학술논문
X-ray polarimetry and spectroscopy of the neutron star low-mass X-ray binary GX 9+9: an in-depth study with IXPE and NuSTAR
Document Type
Working Paper
Author
Ursini, F.; Farinelli, R.; Gnarini, A.; Poutanen, J.; Bianchi, S.; Capitanio, F.; Di Marco, A.; Fabiani, S.; La Monaca, F.; Malacaria, C.; Matt, G.; Mikušincová, R.; Cocchi, M.; Kaaret, P.; Kajava, J. J. E.; Pilia, M.; Zhang, W.; Agudo, I.; Antonelli, L. A.; Bachetti, M.; Baldini, L.; Baumgartner, W. H.; Bellazzini, R.; Bongiorno, S. D.; Bonino, R.; Brez, A.; Bucciantini, N.; Castellano, S.; Cavazzuti, E.; Chen, C. -T.; Ciprini, S.; Costa, E.; De Rosa, A.; Del Monte, E.; Di Gesu, L.; Di Lalla, N.; Donnarumma, I.; Doroshenko, V.; Dovčiak, M.; Ehlert, S. R.; Enoto, T.; Evangelista, Y.; Ferrazzoli, R.; Garcia, J. A.; Gunji, S.; Hayashida, K.; Heyl, J.; Iwakiri, W.; Jorstad, S. G.; Karas, V.; Kislat, F.; Kitaguchi, T.; Kolodziejczak, J. J.; Krawczynski, H.; Latronico, L.; Liodakis, I.; Maldera, S.; Manfreda, A.; Marin, F.; Marinucci, A.; Marscher, A. P.; Marshall, H. L.; Massaro, F.; Mitsuishi, I.; Mizuno, T.; Muleri, F.; Negro, M.; Ng, C. -Y.; O'Dell, S. L.; Omodei, N.; Oppedisano, C.; Papitto, A.; Pavlov, G. G.; Peirson, A. L.; Perri, M.; Pesce-Rollins, M.; Petrucci, P. -O.; Possenti, A.; Puccetti, S.; Ramsey, B. D.; Rankin, J.; Ratheesh, A.; Roberts, O. J.; Romani, R. W.; Sgrò, C.; Slane, P.; Soffitta, P.; Spandre, G.; Swartz, D. A.; Tamagawa, T.; Tavecchio, F.; Taverna, R.; Tawara, Y.; Tennant, A. F.; Thomas, N. E.; Tombesi, F.; Trois, A.; Tsygankov, S. S.; Turolla, R.; Vink, J.; Weisskopf, M. C.; Wu, K.; Xie, F.; Zane, S.
Source
A&A 676, A20 (2023)
Subject
Language
Abstract
We report on a comprehensive analysis of simultaneous X-ray polarimetric and spectral data of the bright atoll source GX 9+9 with the Imaging X-ray Polarimetry Explorer (IXPE) and NuSTAR. The source is significantly polarized in the 4--8 keV band, with a degree of $2.2\% \pm 0.5\%$ (uncertainty at the 68% confidence level). The NuSTAR broad-band spectrum clearly shows an iron line, and is well described by a model including thermal disk emission, a Comptonized component, and reflection. From a spectro-polarimetric fit, we obtain an upper limit to the polarization degree of the disk of 4% (at 99% confidence level), while the contribution of Comptonized and reflected radiation cannot be conclusively separated. However, the polarization is consistent with resulting from a combination of Comptonization in a boundary or spreading layer, plus reflection off the disc, which gives a significant contribution in any realistic scenario.
Comment: 10 pages, accepted for publication in A&A
Comment: 10 pages, accepted for publication in A&A