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astro-ph.SR · Solar and Stellar Astrophysicsastro-ph.HE · High Energy Astrophysical Phenomenaastro-ph.IM · Instrumentation and Methods for Astrophysics

Complex periodic M dwarfs within 150 pc are RACS/VLASS radio sources 3-8 times more often than matched young rapid rotators, also at equal X-ray luminosity, but are not more often eRASS1 X-ray sources

Complex periodic variables (CPVs) are young, rapidly rotating M dwarfs with sharp periodic dips. One model puts cool material in a large magnetosphere. We tested if CPVs are radio and X-ray sources more often than similar stars. We used 153 CPVs from a prior SCI TESS census of 46,947 fast-rotating red dwarfs within 150 pc. The other 46,756 stars are the controls. For each CPV, we selected the 30 nearest controls in distance, BP-RP colour, rotation period, height above the main sequence (youth) and sky position. We moved the Gaia DR3 positions to the survey epochs and cross-matched all stars with RACS-low, RACS-mid, RACS-high, RACS-low3, VLASS epoch 1 and LoTSS DR2, and with the eRASS1 coronal identifications of Freund et al. (2024). Results: 12 of 153 CPVs (7.8%) are radio sources. The matched controls give 1.60 expected (O/E = 7.5, 95% CI 4.1-11.8, p = 1.2e-8). A conservative rate estimator gives O/E = 3.0 (p = 6.6e-4). Chance coincidences give 0.24 expected CPV detections. In eRASS1-detected stars matched also in L_X, 9 of 62 CPVs are radio sources against 1.07 expected (O/E = 8.4; conservative 4.4, p = 1.3e-4). In X-rays, 62 of 119 CPVs are detected against 66.3 expected (O/E = 0.93, p = 0.85), and the median log L_X/L_bol is the same (-3.14 against -3.13). Without the youth term, a false X-ray excess (O/E = 1.8) appears. 8 of the 12 radio CPVs have no entry in the Sydney Radio Star Catalogue. The result agrees with an extra, non-coronal radio component in CPVs. Limits: single-epoch surveys near 1-3 mJy; 12 detections; 8 of 12 have RUWE > 1.4 (without RUWE > 1.4 stars, O/E = 5.2, p = 6e-3); single-survey tests are not significant with the conservative estimator; CPVs are photometric candidates. The package has all code, the cross-match data, the results and the figures.

complex periodic variables · scallop-shell stars · M dwarfs · young stars · stellar radio emission · stellar X-ray emission · RACS · VLASS · LoTSS · eRASS1 · ASKAP · magnetospheres · rapid rotators · matched control sample · Gudel-Benz relation · TESS · Gaia DR3

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References

19
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    Source of the 46,947 parent stars, the 153 CPVs (class, literature status, youth flags, radio catalogue flags) and the vetted candidate list that defines the excluded group.

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    Bouma et al. (2024) CPV catalogue; its table defines part of the excluded group and the B24 variants.

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    Gaia DR3 positions, proper motions, parallaxes, photometry and RUWE.

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    Gudel & Benz (1993) X-ray to radio luminosity relation; comparison in Figure 4.

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    TESS mission (Ricker et al. 2015); source of the light curves of the prior CPV census.

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