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|Title:||Investigating the origin of optical and X-ray pulsations of the transitional millisecond pulsar PSR J1023+0038||Authors:||Illiano, G.
Miraval Zanon, A.
Coti Zelati, F.
DE MARTINO, Domitilla
Hernandez Diaz, M.
ISRAEL, Gian Luca
Perez Ventura, H.
Torres, D. F.
|Issue Date:||2023||Journal:||ASTRONOMY & ASTROPHYSICS||Number:||669||First Page:||A26||Abstract:||Context. PSR J1023+0038 is the first millisecond pulsar that was ever observed as an optical and UV pulsar. So far, it is the only optical transitional millisecond pulsar. The rotation- and accretion-powered emission mechanisms hardly individually explain the observed characteristics of optical pulsations. A synergistic model, combining these standard emission processes, was proposed to explain the origin of the X-ray/UV/optical pulsations. <BR /> Aims: We study the phase lag between the pulses in the optical and X-ray bands to gain insight into the physical mechanisms that cause it. <BR /> Methods: We performed a detailed timing analysis of simultaneous or quasi-simultaneous observations in the X-ray band, acquired with the XMM-Newton and NICER satellites, and in the optical band, with the fast photometers SiFAP2 (mounted at the 3.6 m Telescopio Nazionale Galileo) and Aqueye+ (mounted at the 1.8 m Copernicus Telescope). We estimated the time lag of the optical pulsation with respect to that in the X-rays by modeling the folded pulse profiles with two harmonic components. <BR /> Results: Optical pulses lag the X-ray pulses by ∼150 μs in observations acquired with instruments (NICER and Aqueye+) whose absolute timing uncertainty is much smaller than the measured lag. We also show that the phase lag between optical and X-ray pulsations lies in a limited range of values, δϕ ∈ (0 − 0.15), which is maintained over timescales of about five years. This indicates that both pulsations originate from the same region, and it supports the hypothesis of a common emission mechanism. Our results are interpreted in the shock-driven mini pulsar nebula scenario. This scenario suggests that optical and X-ray pulses are produced by synchrotron emission from the shock that formed within a few light cylinder radii away (∼100 km) from the pulsar, where its striped wind encounters the accretion disk inflow.||URI:||http://hdl.handle.net/20.500.12386/33969||URL:||http://arxiv.org/abs/2211.12975v1
|Appears in Collections:||1.01 Articoli in rivista|
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checked on Jun 9, 2023
checked on Jun 9, 2023
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