Evolving optical polarisation of the black hole X-ray binary MAXI J1820+070

Alexandra Veledina, Andrei V. Berdyugin, Ilia A. Kosenkov, Jari J. E. Kajava, Sergey S. Tsygankov, Vilppu Piirola, Svetlana V. Berdyugina, Takeshi Sakanoi, Masato Kagitani, Vadim Kravtsov, Juri Poutanen

Research output: Contribution to journalArticleResearchpeer-review

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Abstract

Aims: The optical emission of black hole transients increases by several magnitudes during the X-ray outbursts. Whether the extra light arises from the X-ray heated outer disc, from the inner hot accretion flow, or from the jet is currently debated. Optical polarisation measurements are able to distinguish the relative contributions of these components. Methods: We present the results of BVR polarisation measurements of the black hole X-ray binary MAXI J1820+070 during the period of March-April 2018. Results: We detect small, ˜0.7%, but statistically significant polarisation, part of which is of interstellar origin. Depending on the interstellar polarisation estimate, the intrinsic polarisation degree of the source is between ˜0.3% and 0.7%, and the polarisation position angle is between ˜10 ° -30°. We show that the polarisation increases after MJD 58222 (2018 April 14). The change is of the order of 0.1% and is most pronounced in the R band. The change of the source Stokes parameters occurs simultaneously with the drop of the observed V-band flux and a slow softening of the X-ray spectrum. The Stokes vectors of intrinsic polarisation before and after the drop are parallel, at least in the V and R filters. Conclusions: We suggest that the increased polarisation is due to the decreasing contribution of the non-polarized component, which we associate with the the hot flow or jet emission. The low polarisation can result from the tangled geometry of the magnetic field or from the Faraday rotation in the dense, ionised, and magnetised medium close to the black hole. The polarized optical emission is likely produced by the irradiated disc or by scattering of its radiation in the optically thin outflow.
Original languageEnglish
JournalASTRONOMY & ASTROPHYSICS
Volume623
Issue numberA75
DOIs
StatePublished - Mar 2019

Keywords

  • polarization
  • stars: black holes
  • stars: individual: MAXI J1820+070
  • X-rays: binaries

Cite this

Veledina, A., Berdyugin, A. V., Kosenkov, I. A., Kajava, J. J. E., Tsygankov, S. S., Piirola, V., ... Poutanen, J. (2019). Evolving optical polarisation of the black hole X-ray binary MAXI J1820+070. ASTRONOMY & ASTROPHYSICS, 623(A75). https://doi.org/10.1051/0004-6361/201834140
Veledina, Alexandra ; Berdyugin, Andrei V. ; Kosenkov, Ilia A. ; Kajava, Jari J. E. ; Tsygankov, Sergey S. ; Piirola, Vilppu ; Berdyugina, Svetlana V. ; Sakanoi, Takeshi ; Kagitani, Masato ; Kravtsov, Vadim ; Poutanen, Juri. / Evolving optical polarisation of the black hole X-ray binary MAXI J1820+070. In: ASTRONOMY & ASTROPHYSICS. 2019 ; Vol. 623, No. A75.
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title = "Evolving optical polarisation of the black hole X-ray binary MAXI J1820+070",
abstract = "Aims: The optical emission of black hole transients increases by several magnitudes during the X-ray outbursts. Whether the extra light arises from the X-ray heated outer disc, from the inner hot accretion flow, or from the jet is currently debated. Optical polarisation measurements are able to distinguish the relative contributions of these components. Methods: We present the results of BVR polarisation measurements of the black hole X-ray binary MAXI J1820+070 during the period of March-April 2018. Results: We detect small, ˜0.7{\%}, but statistically significant polarisation, part of which is of interstellar origin. Depending on the interstellar polarisation estimate, the intrinsic polarisation degree of the source is between ˜0.3{\%} and 0.7{\%}, and the polarisation position angle is between ˜10 ° -30°. We show that the polarisation increases after MJD 58222 (2018 April 14). The change is of the order of 0.1{\%} and is most pronounced in the R band. The change of the source Stokes parameters occurs simultaneously with the drop of the observed V-band flux and a slow softening of the X-ray spectrum. The Stokes vectors of intrinsic polarisation before and after the drop are parallel, at least in the V and R filters. Conclusions: We suggest that the increased polarisation is due to the decreasing contribution of the non-polarized component, which we associate with the the hot flow or jet emission. The low polarisation can result from the tangled geometry of the magnetic field or from the Faraday rotation in the dense, ionised, and magnetised medium close to the black hole. The polarized optical emission is likely produced by the irradiated disc or by scattering of its radiation in the optically thin outflow.",
keywords = "polarization, stars: black holes, stars: individual: MAXI J1820+070, X-rays: binaries",
author = "Alexandra Veledina and Berdyugin, {Andrei V.} and Kosenkov, {Ilia A.} and Kajava, {Jari J. E.} and Tsygankov, {Sergey S.} and Vilppu Piirola and Berdyugina, {Svetlana V.} and Takeshi Sakanoi and Masato Kagitani and Vadim Kravtsov and Juri Poutanen",
year = "2019",
month = "3",
doi = "10.1051/0004-6361/201834140",
language = "English",
volume = "623",
journal = "ASTRONOMY & ASTROPHYSICS",
issn = "0004-6361",
publisher = "EDP Sciences",
number = "A75",

}

Veledina, A, Berdyugin, AV, Kosenkov, IA, Kajava, JJE, Tsygankov, SS, Piirola, V, Berdyugina, SV, Sakanoi, T, Kagitani, M, Kravtsov, V & Poutanen, J 2019, 'Evolving optical polarisation of the black hole X-ray binary MAXI J1820+070', ASTRONOMY & ASTROPHYSICS, vol. 623, no. A75. https://doi.org/10.1051/0004-6361/201834140

Evolving optical polarisation of the black hole X-ray binary MAXI J1820+070. / Veledina, Alexandra; Berdyugin, Andrei V.; Kosenkov, Ilia A.; Kajava, Jari J. E.; Tsygankov, Sergey S.; Piirola, Vilppu; Berdyugina, Svetlana V.; Sakanoi, Takeshi; Kagitani, Masato; Kravtsov, Vadim; Poutanen, Juri.

In: ASTRONOMY & ASTROPHYSICS, Vol. 623, No. A75, 03.2019.

Research output: Contribution to journalArticleResearchpeer-review

TY - JOUR

T1 - Evolving optical polarisation of the black hole X-ray binary MAXI J1820+070

AU - Veledina, Alexandra

AU - Berdyugin, Andrei V.

AU - Kosenkov, Ilia A.

AU - Kajava, Jari J. E.

AU - Tsygankov, Sergey S.

AU - Piirola, Vilppu

AU - Berdyugina, Svetlana V.

AU - Sakanoi, Takeshi

AU - Kagitani, Masato

AU - Kravtsov, Vadim

AU - Poutanen, Juri

PY - 2019/3

Y1 - 2019/3

N2 - Aims: The optical emission of black hole transients increases by several magnitudes during the X-ray outbursts. Whether the extra light arises from the X-ray heated outer disc, from the inner hot accretion flow, or from the jet is currently debated. Optical polarisation measurements are able to distinguish the relative contributions of these components. Methods: We present the results of BVR polarisation measurements of the black hole X-ray binary MAXI J1820+070 during the period of March-April 2018. Results: We detect small, ˜0.7%, but statistically significant polarisation, part of which is of interstellar origin. Depending on the interstellar polarisation estimate, the intrinsic polarisation degree of the source is between ˜0.3% and 0.7%, and the polarisation position angle is between ˜10 ° -30°. We show that the polarisation increases after MJD 58222 (2018 April 14). The change is of the order of 0.1% and is most pronounced in the R band. The change of the source Stokes parameters occurs simultaneously with the drop of the observed V-band flux and a slow softening of the X-ray spectrum. The Stokes vectors of intrinsic polarisation before and after the drop are parallel, at least in the V and R filters. Conclusions: We suggest that the increased polarisation is due to the decreasing contribution of the non-polarized component, which we associate with the the hot flow or jet emission. The low polarisation can result from the tangled geometry of the magnetic field or from the Faraday rotation in the dense, ionised, and magnetised medium close to the black hole. The polarized optical emission is likely produced by the irradiated disc or by scattering of its radiation in the optically thin outflow.

AB - Aims: The optical emission of black hole transients increases by several magnitudes during the X-ray outbursts. Whether the extra light arises from the X-ray heated outer disc, from the inner hot accretion flow, or from the jet is currently debated. Optical polarisation measurements are able to distinguish the relative contributions of these components. Methods: We present the results of BVR polarisation measurements of the black hole X-ray binary MAXI J1820+070 during the period of March-April 2018. Results: We detect small, ˜0.7%, but statistically significant polarisation, part of which is of interstellar origin. Depending on the interstellar polarisation estimate, the intrinsic polarisation degree of the source is between ˜0.3% and 0.7%, and the polarisation position angle is between ˜10 ° -30°. We show that the polarisation increases after MJD 58222 (2018 April 14). The change is of the order of 0.1% and is most pronounced in the R band. The change of the source Stokes parameters occurs simultaneously with the drop of the observed V-band flux and a slow softening of the X-ray spectrum. The Stokes vectors of intrinsic polarisation before and after the drop are parallel, at least in the V and R filters. Conclusions: We suggest that the increased polarisation is due to the decreasing contribution of the non-polarized component, which we associate with the the hot flow or jet emission. The low polarisation can result from the tangled geometry of the magnetic field or from the Faraday rotation in the dense, ionised, and magnetised medium close to the black hole. The polarized optical emission is likely produced by the irradiated disc or by scattering of its radiation in the optically thin outflow.

KW - polarization

KW - stars: black holes

KW - stars: individual: MAXI J1820+070

KW - X-rays: binaries

U2 - 10.1051/0004-6361/201834140

DO - 10.1051/0004-6361/201834140

M3 - Article

VL - 623

JO - ASTRONOMY & ASTROPHYSICS

JF - ASTRONOMY & ASTROPHYSICS

SN - 0004-6361

IS - A75

ER -

Veledina A, Berdyugin AV, Kosenkov IA, Kajava JJE, Tsygankov SS, Piirola V et al. Evolving optical polarisation of the black hole X-ray binary MAXI J1820+070. ASTRONOMY & ASTROPHYSICS. 2019 Mar;623(A75). https://doi.org/10.1051/0004-6361/201834140