2024-12-06 NASA
＜関連情報＞
- https://www.nasa.gov/missions/ixpe/nasas-ixpe-details-shapes-of-structures-at-newly-discovered-black-hole/
- https://iopscience.iop.org/article/10.3847/2041-8213/ad0781
- https://iopscience.iop.org/article/10.3847/1538-4357/ad3faf
- https://iopscience.iop.org/article/10.3847/2041-8213/ad402e/meta
- https://www.aanda.org/articles/aa/full_html/2024/06/aa50566-24/aa50566-24.html
ブラックホール過渡現象Swift J1727.8-1613からX線偏光を発見 Discovery of X-Ray Polarization from the Black Hole Transient Swift J1727.8−1613
Alexandra Veledina, Fabio Muleri, Michal Dovčiak, Juri Poutanen, Ajay Ratheesh, Fiamma Capitanio, Giorgio Matt, Paolo Soffitta, Allyn F. Tennant, Michela Negro,…
The Astrophysical Journal Letters Published: 2023 November 21
DOI:10.3847/2041-8213/ad0781
Abstract
We report the first detection of the X-ray polarization of the bright transient Swift J1727.8−1613 with the Imaging X-ray Polarimetry Explorer. The observation was performed at the beginning of the 2023 discovery outburst, when the source resided in the bright hard state. We find a time- and energy-averaged polarization degree of 4.1% ± 0.2% and a polarization angle of 2
2 ± 13 (errors at 68% confidence level; this translates to ∼20σ significance of the polarization detection). This finding suggests that the hot corona emitting the bulk of the detected X-rays is elongated, rather than spherical. The X-ray polarization angle is consistent with that found in submillimeter wavelengths. Since the submillimeter polarization was found to be aligned with the jet direction in other X-ray binaries, this indicates that the corona is elongated orthogonal to the jet.
ブラックホール過渡現象Swift J1727.8-1613の状態遷移中のX線偏光を追跡する Tracking the X-Ray Polarization of the Black Hole Transient Swift J1727.8–1613 during a State Transition
Adam Ingram, Niek Bollemeijer, Alexandra Veledina, Michal Dovčiak, Juri Poutanen, Elise Egron, Thomas D. Russell, Sergei A. Trushkin, Michela Negro, Ajay Ratheesh,…
The Astrophysical Journal Published: 2024 June 13
DOI:10.3847/1538-4357/ad3faf
Abstract
We report on an observational campaign on the bright black hole (BH) X-ray binary Swift J1727.8–1613 centered around five observations by the Imaging X-ray Polarimetry Explorer. These observations track for the first time the evolution of the X-ray polarization of a BH X-ray binary across a hard to soft state transition. The 2–8 keV polarization degree decreased from ∼4% to ∼3% across the five observations, but the polarization angle remained oriented in the north–south direction throughout. Based on observations with the Australia Telescope Compact Array, we find that the intrinsic 7.25 GHz radio polarization aligns with the X-ray polarization. Assuming the radio polarization aligns with the jet direction (which can be tested in the future with higher-spatial-resolution images of the jet), our results imply that the X-ray corona is extended in the disk plane, rather than along the jet axis, for the entire hard intermediate state. This in turn implies that the long (≳10 ms) soft lags that we measure with the Neutron star Interior Composition ExploreR are dominated by processes other than pure light-crossing delays. Moreover, we find that the evolution of the soft lag amplitude with spectral state does not follow the trend seen for other sources, implying that Swift J1727.8–1613 is a member of a hitherto undersampled subpopulation.
ソフトスペクトル状態におけるスウィフトJ1727.8-1613のX線偏光の劇的な低下 Dramatic Drop in the X-Ray Polarization of Swift J1727.8–1613 in the Soft Spectral State
Jiří Svoboda, Michal Dovčiak, James F. Steiner, Philip Kaaret, Jakub Podgorný, Juri Poutanen, Alexandra Veledina, Fabio Muleri, Roberto Taverna, Henric Krawczynski,…
The Astrophysical Journal Letters Published 2024 May 7
DOI:10.3847/2041-8213/ad402e
Abstract
Black hole X-ray binaries exhibit different spectral and timing properties in different accretion states. The X-ray outburst of a recently discovered and extraordinarily bright source, Swift J1727.8–1613, has enabled the first investigation of how the X-ray polarization properties of a source evolve with spectral state. The 2–8 keV polarization degree was previously measured by the Imaging X-ray Polarimetry Explorer (IXPE) to be ≈4% in the hard and hard intermediate states. Here we present new IXPE results taken in the soft state, with the X-ray flux dominated by the thermal accretion disk emission. We find that the polarization degree has dropped dramatically to ≲1%. This result indicates that the measured X-ray polarization is largely sensitive to the accretion state and the polarization fraction is significantly higher in the hard state when the X-ray emission is dominated by upscattered radiation in the X-ray corona. The combined polarization measurements in the soft and hard states disfavor a very high or low inclination of the system.
スウィフトJ1727.8-1613のソフトからハードへのスペクトル遷移後のX線偏光の回復 Recovery of the X-ray polarisation of Swift J1727.8−1613 after the soft-to-hard spectral transition
J. Podgorný, J. Svoboda, M. Dovčiak, A. Veledina, J. Poutanen, P. Kaaret, S. Bianchi, A. Ingram, F. Capitanio, S. R. Datta, E. Egron, H. Krawczynski, G. Matt, F. Muleri, P.-O. Petrucci, T. D. Russell, J. F. Steiner, N. Bollemeijer, M. Brigitte, N. Castro Segura, R. Emami, J. A. García, K. Hu, M. N. Iacolina, V. Kravtsov, L. Marra, G. Mastroserio, T. Muñoz-Darias, E. Nathan, M. Negro, A. Ratheesh, N. Rodriguez Cavero, R. Taverna, F. Tombesi, Y. J. Yang, W. Zhang and Y. Zhang,…
Astronomy & Astrophysics Published:12 June 2024
DOI:https://doi.org/10.1051/0004-6361/202450566
Abstract
We report on the detection of X-ray polarisation in the black-hole X-ray binary Swift J1727.8−1613 during its dim hard spectral state by the Imaging X-ray Polarimetry Explorer (IXPE). This is the first detection of X-ray polarisation at the transition from the soft to the hard state in an X-ray binary. We find an averaged 2–8 keV polarisation degree of (3.3 ± 0.4)% and a corresponding polarisation angle of 3° ±4°, which matches the polarisation detected during the rising stage of the outburst, in September–October 2023, within 1σ uncertainty. The observational campaign complements previous studies of this source and enables comparison of the X-ray polarisation properties of a single transient across the X-ray hardness-intensity diagram. The complete recovery of the X-ray polarisation properties, including the energy dependence, came after a dramatic drop in the X-ray polarisation during the soft state. The new IXPE observations in the dim hard state at the reverse transition indicate that the accretion properties, including the geometry of the corona, appear to be strikingly similar to the bright hard state during the outburst rise despite the X-ray luminosities differing by two orders of magnitude.
