S. Motta

Brera Astronomical Observatory

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T. Belloni

Brera Astronomical Observatory

R. P. Fender

University of Sheffield

T. Muñoz‐Darias

Instituto de Astrofísica de Canarias

J. C. A. Miller‐Jones

International Centre for Radio Astronomy Research

D. Altamirano

University of Southampton

P. Casella

Astronomical Observatory of Rome

E. Kuulkers

European Space Research and Technology Centre

P. A. Woudt

University of Cape Town

Joe Bright

University of Oxford

M. Del Santo

National Institute for Astrophysics

Cooperative Institutions

National Institute for Astrophysics

293

Centre National de la Recherche Scientifique

154

Institute for Space Astrophysics and Planetology

129

University of Amsterdam

104

Goddard Space Flight Center

100

John Wiley & Sons (United Kingdom)

Macquarie University

Center for Astrophysics Harvard & Smithsonian

University of Geneva

John Wiley & Sons (United States)

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Highly Significant Detection of X-Ray Polarization from the Brightest Accreting Neutron Star Sco X-1

arXiv (Cornell University) (2023)

Fabio La Monaca Alessandro Di Marco Juri Poutanen Matteo Bachetti S. Motta

The Imaging X-ray Polarimetry Explorer (IXPE) measured with high significance the X-ray polarization of the brightest Z-source Scorpius X-1, resulting in the nominal 2-8 keV energy band in a polarization degree of 1.0(0.2)% and a polarization angle of 8(6){\deg} at 90% of confidence level. This observation was strictly simultaneous with observations performed by NICER, NuSTAR, and Insight-HXMT, which allowed for a precise characterization of its broad-band spectrum from soft to hard X-rays. The source has been observed mainly in its soft state, with short periods of flaring. We also observed low-frequency quasi-periodic oscillations. From a spectro-polarimetric analysis, we associate a polarization to the accretion disk at <3.2% at 90% of confidence level, compatible with expectations for an electron-scattering dominated optically thick atmosphere at the Sco X-1 inclination of 44{\deg}; for the higher-energy Comptonized component, we obtain a polarization of 1.3(0.4)%, in agreement with expectations for a slab of Thomson optical depth of ~7 and an electron temperature of ~3 keV. A polarization rotation with respect to previous observations by OSO-8 and PolarLight, and also with respect to the radio-jet position angle, is observed. This result may indicate a variation of the polarization with the source state that can be related to relativistic precession or to a change in the corona geometry with the accretion flow.

Position angle

Thomson scattering

10.48550/arxiv.2311.06359

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Swift observations of the ultraluminous X-ray source XMMU J004243.6+412519 in M31

Monthly Notices of the Royal Astronomical Society (2012)

P. Esposito S. Motta Fabio Pintore L. Zampieri L. Tomasella

We report on a multi-wavelength study of the recently discovered X-ray transient XMMU J004243.6+412519 in M31, based on data collected with Swift and the 1.8-m Copernico Telescope at Cima Ekar in Asiago (Italy) between 2012 February and August. Undetected in all previous observations, in 2012 January XMMU J004243.6+412519 suddenly turned on, showing powerful X-ray emission with a luminosity of ∼1038 erg s−1 (assuming a distance of 780 kpc). In the following weeks, it reached a luminosity higher than ∼1039 erg s−1, in the typical range of ultraluminous X-ray sources (ULXs). For at least ∼40 d the source luminosity remained fairly constant, then it faded below ≈1038 erg s−1 in the following ∼200 d. The source spectrum, which can be well described by multi-colour disc blackbody model, progressively softened during the decay (the temperature changed from kT ∼ 0.9 keV to ∼0.4 keV). No emission from XMMU J004243.6+412519 was detected down to 22 mag in the optical band and to 23–24 mag in the near ultraviolet. We compare the properties of XMMU J004243.6+412519 with those of other known ULXs and Galactic black hole transients, finding more similarities with the latter.

Black-body radiation

Swift

Black hole (networking)

10.1093/mnras/sts248

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Citations (10)

On the different flavours of Lense–Thirring precession around accreting stellar mass black holes

Monthly Notices of the Royal Astronomical Society (2017)

S. Motta Alessia Franchini Giuseppe Lodato Guglielmo Mastroserio

Type-C QPOs in X-ray binaries have been often interpreted as a consequence of relativistic Lense-Thirring precession around a spinning black hole and they potentially offer a way to measure black hole spins and masses. The connection between relativistic precession and the resulting QPO has been made either in terms of a simplified model involving a single test particle producing the QPO, or in terms of a global model where a geometrically thick accretion flow precesses coherently as a rigid body. In this paper, we analyse similarities and differences between these two models, sometimes considered as in opposition to each other. We demonstrate that the former is the limiting case of the latter when the radial extent of the precessing flow is very small, and that solid lower limits to the black hole spin can be obtained by considering the test particle model alone. We also show that the global precession model naturally accounts for the range of frequencies observed for Type-C QPOs without the need to invoke a truncation of the inner accretion flow before it reaches the innermost stable circular orbit. Finally, we show that, in order to maintain rigid precession, the thick accretion flow should be radially narrow, and that if it extends beyond $10-10^2$ gravitational radii it aligns with the black hole spin too fast to produce a coherent QPO.

Precession

Black hole (networking)

Strong gravity

10.1093/mnras/stx2358

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Citations (40)

The Large Observatory for X-ray Timing (LOFT)

Experimental Astronomy (2011)

M. Feroci L. Stella M. van der Klis T. J. L. Courvoisier M. Hernanz

Spectral resolution

10.1007/s10686-011-9237-2

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Citations (195)

A stellar-mass BH in a transient, low luminosity ULX in M31?

arXiv (Cornell University) (2013)

Fabio Pintore P. Esposito S. Motta L. Zampieri

We present a multi-wavelenght study of the recently discovered Ultraluminous X-ray transient XMMUJ004243.6+412519 (ULX2 hereafter) in M31, based on Swift data and the 1.8-m Copernico Telescope in Asiago (Italy). Undetected until January 2012, the source suddenly showed a powerful X-ray emission with a luminosity of 1e38 erg/s (assuming a distance of 780 kpc). In the following weeks, its luminosity overcame 1e39 erg/s, remaining fairly constant for at least 40 days and fading below 1e38 erg/s in the next 200 days. The spectrum can be well described by a single multi-color disk blackbody model which progressively softened during the decay (from kT=0.9 keV to 0.4 keV). No emission from ULX2 was detected down to 22 mag in the optical band and to 23-24 mag in the near ultraviolet. We compare its properties with those of other known ULXs and Galactic black hole transients, finding more similarities with the latter.

Transient (computer programming)

10.48550/arxiv.1305.1862

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Swift observation of the rebrightening in MAXI J1820+070

ATel (2019)

Arash Bahramian S. Motta Pikky Atri J. C. A. Miller‐Jones

Swift

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MeerKAT discovery of radio emission from the Vela X-1 bow shock

J. van den Eijnden Ian Heywood R. P. Fender S. Mohamed G. R. Sivakoff

Vela X-1 is a runaway X-ray binary system hosting a massive donor star, whose strong stellar wind creates a bow shock as it interacts with the interstellar medium. This bow shock has previously been detected in H$\alpha$ and IR, but, similar to all but one bow shock from a massive runaway star (BD+43$^{\rm o}$3654), has escaped detection in other wavebands. We report on the discovery of $1.3$ GHz radio emission from the Vela X-1 bow shock with the MeerKAT telescope. The MeerKAT observations reveal how the radio emission closely traces the H$\alpha$ line emission, both in the bow shock and in the larger-scale diffuse structures known from existing H$\alpha$ surveys. The Vela X-1 bow shock is the first stellar-wind-driven radio bow shock detected around an X-ray binary. In the absence of a radio spectral index measurement, we explore other avenues to constrain the radio emission mechanism. We find that thermal/free-free emission can account for the radio and H$\alpha$ properties, for a combination of electron temperature and density consistent with earlier estimates of ISM density and the shock enhancement. In this explanation, the presence of a local ISM over-density is essential for the detection of radio emission. Alternatively, we consider a non-thermal/synchrotron scenario, evaluating the magnetic field and broad-band spectrum of the shock. However, we find that exceptionally high fractions ($\gtrsim 13$%) of the kinetic wind power would need to be injected into the relativistic electron population to explain the radio emission. Assuming lower fractions implies a hybrid scenario, dominated by free-free radio emission. Finally, we speculate about the detectability of radio bow shocks and whether it requires exceptional ISM or stellar wind properties.

Vela

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The black hole candidate MAXI J1659−152: spectral and timing analysis during its 2010 outburst

Monthly Notices of the Royal Astronomical Society (2011)

T. Muñoz‐Darias S. Motta H. Stiele T. Belloni

We present a comprehensive spectral-timing study of the black hole candidate MAXI J1659-152 during its 2010 outburst. We analysed 65 RXTE observations taken along this period and computed the fundamental diagrams commonly used to study black hole transients. We fitted power density and energy spectra and studied the evolution of the spectral and timing parameters along the outburst. We discuss the evolution of the variability observed at different energy bands on the basis of the relative contribution of the disc and hard components to the energy spectrum of the source. We conclude that hard emission accounts for the observed fast variability, it being strongly quenched when type-B oscillations are observed. We find that both disc and hard emission are responsible for local count-rate peaks until the system reaches the soft state. From that point, the peaks are only observed in the hard component, whereas the thermal component drops monotonically probably following the accretion rate decrease. We have also computed time-lags between soft and hard X-ray variability confirming that lags are larger during the hard-to-soft transition than during the hard state.

Black hole (networking)

Spectral Analysis

Static timing analysis

10.1111/j.1365-2966.2011.18702.x

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Citations (48)

The black hole transient MAXI J1348–630: evolution of the compact and transient jets during its 2019/2020 outburst

Monthly Notices of the Royal Astronomical Society (2021)

Francesco Carotenuto S. Corbel Evangelia Tremou T. D. Russell A. K. Tzioumis

ABSTRACT We present the radio and X-ray monitoring campaign of the 2019/2020 outburst of MAXI J1348–630, a new black hole X-ray binary (BH XRB) discovered in 2019 January. We observed MAXI J1348–630 for ∼14 months in the radio band with MeerKAT and the Australia Telescope Compact Array, and in the X-rays with MAXI and Swift/XRT. Throughout the outburst, we detected and tracked the evolution of compact and transient jets. Following the main outburst, the system underwent at least four hard-state-only re-flares, during which compact jets were again detected. For the major outburst, we observed the rise, quenching and reactivation of compact jets, as well as two single-sided discrete ejecta travelling away from the BH, launched ∼2 months apart. These ejecta displayed the highest proper motion (≳100 mas d−1) ever measured for an accreting BH binary. From the jet motion, we constrain the ejecta inclination and speed to be ≤46○ and ≥0.69 c, and the opening angle and transverse expansion speed of the first component to be ≤6○ and ≤0.05 c. We also infer that the first ejection happened at the hard-to-soft state transition, before a strong radio flare, while the second ejection was launched during a short excursion from the soft to the intermediate state. After travelling with constant speed, the first component underwent a strong deceleration, which was covered with unprecedented detail and suggested that MAXI J1348–630 could be located inside a low-density cavity in the interstellar medium, as already proposed for XTE J1550–564 and H1743–322.

Transient (computer programming)

Black hole (networking)

X-ray transient

10.1093/mnras/stab864

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Citations (51)

Continued optical/UV observations of V404 Cyg with Swift/UVOT

ATel (2015)

S. R. Oates S. Motta E. Kuulkers N. P. M. Kuin D. Altamirano

Swift

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Citations (2)