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Abstract Recently Gagné et al. suggested that young moving groups with similar kinematic properties could be part of larger dissolving structures. One example was IC 2602 as the core of a group of associations, including its corona (CIC 2602), Tucana-Horologium (THA), and parts of Theia 92. We explore this hypothesis by measuring the rotation periods of 953 objects selected using Gaia DR3 kinematics from IC 2602, CIC 2602, Theia 92, and a newly identified group of stars that bridge IC 2602 and THA. We use Transiting Exoplanet Survey Satellite (TESS) full frame images to measure new rotation periods and combine these with the rotation periods for THA from Popinchalk et al. to compare their rotation period distributions and other youth indicators where available to examine if the groups could be coeval. We find strong agreement between the rotation distributions of IC 2602, CIC 2602, and THA, suggesting a shared age of ∼40 Myr, and which in combination could serve as an example of a typical distribution at this age. Theia 92 does not agree at the same level, and we explore the potential kinematic reasons it does not match the rotation period distribution of the larger groups. Additionally, in our light curve analysis we identify ∼50 potential binaries, as well as four new M dwarf complex rotators that show major morphological changes between TESS cycles. Finally, using the amplitudes of the rotation periods we measured, we find strong agreement with the amplitude–age relation presented in Morris for our 40 Myr groups. 

Abstract Low-mass (≲1.2M_⊙) main-sequence stars lose angular momentum over time, leading to a decrease in their magnetic activity. The details of this rotation–activity relation remain poorly understood, however. Using observations of members of the ≈700 Myr old Praesepe and Hyades open clusters, we aim to characterize the rotation–activity relation for different tracers of activity at this age. To complement published data, we obtained new optical spectra for 250 Praesepe stars, new X-ray detections for 10, and new rotation periods for 28. These numbers for Hyads are 131, 23, and 137, respectively. The latter increases the number of Hyads with periods by 50%. We used these data to measure the fractional Hαand X-ray luminosities,L_Hα/L_bolandL_X/L_bol, and to calculate Rossby numbersR_o. We found that at ≈700 Myr almost all M dwarfs exhibit Hαemission, with binaries having the same overall color–Hαequivalent width distribution as single stars. In theR_o–L_Hα/L_bolplane, unsaturated single stars follow a power law with indexβ= −5.9 ± 0.8 forR_o> 0.3. In theR_o–L_X/L_bolplane, we see evidence for supersaturation for single stars withR_o≲ 0.01, following a power law with index ${\beta }_{\sup }={0.5}_{-0.1}^{+0.2}$, supporting the hypothesis that the coronae of these stars are being centrifugally stripped. We found that the criticalR_ovalue at which activity saturates is smaller forL_X/L_bolthan forL_Hα/L_bol. Finally, we observed an almost 1:1 relation betweenL_Hα/L_bolandL_X/L_bol, suggesting that both the corona and the chromosphere experience similar magnetic heating.