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Start Over Author "Santo, M." Journal monthly notices of the royal astronomical society
31 results on '"Santo, M."'

1. The accretion/ejection link in the neutron star X-ray binary 4U 1820-30 I: A boundary layer-jet coupling?

Author

Marino, A, primary, Russell, T D, additional, Del Santo, M, additional, Beri, A, additional, Sanna, A, additional, Zelati, F Coti, additional, Degenaar, N, additional, Altamirano, D, additional, Ambrosi, E, additional, Anitra, A, additional, Carotenuto, F, additional, D’Aì, A, additional, Di Salvo, T, additional, Manca, A, additional, Motta, S E, additional, Pinto, C, additional, Pintore, F, additional, Rea, N, additional, and van den Eijnden, J, additional

Published
2023
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2. Unveiling the disc structure in ultraluminous X-ray source NGC 55 ULX-1

Author

Barra, F, primary, Pinto, C, additional, Walton, D J, additional, Kosec, P, additional, D’Aì, A, additional, Di Salvo, T, additional, Del Santo, M, additional, Earnshaw, H, additional, Fabian, A C, additional, Fuerst, F, additional, Marino, A, additional, Pintore, F, additional, Robba, A, additional, and Roberts, T P, additional

Published
2022
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3. A transient ultraluminous X-ray source in NGC 55

Author

Robba, A, primary, Pinto, C, additional, Pintore, F, additional, Rodriguez, G, additional, Ambrosi, E, additional, Barra, F, additional, Cusumano, G, additional, D’Aì, A, additional, Del Santo, M, additional, Kosec, P, additional, Marino, A, additional, Middleton, M, additional, Roberts, T, additional, Salvaggio, C, additional, Soria, R, additional, Wolter, A, additional, and Walton, D, additional

Published
2022
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6. The Chameleon on the branches: spectral state transition and dips in NGC 247 ULX-1

Author

D’Aì, A, primary, Pinto, C, additional, Del Santo, M, additional, Pintore, F, additional, Soria, R, additional, Robba, A, additional, Ambrosi, E, additional, Alston, W, additional, Barret, D, additional, Fabian, A C, additional, Fürst, F, additional, Kara, E, additional, Kosec, P, additional, Middleton, M, additional, Roberts, T, additional, Rodriguez-Castillo, G, additional, and Walton, D J, additional

Published
2021
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7. XMM-Newton campaign on the ultraluminous X-ray source NGC 247 ULX-1: outflows

Author

Pinto, C, primary, Soria, R, additional, Walton, D J, additional, D’Aì, A, additional, Pintore, F, additional, Kosec, P, additional, Alston, W N, additional, Fuerst, F, additional, Middleton, M J, additional, Roberts, T P, additional, Del Santo, M, additional, Barret, D, additional, Ambrosi, E, additional, Robba, A, additional, Earnshaw, H, additional, and Fabian, A C, additional

Published
2021
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8. transient ultraluminous X-ray source in NGC 55.

Author

Robba, A, Pinto, C, Pintore, F, Rodriguez, G, Ambrosi, E, Barra, F, Cusumano, G, D'Aì, A, Del Santo, M, Kosec, P, Marino, A, Middleton, M, Roberts, T, Salvaggio, C, Soria, R, Wolter, A, and Walton, D

Subjects
X-rays, X-ray spectra, ACCRETION (Astrophysics), ACCRETION disks, X-ray binaries
Abstract

Ultraluminous X-ray sources (ULXs) are a class of accreting compact objects with X-ray luminosities above 1039 erg s−1. The average number of ULXs per galaxy is still not well-constrained, especially given the uncertainty on the fraction of ULX transients. Here, we report the identification of a new transient ULX in the galaxy NGC 55 (which we label as ULX-2), thanks to recent XMM–Newton and the Neil Gehrels Swift Observatory observations. This object was previously classified as a transient X-ray source with a luminosity around a few 1038 erg s−1 in a 2010 XMM–Newton observation. Thanks to new and deeper observations (∼130 ks each), we show that the source reaches a luminosity peak >1.6 × 1039 erg s−1. The X-ray spectrum of ULX-2 is much softer than in previous observations and fits in the class of soft ULXs. It can be well-described using a model with two thermal components, as often found in ULXs. The time-scales of the X-ray variability are of the order of a month and are likely driven by small changes in the accretion rate or due to super-orbital modulations, attributed to precession of the accretion disc, which is similar to other ULXs. [ABSTRACT FROM AUTHOR]

Published
2022
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9. Quasi-periodic dipping in the ultraluminous X-ray source, NGC 247 ULX-1

Author

Alston, W N, primary, Pinto, C, additional, Barret, D, additional, D’Aì, A, additional, Del Santo, M, additional, Earnshaw, H, additional, Fabian, A C, additional, Fuerst, F, additional, Kara, E, additional, Kosec, P, additional, Middleton, M J, additional, Parker, M L, additional, Pintore, F, additional, Robba, A, additional, Roberts, T P, additional, Sathyaprakash, R, additional, Walton, D, additional, and Ambrosi, E, additional

Published
2021
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10. Observations of a radio-bright, X-ray obscured GRS 1915+105

Author

Motta, S E, primary, Kajava, J J E, additional, Giustini, M, additional, Williams, D R A, additional, Del Santo, M, additional, Fender, R, additional, Green, D A, additional, Heywood, I, additional, Rhodes, L, additional, Segreto, A, additional, Sivakoff, G, additional, and Woudt, P A, additional

Published
2021
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14. Chameleon on the branches: spectral state transition and dips in NGC 247 ULX-1.

Author

D'Aì, A, Pinto, C, Del Santo, M, Pintore, F, Soria, R, Robba, A, Ambrosi, E, Alston, W, Barret, D, Fabian, A C, Fürst, F, Kara, E, Kosec, P, Middleton, M, Roberts, T, Rodriguez-Castillo, G, and Walton, D J

Subjects
SOFT X rays, HEAT flux, X-ray binaries, RADIATION
Abstract

Soft Ultra-Luminous X-ray (ULXs) sources are a subclass of the ULXs that can switch from a supersoft spectral state, where most of the luminosity is emitted below 1 keV, to a soft spectral state with significant emission above 1 keV. In a few systems, dips have been observed. The mechanism behind this state transition and the dips nature are still debated. To investigate these issues, we obtained a long XMM–Newton monitoring campaign of a member of this class, NGC 247 ULX-1. We computed the hardness–intensity diagram for the whole data set and identified two different branches: the normal branch and the dipping branch, which we study with four and three hardness–intensity resolved spectra, respectively. All seven spectra are well described by two thermal components: a colder (kT bb ∼ 0.1–0.2 keV) blackbody, interpreted as emission from the photosphere of a radiatively driven wind, and a hotter (kT disc ∼ 0.6 keV) multicolour disc blackbody, likely due to reprocessing of radiation emitted from the innermost regions. In addition, a complex pattern of emission and absorption lines has been taken into account based on previous high-resolution spectroscopic results. We studied the evolution of spectral parameters and flux of the two thermal components along the two branches and discuss two scenarios possibly connecting the state transition and the dipping phenomenon. One is based on geometrical occultation of the emitting regions, the other invokes the onset of a propeller effect. [ABSTRACT FROM AUTHOR]

Published
2021
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19. The long outburst of the black hole transient GRS 1716–249 observed in the X-ray and radio band.

Author

Bassi, T, Del Santo, M, D'Aì, A, Motta, S E, Malzac, J, Segreto, A, Miller-Jones, J C A, Atri, P, Plotkin, R M, and Belloni, T M

Subjects
*RADIO sources (Astronomy), *BLACK holes, *ASTRONOMICAL observations, *DISKS (Astrophysics), *STELLAR luminosity function, *X-ray binaries
Abstract

We present the spectral and timing analysis of X-ray observations performed on the Galactic black hole transient GRS 1716–249 during the 2016–2017 outburst. The source was almost continuously observed with the Neil Gehrels Swift Observatory from 2016 December until 2017 October. The X-ray hardness ratio and timing evolution indicate that the source approached the soft state three times during the outburst, even though it never reached the canonical soft spectral state. Thus, GRS 1716–249 increases the number of black hole transients showing outbursts with 'failed' state transition. During the softening events, XRT and BAT broad-band spectral modelling, performed with thermal Comptonization plus a multicolour disc black-body, showed a photon index (Γ < 2) and an inner disc temperature (kT in= 0.2–0.5 keV) characteristic of the hard intermediate state. This is in agreement with the root mean square amplitude of the flux variability (rms > 10 |${{\ \rm per\ cent}}$|⁠). We find that, coherently with a scenario in which the disc moves closer to the compact object, the accretion disc inner radius decreases with the increase of the inner disc temperature, until a certain point when the temperature starts to increase at constant radius. This, in addition with the spectral analysis results, suggests that either the accretion disc reached the innermost stable circular orbit during the hard intermediate state or the hot accretion flow might recondensate in an inner mini-disc. We report on the radio observations performed during the outburst finding that GRS 1716–249 is located on the radio-quiet 'outlier' branch of the radio/X-ray luminosity plane. [ABSTRACT FROM AUTHOR]

Published
2019
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21. Spectral and timing evolution of the bright failed outburst of the transient black hole Swift J174510.8−262411

Author

Santo, M. Del, primary, Belloni, T. M., additional, Tomsick, J. A., additional, Sbarufatti, B., additional, Cadolle Bel, M., additional, Casella, P., additional, Castro-Tirado, A., additional, Corbel, S., additional, Grinberg, V., additional, Homan, J., additional, Kalemci, E., additional, Motta, S., additional, Muñoz-Darias, T., additional, Pottschmidt, K., additional, Rodriguez, J., additional, and Wilms, J., additional

Published
2016
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23. Spectral and timing evolution of the bright failed outburst of the transient black hole Swift J174510.8-262411.

Author

Del Santo, M., Belloni, T. M., Tomsick, J. A., Sbarufatti, B., Bel, M. Cadolle, Casella, P., Castro-Tirado, A., Corbel, S., Grinberg, V., Homan, J., Kalemci, E., Motta, S., Muñoz-Darias, T., Pottschmidt, K., Rodriguez, J., and Wilms, J.

Subjects
*OPTICAL depth (Astrophysics), *SPECTRAL imaging, *BLACK holes, *GALACTIC X-ray sources, *THERMAL electrons
Abstract

We studied time variability and spectral evolution of the Galactic black hole transient Swift J174510.8-262411 during the first phase of its outburst. INTEGRAL and Swift observations collected from 2012 September 16 until October 30 have been used. The total squared fractional rms values did not drop below 5 per cent and quasi-periodic oscillations (QPOs), when present, were type-C, indicating that the source never made the transition to the soft-intermediate state. Even though the source was very bright (up to 1 Crab in hard X-rays), it showed a so called failed outburst as it never reached the soft state. XRT and IBIS broad-band spectra, well represented by a hybrid thermal/non-thermal Comptonization model, showed physical parameters characteristic of the hard and intermediate states. In particular, the derived temperature of the geometrically thin disc blackbody was about 0.6 keV at maximum. We found a clear decline of the optical depth of the corona electrons (close to values of 0.1), as well as of the total compactness ratio lh/ls. The hard-to-hard/intermediate state spectral transition is mainly driven by the increase in the soft photon flux in the corona, rather than small variations of the electron heating. This, associated with the increasing of the disc temperature, is consistent with a disc moving towards the compact object scenario, i.e. the truncated-disc model. Moreover, this scenario is consistent with the decreasing fractional squared rms and increasing of the noise and QPO frequency. In our final group of observations, we found that the contribution from the non-thermal Comptonization to the total power supplied to the plasma is 0.59+0.02 -0.05 and that the thermal electrons cool to kTe < 26 keV. [ABSTRACT FROM AUTHOR]

Published
2016
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