Short term variability of DS Tuc A observed with TESS
Journal
Date Issued
2022
Author(s)
Abstract
Impulsive short term variations occur in all kinds of solar-type stars. They
are the results of complex phenomena such as the stellar magnetic field
reconnection, low-level variability or in some cases even star-planet
interactions. The radiation arising from these events is often highly energetic
and, in stars hosting planets, may interact with the planetary atmospheres.
Studying the rate of these energetic phenomena is fundamental to understand
their role in modifying the chemical composition or, in some extreme cases, to
the disruption of the planetary atmospheres. Here, we present a new procedure
developed to identify the impulsive events in TESS light curves. Our goal is to
have a simple and effective tool to study the short-term activity of a star
using only its light curve, in order to derive its distribution and energetic.
As our first case, we studied the system DS Tuc. Our technique consists of
fitting the TESS light curves using iteratively Gaussian processes in order to
remove all the long-term stellar activity contributions. Then, we identify the
impulsive events and, derive amplitudes, time scales and the amount of energy
emitted. We validate our procedure using the AU Mic TESS light curves obtaining
results consistent with those presented in the literature. We estimate the
frequency distribution of energetic events for DS Tuc. In particular, we find
that there are approx 2 events per day with energy greater than 2x10^32 erg. We
find evidence for a favoured stellar phase for short term activity on AU Mic,
and also indications of short term activity in phase with the planetary orbit.
For DS Tuc we find that the events distribution is not equally spaced in time
but often grouped. The resulting distribution may be used to estimate the
impact of short term variability on planetary atmosphere chemical compositions.
Volume
661
Start page
A148
Issn Identifier
0004-6361
Rights
open.access
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