Evidence for a Black Hole Spin–Orbit Misalignment in the X-Ray Binary Cyg X-1

Zdziarski, A. A.; Veledina, Alexandra; Szanecki, Michał; Green, David A.; Bright, J. S.; Williams, D.

doi:10.3847/2041-8213/ace2c9

Cited by 5 publications

(1 citation statement)

References 53 publications

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“…We measured the location of the bright core in the VLBA image, which is likely consistent with the location of the central BH. In Cyg X-1, where the base of the jet is highly free-free absorbed by the strong stellar wind of the supergiant companion (see, e.g., Miller-Jones et al 2021), the distance between the BH and the synchrotron photosphere (where the compact "core" emission originates from) is between ∼1 and 3 × 10 13 cm at 8.4 GHz (Zdziarski et al 2023). Accounting for the scaling of the photosphere distance (z 0 ) with luminosity as µ n z L 0 0.47 (Heinz 2006;Zdziarski et al 2023), this would correspond to a distance of no more than 1-3 mas downstream from the location of the BH in J1727, which is within the beam of the VLBA observation projected along the jet axis.…”

Section: Core Locationmentioning

confidence: 99%

Swift J1727.8–1613 Has the Largest Resolved Continuous Jet Ever Seen in an X-Ray Binary

Wood,

Miller-Jones,

Bahramian

et al. 2024

ApJL

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Multiwavelength polarimetry and radio observations of Swift J1727.8–1613 at the beginning of its recent 2023 outburst suggested the presence of a bright compact jet aligned in the north–south direction, which could not be confirmed without high-angular-resolution images. Using the Very Long Baseline Array and the Long Baseline Array, we imaged Swift J1727.8–1613 during the hard/hard-intermediate state, revealing a bright core and a large, two-sided, asymmetrical, resolved jet. The jet extends in the north–south direction, at a position angle of −0.60° ± 0.07° east of north. At 8.4 GHz, the entire resolved jet structure is ∼ 110 ( d / 2.7 kpc ) / sin i au long, with the southern approaching jet extending ∼ 80 ( d / 2.7 kpc ) / sin i au from the core, where d is the distance to the source and i is the inclination of the jet axis to the line of sight. These images reveal the most resolved continuous X-ray binary jet, and possibly the most physically extended continuous X-ray binary jet ever observed. Based on the brightness ratio of the approaching and receding jets, we put a lower limit on the intrinsic jet speed of β ≥ 0.27 and an upper limit on the jet inclination of i ≤ 74°. In our first observation we also detected a rapidly fading discrete jet knot 66.89 ± 0.04 mas south of the core, with a proper motion of 0.66 ± 0.05 mas hr−1, which we interpret as the result of a downstream internal shock or a jet–interstellar medium interaction, as opposed to a transient relativistic jet launched at the beginning of the outburst.

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Section: Core Locationmentioning

confidence: 99%

Swift J1727.8–1613 Has the Largest Resolved Continuous Jet Ever Seen in an X-Ray Binary

Wood,

Miller-Jones,

Bahramian

et al. 2024

ApJL

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Peering into the tilted heart of Cyg X-1 with high-precision optical polarimetry

Kravtsov,

Veledina,

Berdyugin

et al. 2023

A&A

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We present high-precision optical polarimetric observations of the black hole X-ray binary Cygnus X-1 that span several cycles of its 5.6-day orbital period. The week-long observations on two telescopes located in opposite hemispheres allowed us to track the evolution of the polarization within one orbital cycle with the highest temporal resolution to date. Using the field stars, we determined the interstellar polarization in the source direction and subsequently its intrinsic polarization Pint = 0.82%±0.15% with a polarization angle θint = 155° ±5°. The optical polarization angle is aligned with that in the X-rays recently obtained with the Imaging X-ray Polarimetry Explorer. Furthermore, it is consistent within the uncertainties with the position angle of the radio ejections. We show that the intrinsic polarization degree is variable with the orbital period with an amplitude of ∼0.2% and discuss various sites of its production. Assuming that the polarization arises from a single Thomson scattering of the primary star radiation by the matter that follows the black hole in its orbital motion, we constrained the inclination of the binary orbit i > 120° and its eccentricity e < 0.08. The asymmetric shape of the orbital profiles of the Stokes parameters also implies the asymmetry of the scattering matter distribution in the orbital plane, which may arise from the tilted accretion disk. We compared our data to the polarimetric observations made in 1975–1987 and find good agrement within 1° between the intrinsic polarization angles. On the other hand, the polarization degree decreased by 0.4% over half a century, suggesting secular changes in the geometry of the accreting matter.

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X-ray polarization properties of thermal-radiative disc winds in binary systems

Tomaru,

Done,

Odaka

2023

Monthly Notices of the Royal Astronomical Society

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New X-ray polarization results are challenging our understanding of the accretion flow geometry in black hole binary systems. Even spectra dominated by a standard disc can give unexpected results, such as the high-inclination black hole binary 4U 1630−472, where the observed X-ray polarization is much higher than predicted. This system also shows a strong, highly ionized wind, consistent with thermal-radiative driving from the outer disc, leading to speculation that scattering in the wind is responsible for the unexpectedly high polarization degree from a standard optically thick disc. Here, we show that this is not the case. The optically thin(ish) wind polarizes the scattered light in a direction orthogonal to that predicted from a standard optically thick disc, reducing about 2 per cent rather than enhancing the predicted polarization of the total emission. This value is consistent with the polarization difference between the disc-dominated soft state, where absorption lines by the wind are clearly seen, and the steep power-law state, where no absorption lines are seen. If this difference is genuinely due to the presence or absence of wind, the total polarization direction must be orthogonal to the disc plane rather than parallel as expected from optically thick material.

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Evidence for a Black Hole Spin–Orbit Misalignment in the X-Ray Binary Cyg X-1

Cited by 5 publications

References 53 publications

Swift J1727.8–1613 Has the Largest Resolved Continuous Jet Ever Seen in an X-Ray Binary

Swift J1727.8–1613 Has the Largest Resolved Continuous Jet Ever Seen in an X-Ray Binary

Peering into the tilted heart of Cyg X-1 with high-precision optical polarimetry

X-ray polarization properties of thermal-radiative disc winds in binary systems

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