Examinando por Autor "Giustini, M."

Mostrando 1 - 6 de 6

Acceso Abierto
Observations of a radio-bright, X-ray obscured GRS 1915+105
(Oxford Academics: Oxford University Press, 2021-02-24) Motta, Sara E.; Kajava, J. J. E.; Giustini, M.; Williams, D. R. A.; Del Santo, M.; Fender, R.; Green, D. A.; Heywood, I.; Rhodes, L.; Segreto, A.; Sivakoff, G.; Woudt, P. A.; Science and Technology Facilities Council (STFC); Agencia Estatal de Investigación (AEI); Comunidad de Madrid; Istituto Nazionale di Astrofisica (INAF); European Commission (EC); Motta, S. E. [0000-0002-6154-5843]; Kajava, J. J. E. [0000-0002-3010-8333]; Williams, D. R. A. [0000-0001-7361-0246]; Del Santo, M. [0000-0002-1793-1050]; Green, D. A. [0000-0003-3189-9998]; Woudt, P. A. [0000-0002-6896-1655]
The Galactic black hole transient GRS 1915+105 is famous for its markedly variable X-ray and radio behaviour, and for being the archetypal galactic source of relativistic jets. It entered an X-ray outburst in 1992 and has been active ever since. Since 2018 GRS 1915+105 has declined into an extended low-flux X-ray plateau, occasionally interrupted by multiwavelength flares. Here, we report the radio and X-ray properties of GRS 1915+105 collected in this new phase, and compare the recent data to historic observations. We find that while the X-ray emission remained unprecedentedly low for most of the time following the decline in 2018, the radio emission shows a clear mode change half way through the extended X-ray plateau in 2019 June: from low flux (∼3 mJy) and limited variability, to marked flaring with fluxes two orders of magnitude larger. GRS 1915+105 appears to have entered a low-luminosity canonical hard state, and then transitioned to an unusual accretion phase, characterized by heavy X-ray absorption/obscuration. Hence, we argue that a local absorber hides from the observer the accretion processes feeding the variable jet responsible for the radio flaring. The radio–X-ray correlation suggests that the current low X-ray flux state may be a signature of a super-Eddington state akin to the X-ray binaries SS433 or V404 Cyg.
Acceso Abierto
On Synthetic Absorption Line Profiles of Thermally Driven Winds from Active Galactic Nuclei
(IOP Science Publishing, 2021-06-22) Ganguly, S.; Proga, D.; Waters, T.; Dannen, R. C.; Dyda, S.; Giustini, M.; Kallman, T.; Raymond, J.; Miller, J.; Rodríguez Hidalgo, P.; National Aeronautics and Space Administration (NASA); Comunidad de Madrid; Ganguly, S. [0000-0002-8256-5982]; Proga, D. [0000-0002-6336-5125]; Waters, T. [0000-0002-5205-9472]; Dannen, R. C. [0000-0002-5160-8716]; Dyda, S. [0000-0002-1954-8864]; Giustini, M. [0000-0002-1329-658X]; Kallman, T. [0000-0002-5779-6906]; Raymond, J. [0000-0002-7868-1622]; Miller, J. [0000-0001-6432-7860]; Rodríguez Hidalgo, P. [0000-0003-0677-785X]
The warm absorbers observed in more than half of all nearby active galactic nuclei are tracers of ionized outflows located at parsec-scale distances from the central engine. If the smallest inferred ionization parameters correspond to plasma at a few 104 K, then the gas undergoes a transition from being bound to unbound, provided it is further heated to ∼106 K at larger radii. Dannen et al. recently discovered that, under these circumstances, thermally driven wind solutions are unsteady and even show very dense clumps due to thermal instability. To explore the observational consequences of these new wind solutions, we compute line profiles based on the one-dimensional simulations of Dannen et al. We show how the line profiles from even a simple steady-state wind solution depend on the ionization energy (IE) of absorbing ions, which is a reflection of the wind ionization stratification. To organize the diversity of the line shapes, we group them into four categories: weak Gaussians, saturated boxy profiles with and without an extended blue wing, and broad weak profiles. The lines with profiles in the last two categories are produced by ions with the highest IE that probe the fastest regions. Their maximum blueshifts agree with the highest flow velocities in thermally unstable models, both steady-state and clumpy versions. In contrast, the maximum blueshifts of the highest-IE lines in thermally stable models can be less than half of the actual solution velocities. Clumpy solutions can additionally imprint distinguishable absorption troughs at widely separated velocities.
Acceso Abierto
The first broad-band X-ray view of the narrow-line Seyfert 1 Ton S180
(Oxford Academics: Oxford University Press, 2020-07-15) Matzeu, G. A.; Nardini, E.; Parker, M. L.; Reeves, J. N.; Braito, V.; Porquet, D.; Middei, R.; Kammoun, E.; Lusso, E.; Alston, W. N.; Giustini, M.; Lobban, A. P.; Joyce, A. M.; Igo, Z.; Ebrero, J.; Ballo, L.; Santos Lleó, M.; Schartel, N.; European Research Council (ERC); European Commission (EC); Agenzia Spaziale Italiana (ASI); Istituto Nazionale di Astrofisica (INAF); Comunidad de Madrid; National Aeronautics and Space Administration (NASA); Giustini, M. [0000-0002-1329-658X]; Kammoun, E. [0000-0002-0273-218X]; Braito, V. [0000-0002-2629-4989]; Matzeu, G. [0000-0003-1994-5322]; Parker, M. [0000-0002-8466-7317]; Lobban, A. [0000-0002-6433-1357]; Santos Lleo, M. [0000-0001-5948-8360]; Middei, R. [0000-0001-9815-9092]; Igo, Z. [0000-0001-9274-1145]; Alston, W. [0000-0003-2658-6559]; Unidad de Excelencia Científica María de Maeztu Centro de Astrobiología del Instituto Nacional de Técnica Aeroespacial y CSIC, MDM-2017-0737
We present joint XMM-Newton and NuSTAR observations of the 'bare' narrow-line Seyfert 1 Ton S180 (z = 0.062), carried out in 2016 and providing the first hardX-ray view of this luminous galaxy. We find that the 0.4-30 keV band cannot be self-consistently reproduced by relativistic reflection models, which fail to account simultaneously for the soft and hard X-ray emission. The smooth soft excess prefers extreme blurring parameters, confirmed by the nearly featureless nature of the Reflection Grating Spectrometer (RGS) spectrum, while the moderately broad Fe K line and the modest hard excess above 10 keV appear to arise in a milder gravity regime. By allowing a different origin of the soft excess, the broad-band X-ray spectrum and overall spectral energy distribution (SED) are well explained by a combination of (a) direct thermal emission from the accretion disc, dominating from the optical to the far/extreme UV; (b) Comptonization of seed disc photons by a warm (kT(e) similar to 0.3 keV) and optically thick (tau similar to 10) corona, mostly contributing to the soft X-rays; (c) Comptonization by a standard hot (kT(e) greater than or similar to 100 keV) and optically thin (tau < 0.5) corona, responsible for the primary X-ray continuum; and (d) reflection from the mid/outer part of the disc. The two coronae are suggested to be rather compact, with R-hot less than or similar to R-warm less than or similar to 10 r(g). Our SED analysis implies that Ton S180 accretes at super-Eddington rates. This is a key condition for the launch of a wind, marginal (i.e. 3.1 sigma significance) evidence of which is indeed found in the RGS spectrum.
Restringido
The quest for dual and binary supermassive black holes: A multi-messenger view
(Elsevier BV, 2019-12-12) De Rosa, A.; Vignali, C.; Bogdanovic, T.; Capelo, P. R.; Charisi, M.; Dotti, M.; Husemann, B.; Lusso, E.; Mayer, L.; Paragi, Z.; Runnoe, J.; Sesana, A.; Steinborn, L.; Bianchi, S.; Colpi, M.; Del Valle, L.; Frey, S.; Gabányi, K. É.; Giustini, M.; Guainazzi, M.; Haiman, Z.; Herrera Ruiz, N.; Herrero Illana, R.; Iwasawa, K.; Komossa, S.; Lena, D.; Loiseau, N.; Pérez Torres, M.; Piconcelli, E.; Volonteri, M.; Agenzia Spaziale Italiana (ASI); Istituto Nazionale Astrofisica (INAF); National Aeronautics and Space Administration (NASA); Hungarian Scientific Research Fund (OTKA); Hungarian Academy of Sciences (MTA); Deutsche Forschungsgemeinschaft (DFG); European Union COFUND/Durham Junior Research Fellowship (EU); European Research Council (ERC); Swiss National Science Foundation (SNSF); Federal Ministry of Education & Research (BMBF); Ministerio de Economía y Competitividad (MINECO); Comunidad de Madrid; Agencia Estatal de Investigación (AEI); Lena, D. [0000-0003-4184-6152]; Loiseau, N. [0000-0001-5471-3776]; Haiman, Z. [0000-0003-3633-5403]; De Rosa, A. [0000-0001-5668-6863]; Husemann, B. [0000-0003-2901-6842]; Centros de Excelencia Severo Ochoa, INSTITUTO DE ASTROFISICA DE ANDALUCIA (IAA), SEV-2017-0709; Unidad de Excelencia Científica María de Maeztu Instituto de Ciencias del Cosmos (ICCUB), MDM-2014-0369; Unidad de Excelencia Científica María de Maeztu Centro de Astrobiología del Instituto Nacional de Técnica Aeroespacial y CSIC, MDM-2017-0737
The quest for binary and dual supermassive black holes (SMBHs) at the dawn of the multi-messenger era is compelling. Detecting dual active galactic nuclei (AGN) - active SMBHs at projected separations larger than several parsecs - and binary AGN - probing the scale where SMBHs are bound in a Keplerian binary - is an observational challenge. The study of AGN pairs (either dual or binary) also represents an overarching theoretical problem in cosmology and astrophysics. The AGN triggering calls for detailed knowledge of the hydrodynamical conditions of gas in the imminent surroundings of the SMBHs and, at the same time, their duality calls for detailed knowledge on how galaxies assemble through major and minor mergers and grow fed by matter along the filaments of the cosmic web. This review describes the techniques used across the electromagnetic spectrum to detect dual and binary AGN candidates and proposes new avenues for their search. The current observational status is compared with the state-of-the-art numerical simulations and models for formation of dual and binary AGN. Binary SMBHs are among the loudest sources of gravitational waves (GWs) in the Universe. The search for a background of GWs at nHz frequencies from inspiralling SMBHs at low redshifts, and the direct detection of signals from their coalescence by the Laser Interferometer Space Antenna in the next decade, make this a theme of major interest for multi-messenger astrophysics. This review discusses the future facilities and observational strategies that are likely to significantly advance this fascinating field.
Acceso Abierto
The WISSH quasars project VII. The impact of extreme radiative field in the accretion disc and X-ray corona interplay
(EDP Sciences, 2020-03-10) Zappacosta, L.; Piconcelli, E.; Giustini, M.; Vietri, G.; Duras, F.; Miniutti, G.; Bischetti, M.; Bongiorno, A.; Brusa, M.; Chiaberge, M.; Comastri, A.; Feruglio, C.; Luminari, A.; Marconi, A.; Ricci, C.; Vignali, C.; Fiore, F.; Comisión Nacional de Investigación Científica y Tecnológica (CONICYT); Agenzia Spaziale Italiana (ASI); Agencia Estatal de Investigación (AEI); Comunidad de Madrid; Zappacosta, L. [0000-0002-4205-6884]; Piconcelli, E. [0000-0001-9095-2782]; Guistini, M. [0000-0002-1329-658X]; Vietri, G. [0000-0001-9155-8875]; Miniutti, G. [0000-0003-0707-4531]; Bischetti, M. [0000-0002-4314-021X]; Bongiorno, A. [0000-0002-0101-6624]; Chiaberge, M. [0000-0003-1564-3802]; Comastri, A. [0000-0003-3451-9970]; Luminari, A. [0000-0002-1035-8618]; Marconi, A. [0000-0002-9889-4238]; Ricci, C. [0000-0001-5231-2645]; Vignali, C. [0000-0002-8853-9611]; Fiore, F. [0000-0002-4031-4157]; Unidad de Excelencia Científica María de Maeztu Centro de Astrobiología del Instituto Nacional de Técnica Aeroespacial y CSIC, MDM-2017-0737
Hyper-luminous quasars (L-bol & x2004;greater than or similar to & x2004;10(47) erg s(-1)) are ideal laboratories to study the interaction and impact of the extreme radiative field and the most powerful winds in the active galactic nuclei (AGN) nuclear regions. They typically exhibit low coronal X-ray luminosity (L-X) compared to the ultraviolet (UV) and mid-infrared (MIR) radiative outputs (L-UV and L-UV); a non-negligible fraction of them report even similar to 1 dex weaker L-X compared to the prediction of the well established L-X-L-UV and L-X-L-UV relations followed by the bulk of the AGN population. In our WISE/SDSS-selected Hyper-luminous (WISSH) z & x2004;=& x2004;2 - 4 broad-line quasar sample, we report on the discovery of a dependence between the intrinsic 2-10 keV luminosity (L2 - 10) and the blueshifted velocity of the CIV emission line (v(CIV)) that is indicative of accretion disc winds. In particular, sources with the fastest winds (v(CIV) greater than or similar to 3000 km s(-1)) possess similar to 0.5-1 dex lower L2 - 10 than sources with negligible v(CIV). No similar dependence is found on L-UV, L-UV, L-bol, the photon index, or the absorption column density. We interpret these findings in the context of accretion disc wind models. Both magnetohydrodynamic and line-driven models can qualitatively explain the reported relations as a consequence of X-ray shielding from the inner wind regions. In case of line-driven winds, the launch of fast winds is favoured by a reduced X-ray emission, and we speculate that these winds may play a role in directly limiting the coronal hard X-ray production.
Acceso Abierto
X-ray quasi-periodic eruptions from the galactic nucleus of RX J1301.9+2747
(EDP Sciences, 2020-04-09) Giustini, M.; Miniutti, G.; Saxton, R. D.; Agencia Estatal de Investigación (AEI); Comunidad de Madrid; Giustini, M. [0000-0002-1329-658X]; Miniutti, G. [0000-0003-0707-4531]; Unidad de Excelencia Científica María de Maeztu Centro de Astrobiología del Instituto Nacional de Técnica Aeroespacial y CSIC, MDM-2017-0737
Following the recent discovery of X-ray quasi-periodic eruptions (QPEs) coming from the nucleus of the galaxy GSN 069, here we report on the detection of QPEs in the active galaxy named RX J1301.9+2747. QPEs are rapid and recurrent increases of the X-ray count-rate by more than one order of magnitude with respect to a stable quiescent level. During a XMM-Newton observation lasting 48 ks that was performed on 30 and 31 May 2019, three strong QPEs lasting about half an hour each were detected in the light curves of RX J1301.9+2747. The first two QPEs are separated by a longer recurrence time (about 20 ks) compared to the second and third (about 13 ks). This pattern is consistent with the alternating long-short recurrence times of the GSN 069 QPEs, although the difference between the consecutive recurrence times is significantly smaller in GSN 069. Longer X-ray observations will better clarify the temporal pattern of the QPEs in RX J1301.9+2747 and will allow a detailed comparison with GSN 069 to be performed. The X-ray spectral properties of QPEs in the two sources are remarkably similar, with QPEs representing fast transitions from a relatively cold and likely disk-dominated state to a state that is characterized by a warmer emission similar to the so-called soft X-ray excess, a component that is almost ubiquitously seen in the X-ray spectra of unobscured, radiatively efficient active galaxies. Previous X-ray observations of RX J1301.9+2747 in 2000 and 2009 strongly suggest that QPEs have been present for at least the past 18.5 yr. The detection of QPEs from a second galactic nucleus after GSN 069 rules out contamination by a Galactic source in both cases, such that QPEs ought to be considered a novel extragalactic phenomenon associated with accreting supermassive black holes.