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The rapidly rotating Ross 154 – by Mikko Tuomi

27 Jul 2017, 12:52 UTC
The rapidly rotating Ross 154 – by Mikko Tuomi M. Weiss/CfA
(200 words excerpt, click title or image to see full post)

Perhaps the least known star in the Red Dots campaign, Ross 154, is a rapidly rotating M dwarf star that shows elevated activity levels and and flares on its surface. This makes the Red Dots campaign targets more diverse than they otherwise would be – rapid rotation is typically interpreted as a sign of young age of such stellar objects as the rotation period is thought to gradually increase due to magnetic friction resulting in old M dwarfs with slow rotation rates such as Proxima Centauri whose rotation period has been estimated to be 83 days1. Indeed, Ross 154 has been estimated to have an age of less than one billion years2.
The rotation of Ross 154 induces a clear photometric cycle of 2.87 days in our All Sky Automated Survey V-band observations but the brightness of the star also varies with another cycle of 740 days that we interpret to be caused by the star’s magnetic cycle (Fig. 1). Knowing these two “fundamental” cycles helps interpreting any and all periodicities in the radial velocity data because periodicities that are independent from both rotation and magnetic activity cycle could correspond to planets orbiting the star.
Fig. 1. Likelihood-ratio periodogram of ...

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