A1 Refereed original research article in a scientific journal
IXPE observation confirms a high spin in the accreting black hole 4U 1957+115
Authors: Marra L., Brigitte M., Cavero N.R., Chun S., Steiner J.F., Dovčiak M., Nowak M., Bianchi S., Capitanio F., Ingram A., Matt G., Muleri F., Podgorný J., Poutanen J., Svoboda J., Taverna R., Ursini F., Veledina A., De Rosa A., García J.A., Lutovinov A.A., Mereminskiy I.A., Farinelli R., Gunji S., Kaaret P., Kallman T., Krawczynski H., Kan Y., Hu K., Marinucci A., Mastroserio G., Mikus̆incová R., Parra M., Petrucci P.O., Ratheesh A., Soffitta P., Tombesi F., Zane S., 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., Ciprini S., Costa E., Del Monte E., Di Gesu L., Di Lalla N., Di Marco A., Donnarumma I., Doroshenko V., Ehlert S.R., Enoto T., Evangelista Y., Fabiani S., Ferrazzoli R., Hayashida K., Heyl J., Iwakiri W., Jorstad S.G., Karas V., Kislat F., Kitaguchi T., Kolodziejczak J.J., La Monaca F., Latronico L., Liodakis I., Maldera S., Manfreda A., Marin F., Marscher A.P., Marshall H.L., Massaro F., Mitsuishi I., Mizuno T., 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., Pilia M., Possenti A., Puccetti S., Ramsey B.D., Rankin J., Roberts O.J., Romani R.W., Sgrò C., Slane P., Spandre G., Swartz D.A., Tamagawa T., Tavecchio F., Tawara Y., Tennant A.F., Thomas N.E., Trois A., Tsygankov S.S., Turolla R., Vink J., Weisskopf M.C., Wu K., Xie F.
Publisher: EDP Sciences
Publication year: 2024
Journal: Astronomy and Astrophysics
Journal name in source: Astronomy and Astrophysics
Article number: A95
Volume: 684
DOI: https://doi.org/10.1051/0004-6361/202348277
Web address : https://doi.org/10.1051/0004-6361/202348277
Self-archived copy’s web address: https://research.utu.fi/converis/portal/detail/Publication/393482491
We present the results of the first X-ray polarimetric observation of the low-mass X-ray binary 4U 1957+115, performed with the Imaging X-ray Polarimetry Explorer in May 2023. The binary system has been in a high-soft spectral state since its discovery and is thought to host a black hole. The ∼571 ks observation reveals a linear polarisation degree of 1.9% ± 0.6% and a polarisation angle of −41◦. 8 ± 7◦. 9 in the 2–8 keV energy range. Spectral modelling is consistent with the dominant contribution coming from the standard accretion disc, while polarimetric data suggest a significant role of returning radiation: photons that are bent by strong gravity effects and forced to return to the disc surface, where they can be reflected before eventually reaching the observer. In this setting, we find that models with a black hole spin lower than 0.96 and an inclination lower than 50◦ are disfavoured.
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