NGTS clusters survey - I. Rotation in Blanco 1

These stars span F5-M3 spectral types (1.2M_{sun}_>~M>~0.3M_{sun}_) and increase the number of known rotation periods in Blanco 1 by a factor of four. We determine rotation periods using three methods: Gaussian process (GP) regression, generalized autocorrelation function (G-ACF), and Lomb-Scargle (LS) periodogram, and find that the GP and G-ACF methods are more applicable to evolving spot modulation patterns.

Between mid-F and mid-K spectral types, single stars follow a well-defined rotation sequence from ~2 to 10d, whereas stars in photometric multiple systems typically rotate faster. This may suggest that the presence of a moderate-to-high mass ratio companion inhibits angular momentum loss mechanisms during the early pre-main sequence, and this signature has not been erased at ~100Myr. The majority of mid-F to mid-K stars display evolving modulation patterns, whereas most M stars show stable modulation signals.