IXPE and XMM-Newton Observations of the Soft Gamma Repeater SGR 1806-20
Abstract
Recent observations with the Imaging X-ray Polarimetry Explorer (IXPE) of two anomalous X-ray pulsars provided evidence that X-ray emission from magnetar sources is strongly polarized. Here we report on the joint IXPE and XMM-Newton observations of the soft γ-repeater SGR 1806-20. The spectral and timing properties of SGR 1806-20 derived from XMM-Newton data are in broad agreement with previous measurements; however, we found the source at an all-time low persistent flux level. No significant polarization was measured apart from the 4-5 keV energy range, where a probable detection with PD = 31.6% ± 10.5% and $\mathrm{PA}=-17\buildrel{\circ}\over{.} {6}_{-15\buildrel{\circ}\over{.} 0}^{+15\buildrel{\circ}\over{.} 5}$ was obtained. The resulting polarization signal, together with the upper limits we derive at lower and higher energies (2-4 and 5-8 keV, respectively), is compatible with a picture in which thermal radiation from the condensed star surface is reprocessed by resonant Compton scattering in the magnetosphere, similar to what was proposed for the bright magnetar 4U 0142+61.
- Publication:
-
The Astrophysical Journal
- Pub Date:
- September 2023
- DOI:
- 10.3847/1538-4357/aced05
- arXiv:
- arXiv:2308.01238
- Bibcode:
- 2023ApJ...954...88T
- Keywords:
-
- Neutron stars;
- Magnetars;
- Polarimetry;
- X-ray sources;
- 1108;
- 992;
- 1278;
- 1822;
- Astrophysics - High Energy Astrophysical Phenomena;
- Astrophysics - Instrumentation and Methods for Astrophysics
- E-Print:
- 11 pages, 3 figures, accepted for publication in ApJ