray, ultraviolet (UV), and optical observations. The data set includes observations from Swift , XMM - Newton, and NuSTAR, the Very Large Telescope, and the Himalayan Chandra Telescope. Our multiwavelength light-curve analysis reveals flux variations across X-ray to optical/UV bands, with an increased variability amplitude at shorter wavelengths. X-ray spectral analysis indicates the presence of intrinsic absorption during the 2016 and 2022 observations; however, this absorption disappeared before and after these epochs. The presence and absence of the absorber are attributed to clouds moving in and out of the line of sight. During the long-term monitoring period, the bolometric luminosity of the source varies between (1.32 and 17) × 10 43 erg s −1 . Optical spectroscopic monitoring reveals changing-look (CL) behavior in NGC 3822, characterized by the appearance and disappearance of broad emission lines (BELs). These CL transitions are associated with changes in the Eddington ratio rather than changes in the obscuration. The BELs appear only when the Eddington ratio is relatively high (∼3.8 × 10 −3 ) and disappear when it drops to a lower value (∼0.9 × 10 −3 ).

Abstract The polar mid-infrared (MIR) emission detected within tens to hundreds of parsecs in some active galactic nuclei (AGN) has been associated with dusty winds driven away by radiation pressure. The physical characterization of this extended polar emission remains uncertain. Here, we combine 10–21 μ m JWST/Mid-InfRared Instrument (MIRI) imaging observations with 7–25 μ m JWST/MIRI MRS integral field spectroscopic observations of six nearby, D ¯ = 35.4 ± 4.6 Mpc, AGN from the GATOS Survey to quantify the nature of the extended MIR emission at ∼75 pc resolution at 21 μ m. These AGN have similar bolometric luminosities, log 10 ( L ¯ bol [ erg s − 1 ] ) = 44.0 ± 0.3 , span a wide range of optical outflow rates, M ̇ = 0.003–0.21 M ⊙ yr −1 , column densities, log 10 ( N H X − ray [ cm − 2 ] ) = 22.2–24.3, and Eddington ratios, λ Edd = 0.005–0.06. We cross-correlate the line-only and continuum-only images and find a poor correlation, which indicates that the extended MIR continuum emission is spatially uncorrelated with the warm outflows associated with narrow emission lines within 10–15 μ m. Line emission is resolved along the jet axis, while dust emission is perpendicular to it. The 75–450 pc continuum emission has a fairly constant dust temperature, T d = 13 2 − 7 + 7 K, and mass, M d = 72 8 − 27 + 29 M ⊙ . Using the conditions of energy balance between radiation-pressure and gravity ( λ Edd versus N H ), we find that our AGN sample is in the gravitationally bounded regime consistent with no detection of dusty winds. At 10 μ m, the level of extended line emission contribution is correlated with the outflow kinetic energy and mass outflow rates. We find no correlation with the AGN properties. These results indicate that the radio jet may be triggering the gas outflow and line emission, while the extended dust emission is distributed in molecular clouds and/or shocked regions.

Characterizations of giant exoplanets such as β Pictoris b (hereafter β Pic b) are now routinely performed with multiple spectrographs and imagers exploring different spectral bandwidths and resolutions, allowing for atmospheric retrieval of spectra with or without the conservation of the planet spectral continuum. The accounting of data multimodality in the analysis could provide a more comprehensive determination of the planets physical and chemical properties and inform on their formation history. We present the first VLTI observations at R_ łambda ∼ 4,000 of β Pic b obtained for an exoplanet with GRAVITY at such a high resolution. We upgraded the forward modelling code ForMoSA to account for the data multimodality, including low-, medium-, and high-resolution spectroscopy based on both a direct model-data comparison and an analysis of cross-correlation signals. We used the ForMoSA code to refine the constraints on the atmospheric properties of the exoplanet and evaluated the sensitivity of the retrieved values to the input dataset. We obtained four high-signal-to-noise (S/N ∼ 20) spectra of β Pic b in the K band with GRAVITY at R_ łambda ∼ 4,000 conserving both the pseudo-continuum and the pattern of molecular absorptions. We used ForMoSA with four grids of self-consistent forward models (Exo-REM, ATMO, BT-Settl, and Sonora) to explore different log(g), metallicity, C/O, and ^12CO/^13CO ratio values. We then combined the GRAVITY spectra with published 1--5 µm photometry (NaCo, VisAO, NICI, and SPHERE), low-to-medium-resolution (R_ łambda łeq 700 broadband, 0.9--7 µm) spectra, and echelle spectra covering narrower bandwidths (R_ łambda ∼ 100,000, 2.1--5.2 µm). Sonora and Exo-REM are statistically preferred among all four models, regardless of the dataset used. Exo-REM predicts $ K and log(g) $=4.46^ $ dex when using only the GRAVITY epochs, whereas we have $ K log(g) $=4.00±0.01$ dex when incorporating all available datasets. The inclusion of archival data significantly affects all retrieved posteriors. When using all datasets, C/O mostly remains solar ($0.552^ $), while M/H reaches super-solar values (0.50 ± 0.01). We report the first tentative constraint on the isotopic ratio log(^12CO/^13CO) = 1.12^ in β Pic b's atmosphere; however, we note that this detection remains inconclusive due to telluric residuals affecting both the GRAVITY and SINFONI data. Additionally, we estimated the bolometric luminosity as log(L/L dex. Using a system age of 23 ± 3 Myr, along with this bolometric luminosity and the constraints on the dynamical mass of β Pic b, we were able to constrain the maximum of heavy element content of the planet to be on the order of 5% (20--80 M_ Earth xspace). The joint access to the pseudo-continuum and molecular lines in the K band provided by GRAVITY have a significant impact on the retrieved metallicity, possibly owing to the collision-induced absorption driving the continuum shape of the K band. The echelle spectra do not dominate the final fit with respect to lower resolution data covering a broader portion of the spectral energy distribution and the latter keeps encapsulating more robust information on Future multimodal frameworks should include a weighting scheme to account for the bandwidth and central wavelength of the observations.

Abstract Luminosity outbursts of FU~Ori-type objects (FUors) allow us to observe in the gas the molecules that are typically present in the ice in protoplanetary discs. In particular, the fraction of deuterated water, which is usually is mostly frozen in the midplane of a protoplanetary disc, has been measured for the first time in the gas of the disc around a FUor V883~Ori.
We test the hypothesis that the observed high HDO/H$_{2}$O ratio in the V883~Ori protoplanetary disc can be explained by luminosity outbursts of different amplitude, including a series of two consecutive outbursts. Using the ANDES astrochemical code, we modelled the distributions of water and deuterated water abundances under the action of luminosity outbursts of different amplitudes (from 400 to 10\,000\,$L_{\odot}$) and at different stellar luminosities at the pre-outburst stage. We show that the best agreement with the observed HDO/H$_{2}$O profile is obtained for outburst amplitudes of 2\,000 and 10\,000\,$L_{\odot}$, while the observed bolometric luminosity of V883~Ori does not exceed 400\,$L_{\odot}$. We discuss possible reasons for this discrepancy, including the presence of past luminosity outbursts, the age of the star, and the influence of additional heating mechanisms in the midplane of the protoplanetary disc. We also consider how the high observed $\rm HDO/H_{2}O$ ratio may be related to the evolution of the chemical composition of the ice in the protoplanetary disc and the chemical processes activated under outburst conditions.

Abstract Stellar and planetary magnetic fields play a crucial role in the habitability of a planet and the integrity of its atmosphere. The recently claimed detection of biosignatures, methane, carbon dioxide and dimethyl sulfide/disulfide, in the atmosphere of K2-18 b, a sub-Neptune orbiting an M dwarf star present an intriguing question regarding the stellar magnetic environment and the resistance of the planet’s magnetosphere (if it exists) to erosion by magnetic activity from the host. To probe for radio emission from the system, we have conducted observations using the Karl G. Jansky Very Large Array (VLA) at S, C and X-bands (2-4, 4.5-7.5 and 8-10 GHz respectively) to search for coherent and incoherent radio emission. We detect no radio emission associated with incoherent emission mechanisms. We report 3σ Stokes I upper limits of $49.8\ \mu \rm {Jybeam}^{-1}$ at S-band, $17.7\ \mu \rm {Jybeam}^{-1}$at C-band and $18.0\ \mu \rm {Jybeam}^{-1}$ at X-band and an upper limit of the ratio of the radio to the total bolometric luminosity of log LR/log Lbol < −8.8. We have also searched for short duration bursts associated with coherent emission mechanisms at C and X-bands . No signals above a 3σ significance threshold are detected. Although no signals are detected our radio observations offer constraints, albeit limited, on the stellar magnetic environment supporting recent X-ray observations indicating K2-18 is a very faint emitter. Our results also contextualise any planetary transmission spectra by providing constraints on the activity level of the host.

Abstract θ1 Ori E is a very young and relatively massive pre-main sequence (PMS) spectroscopic and eclipsing binary with nearly identical components. We analyze Échelle spectra of the system obtained over fifteen years and report 91 radial velocities measured from cross-correlating the observations with a suitable synthetic spectrum. The spectra of individual binary components are indistinguishable from each other, with a composite spectral type around G4 III. The projected equatorial velocity is estimated to be v sin i = 32 ± 3kms−1, consistent with rotational synchronization. We find that the circular orbit has Porb = 9.89522 ± 0.00003d, K1 = 83.36 ± 0.29kms−1, K2 = 84.57 ± 0.28kms−1, and asini = 32.84 ± 0.08 R⊙. The mass ratio is q = 0.9856 ± 0.0047, indicating nearly identical but significantly different masses. The systemic velocity of the binary, γ = 29.7 ± 0.2kms−1, is similar to that of other Trapezium members. Using Spitzer light curves and our results, we derive M1 = 2.755 ± 0.043 M⊙, M2 = 2.720 ± 0.043 M⊙, R1 = 6.26 ± 0.31 R⊙ and R2 = 6.25 ± 0.30 R⊙. Together with our estimate of the effective temperature, Teff = 5150 ± 200 K, a bolometric luminosity of 28.8 ± 4.6 L⊙ is derived for each component. Compared to evolutionary models of PMS stars, the binary age turns out to be less than or equal to ∼105 years. Its components are probably the most massive stars known with masses determined with precision better than 2 per cent, with both being PMS stars.

Abstract Recently discovered supermassive black holes with masses of ∼108 M⊙ at redshifts z ∼ 9–11 in active galactic nuclei (AGN) pose severe challenges to our understanding of supermassive black hole formation. One proposed channel are rapidly accreting supermassive PopIII stars (SMSs) that form in large primordial gas halos and grow up to <106 M⊙. They eventually collapse due to the general relativistic instability and could lead to supernova-like explosions. This releases massive and energetic ejecta that then interact with the halo medium via an optically thick shock. We develop a semi-analytic model to compute the shock properties, bolometric luminosity, emission spectrum and photometry over time. The initial data is informed by stellar evolution and general relativistic SMS collapse simulations. We find that SMS explosion light curves reach a brightness ∼1045-47 erg/s and last 10–200 years in the source frame – up to 250–3000 years with cosmic time dilation. This makes them quasi-persistent sources which vary indistinguishably to little red dots and AGN within 0.5–9 (1 + z) yrs. Bright SMS explosions are observable in long-wavelength JWST filters up to z ≤ 20 (24–26 mag) and pulsating SMSs up to z ≤ 15. EUCLID and the Roman space telescope (RST) can detect SMS explosions at z < 11–12. Their deep fields could constrain the SMS rate down to 10−11Mpc−3yr−1, which is much deeper than JWST bounds. Based on cosmological simulations and observed star formation rates, we expect to image up to several hundred SMS explosions with EUCLID and dozens with RST deep fields.

Direct observations of exoplanet and brown dwarf companions with near-infrared interferometry, first enabled by the dual-field mode of VLTI/GRAVITY, provide unique measurements of the objects' orbital motions and atmospheric compositions. Here we compile a homogeneous library of all exoplanet and brown dwarf K -band spectra observed by GRAVITY thus far. This ExoGRAVITY Spectral Library is made publicly available online. We re-reduced all the available GRAVITY dual-field high-contrast data in a uniform and highly automated way and, where companions were detected, extracted their ∼2.0--$2.4 K -band contrast spectra. We then derived stellar model atmospheres for all the employed flux references (either the host star or the swap calibrator), which we used to convert the companion contrast into companion flux spectra. Solely from the resulting GRAVITY K -band flux spectra, we extracted spectral types, spectral indices, and bulk physical properties for all the companions. Finally, and with the help of age constraints from the literature, we also derived isochronal masses for most of the companions using evolutionary models. The resulting library contains R ∼ 500 GRAVITY K -band spectra of 39 substellar companions from late M to late T spectral types, including the entire L--T transition. Throughout this transition, a shift from CO-dominated late M- and L-type dwarfs to CH$ _4-dominated T-type dwarfs can be observed in the K -band. The GRAVITY spectra alone constrain the objects' bolometric luminosity to typically within ±0.15$ dex. The derived isochronal masses agree with dynamical masses from the literature where available, except for HD 4113 c for which we confirm its previously reported potential underluminosity. Medium-resolution spectroscopy of substellar companions with GRAVITY provides insight into the carbon chemistry and the cloudiness of these objects' atmospheres. It also constrains these objects' bolometric luminosities, which can yield measurements of their formation entropy if combined with dynamical masses, for instance from Gaia and GRAVITY astrometry.

Abstract We perform two-dimensional, multigroup radiation hydrodynamic simulations to explore the observational properties of a solar-like star colliding with an accretion disk around a supermassive black hole at a separation of ∼100 gravitational radii. We find that the star-disk collision produces ejecta on both sides of the disk. As the ejecta expand and cool, transient flares arise, reaching peak bolometric luminosity of up to L ≳ 10 43 erg s −1 . We estimate that the typical light curve rises and decays on an hour timescale. The spectral energy distribution (SED) peaks in 20–50 eV. The optical depth in soft X-rays is lower than the frequency-integrated optical depth, yielding 100 eV–1 keV luminosity νL ν ≳ 10 42 erg s −1 . The ejecta aligned with the star’s incident direction shows breakout emission, leading to asymmetric SED evolution of the two ejecta. The SED evolution is roughly consistent with those seen in short-period quasiperiodic eruptions, which have eruption durations ranging from subhour to hours, but the ejecta cooling emission alone may not be sufficient to explain the longer duration flares. Increasing incident velocity generally produces a brighter and harder flare. A larger disk scale height prolongs the breakout emission but leads to a somewhat softer SED. A higher disk surface density can lead to higher ejecta temperature, reducing bound–free opacity and increasing luminosity. When lowering the disk surface density, we find that the ejecta becomes optically thin when the scattering optical depth across the disk is at the order of τ disk ∼ 200, and the ejecta disappear when τ disk ∼ 10.

We present a comprehensive study of five nearby active galaxies featuring large (tens of kiloparsecs) extended emission-line regions (EELRs). The study is based on large-format, integral-field spectroscopic observations conducted with the Multi Unit Spectroscopic Explorer (MUSE) at the Very Large Telescope (VLT). The spatially resolved kinematics of the ionized gas and stellar components show signs of rotation, bi-conical outflows, and complex behavior likely associated with past interactions. An analysis of the physical conditions of the EELRs indicates that in these systems the active galactic nucleus (AGN) is the primary ionization source. Using radiative transfer simulations, we compared the ionization state across the EELRs to estimate the required AGN bolometric luminosities at different radial distances. Then, considering the projected light travel time, we reconstructed the inferred AGN luminosity curves. We find that all sources are consistent with a fading trend in intrinsic AGN luminosity by 0.2–3 dex over timescales of 40 000 to 80 000 years, with a time dependence consistent with previous studies of fading AGNs. These results support the hypothesis that most AGNs undergo significant fluctuations in their accretion rates over multiple timescales ranging from 10 000 to 1 000 000 years, as proposed by existing theoretical models. These results provide new insights into the transient phases of AGN activity on previously unexplored scales and their potential long-term impact on their host galaxies through various feedback mechanisms.

Abstract Accreting supermassive black holes at the centres of galaxies are the engine of active galactic nuclei (AGN). X-ray light curves of unabsorbed AGN show dramatic random variability on timescales ranging from seconds to years. The power spectrum of the fluctuations is usually well-modelled with a power law that decays as 1/f at low frequencies, and which bends to 1/f2 − 3 at high frequencies. The timescale associated with the bend correlates well with the mass of the black hole and may also correlate with bolometric luminosity in the ‘X-ray variability plane’. Because AGN light curves are usually irregularly sampled, the estimation of AGN power spectra is challenging. In a previous paper, we introduced a new method to estimate the parameters of bending power law power spectra from AGN light curves. We apply this method to a sample of 56 variable and unabsorbed AGN, observed with XMM-Newton and Swift in the 0.3 − 1.5 keV band over the past two decades. We obtain estimates of the bends in 50 sources, which is the largest sample of X-ray bends in the soft band. We also find that the high-frequency power spectrum is often steeper than 2. We update the X-ray variability plane with new bend timescale measurements spanning from 7 min to 62 days. We report the detections of low-frequency bends in the power spectra of five AGN, three of which are previously unpublished: 1H 1934-063, Mkn 766 and Mkn 279.

ABSTRACT We present synthetic light curves and spectra from three-dimensional (3D) Monte Carlo radiative transfer simulations based on a 3D core-collapse supernova explosion model of an ultra-stripped $3.5\, \mathrm{M}_{\odot }$ progenitor. Our calculations predict a fast and faint transient with $\Delta m_{15} \sim 1\!-\!2\, \mathrm{mag}$ and peak bolometric luminosity between $-15.3$ and $-16.4\, \mathrm{mag}$. Due to a large-scale unipolar asymmetry in the distribution of $^{56}\mathrm{Ni}$, there is a pronounced viewing-angle dependence with about $1\, \mathrm{mag}$ difference between the directions of highest and lowest luminosity. The predicted spectra for this rare class of explosions do not yet match any observed counterpart. They are dominated by prominent Mg II lines, but features from O, C, Si, and Ca are also found. In particular, the O I line at ${7}\mathord {,}{774}\, {\mathring{\rm A}}$ appears as a blended feature together with Mg II emission. Our model is not only faster and fainter than the observed Ib/c supernova population, but also shows a correlation between higher peak luminosity and larger $\Delta m_{15}$ that is not present in observational samples. A possible explanation is that the unusually small ejecta mass of our model accentuates the viewing-angle dependence of the photometry. We suggest that the viewing-angle dependence of the photometry may be used to constrain asymmetries in explosion models of more typical stripped-envelope supernova progenitors in future.

Aims. To improve our knowledge of the nuclear emission of luminous quasi-stellar objects (QSOs) at Cosmic Noon, we studied the X-ray emission of the WISE/SDSS-selected hyper-luminous (WISSH) QSO sample. It consists of 85 broad-line active galactic nuclei (AGN) with bolometric luminosities Lbol > few × 1047 erg s−1 at z ≈ 2 − 4. Our goal is to characterise their X-ray spectral properties and investigate the relation between the X-ray luminosity and the energy output in other bands. To this end, we compared the nuclear properties of powerful QSOs with those derived for the majority of the AGN population. Methods. We were able to perform X-ray spectral analysis for about one-half of the sample. For 16 sources, we applied the hardness ratio analysis, while for the remaining sources we estimated their 2 − 10 keV intrinsic luminosity L2 − 10; only 8 sources were not detected. Results. We report a large dispersion in L2 − 10 despite the narrow distribution in Lbol, 2500 Å intrinsic luminosity L2500 Å, and 6 μm intrinsic luminosity λL6 μm of WISSH QSOs (approximately one-third of the sources classified as X-ray-weak QSOs). This suggests that the properties of the X-ray corona and inner accretion flow in hyper-luminous QSOs can be significantly different from those of typical less powerful AGN. The distribution of the X-ray spectral index does not differ from that of AGN at lower redshift and lower Lbol, and does not depend on the Eddington ratio (λEdd) and X-ray weakness. The majority of WISSH QSOs, for which it was possible to estimate the presence of intrinsic absorption (≈65% of the sample), exhibit little to no obscuration (i.e. column density NH ≤ 5 × 1022 cm−2). Among the X-ray obscured sources, we find some blue QSOs without broad absorption lines (BALs) that fall within the ‘forbidden region’ of the Log(NH)−Log(λEdd) plane, which is typically occupied by dust-reddened QSOs and is associated with intense feedback processes. Additionally, we confirm a significant correlation between L2 − 10 and velocity shift of the CIV emission line, a tracer of nuclear ionised outflows. Conclusions. Multi-wavelength observations of the broad-line WISSH quasars at Cosmic Noon and, in particular, their complete X-ray coverage, allow us to properly investigate the accretion disk–corona interplay to the highest luminosity regime. The distribution of bolometric corrections kbol and X-ray–to–optical indices αOX of the WISSH quasars is strikingly broad, suggesting that caution should be exercised when using Lbol, L2500 Å, and λL6 μm to estimate the X-ray emission of individual luminous QSOs.