{
  "abstract": "High-time-resolution optical and UV observations have revealed bright coherent pulsations from accreting millisecond pulsars, exceeding the luminosity expected from thermal emission from NS hotspots or X-ray reflection by the accretion disk. Characterizing optical pulsations over a wide range of accretion rates through coordinated multi-wavelength observations can shed light on their origin. We present a timing study of the AMSP SAX J1808.4-3658 during its 2022 outburst and quiescence, using optical TNG/SiFAP2 observations, simultaneous NICER X-ray data, LCO optical monitoring, and MeerKAT radio observations in quiescence. During the outburst, we detect coherent optical pulsations with pulsed luminosities of 1.3x10^(30)erg/s. Combined with previous detections, our results suggest that the optical pulsed amplitude increases as the X-ray flux decreases. The X-ray and optical pulsed luminosities show opposite trends with X-ray luminosity, suggesting different responses to changes in the accretion rate. We measure X-ray-to-optical delays of 0.88+-0.04ms and 0.51+-0.03 ms in two outburst observations, indicating that the relative timing between the signals is not constant. Together with the spectral energy distribution, these results support different emission mechanisms: non-thermal emission from relativistic particles for optical pulsations and channeled accretion onto the NS surface for X-ray pulsations. During quiescence, we detect no coherent optical pulsations, obtaining a 95% confidence upper limit of <2.2x10^(29)erg/s on the optical pulsed luminosity, corresponding to an optical efficiency comparable to those of spider radio millisecond pulsars. Simultaneous MeerKAT observations reveal no radio pulsations down to ~10μJy, significantly improving previous constraints but not excluding an active rotation-powered pulsar whose radio emission may be absorbed by intra-binary material.",
  "abstract_shown": true,
  "affiliations": [],
  "article_type": null,
  "arxiv": "2610.18322",
  "author_total": 28,
  "authors": [
    {
      "name": "C. Ballocco"
    },
    {
      "name": "A. Miraval Zanon"
    },
    {
      "name": "A. Papitto"
    },
    {
      "name": "M. Burgay"
    },
    {
      "name": "M. C. Baglio"
    },
    {
      "name": "C. Malacaria"
    },
    {
      "name": "F. Ambrosino"
    },
    {
      "name": "A. Possenti"
    },
    {
      "name": "G. Illiano"
    },
    {
      "name": "E. D. Barr"
    },
    {
      "name": "R. P. Breton"
    },
    {
      "name": "L. Burderi"
    },
    {
      "name": "S. Campana"
    },
    {
      "name": "C. J. Clark"
    },
    {
      "name": "F. Coti Zelati"
    },
    {
      "name": "D. de Martino"
    },
    {
      "name": "T. Di Salvo"
    },
    {
      "name": "M. Kramer"
    },
    {
      "name": "R. La Placa"
    },
    {
      "name": "F. Lewis"
    },
    {
      "name": "A. Marino"
    },
    {
      "name": "D. M. Russell"
    },
    {
      "name": "A. Sanna"
    },
    {
      "name": "L. Stella"
    },
    {
      "name": "B. Stappers"
    },
    {
      "name": "J. D. Turner"
    },
    {
      "name": "M. Cecconi"
    },
    {
      "name": "A. Ghedina"
    }
  ],
  "bibtex": "https://research.draconitic.com/paper/72x7m762hm7ba.bib",
  "cited_by": 0,
  "doi": "10.48550/arxiv.2610.18322",
  "fulltext_url": null,
  "id": "72x7m762hm7ba",
  "issns": [],
  "landing_url": "https://arxiv.org/abs/2610.18322",
  "language": null,
  "licence": "LicenseRef-arXiv-nonexclusive-1.0",
  "licence_label": "arXiv licence",
  "licence_source": "article",
  "licence_url": "http://arxiv.org/licenses/nonexclusive-distrib/1.0/",
  "metadata_licence": "CC0-1.0",
  "native_subjects": [
    [
      "arxiv",
      "astro-ph.HE"
    ]
  ],
  "openalex": null,
  "pdf_url": "https://arxiv.org/pdf/2610.18322",
  "pmcid": null,
  "pmid": null,
  "published": "2026-10-13",
  "publisher": null,
  "ris": "https://research.draconitic.com/paper/72x7m762hm7ba.ris",
  "sources": [
    {
      "first_seen": "2026-10-30T12:29:11Z",
      "native_id": "2610.18322",
      "source": "arxiv",
      "url": "https://arxiv.org/abs/2610.18322"
    }
  ],
  "subjects": [
    {
      "field": "astronomy",
      "origin": "arxiv:astro-ph.HE",
      "subfield": "high-energy-astrophysics"
    }
  ],
  "title": "Two sides of the same spin: tracking optical and radio pulsations of SAX J1808.4-3658 from outburst to quiescence",
  "title_text": "Two sides of the same spin: tracking optical and radio pulsations of SAX J1808.4-3658 from outburst to quiescence",
  "type": "preprint",
  "updated_at": "2026-10-30T12:29:11Z",
  "url": "https://research.draconitic.com/paper/72x7m762hm7ba",
  "venue": "arXiv",
  "versions": []
}