Investigation of the rotation-activity relation for a sample of SuperWASP and ASAS-SN field stars

Abstract

It is well established that late-type main-sequence stars display a relationship between X-ray activity and the Rossby number, $Ro$, the ratio of rotation period to the convective turnover time. This manifests itself as a saturated regime (where X-ray activity is constant) and an unsaturated regime (where X-ray activity anti-correlates with the Rossby number). However, this relationship breaks down for the fastest rotators. We cross-correlated SuperWASP visually classified photometric light curves and ASAS-SN automatically classified photometric light curves with XMM-Newton X-ray observations to identify 3,178 stars displaying a photometrically defined rotational modulation in their light curve and corresponding X-ray observations. We fitted a power-law to characterise the rotation-activity relation of 900 main-sequence stars. We identified that automatically classified rotationally modulated light curves are not as reliable as visually classified light curves for this work. We found a power-law index in the unsaturated regime of G- to M-type stars of $\beta =-1.84\pm 0.18$ for the SuperWASP catalogue, in line with the canonical value of $\beta =-2$. We find evidence of supersaturation in the fastest rotating K-type stars, with a power-law index of ${\beta }_s=1.42\pm 0.26$.

Accepted for publication in PASA. 14 pages, 12 figures, 3 tables

References in corpus (1)

• X-ray Flares in Orion Low Mass Stars

Cited by in corpus (4)

• The Factory and the Beehive. IV. A Comprehensive Study of the Rotation X-ray Activity Relation in Praesepe and the Hyades
• SuperWASP Variable Stars: Classifying Light Curves Using Citizen Science
• The Factory and the Beehive. V. Chromospheric and Coronal Activity and Its Dependence on Rotation in Praesepe and the Hyades
• The corona -- chromosphere connection studied with simultaneous eROSITA and TIGRE observations