Abstract
Understanding our Galaxy’s structure, formation, and evolution will, over the next decades, continue to benefit from the wonderful large survey by Gaia, for astrometric, kinematic, and spectroscopic characterization, and by large spectroscopic surveys for chemical characterization. The weak link for full exploitation of these data is age characterization, and stellar age estimation relies predominantly on mass estimates. The ideas presented in this White Paper shows that a seismology survey is the way out of this situation and a natural complement to existing and planned surveys. These ideas are strongly rooted in the past decade’s experience of the so-called Seismology revolution, initiated with CoRoT and Kepler. The case of red giant stars is used here as the best current illustration of what we can expect from seismology for large samples, but premises for similar developments exist in various other classes of stars covering other ranges of age or mass. Whatever the star considered, the first information provided by stellar pulsations is always related to the mean density and thus to the mass (and age). In order to satisfy the need for long-duration and all-sky coverage, we rely on a new instrumental concept which decouples integration time and sampling time. We thus propose a long (~1 year) all-sky survey which would perfectly fit between TESS, PLATO, and the Rubin Observatory (previously known as LSST) surveys to offer a time domain complement to the current and planned astrometric and spectroscopic surveys. The fine characterization of host stars is also a key aspect for the interpretation and exploitation of the various projects -- anticipated in the framework of the Voyage 2050 programme -- searching for atmospheric characterization of terrestrial planets or, more specifically, looking for a signature of life, in distant planets.
Highlights
Understanding our Galaxy’s structure, formation, and evolution will, over the decades, continue to benefit from the wonderful large survey by Gaia, for astrometric, kinematic, and spectroscopic characterization, and by large spectroscopic surveys for chemical characterization
Completed by the associated large spectroscopic surveys, Gaia is characterizing in detail and with a unique precision, positions, proper motions, and magnitudes for about a billion stars, and 3D motions, effective temperatures, and chemical compositions for several tens of millions of stars over a large part of our Galaxy and nearby satellite galaxies (e.g., [2])
To reach a more precise view of the situation, it is essential to enrich the very precise astrometric-kinematic-chemical view of the Galaxy provided by Gaia and large spectroscopic surveys with high precision ages which can be provided through seismic information
Summary
Galactic archaeology has entered a new era with the data provided by the Gaia mission, providing new insights into fundamental questions about the build-up of our Galaxy. Completed by the associated large spectroscopic surveys (such as APOGEE and WEAVE), Gaia is characterizing in detail and with a unique precision, positions (including distances), proper motions, and magnitudes for about a billion stars, and 3D motions, effective temperatures, and chemical compositions for several tens of millions of stars over a large part of our Galaxy and nearby satellite galaxies (e.g., [2]) These precise data shed a new light on the above fundamental questions about how our Galaxy has formed and evolved. With CoRoT [10] and Kepler [11], we have learned to derive this information from photometric light curves of tens of thousands of stars and we can foresee an upgrade of this capacity in the number of stars and in type of stars and in type of applications This is why we are firmly convinced that it will be a top priority for the scientific community in 2035–50 to improve our view and understanding of our Galaxy, by adding a time domain dimension to the Gaia Survey. This variability can be due to stellar pulsations, and to other phenomena like rotation modulation associated with activity or binary tide effects, granulation, to name a few
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