{
  "abstract": "The Mid-Infrared Instrument (MIRI) on board the James Webb Space Telescope (JWST) provides Low Resolution Spectroscopy (LRS) over 5-12 um at a resolving power of R ~ 100. To date, all MIRI LRS time-series observations (TSOs) have been carried out in slitless mode, since long-duration pointing stability within the narrow 4.7'' x 0.51'' slit could not previously be guaranteed, leading to the possibility of degraded TSOs due to jitter. Commissioning activities established the telescope jitter to be less than 1 milliarcsecond (mas), four times less than the initial requirement. It was, therefore, worth assessing the suitability of the MIRI LRS slit as a TSO mode for precision time-domain science; this is the aim of the Cycle 3 program (PID 6219, PI: A. Dyrek). We observed a transit of the exoplanet HAT-P-12b over ~10 hours and compared the results to archival slitless observations of the same target (PID 1281, PI: P.-O. Lagage). Two independent data reductions of the transit spectra of both slit and slitless configurations are consistent within 1 sigma, validating the feasibility of the new mode. A joint fit of the slit and slitless observations confirms the presence of a spectral feature near 7.5 um. Using measured JWST pointing variations, we estimated slit-loss variations to be smaller than 40 ppm at 10 um. The drawback of the slitless mode is a higher background. Compellingly, the slit background is ~ 38 times lower on average than in slitless mode, improving sensitivity for faint targets (Jmag ~ 13-15). We also identified time-correlated noise unique to the slit dataset at long wavelengths, which requires further investigation. This new capability of TSOs in slit mode, which will be supported in Cycle 7 (in 2028), opens a new avenue for precision time-series astronomy for faint targets with JWST/MIRI.",
  "abstract_shown": true,
  "affiliations": [],
  "article_type": "Journal reference: Proceedings Volume 14145, 2026",
  "arxiv": "2608.04110",
  "author_total": 10,
  "authors": [
    {
      "name": "Achrene Dyrek"
    },
    {
      "name": "Taylor J. Bell"
    },
    {
      "name": "Pierre-Olivier Lagage"
    },
    {
      "name": "Sarah Kendrew"
    },
    {
      "name": "Gareb Fernandez-Rodriguez"
    },
    {
      "name": "Thomas Greene"
    },
    {
      "name": "Giuseppe Morello"
    },
    {
      "name": "Michiel Min"
    },
    {
      "name": "Mael Voyer"
    },
    {
      "name": "Hannu Parviainen"
    }
  ],
  "bibtex": "https://research.draconitic.com/paper/1yhpv4ztzk9va.bib",
  "cited_by": 0,
  "doi": "10.48550/arxiv.2608.04110",
  "fulltext_url": null,
  "id": "1yhpv4ztzk9va",
  "issns": [],
  "landing_url": "https://arxiv.org/abs/2608.04110",
  "language": null,
  "licence": "CC-BY-4.0",
  "licence_label": "CC BY 4.0",
  "licence_source": "article",
  "licence_url": "http://creativecommons.org/licenses/by/4.0/",
  "metadata_licence": "CC0-1.0",
  "native_subjects": [
    [
      "arxiv",
      "astro-ph.EP"
    ],
    [
      "arxiv",
      "astro-ph.IM"
    ]
  ],
  "openalex": null,
  "pdf_url": "https://arxiv.org/pdf/2608.04110",
  "pmcid": null,
  "pmid": null,
  "published": "2026-08-04",
  "publisher": null,
  "ris": "https://research.draconitic.com/paper/1yhpv4ztzk9va.ris",
  "sources": [
    {
      "first_seen": "2026-10-30T12:25:12Z",
      "native_id": "2608.04110",
      "source": "arxiv",
      "url": "https://arxiv.org/abs/2608.04110"
    }
  ],
  "subjects": [
    {
      "field": "astronomy",
      "origin": "arxiv:astro-ph.IM",
      "subfield": "instrumentation-methods"
    },
    {
      "field": "astronomy",
      "origin": "arxiv:astro-ph.EP",
      "subfield": "planetary"
    }
  ],
  "title": "A new window in time: a mid-infrared slit spectroscopy mode for precision time-series astronomy with JWST/MIRI",
  "title_text": "A new window in time: a mid-infrared slit spectroscopy mode for precision time-series astronomy with JWST/MIRI",
  "type": "preprint",
  "updated_at": "2026-10-30T12:25:12Z",
  "url": "https://research.draconitic.com/paper/1yhpv4ztzk9va",
  "venue": "arXiv",
  "versions": [
    {
      "doi": "10.1117/12.3101329",
      "pid": null,
      "relation": "published-as",
      "title": null,
      "venue": null
    }
  ]
}