Browsing by Author "Ricci, C."

Now showing 1 - 12 of 12
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    A comprehensive analysis of the hard X-ray spectra of bright Seyfert galaxies
    (2016) Lubinski, P.; Beckmann, V.; Gibaud, L.; Paltani, S.; Papadakis, I. E.; Ricci, C.; Soldi, S.; Turler, M.; Walter, R.; Zdziarski, A. A.
    Hard X-ray spectra of 28 bright Seyfert galaxies observed with INTEGRAL were analysed together with the X-ray spectra from XMM-Newton, Suzaku and RXTE. These broad-band data were fitted with a model assuming a thermal Comptonization as a primary continuum component. We tested several model options through a fitting of the Comptonized continuum accompanied by a complex absorption and a Compton reflection. Both the large data set used and the model space explored allowed us to accurately determine a mean temperature kTe of the electron plasma, the Compton parameter y and the Compton reflection strength R for the majority of objects in the sample. Our main finding is that a vast majority of the sample (20 objects) is characterized by kT(e) < 100 keV, and only for two objects we found kT(e) > 200 keV. The median kTe for entire sample is 48(-14)(+57) keV. The distribution of the y parameter is bimodal, with a broad component centred at approximate to 0.8 and a narrow peak at approximate to 1.1. A complex, dual absorber model improved the fit for all data sets, compared to a simple absorption model, reducing the fitted strength of Compton reflection by a factor of about 2. Modest reflection (median R approximate to 0.32) together with a high ratio of Comptonized to seed photon fluxes point towards a geometry with a compact hard X-ray emitting region well separated from the accretion disc. Our results imply that the template Seyferts spectra used in the population synthesis models of active galactic nuclei (AGN) should be revised.
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    A GROWTH-RATE INDICATOR FOR COMPTON-THICK ACTIVE GALACTIC NUCLEI
    (2016) Brightman, M.; Masini, A.; Ballantyne, D. R.; Balokovic, M.; Brandt, W. N.; Chen, C. -T.; Comastri, A.; Farrah, D.; Gandhi, P.; Harrison, F. A.; Ricci, C.; Stern, D.; Walton, D. J.
    Due to their heavily obscured central engines, the growth rate of Compton-thick (CT) active galactic nuclei (AGNs) is difficult to measure. A statistically significant correlation between the Eddington ratio, lambda(Edd), and the X-ray power-law index, Gamma, observed in unobscured AGNs offers an estimate of their growth rate from X-ray spectroscopy (albeit with large scatter). However, since X-rays undergo reprocessing by Compton scattering and photoelectric absorption when the line of sight to the central engine is heavily obscured, the recovery of the intrinsic Gamma is challenging. Here we study a sample of local, predominantly CT megamaser AGNs, where the black hole mass, and thus Eddington luminosity, are well known. We compile results of the X-ray spectral fitting of these sources with sensitive high-energy (E > 10 keV) NuSTAR data, where X-ray torus models, which take into account the reprocessing effects have been used to recover the intrinsic Gamma values and X-ray luminosities, L-X. With a simple bolometric correction to L-X to calculate lambda(Edd), we find a statistically significant correlation between Gamma and lambda(Edd) (p = 0.007). A linear fit to the data yields Gamma = (0.41 +/- 0.18)log(10)lambda(Edd) + (2.38 +/- 0.20), which is statistically consistent with results for unobscured AGNs. This result implies that torus modeling successfully recovers the intrinsic AGN parameters. Since the megamasers have low-mass black holes (M-BH approximate to 10(6)-10(7) M-circle dot) and are highly inclined, our results extend the Gamma-lambda(Edd) relationship to lower masses and argue against strong orientation effects in the corona, in support of AGN unification. Finally this result supports the use of Gamma as a growth-rate indicator for accreting black holes, even for CT AGNs.
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    A hard X-ray view of luminous and ultra-luminous infrared galaxies in GOALS - I. AGN obscuration along the merger sequence
    (2021) Ricci, C.; Privon, G. C.; Pfeifle, R. W.; Armus, L.; Iwasawa, K.; Torres-Albà, N.; Satyapal, S.; Bauer, F. E.; Treister, E.; Ho, L. C.; Aalto, S.; Arévalo, P.; Barcos-Muñoz, L.; Charmandaris, V.; Diaz-Santos, T.; Evans, A. S.; Gao, T.; Inami, H.; Koss, M. J.; Lansbury, G.; Linden, S. T.; Medling, A.; Sanders, D. B.; Song, Y.; Stern, D.; U, V.; Ueda, Y.; Yamada, S.
    The merger of two or more galaxies can enhance the inflow of material from galactic scales into the close environments of active galactic nuclei (AGNs), obscuring and feeding the supermassive black hole (SMBH). Both recent simulations and observations of AGN in mergers have confirmed that mergers are related to strong nuclear obscuration. However, it is still unclear how AGN obscuration evolves in the last phases of the merger process. We study a sample of 60 luminous and ultra-luminous IR galaxies (U/LIRGs) from the GOALS sample observed by NuSTAR. We find that the fraction of AGNs that are Compton thick (CT;N-H >= 10(24)cm(-2) ) peaks at at a late merger stage, prior to coalescence, when the nuclei have projected separations (d(sep)) of 0.4-6 kpc. A similar peak is also observed in the median N-H [[(1.6 +/- 0.5) x 10(24) cm(-2)].]. The vast majority (85(-9)(+7) per cent)) of the AGNs in the final merger stages (d(sep) less than or similar to 10 kpc) are heavily obscured (N-H = 10(23) cm(-2)), and the median N-H of the accreting SMBHs in our sample is systematically higher than that of local hard X-ray-selected AGN, regardless of the merger stage. This implies that these objects have very obscured nuclear environments, with the gas almost completely covering the AGN in late mergers. CT AGNs tend to have systematically higher absorption-corrected X-ray luminosities than less obscured sources. This could either be due to an evolutionary effect, with more obscured sources accreting more rapidly because they have more gas available in their surroundings, or to a selection bias. The latter scenario would imply that we are still missing a large fraction of heavily obscured, lower luminosity (L2-10 less than or similar to 10(43) erg s(-1)) AGNs in U/LIRGs.
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    AT 2021hdr: A candidate tidal disruption of a gas cloud by a binary super massive black hole system
    (EDP Sciences, 2024) Hernández-García, L.; Muñoz-Arancibia, A. M.; Lira, P.; Bruni, G.; Cuadra, J.; Arévalo, P.; Sánchez-Sáez, P.; Bernal, S.; Bauer, Franz Erik; Catelan, Márcio; Panessa, F.; Pávez-Herrera, M.; Ricci, C.; Reyes-Jainaga, I.; Ailawadhi, B.; Chavushyan, V.; Dastidar, R.; Deconto-Machado, A.; Forster, F.; Gangopadhyay, A.; García-Pérez, A.; Márquez, I.; Masegosa, J.; Misra, K.; Patiño-Alvarez, V. M.; Puig-Subira, M.; Rodi, J.; Singh, M.
    With a growing number of facilities able to monitor the entire sky and produce light curves with a cadence of days, in recent years there has been an increased rate of detection of sources whose variability deviates from standard behavior, revealing a variety of exotic nuclear transients. The aim of the present study is to disentangle the nature of the transient AT 2021hdr, whose optical light curve used to be consistent with a classic Seyfert 1 nucleus, which was also confirmed by its optical spectrum and high-energy properties. From late 2021, AT 2021hdr started to present sudden brightening episodes in the form of oscillating peaks in the Zwicky Transient Facility (ZTF) alert stream, and the same shape is observed in X-rays and UV from Swift data. The oscillations occur every ≈60-90 days with amplitudes of ≈0.2 mag in the g and r bands. Very Long Baseline Array (VLBA) observations show no radio emission at milliarcseconds scale. It is argued that these findings are inconsistent with a standard tidal disruption event (TDE), a binary supermassive black hole (BSMBH), or a changing-look active galactic nucleus (AGN); neither does this object resemble previous observed AGN flares, and disk or jet instabilities are an unlikely scenario. Here, we propose that the behavior of AT 2021hdr might be due to the tidal disruption of a gas cloud by a BSMBH. In this scenario, we estimate that the putative binary has a separation of ≈0.83 mpc and would merge in ≈7 × 104 years. This galaxy is located at 9 kpc from a companion galaxy, and in this work we report this merger for the first time. The oscillations are not related to the companion galaxy.
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    BASS XXXI: Outflow scaling relations in low redshift X-ray AGN host galaxies with MUSE
    (2022) Kakkad, D.; Sani, E.; Rojas, A. F.; Mallmann, Nicolas D.; Veilleux, S.; Bauer, Franz E.; Ricci, F.; Mushotzky, R.; Koss, M.; Ricci, C.; Treister, E.; Privon, George C.; Nguyen, N.; Bär, R.; Harrison, F.; Oh, K.; Powell, M.; Riffel, R.; Stern, D.; Trakhtenbrot, B.; Urry, C. M.
    Ionized gas kinematics provide crucial evidence of the impact that active galactic nuclei (AGNs) have in regulating star formation in their host galaxies. Although the presence of outflows in AGN host galaxies has been firmly established, the calculation of outflow properties such as mass outflow rates and kinetic energy remains challenging. We present the [O iii]lambda 5007 ionized gas outflow properties of 22 z<0.1 X-ray AGN, derived from the BAT AGN Spectroscopic Survey using MUSE/VLT. With an average spatial resolution of 1 arcsec (0.1-1.2 kpc), the observations resolve the ionized gas clouds down to sub-kiloparsec scales. Resolved maps show that the [O iii] velocity dispersion is, on average, higher in regions ionized by the AGN, compared to star formation. We calculate the instantaneous outflow rates in individual MUSE spaxels by constructing resolved mass outflow rate maps, incorporating variable outflow density and velocity. We compare the instantaneous values with time-averaged outflow rates by placing mock fibres and slits on the MUSE field-of-view, a method often used in the literature. The instantaneous outflow rates (0.2-275 M-circle dot yr(-1)) tend to be two orders of magnitude higher than the time-averaged outflow rates (0.001-40 M-circle dot yr(-1)). The outflow rates correlate with the AGN bolometric luminosity (L-bol similar to 10(42.71)-10(45.62) erg s(-1)) but we find no correlations with black hole mass (10(6.1)-10(8.9) M-circle dot), Eddington ratio (0.002-1.1), and radio luminosity (10(21)-10(26) W Hz(-1)). We find the median coupling between the kinetic energy and L-bol to be 1 per cent, consistent with the theoretical predictions for an AGN-driven outflow.
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    BASS XXXVII: The Role of Radiative Feedback in the Growth and Obscuration Properties of Nearby Supermassive Black Holes
    (2022) Ricci, C.; Ananna, T. T.; Temple, M. J.; Urry, C. M.; Koss, M. J.; Trakhtenbrot, B.; Ueda, Y.; Stern, D.; Bauer, F. E.; Treister, E.; Privon, G. C.; Oh, K.; Paltani, S.; Stalevski, M.; Ho, L. C.; Fabian, A. C.; Mushotzky, R.; Chang, C. S.; Ricci, F.; Kakkad, D.; Sartori, L.; Baer, R.; Caglar, T.; Powell, M.; Harrison, F.
    We study the relation between obscuration and supermassive black hole (SMBH) accretion using a large sample of hard X-ray selected active galactic nuclei (AGNs). We find a strong decrease in the fraction of obscured sources above the Eddington limit for dusty gas (log lambda(Edd) >= -2) confirming earlier results, and consistent with the radiation-regulated unification model. This also explains the difference in the Eddington ratio distribution functions (ERDFs) of type 1 and type 2 AGNs obtained by a recent study. The break in the ERDF of nearby AGNs is at log lambda*(Edd) = -1.34 +/- 0.07. This corresponds to the lambda(Edd) where AGNs transition from having most of their sky covered by obscuring material to being mostly devoid of absorbing material. A similar trend is observed for the luminosity function, which implies that most of the SMBH growth in the local universe happens when the AGN is covered by a large reservoir of gas and dust. These results could be explained with a radiation-regulated growth model, in which AGNs move in the N-H-lambda(Edd) plane during their life cycle. The growth episode starts with the AGN mostly unobscured and accreting at low lambda(Edd). As the SMBH is further fueled, lambda(Edd), N-H and the covering factor increase, leading the AGN to be preferentially observed as obscured. Once lambda(Edd) reaches the Eddington limit for dusty gas, the covering factor and N-H rapidly decrease, leading the AGN to be typically observed as unobscured. As the remaining fuel is depleted, the SMBH goes back into a quiescent phase.
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    BASS. XLII. The Relation between the Covering Factor of Dusty Gas and the Eddington Ratio in Nearby Active Galactic Nuclei
    Ricci, C.; Ichikawa, K.; Stalevski, M.; Kawamuro, T.; Yamada, S.; Ueda, Y.; Mushotzky, R.; Privon, G. C.; Koss, M. J.; Trakhtenbrot, B.; Fabian, A. C.; Ho, L. C.; Asmus, D.; Bauer, Franz Erik; Chang, C. S.; Gupta, K. K.; Oh, K.; Powell, M.; Pfeifle, R. W.; Rojas, A.; Ricci, F.; Temple, M. J.; Toba, Y.; Tortosa, A.; Treister, Ezequiel; Harrison, F.; Stern, D.; Urry, C. M.
    Accreting supermassive black holes (SMBHs) located at the centers of galaxies are typically surrounded by large quantities of gas and dust. The structure and evolution of this circumnuclear material can be studied at different wavelengths, from the submillimeter to the X-ray. Recent X-ray studies have shown that the covering factor of the obscuring material tends to decrease with increasing Eddington ratio, likely due to radiative feedback on dusty gas. Here we study a sample of 549 nearby (z less than or similar to 0.1) hard X-ray (14-195 keV) selected nonblazar active galactic nuclei (AGN) and use the ratio between the AGN infrared and bolometric luminosity as a proxy of the covering factor. We find that, in agreement with what has been found by X-ray studies of the same sample, the covering factor decreases with increasing Eddington ratio. We also confirm previous findings that showed that obscured AGN typically have larger covering factors than unobscured sources. Finally, we find that the median covering factors of AGN located in different regions of the column density-Eddington ratio diagram are in good agreement with what would be expected from a radiation-regulated growth of SMBHs.
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    BASS. XXXIII. Swift-BAT Blazars and Their Jets through Cosmic Time
    (2022) Marcotulli, L.; Ajello, M.; Urry, C. M.; Paliya, V. S.; Koss, M.; Oh, K.; Madejski, G.; Ueda, Y.; Balokovic, M.; Trakhtenbrot, B.; Ricci, F.; Ricci, C.; Stern, D.; Harrison, F.; Powell, M. C.
    We derive the most up-to-date Swift-Burst Alert Telescope (BAT) blazar luminosity function in the 14-195 keV range, making use of a clean sample of 118 blazars detected in the BAT 105 month survey catalog, with newly obtained redshifts from the BAT Active Galatic Nucleus Spectroscopic Survey. We determine the best-fit X-ray luminosity function for the whole blazar population, as well as for flat-spectrum radio quasars (FSRQs) alone. The main results are: (1) at any redshift, BAT detects the most luminous blazars, above any possible break in their luminosity distribution, which means we cannot differentiate between density and luminosity evolution; (2) the whole blazar population, dominated by FSRQs, evolves positively up to redshift z similar to 4.3, confirming earlier results and implying lower number densities of blazars at higher redshifts than previously estimated. The contribution of this source class to the cosmic X-ray background at 14-195 keV can range from 5%-18%, while possibly accounting for 100% of the MeV background. We also derived the average 14 keV-10 GeV spectral energy distribution for BAT blazars, which allows us to predict the number counts of sources in the MeV range, as well as the expected number of high-energy (>100 TeV) neutrinos. A mission like COSI will detect 40 MeV blazars, of which two may have coincident neutrino detections. Finally, taking into account beaming selection effects, the distribution and properties of the parent population of these extragalactic jets are derived. We find that the distribution of viewing angles is quite narrow, with most sources aligned within <5 degrees of the line of sight. Moreover, the average Lorentz factor, Gamma = 8-12, is lower than previously suggested for these powerful sources.
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    BAT AGN Spectroscopic Survey XXVII: scattered X-Ray radiation in obscured active galactic nuclei
    (2021) Gupta, K. K.; Ricci, C.; Tortosa, A.; Ueda, Y.; Kawamuro, T.; Koss, M.; Trakhtenbrot, B.; Oh, K.; Bauer, F. E.; Ricci, F.; Privon, G. C.; Zappacosta, L.; Stern, D.; Kakkad, D.; Piconcelli, E.; Veilleux, S.; Mushotzky, R.; Caglar, T.; Ichikawa, K.; Elagali, A.; Powell, M. C.; Urry, C. M.; Harrison, F.
    Accreting supermassive black holes (SMBHs), also known as active galactic nuclei (AGN), are generally surrounded by large amounts of gas and dust. This surrounding material reprocesses the primary X-ray emission produced close to the SMBH and gives rise to several components in the broadband X-ray spectra of AGN, including a power-law possibly associated with Thomson-scattered radiation. In this work, we study the properties of this scattered component for a sample of 386 hard-X-ray-selected, nearby (z similar to 0.03) obscured AGN from the 70-month Swift/BAT catalogue. We investigate how the fraction of Thomson-scattered radiation correlates with different physical properties of AGN, such as line-of-sight column density, X-ray luminosity, black hole mass, and Eddington ratio. We find a significant negative correlation between the scattering fraction and the column density. Based on a large number of spectral simulations, we exclude the possibility that this anticorrelation is due to degeneracies between the parameters. The negative correlation also persists when considering different ranges of luminosity, black hole mass, and Eddington ratio. We discuss how this correlation might be either due to the angle dependence of the Thomson cross-section or to more obscured sources having a higher covering factor of the torus. We also find a positive correlation between the scattering fraction and the ratio of [OIII] lambda 5007 to X-ray luminosity. This result is consistent with previous studies and suggests that the Thomson-scattered component is associated with the narrow-line region.
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    Dark matter line searches with the Cherenkov Telescope Array
    (2024) Abe, S.; Abhir, J.; Abhishek, A.; Acero, F.; Acharyya, A.; Adam, R.; Aguasca-Cabot, A.; Agudo, I.; Aguirre-Santaella, A.; Alfaro, J.; Alfaro, R.; Alvarez-Crespo, N.; Alves Batista, R.; Amans, J. -P.; Amato, E.; Ambrosi, G.; Angel, L.; Aramo, C.; Arcaro, C.; Arnesen, T. T. H.; Arrabito, L.; Asano, K.; Ascasibar, Y.; Aschersleben, J.; Ashkar, H.; Backes, M.; Baktash, A.; Balazs, C.; Balbo, M.; Baquero Larriva, A.; Martins, V. Barbosa; Barres de Almeida, U.; Barrio, J. A.; Batkovic, I.; Batzofin, R.; Baxter, J.; Becerra Gonzalez, J.; Beck, G.; Benbow, W.; Berge, D.; Bernardini, E.; Bernete, J.; Bernloehr, K.; Berti, A.; Bertucci, B.; Bhattacharjee, P.; Bhattacharyya, S.; Bigongiari, C.; Biland, A.; Bissaldi, E.; Biteau, J.; Blanch, O.; Blazek, J.; Bocchino, F.; Boisson, C.; Bolmont, J.; Bonnoli, G.; Bonollo, A.; Bordas, P.; Bosnjak, Z.; Bottacini, E.; Bottcher, M.; Bringmann, T.; Bronzini, E.; Brose, R.; Brown, A. M.; Brunelli, G.; Bulgarelli, A.; Bulik, T.; Burelli, I.; Burmistrov, L.; Burton, M.; Buscemi, M.; Bylund, T.; Cailleux, J.; Campoy-Ordaz, A.; Cantlay, B. K.; Capasso, G.; Caproni, A.; Capuzzo-Dolcetta, R.; Caraveo, P.; Caroff, S.; Carosi, A.; Carosi, R.; Carquin, E.; Carrasco, M. -S.; Cassol, F.; Castaldini, L.; Castrejon, N.; Castro-Tirado, A. J.; Cerasole, D.; Cerruti, M.; Chadwick, P. M.; Chaty, S.; Chen, A. W.; Chernyakova, M.; Chiavassa, A.; Chudoba, J.; Chytka, L.; Cicciari, G. M.; Cifuentes, A.; Coimbra Araujo, C. H.; Colapietro, M.; Conforti, V.; Conte, F.; Contreras, J. L.; Costa, A.; Costantini, H.; Cotter, G.; Cristofari, P.; Cuevas, O.; Curtis-Ginsberg, Z.; D'Amico, G.; D'Ammando, F.; Dai, S.; Dalchenko, M.; Dazzi, F.; De Angelis, A.; de Lavergne, M. de Bony; De Caprio, V.; de Gouveia Dal Pino, E. M.; De Lotto, B.; De Lucia, M.; de Menezes, R.; de Naurois, M.; de Souza, V.; del Peral, L.; del Valle, M. V.; Delgado Giler, A. G.; Delgado Mengual, J.; Delgado, C.; Dell'aiera, M.; della Volpe, D.; Depaoli, D.; Di Girolamo, T.; Di Piano, A.; Di Pierro, F.; Di Tria, R.; Di Venere, L.; Diaz, C.; Diebold, S.; Dinesh, A.; Djuvsland, J.; Dominik, R. M.; Prester, D. Dominis; Donini, A.; Dorner, D.; Doerner, J.; Doro, M.; Dournaux, J. -L.; Duangchan, C.; Dubos, C.; Ducci, L.; Dwarkadas, V. V.; Ebr, J.; Eckner, C.; Egberts, K.; Einecke, S.; Elsaesser, D.; Emery, G.; Errando, M.; Escanuela, C.; Escarate, P.; Godoy, M. Escobar; Escudero, J.; Esposito, P.; Ettori, S.; Falceta-Goncalves, D.; Fedorova, E.; Fegan, S.; Feng, Q.; Ferrand, G.; Ferrarotto, F.; Fiandrini, E.; Fiasson, A.; Filipovic, M.; Fioretti, V.; Fiori, M.; Foffano, L.; Font Guiteras, L.; Fontaine, G.; Froese, S.; Fukazawa, Y.; Fukui, Y.; Furniss, A.; Galanti, G.; Galaz, G.; Galelli, C.; Gallozzi, S.; Gammaldi, V.; Garczarczyk, M.; Gasbarra, C.; Gasparrini, D.; Ghalumyan, A.; Gianotti, F.; Giarrusso, M.; Giesbrecht Formiga Paiva, J. G.; Giglietto, N.; Giordano, F.; Giuffrida, R.; Glicenstein, J. -F.; Glombitza, J.; Goldoni, P.; Gonzalez, J. M.; Gonzalez, M. M.; Goulart Coelho, J.; Gradetzke, T.; Granot, J.; Grasso, D.; Grau, R.; Greaux, L.; Green, D.; Green, J. G.; Grolleron, G.; Guedes, L. M. V.; Gueta, O.; Hackfeld, J.; Hadasch, D.; Hamal, P.; Hanlon, W.; Hara, S.; Harvey, V. M.; Hassan, T.; Hayashi, K.; Hess, B.; Heckmann, L.; Heller, M.; Hernandez Cadena, S.; Hervet, O.; Hinton, J.; Hiroshima, N.; Hnatyk, B.; Hnatyk, R.; Hofmann, W.; Holder, J.; Horan, D.; Horvath, P.; Hovatta, T.; Hrabovsky, M.; Hrupec, D.; Iarlori, M.; Inada, T.; Incardona, F.; Inoue, S.; Inoue, Y.; Iocco, F.; Iori, M.; Ishio, K.; Jamrozy, M.; Janecek, P.; Jankowsky, F.; Jean, P.; Jimenez Quiles, J.; Jin, W.; Juramy-Gilles, C.; Jurysek, J.; Kagaya, M.; Kalekin, O.; Karas, V.; Katagiri, H.; Kataoka, J.; Kaufmann, S.; Kazanas, D.; Kerszberg, D.; Kieda, D. B.; Kleiner, T.; Kluge, G.; Kobayashi, Y.; Kohri, K.; Komin, N.; Kornecki, P.; Kosack, K.; Kowal, G.; Kubo, H.; Kushida, J.; La Barbera, A.; La Palombara, N.; Lainez, M.; Lamastra, A.; Lapington, J.; Laporte, P.; Lazarevic, S.; Lazendic-Galloway, J.; Lemoine-Goumard, M.; Lenain, J. -P.; Leone, F.; Leonora, E.; Leto, G.; Lindfors, E.; Linhoff, M.; Liodakis, I.; Lipniacka, A.; Lombardi, S.; Longo, F.; Lopez-Coto, R.; Lopez-Moya, M.; Lopez-Oramas, A.; Loporchio, S.; Lozano Bahilo, J.; Luque-Escamilla, P. L.; Macias, O.; Majumdar, P.; Mallamaci, M.; Malyshev, D.; Mandat, D.; Manico, G.; Mariotti, M.; Marquez, I.; Marquez, P.; Marsella, G.; Marti, J.; Martinez, G. A.; Martinez, M.; Martinez, O.; Marty, C.; Mas-Aguilar, A.; Mastropietro, M.; Mazin, D.; Menchiari, S.; Mestre, E.; Meunier, J. -L.; Meyer, D. M. -A.; Meyer, M.; Miceli, D.; Miceli, M.; Michailidis, M.; Michalowski, J.; Miener, T.; Miranda, J. M.; Mitchell, A.; Mizote, M.; Mizuno, T.; Moderski, R.; Molero, M.; Molfese, C.; Molina, E.; Montaruli, T.; Moralejo, A.; Morcuende, D.; Morselli, A.; Moulin, E.; Moya Zamanillo, V.; Munari, K.; Murach, T.; Muraczewski, A.; Muraishi, H.; Nakamori, T.; Nayak, A.; Nemmen, R.; Neto, J. P.; Nickel, L.; Niemiec, J.; Nieto, D.; Nievas Rosillo, M.; Nikolajuk, M.; Nikolic, L.; Nishijima, K.; Noda, K.; Nosek, D.; Novotny, V.; Nozaki, S.; Ohishi, M.; Ohtani, Y.; Okumura, A.; Olive, J. -F.; Ong, R. A.; Orienti, M.; Orito, R.; Orlandini, M.; Orlando, E.; Orlando, S.; Ostrowski, M.; Otero-Santos, J.; Oya, I.; Pagano, I.; Pagliaro, A.; Palatiello, M.; Panebianco, G.; Paneque, D.; Pantaleo, F. R.; Paredes, J. M.; Parmiggiani, N.; Patricelli, B.; Pe'er, A.; Pech, M.; Pecimotika, M.; Pensec, U.; Peresano, M.; Perez-Romero, J.; Persic, M.; Peters, K. P.; Petruk, O.; Piano, G.; Pierre, E.; Pietropaolo, E.; Pihet, M.; Pinchbeck, L.; Pirola, G.; Pittori, C.; Plard, C.; Podobnik, F.; Pohl, M.; Pollet, V.; Ponti, G.; Prandini, E.; Principe, G.; Priyadarshi, C.; Produit, N.; Prouza, M.; Pueschel, E.; Puehlhofer, G.; Pumo, M. L.; Queiroz, F.; Quirrenbach, A.; Raino, S.; Rando, R.; Razzaque, S.; Regeard, M.; Reimer, A.; Reimer, O.; Reisenegger, A.; Rhode, W.; Ribeiro, D.; Ribo, M.; Ricci, C.; Richtler, T.; Rico, J.; Rieger, F.; Riitano, L.; Rizi, V.; Roache, E.; Fernandez, G. Rodriguez; Rodriguez Frias, M. D.; Rodriguez-Vazquez, J. J.; Romano, P.; Romeo, G.; Rosado, J.; de Leon, A. Rosales; Rowell, G.; Rudak, B.; Ruiter, A. J.; Rulten, C. B.; Sadeh, I.; Saha, L.; Saito, T.; Salzmann, H.; Sanchez-Conde, M.; Sandaker, H.; Sangiorgi, P.; Sano, H.; Santander, M.; Santos-Lima, R.; Sapienza, V.; Saric, T.; Sarkar, A.; Sarkar, S.; Saturni, F. G.; Savarese, S.; Scherer, A.; Schiavone, F.; Schipani, P.; Schleicher, B.; Schovanek, P.; Schubert, J. L.; Schwanke, U.; Seglar Arroyo, M.; Seitenzahl, I. R.; Sergijenko, O.; Servillat, M.; Siegert, T.; Siejkowski, H.; Siqueira, C.; Sliusar, V.; Slowikowska, A.; Sol, H.; Spencer, S. T.; Spiga, D.; Stamerra, A.; Stanic, S.; Starecki, T.; Starling, R.; Stawarz, L.; Steppa, C.; Hatlen, E. Saether; Stolarczyk, T.; Striskovic, J.; Suda, Y.; Swierk, P.; Tajima, H.; Tak, D.; Takahashi, M.; Takeishi, R.; Tavernier, T.; Tejedor, L. A.; Terauchi, K.; Teshima, M.; Testa, V.; Tian, W. W.; Tibaldo, L.; Tibolla, O.; Todero Peixoto, C. J.; Torradeflot, F.; Torres, D. F.; Tosti, G.; Tothill, N.; Toussenel, F.; Tramacere, A.; Travnicek, P.; Tripodo, G.; Trois, A.; Truzzi, S.; Tutone, A.; Vaclavek, L.; Vacula, M.; Vallania, P.; Valles, R.; van Eldik, C.; van Scherpenberg, J.; Vandenbroucke, J.; Vassiliev, V.; Vazquez Acosta, M.; Vecchi, M.; Ventura, S.; Vercellone, S.; Verna, G.; Viana, A.; Viaux, N.; Vigliano, A.; Vignatti, J.; Vigorito, C. F.; Villanueva, J.; Visentin, E.; Vitale, V.; Vodeb, V.; Voisin, V.; Voitsekhovskyi, V.; Vorobiov, S.; Voutsinas, G.; Vovk, I.; Vuillaume, T.; Wagner, S. J.; Walter, R.; White, M.; White, R.; Wierzcholska, A.; Will, M.; Williams, D. A.; Wohlleben, F.; Wolter, A.; Yamamoto, T.; Yang, L.; Yoshida, T.; Yoshikoshi, T.; Zaharijas, G.; Zampieri, L.; Sanchez, R. Zanmar; Zavrtanik, D.; Zavrtanik, M.; Zdziarski, A. A.; Zech, A.; Zhang, W.; Zhdanov, V. I.; Zietara, K.; Zivec, M.; Zuriaga-Puig, J.
    Monochromatic gamma-ray signals constitute a potential smoking gun signature for annihilating or decaying dark matter particles that could relatively easily be distinguished from astrophysical or instrumental backgrounds. We provide an updated assessment of the sensitivity of the Cherenkov Telescope Array (CTA) to such signals, based on observations of the Galactic centre region as well as of selected dwarf spheroidal galaxies. We find that current limits and detection prospects for dark matter masses above 300 GeV will be significantly improved, by up to an order of magnitude in the multi-TeV range. This demonstrates that CTA will set a new standard for gamma-ray astronomy also in this respect, as the world's largest and most sensitive high-energy gamma-ray observatory, in particular due to its exquisite energy resolution at TeV energies and the adopted observational strategy focussing on regions with large dark matter densities. Throughout our analysis, we use up-to-date instrument response functions, and we thoroughly model the effect of instrumental systematic uncertainties in our statistical treatment. We further present results for other potential signatures with sharp spectral features, e.g. box-shaped spectra, that would likewise very clearly point to a particle dark matter origin.
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    Joint ALMA/X-ray monitoring of the radio-quiet type 1 active galactic nucleus IC 4329A
    (2024) Shablovinskaya, E.; Ricci, C.; Chang, C. -s.; Tortosa, A.; del Palacio, S.; Kawamuro, T.; Aalto, S.; Arzoumanian, Z.; Balokovic, M.; Bauer, F. E.; Gendreau, K. C.; Ho, L. C.; Kakkad, D.; Kara, E.; Koss, M. J.; Liu, T.; Loewenstein, M.; Mushotzky, R.; Paltani, S.; Privon, G. C.; Smith, K.; Tombesi, F.; Trakhtenbrot, B.
    The origin of a compact millimeter (mm, 100-250 GHz) emission in radio-quiet active galactic nuclei (RQ AGN) remains debated. Recent studies propose a connection with self-absorbed synchrotron emission from the accretion disk X-ray corona. We present the first joint ALMA (similar to 100 GHz) and X-ray (NICER/XMM-Newton/Swift; 2-10 keV) observations of the unobscured RQ AGN, IC 4329A (z = 0.016). The time-averaged mm-to-X-ray flux ratio aligns with recently established trends for larger samples, but with a tighter scatter (similar to 0.1 dex) compared to previous studies. However, there is no significant correlation on timescales of less than 20 days. The compact mm emission exhibits a spectral index of -0.23 +/- 0.18, remains unresolved with a 13 pc upper limit, and shows no jet signatures. Notably, the mm flux density varies significantly (by factor of 3) within four days, exceeding the contemporaneous X-ray variability and showing the largest mm variations ever detected in RQ AGN over daily timescales. The high amplitude variability rules out scenarios of heated dust and thermal free-free emission, pointing toward a synchrotron origin for the mm radiation in a source of similar to 1 light day (similar to 120 gravitational radii) size. While the exact source is not yet certain, an X-ray corona scenario emerges as the most plausible compared to a scaled-down jet or outflow-driven shocks.
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    SDSS1335+0728: The awakening of a ∼106 M⊙ black hole
    (2024) Sanchez-Saez, P.; Hernandez-Garcia, L.; Bernal, S.; Bayo, A.; Calistro Rivera, G.; Bauer, F. E.; Ricci, C.; Merloni, A.; Graham, M. J.; Cartier, R.; Arevalo, P.; Assef, R. J.; Concas, A.; Homan, D.; Krumpe, M.; Lira, P.; Malyali, A.; Martinez-Aldama, M. L.; Arancibia, A. M. Munoz; Rau, A.; Bruni, G.; Foerster, F.; Pavez-Herrera, M.; Tubin-Arenas, D.; Brightman, M.
    Context. The early-type galaxy SDSS J133519.91+072807.4 (hereafter SDSS1335+0728), which had exhibited no prior optical variations during the preceding two decades, began showing significant nuclear variability in the Zwicky Transient Facility (ZTF) alert stream from December 2019 (as ZTF19acnskyy). This variability behaviour, coupled with the host-galaxy properties, suggests that SDSS1335+0728 hosts a similar to 106 M-circle dot black hole (BH) that is currently in the process of "turning on". Aims. We present a multi-wavelength photometric analysis and spectroscopic follow-up performed with the aim of better understanding the origin of the nuclear variations detected in SDSS1335+0728. Methods. We used archival photometry (from WISE, 2MASS, SDSS, GALEX, eROSITA) and spectroscopic data (from SDSS and LAMOST) to study the state of SDSS1335+0728 prior to December 2019, and new observations from Swift, SOAR/Goodman, VLT/X-shooter, and Keck/LRIS taken after its turn-on to characterise its current state. We analysed the variability of SDSS1335+0728 in the X-ray/UV/optical/mid-infrared range, modelled its spectral energy distribution prior to and after December 2019, and studied the evolution of its UV/optical spectra. Results. From our multi-wavelength photometric analysis, we find that: (a) since 2021, the UV flux (from Swift/UVOT observations) is four times brighter than the flux reported by GALEX in 2004; (b) since June 2022, the mid-infrared flux has risen more than two times, and the W1 - W2 WISE colour has become redder; and (c) since February 2024, the source has begun showing X-ray emission. From our spectroscopic follow-up, we see that (i) the narrow emission line ratios are now consistent with a more energetic ionising continuum; (ii) broad emission lines are not detected; and (iii) the [OIII] line increased its flux similar to 3.6 years after the first ZTF alert, which implies a relatively compact narrow-line-emitting region. Conclusions. We conclude that the variations observed in SDSS1335+0728 could be either explained by a similar to 106 M-circle dot AGN that is just turning on or by an exotic tidal disruption event (TDE). If the former is true, SDSS1335+0728 is one of the strongest cases of an AGN observed in the process of activating. If the latter were found to be the case, it would correspond to the longest and faintest TDE ever observed (or another class of still unknown nuclear transient). Future observations of SDSS1335+0728 are crucial to further understand its behaviour.