Article
Astronomy & Astrophysics
Robbie Webbe, A. J. Young
Summary: A new class of X-ray variability, called quasi-periodic eruptions (QPEs), has been identified in four galaxies. Researchers studied the variability in the low-mass active galactic nucleus (AGN) 2XMM J123103.2+110648 to determine if it exhibits characteristics of a QPE host galaxy. By analyzing observational data and applying modeling techniques, it was found that the variability pattern in 2XMM J123103.2+110648 may represent a continuum of quasi-periodic variability, ranging from eruptions to oscillations, caused by a single mechanism. This study suggests the possibility of discovering additional sources that bridge the gap between QPEs and quasi-periodic oscillations (QPOs).
MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY
(2022)
Article
Astronomy & Astrophysics
X. Xiang, D. R. Ballantyne, S. Bianchi, A. De Rosa, G. Matt, R. Middei, P-o Petrucci, A. Rozanska, F. Ursini
Summary: The X-ray spectra of active galactic nuclei (AGNs) often exhibit an excess of emission at energies less than or similar to 2 keV, known as the 'soft excess'. This excess emission could be originated from ionized relativistic reflection from the inner accretion disk or Comptonization of thermal emission in a warm corona. The reXcor model combines these two effects, providing predictions for various soft excess shapes and sizes.
MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY
(2022)
Article
Astronomy & Astrophysics
Mehdy Lefkir, Elias Kammoun, Didier Barret, Peter Boorman, Gabriele Matzeu, Jon M. Miller, Emanuele Nardini, Abderahmen Zoghbi
Summary: In this study, the X-ray properties of the highly variable AGN NGC 7582 are explored using XMM-Newton and NuSTAR archival observations. The results show long-term variability between observations and short-term variability within two observations, which has not been studied before. The best model for the X-ray properties of NGC 7582 is found to be a fully covering clumpy absorber, with obscuring clouds consistent with comet-like or spherical clouds with a non-uniform density profile.
MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY
(2023)
Article
Astronomy & Astrophysics
Kristen C. Dage, Noah Vowell, Erica Thygesen, Arash Bahramian, Daryl Haggard, Konstantinos Kovlakas, Arunav Kundu, Thomas J. Maccarone, Jay Strader, Ryan Urquhart, Stephen E. Zepf
Summary: Through Chandra observations, a study of seven edge-on spiral galaxies revealed 12 candidate ULXs, mostly located in the central regions, highlighting the need for further investigation into transient ULXs.
MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY
(2021)
Article
Astronomy & Astrophysics
P. Chainakun, N. Nakhonthong, W. Luangtip, A. J. Young
Summary: This study investigates the Granger causality between the light curves in different energy bands of active galactic nuclei and finds that the light curves in the hard band can predict those in the soft band. By extracting the Granger lags from 14 observations, significant lags are observed in 12 of them, with most lags ranging from 200 to 500 seconds, corresponding to a light travel distance of 20-50 Schwarzschild radii. Additionally, variations in the Granger lags indicate significant changes in the corona height towards the end of the observation.
MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY
(2023)
Article
Astronomy & Astrophysics
Neeraj Kumari, Arghajit Jana, Sachindra Naik, Prantik Nandi
Summary: We conducted a detailed analysis of a small flaring event in the narrow-line Seyfert 1 galaxy NGC 4051 using XMM-Newton and NuSTAR observations. The flare showed an increase in the count rate and a decrease in the reflection fraction, indicating a change in coronal properties. This suggests that the flaring event was due to changes in the corona rather than the accretion disc.
MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY
(2023)
Article
Astronomy & Astrophysics
Arghajit Jana, Claudio Ricci, Sachindra Naik, Atsushi Tanimoto, Neeraj Kumari, Hsiang-Kuang Chang, Prantik Nandi, Arka Chatterjee, Samar Safi-Harb
Summary: We present a detailed study of the highly obscured active galaxy NGC 4507 and explore the properties of the X-ray source and obscuring material. The primary X-ray emission is stable, with a high equatorial column density and variable line-of-sight column density. The covering factor of Compton-Thick material is around 0.35.
MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY
(2022)
Article
Astronomy & Astrophysics
Jiachen Jiang, Thomas Dauser, Andrew C. Fabian, William N. Alston, Luigi C. Gallo, Michael L. Parker, Christopher S. Reynolds
Summary: This study models the X-ray spectra of IRAS 13224-3809 using multiple flux-resolved XMM-Newton spectra and finds that no additional component is required to fit the soft X-ray excess. The study also calculates the average illumination distance between the corona and the reflection region in IRAS 13224-3809.
MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY
(2022)
Article
Astronomy & Astrophysics
Jiachen Jiang, Askar B. Abdikamalov, Cosimo Bambi, Christopher S. Reynolds
Summary: We re-analyze the XMM-Newton and NuSTAR observing campaigns for the well-studied, X-ray-bright AGN MCG-06-30-15, considering a disc model with finite thickness. By fitting the disc reflection spectra in the data, we find a black hole spin of 0.87-0.99, which is consistent with previous measurements based on razor-thin disc models. Additionally, we assume an isotropic, point-like geometry for the corona, and find that such a geometry overestimates the disc reflection fraction parameter. Thin disc models with a free reflection fraction parameter provide a better fit when considering the disc thickness.
MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY
(2022)
Article
Astronomy & Astrophysics
P. Chainakun, I Fongkaew, S. Hancock, A. J. Young
Summary: Neural network models are developed in this study for predicting the black hole mass, and the accuracy of the predictions is found to be significantly higher compared to traditional linear regression methods. This suggests that neural network techniques are a promising and independent way to estimate the black hole mass. The study also investigates the global relations when the number of reverberating AGNs increases through simulations.
MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY
(2022)
Article
Astronomy & Astrophysics
P. Chainakun, A. Watcharangkool, A. J. Young
Summary: X-ray reflection from an accretion disc in active galactic nuclei produces emission lines that can be analyzed using Riemannian geometrical optics, revealing the influence of the corona on light bending and emission line shapes. Different refractive indices of the corona generate effects such as enhanced line wings and energy shifts, with the tilt angle and extent of the corona affecting the prominence of these effects.
MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY
(2022)
Article
Astronomy & Astrophysics
Jiachen Jiang, Huaqing Cheng, Luigi C. Gallo, Luis C. Ho, Douglas J. K. Buisson, Andrew C. Fabian, Fiona A. Harrison, Michael L. Parker, Christopher S. Reynolds, James F. Steiner, John A. Tomsick, Dominic J. Walton, Weimin Yuan
Summary: The Seyfert 1 galaxy KUG 1141+371 has shown a simultaneous flux increase in the optical and UV bands over the past decade, with the latest observations indicating significant changes in UVW2 flux and steady increase in soft X-ray flux. The study suggests that these multiwavelength luminosity changes are likely due to an increase in mass accretion rate, and detailed X-ray spectral analysis reveals variability in X-ray continuum emission and soft excess emission. Additionally, SED models indicate a simultaneous increase in disc temperature and decreasing inner disc radius with increasing accretion rate. Finally, the study discusses a possible connection between KUG 1141+371 and black hole transients in outburst.
MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY
(2021)
Article
Astronomy & Astrophysics
N. Mankatwit, P. Chainakun, W. Luangtip, A. J. Young
Summary: We use a random forest regressor machine learning model to trace the coronal evolution in two AGNs by analyzing the X-ray reverberation features imprinted on their power spectral density profiles. The model predicts the coronal height based on simulated PSDs and relativistic disc-response functions. The accuracy of the prediction remains high even with the removal of frequency bins dominated by noise. The model supports the correlation between the source height and luminosity in both AGNs under the light-bending scenario.
MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY
(2023)
Article
Astronomy & Astrophysics
P. Chainakun, N. Mankatwit, P. Thongkonsing, A. J. Young
Summary: Researchers have developed machine learning models to extract X-ray reverberation features from AGN PSDs, showing high accuracy even with new PSD shapes. The results demonstrate the potential for ML techniques to shape new methodological directions in X-ray reverberation analysis.
MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY
(2021)
Article
Astronomy & Astrophysics
Zhibo Yu, Jiachen Jiang, Cosimo Bambi, Luigi C. Gallo, Dirk Grupe, Andrew C. Fabian, Christopher S. Reynolds, William N. Brandt
Summary: We present a detailed analysis of XMM-Newton spectra for six narrow-line Seyfert 1 (NLS1) galaxies at redshift z = 0.35-0.92. Compared to lower redshift NLS1s, these galaxies have larger black hole masses and similar or lower Eddington ratios. Our study confirms the presence of strong soft X-ray excess emission below 2 keV. We also explore two physical models for the soft excess and find evidence for a warm corona and potentially relativistic reflection.
MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY
(2023)
Article
Astronomy & Astrophysics
R. Middei, G. A. Matzeu, S. Bianchi, V. Braito, J. Reeves, A. De Rosa, M. Dadina, A. Marinucci, M. Perri, A. Zaino
Summary: A detailed X-ray spectral analysis of the nearby Seyfert 2 galaxy MCG-01-24-12 was conducted based on a multi-epoch data set. The X-ray spectrum was found to be best modeled by a power-law continuum emission with a high energy cut-off, allowing estimation of the properties of the hot corona and discussion of possible outflows despite the short duration of the exposures.
ASTRONOMY & ASTROPHYSICS
(2021)
Article
Astronomy & Astrophysics
P. Severgnini, V Braito, C. Cicone, P. Saracco, C. Vignali, R. Serafinelli, R. Della Ceca, M. Dotti, F. Cusano, D. Paris, G. Pruto, A. Zaino, L. Ballo, M. Landoni
Summary: The study identifies a promising sub-kiloparsec scale dual AGN and highlights the importance of appropriate host galaxy subtraction for accurate estimation of the incidence of dual AGNs at small projected separations.
ASTRONOMY & ASTROPHYSICS
(2021)
Article
Astronomy & Astrophysics
J. N. Reeves, D. Porquet, V. Braito, N. Grosso, A. Lobban
Summary: Six XMM-Newton observations of Mrk 110 from 2004-2020 show a broad component of the OVII line that can be modeled with a face-on accretion disk profile. The derived inclination angle of about 10 degrees is consistent with optical Broad Line Region studies. A significant correlation is measured between the OVII flux and continuum flux, with the line responding to changes in the continuum flux. The density of the line emitting gas is estimated to be n(e)similar to 10^(14) cm(-3), indicating an origin in the accretion disk.
ASTRONOMY & ASTROPHYSICS
(2021)
Article
Astronomy & Astrophysics
D. Porquet, J. N. Reeves, N. Grosso, V Braito, A. Lobban
Summary: This study aimed to characterize the X-ray spectral properties of the bright bare broad-line Seyfert 1 AGN Mrk 110 and the physical processes in its disc-corona system. Results revealed that a combination of soft and hard Comptonisation, along with mildly relativistic disc reflection, effectively reproduced the X-ray continuum, with characteristics of a warm corona and a hot corona. The inferred temperatures of the warm and hot coronae were found to be similar to values in other sub-Eddington AGN, with the hot corona temperature falling within the lower range of those measured in AGN.
ASTRONOMY & ASTROPHYSICS
(2021)
Article
Astronomy & Astrophysics
Andrew Lobban, Andrew King
Summary: The accretion disc theory predicts that an AGN disc can self-gravitate and break up into stars at an outer radius of about 12 light-days, providing a stringent test for the theory. The longest observed AGN light echoes are found to be close to 12 days in the AGN rest frames, indicating a potential relationship between the two. Monitoring these observations further could offer insights into the formation of gas angular momentum in the disc, with longer observed lags providing lower limits on the redshifts of distant AGN.
MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY
(2022)
Article
Astronomy & Astrophysics
V Braito, J. N. Reeves, G. Matzeu, P. Severgnini, L. Ballo, C. Cicone, R. Della Ceca, M. Giustini, M. Sirressi
Summary: The nearby Seyfert 2 galaxy MCG-03-58-007 exhibits a powerful and highly variable disk wind, with two phases of outflowing velocity observed. A new monitoring campaign of MCG-03-58-007 in 2019 confirms the persistence of the disk wind, which has a kinetic power ranging between 0.5% and 10% of the Eddington luminosity. The highly ionized wind shows variability in both opacity and velocity, and it is the first time that such dramatic and fast variability of the outflowing velocity has been observed in a disk wind.
ASTROPHYSICAL JOURNAL
(2022)
Article
Astronomy & Astrophysics
R. Middei, A. Marinucci, V Braito, S. Bianchi, B. De Marco, A. Luminari, G. Matt, E. Nardini, M. Perri, J. N. Reeves, F. Vagnetti
Summary: We report on the short- and long-term X-ray properties of the nearby Seyfert 2 galaxy NGC 2992. The spectral properties of NGC 2992 are dominated by a highly variable nuclear continuum, with significant flux changes observed in the 2-10 keV energy band.
MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY
(2022)
Article
Astronomy & Astrophysics
G. A. Matzeu, M. Lieu, M. T. Costa, J. N. Reeves, V Braito, M. Dadina, E. Nardini, P. G. Boorman, M. L. Parker, S. A. Sim, D. Barret, E. Kammoun, R. Middei, M. Giustini, M. Brusa, J. Perez Cabrera, S. Marchesi
Summary: This study presents a new X-ray Accretion Disc-wind Emulator (xrade) that utilizes a Monte Carlo radiative transfer code and supervised machine learning. The trained emulator can quickly generate synthetic spectra and does not suffer from interpolation issues.
MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY
(2022)
Article
Astronomy & Astrophysics
P. Romano, A. Lahteenmaki, S. Vercellone, L. Foschini, M. Berton, C. M. Raiteri, V. Braito, S. Ciroi, E. Jarvela, S. Baitieri, I. Varglund, M. Tornikoski, S. Suutarinen
Summary: We present the first multi-wavelength Swift monitoring campaign on the nearby narrow-line Seyfert 1 galaxy SDSS J164100.10+345452.7. During the 20-month campaign, two radio flaring episodes were observed. The simultaneous multi-wavelength data confirm the existence of a relativistic jet and reveal an extra absorption component in the X-ray spectra preceding and following the radio flare. The derived total jet power is close to the lowest values measured in the literature.
ASTRONOMY & ASTROPHYSICS
(2023)
Article
Astronomy & Astrophysics
Roberto Serafinelli, Valentina Braito, James N. N. Reeves, Paola Severgnini, Alessandra De Rosa, Roberto Della Ceca, Tracey Jane Turner
Summary: The Unified Model of active galactic nuclei (AGN) fails to explain the variability in sources known as changing-look AGN (CLAGN), which undergo dramatic spectral changes. This variability is thought to be caused by a clumpy medium at smaller distances than the conventional obscuring torus. In this study, the AGN ESO 323-G77 was monitored with NuSTAR and a Compton-thick reflector and two ionized absorbers were detected.
ASTRONOMY & ASTROPHYSICS
(2023)
Article
Astronomy & Astrophysics
J. N. Reeves, V. Braito, D. Porquet, M. Laurenti, A. Lobban, G. Matzeu
Summary: PG 1448+273 is a nearby narrow-line Seyfert 1 galaxy that likely accretes close to the Eddington limit. The first NuSTAR observation of PG 1448+273 in 2022 reveals remarkable variability of its ultrafast outflow, with a much faster component detected compared to the initial detection in 2017. This implies a significant increase in the wind kinetic power over the five-year period.
ASTROPHYSICAL JOURNAL
(2023)
Article
Astronomy & Astrophysics
J. N. Reeves, V Braito, D. Porquet, A. P. Lobban, G. A. Matzeu, E. Nardini
Summary: New Swift monitoring observations of the variable, radio-quiet quasar, PDS 456, show a bright X-ray flare captured in September 2018, with a flux increase of 4 times. The coronal size is inferred to be less than or equal to 30 gravitational radii according to the light crossing argument, with a total flare energy exceeding 10^51 erg. The X-ray flare is produced in the X-ray corona and is accompanied by a hardening of the X-ray emission.
MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY
(2021)
Article
Astronomy & Astrophysics
V Braito, J. N. Reeves, P. Severgnini, R. Della Ceca, L. Ballo, C. Cicone, G. A. Matzeu, R. Serafinelli, M. Sirressi
Summary: Observations of MCG-03-58-007 show that its disc wind is not only powerful but also extremely variable, with two velocity components detected and showing different behaviors in different observations.
MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY
(2021)