1. X-ray and optical polarization aligned with the radio jet ejecta in GX 339-4
- Author
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Mastroserio, G., De Marco, B., Baglio, M. C., Carotenuto, F., Fabiani, S., Russell, T. D., Capitanio, F., Cavecchi, Y., Motta, S., Russell, D. M., Dovciak, M., Del Santo, M., Alabarta, K., Ambrifi, A., Campana, S., Casella, P., Covino, S., Illiano, G., Kara, E., Lai, E. V., Lodato, G., Manca, A., Mariani, I., Marino, A., Miceli, C., Saikia, P., Shaw, A. W., Svoboda, J., Vincentelli, F. M., and Wang, J.
- Subjects
Astrophysics - High Energy Astrophysical Phenomena ,Astrophysics - Instrumentation and Methods for Astrophysics - Abstract
We present the first X-ray polarization measurements of GX 339-4. IXPE observed this source twice during its 2023-2024 outburst, once in the soft-intermediate state and again during a soft state. The observation taken during the intermediate state shows significant ($4\sigma$) polarization degree P = $1.3\% \pm 0.3\%$ and polarization angle $\theta$ = -74\degree $\pm$ 7\degree only in the 3 - 8 keV band. FORS2 at VLT observed the source simultaneously detecting optical polarization in the B, V, R, I bands (between $0.1%$ and $0.7\%$), all roughly aligned with the X-ray polarization. We also detect a discrete jet knot from radio observations taken later in time; this knot would have been ejected from the system around the same time as the hard-to-soft X-ray state transition and a bright radio flare occurred $\sim$3 months earlier. The proper motion of the jet knot provides a direct measurement of the jet orientation angle on the plane of the sky at the time of the ejection. We find that both the X-ray and optical polarization angles are aligned with the direction of the ballistic jet., Comment: Submitted to ApJ
- Published
- 2024