@article{discovery10195874,
       publisher = {American Astronomical Society},
          volume = {968},
           month = {June},
           pages = {76--76},
            note = {Original content from this work may be used under the terms of the Creative Commons Attribution 4.0 licence. Any further distribution of this work must maintain attribution to the author(s) and the title of the work, journal citation and DOI.},
         journal = {Astrophysical Journal},
          number = {2},
            year = {2024},
           title = {Tracking the X-Ray Polarization of the Black Hole Transient Swift J1727.8-1613 during a State Transition},
            issn = {0004-637X},
             url = {https://doi.org/10.3847/1538-4357/ad3faf},
        abstract = {We report on an observational campaign on the bright black hole (BH) X-ray binary Swift J1727.8-1613 centered around five observations by the Imaging X-ray Polarimetry Explorer. These observations track for the first time the evolution of the X-ray polarization of a BH X-ray binary across a hard to soft state transition. The 2-8 keV polarization degree decreased from {$\sim$}4\% to {$\sim$}3\% across the five observations, but the polarization angle remained oriented in the north-south direction throughout. Based on observations with the Australia Telescope Compact Array, we find that the intrinsic 7.25 GHz radio polarization aligns with the X-ray polarization. Assuming the radio polarization aligns with the jet direction (which can be tested in the future with higher-spatial-resolution images of the jet), our results imply that the X-ray corona is extended in the disk plane, rather than along the jet axis, for the entire hard intermediate state. This in turn implies that the long ({$\gtrsim$}10 ms) soft lags that we measure with the Neutron star Interior Composition ExploreR are dominated by processes other than pure light-crossing delays. Moreover, we find that the evolution of the soft lag amplitude with spectral state does not follow the trend seen for other sources, implying that Swift J1727.8-1613 is a member of a hitherto undersampled subpopulation.},
          author = {Ingram, A and Bollemeijer, N and Veledina, A and Dov{\vc}iak, M and Poutanen, J and Egron, E and Russell, TD and Trushkin, SA and Negro, M and Ratheesh, A and Capitanio, F and Connors, R and Neilsen, J and Kraus, A and Iacolina, MN and Pellizzoni, A and Pilia, M and Carotenuto, F and Matt, G and Mastroserio, G and Kaaret, P and Bianchi, S and Garc{\'i}a, JA and Bachetti, M and Wu, K and Costa, E and Ewing, M and Kravtsov, V and Krawczynski, H and Loktev, V and Marinucci, A and Marra, L and Miku{\vs}incov{\'a}, R and Nathan, E and Parra, M and Petrucci, PO and Righini, S and Soffitta, P and Steiner, JF and Svoboda, J and Tombesi, F and Tugliani, S and Ursini, F and Yang, YJ and Zane, S and Zhang, W and Agudo, I and Antonelli, LA and Baldini, L and Baumgartner, WH and Bellazzini, R and Bongiorno, SD and Bonino, R and Brez, A and Bucciantini, N and Castellano, S and Cavazzuti, E and Chen, CT and Ciprini, S and De Rosa, A and Del Monte, E and Di Gesu, L and Di Lalla, N and Di Marco, A and Donnarumma, I and Doroshenko, V and Ehlert, SR and Enoto, T and Evangelista, Y and Fabiani, S and Ferrazzoli, R and Gunji, S and Hayashida, K and Heyl, J and Iwakiri, W and Jorstad, SG and Karas, V and Kislat, F and Kitaguchi, T and Kolodziejczak, JJ and La Monaca, F and Latronico, L and Liodakis, I and Maldera, S and Manfreda, A and Marin, F and Marscher, AP and Marshall, HL and Massaro, F and Mitsuishi, I and Mizuno, T and Muleri, F and Ng, CY and O'Dell, SL and Omodei, N and Oppedisano, C and Papitto, A and Pavlov, GG and Peirson, AL and Perri, M}
}