X-ray Dips and Polarization Angle Swings in GX 13+1

Fuente: arXiv
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Hauptverfasser: Di Marco, Alessandro, La Monaca, Fabio, Bobrikova, Anna, Stella, Luigi, Papitto, Alessandro, Poutanen, Juri, Baglio, Maria Cristina, Bachetti, Matteo, Loktev, Vladislav, Pilia, Maura, Rogantini, Daniele
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Veröffentlicht: 2025
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author Di Marco, Alessandro
La Monaca, Fabio
Bobrikova, Anna
Stella, Luigi
Papitto, Alessandro
Poutanen, Juri
Baglio, Maria Cristina
Bachetti, Matteo
Loktev, Vladislav
Pilia, Maura
Rogantini, Daniele
author_facet Di Marco, Alessandro
La Monaca, Fabio
Bobrikova, Anna
Stella, Luigi
Papitto, Alessandro
Poutanen, Juri
Baglio, Maria Cristina
Bachetti, Matteo
Loktev, Vladislav
Pilia, Maura
Rogantini, Daniele
contents We present the result from the April 2024 observation of the low-mass X-ray binary GX 13+1 with the Imaging X-ray Polarimetry Explorer (IXPE), together with NICER and Swift-XRT coordinated observations. Two light curve dips were observed; during them, the harder Comptonized spectral component was dominant and the polarization degree higher than in the softer, off-dip intervals. Through a joint analysis of the three IXPE observations, which also included the dip from the first observation, we demonstrate that the polarization properties varied in response to the intensity and spectral hardness changes associated with the dips. The polarization degree attained values up to ~4%. The polarization angle showed a swing of ~70° across the dip and off-dip states, comparable to the continuous rotation seen during the first IXPE observation. We discuss these results in the context of models for polarized emission from the accretion disk and the boundary/spreading layer on the neutron star surface. We also draw attention to the role that an extended accretion disk corona or disk wind can play in generating high polarization degrees and, possibly, swings of the polarization angle.
format Preprint
id arxiv_https___arxiv_org_abs_2501_05511
institution arXiv
publishDate 2025
record_format arxiv
spellingShingle X-ray Dips and Polarization Angle Swings in GX 13+1
Di Marco, Alessandro
La Monaca, Fabio
Bobrikova, Anna
Stella, Luigi
Papitto, Alessandro
Poutanen, Juri
Baglio, Maria Cristina
Bachetti, Matteo
Loktev, Vladislav
Pilia, Maura
Rogantini, Daniele
High Energy Astrophysical Phenomena
We present the result from the April 2024 observation of the low-mass X-ray binary GX 13+1 with the Imaging X-ray Polarimetry Explorer (IXPE), together with NICER and Swift-XRT coordinated observations. Two light curve dips were observed; during them, the harder Comptonized spectral component was dominant and the polarization degree higher than in the softer, off-dip intervals. Through a joint analysis of the three IXPE observations, which also included the dip from the first observation, we demonstrate that the polarization properties varied in response to the intensity and spectral hardness changes associated with the dips. The polarization degree attained values up to ~4%. The polarization angle showed a swing of ~70° across the dip and off-dip states, comparable to the continuous rotation seen during the first IXPE observation. We discuss these results in the context of models for polarized emission from the accretion disk and the boundary/spreading layer on the neutron star surface. We also draw attention to the role that an extended accretion disk corona or disk wind can play in generating high polarization degrees and, possibly, swings of the polarization angle.
title X-ray Dips and Polarization Angle Swings in GX 13+1
topic High Energy Astrophysical Phenomena
url https://arxiv.org/abs/2501.05511