Title: HADES RV Programme with HARPS-N at TNG. VII. Rotation and Activity of M-Dwarfs from Time-Series High-Resolution Spectroscopy of Chromospheric Indicators
https://arxiv.org/abs/1712.07375
Authors: A. Suárez Mascareño and many others
First Author’s Institution: Instituto de Astrofísica de Canarias, E-38205 La Laguna, Tenerife, Spain; Observatoire Astronomique de l’Université de Genève, 1290 Versoix, Switzerland
Status: Submitted to arXiv [open access]
Possible planet… or stellar sham?
The search for life as we know it on Earth-like, rocky exoplanets has been a driving force for many telescope missions of the new century. And, as today’s authors point out, M-Dwarfs seem more and more like great places to look.
M-Dwarfs (aka Red Dwarfs) are typically really dim, lightweight stars (relative to the Sun), which seem to account for most of the stars in the universe. Because M-Dwarfs are so small and faint, the signs that planets are orbiting them show up more clearly than for planets orbiting Sun-like stars.
Figure 1: An artist’s gorgeous impression of an M-Dwarf and its orbiting planets. Image Credit: NASA/JPL-Caltech
Consider, for example, the radial velocity (RV) method for detecting planets. This method relies on the fact that, for a star-and-planet system, the star is not completely stationary as the planet orbits around it. Just as the star’s gravity tugs on the planet, so too does the planet’s gravity tug on the star. This tug makes the host star ‘wobble’ around in its own orbit in response to the orbiting planet. The size of this wobble is larger for M-Dwarfs than for Sun-like stars, because M-Dwarfs are so much less massive – which means that the signature wobble for M-Dwarfs, in theory, should be easier for astronomers to detect.
In practice, however, there are other factors that can complicate the detection of this signature wobble for M-Dwarfs – like stellar activity. As time passes and a star rotates, stellar features, like starspots and granules on the star’s surface, can shift, flare, and fade in and out of view. Unfortunately the signals we see from these sorts of stellar activities can have the same magnitude as the signals we see from stellar wobbling due to orbiting rocky planets.
That’s where today’s authors come in. By mapping the distributions of various stellar cycles for a survey of M-Dwarfs, the authors aim to make it easier to distinguish between signals of stellar activity and signals of orbiting planets.
See the full article here .
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