{
  "abstract": "We present a systematic investigation of the connection between magnetic activity and the low-surface-gravity-like near-infrared spectral morphology of late-M dwarfs. Our sample includes TRAPPIST-1 observed with JWST NIRISS/SOSS and 22 late-M dwarfs observed with IRTF/SpeX, together with flare observations from K2, TESS, JWST NIRISS/SOSS, and literature-reported X-ray luminosities. Using one-component PHOENIX/NewEra spectral modeling, we find that all targets are better reproduced by lower-surface-gravity model spectra than by models with the expected high gravities of field late-M dwarfs. The retrieved surface gravities moderately correlate with independently measured gravity-sensitive spectral indices, with the strongest trends seen for FeH$_z$ at 0.998~$μ$m and FeH$_J$ at 1.2~$μ$m, both showing statistically significant Pearson and Spearman correlations with $p<0.005$. They also show strong anti-correlations with flare luminosity and X-ray luminosity: for both relations, Pearson and Spearman coefficients are $<-0.9$, with $p \\leq 1.0\\times10^{-4}$, indicating that more active stars tend to have spectra favoring lower-gravity morphologies. Time-series spectra of TRAPPIST-1 during two large flares show no clear short-timescale variations in selected photospheric indices, suggesting that persistent small-scale magnetic activity may play a more important role than large flares in modifying the photospheric temperature--pressure structure. A simplified radiative-transfer experiment further shows that activity-associated heating can produce lower-gravity-like spectral features even when the input surface gravity is fixed. Our results suggest that underestimated surface gravities in late-M dwarfs may reflect atmospheres modified by frequent, small-scale magnetic activity, such as microflares, producing emergent spectra that mimic lower-gravity morphology.",
  "abstract_shown": true,
  "affiliations": [],
  "article_type": null,
  "arxiv": "2610.31647",
  "author_total": 10,
  "authors": [
    {
      "name": "Chia-Lung Lin"
    },
    {
      "name": "Daniel Apai"
    },
    {
      "name": "Benjamin V. Rackham"
    },
    {
      "name": "Prajwal Niraula"
    },
    {
      "name": "Mark S. Giampapa"
    },
    {
      "name": "Ana Glidden"
    },
    {
      "name": "Julien de Wit"
    },
    {
      "name": "Valeriy Vasilyev"
    },
    {
      "name": "Nadiia Kostogryz"
    },
    {
      "name": "Alexander Shapiro"
    }
  ],
  "bibtex": "https://research.draconitic.com/paper/b5996fgpz9mh4.bib",
  "cited_by": 0,
  "doi": "10.48550/arxiv.2610.31647",
  "fulltext_url": null,
  "id": "b5996fgpz9mh4",
  "issns": [],
  "landing_url": "https://arxiv.org/abs/2610.31647",
  "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.SR"
    ],
    [
      "openalex",
      "3103|Stellar, planetary, and galactic studies"
    ]
  ],
  "openalex": "W7223400591",
  "pdf_url": "https://arxiv.org/pdf/2610.31647",
  "pmcid": null,
  "pmid": null,
  "published": "2026-10-22",
  "publisher": null,
  "ris": "https://research.draconitic.com/paper/b5996fgpz9mh4.ris",
  "sources": [
    {
      "first_seen": "2026-10-30T12:34:34Z",
      "native_id": "2610.31647",
      "source": "arxiv",
      "url": "https://arxiv.org/abs/2610.31647"
    }
  ],
  "subjects": [
    {
      "field": "astronomy",
      "origin": "arxiv:astro-ph.SR",
      "subfield": "stellar"
    }
  ],
  "title": "Magnetic Activity as a Driver of Low-gravity-like Spectral Morphology in Late-M Dwarfs",
  "title_text": "Magnetic Activity as a Driver of Low-gravity-like Spectral Morphology in Late-M Dwarfs",
  "type": "preprint",
  "updated_at": "2026-10-30T12:34:34Z",
  "url": "https://research.draconitic.com/paper/b5996fgpz9mh4",
  "venue": "arXiv",
  "versions": []
}