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arXiv · 2602.02054

X-ray counterparts to stellar MeerKAT Galactic-plane compact radio sources

O. D. Egbo·P. J. Groot·D. A. H. Buckley·J. Robrade·A. D. Schwope·S. Freund·P. C. Schneider·B. Stelzer
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Abstract

Radio emission from magnetically active stars arises mainly from non-thermal processes and complements high-energy X-ray emission. Sensitive, wide-field radio and X-ray surveys now allow identification of larger samples of active stars across the Galaxy. We aim to identify and characterise radio and X-ray-emitting stars in the Galactic plane by combining MeerKAT radio data with soft X-ray observations and assess their consistency with the canonical G\"udel-Benz relation, which links thermal coronal X-rays to non-thermal gyrosynchrotron radio emission. We cross-matched compact sources from the SARAO MeerKAT Galactic Plane Survey with counterparts from the ROSAT All-Sky Survey and the first release of SRG/eROSITA (eRASS1). We computed radio-brightness temperatures and radio-X-ray luminosities to test the relation. We identify 137 stars with both radio and X-ray detections. Their $T_B$ ranges from $10^7$ to $10^{12}$ K, except two outliers: AXJ1600.9-5142 ($4.8 \pm 1.5 \times 10^{12}$ K) and HD~124831 ($8 \pm 1 \times 10^{6}$ K). The remainder are consistent with incoherent gyrosynchrotron emission. The sample lies below the canonical G\"udel-Benz relation, driven by enhanced 1.3 GHz radio luminosities relative to the 5 GHz relation. This suggests the classical relation represents an upper envelope rather than a tight correlation. Additionally, eROSITA detections show early-type stars lie below the typical $\log (L_{\rm X}/L_{\rm bol}) \sim -3$ relation.

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O. D. Egbo, P. J. Groot, D. A. H. Buckley, J. Robrade, A. D. Schwope, S. Freund, P. C. Schneider, B. Stelzer. 2026-02-02. X-ray counterparts to stellar MeerKAT Galactic-plane compact radio sources. https://arxiv.org/abs/2602.02054

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