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http://hdl.handle.net/20.500.12386/26533
Titolo: | Evidence for vacuum birefringence from the first optical-polarimetry measurement of the isolated neutron star RX J1856.5-3754 | Autori: | MIGNANI, Roberto TESTA, Vincenzo González Caniulef, D. Taverna, R. Turolla, R. Zane, S. Wu, K. |
Data pubblicazione: | 2017 | Rivista: | MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY | Numero: | 465 | Fascicolo: | 1 | Da pagina:: | 492 | Abstract: | The `Magnificent Seven' (M7) are a group of radio-quiet isolated neutron stars discovered in the soft X-rays through their purely thermal surface emission. Owing to the large inferred magnetic fields (B ≈ 10<SUP>13</SUP> G), radiation from these sources is expected to be substantially polarized, independently of the mechanism actually responsible for the thermal emission. A large observed polarization degree (PD) is, however, expected only if quantum-electrodynamic (QED) polarization effects are present in the magnetized vacuum around the star. The detection of a strong linearly polarized signal would therefore provide the first observational evidence of QED effects in the strong-field regime. While polarization measurements in the soft X-rays are not feasible yet, optical polarization measurements are within reach also for quite faint targets, like the M7 which have optical counterparts with magnitudes ≈26-28. Here, we report on the measurement of optical linear polarization for the prototype, and brightest member, of the class, RX J1856.5-3754 (V ∼ 25.5), the first ever for one of the M7, obtained with the Very Large Telescope. We measured a PD = 16.43 ± 5.26 per cent and a polarization position angle PA = 145.39° ± 9.44°, computed east of the North Celestial Meridian. The PD that we derive is large enough to support the presence of vacuum birefringence, as predicted by QED. | URI: | http://hdl.handle.net/20.500.12386/26533 | URL: | https://academic.oup.com/mnras/article/465/1/492/2417027 | ISSN: | 0035-8711 | DOI: | 10.1093/mnras/stw2798 | Bibcode ADS: | 2017MNRAS.465..492M | Fulltext: | open |
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