Our knowledge about stellar interiors and stellar evolution has experienced a revolution during the past decades thanks to the exploitation of ultra-precise space missions like Kepler/K2, CoRoT, SoHO and SDO. The best tool by far that we have to learn about stars is asteroseismology. Discoveries provided by asteroseismology extend to galactic archaeology, exoplanetary systems, and even testing dark matter models. However, more data does not always mean more understanding. Almost 20 years have passed since the communication ‘Unsolved Problems in Stellar Pulsation Physics’ presented by Arthur Cox in Leuven and most of the problems are still open. Although we have learnt a lot from space missions there are long-standing problems which remain unsolved and additional problems have emerged with the new data availability.
The literature is full of positive results and findings but there is a wide empty space for publications providing evidence against the fundamental assumptions of the field. These can be valuable pieces of work that researchers struggle to publish because of the bias towards positive results. This Frontiers Research Topic is to offer researchers a place to publish papers that present a critical point of view and pursue new routes to go beyond the limitations of our current understanding of stars and their interiors.
Every researcher has his/her own Moby Dick, and this volume is intended to collect a bestiary of asteroseismology problems, both theoretical and observational, in the era of space missions. This Research Topic accepts both original and review articles, addressing (but not limited to) the following questions:
1) When rotation is included in the calculation of stellar oscillations, for g-modes, the frequently used Traditional Approximation works fine, even for fast-rotating stars, however, the newly discovered inertial modes would require the 2-D modeling. For p-modes, the perturbative approach only works for slow-rotators, and we really need a 2-D model.
2) How can we deal with the non-linear mode interactions, including e.g., resonance mode coupling, non-linear response of stellar medium/atmosphere, the problem of mode-degeneracy.
3) Some high-amplitude delta Scuti stars have shown phase or period changes along time intervals of a few years as observed by Kepler, is it possible to observe stellar evolution in real-time or maybe there are other unknown processes involved that can explain these changes.
4) Asteroseismic inversion, mostly applied to linear modes and pretty much all are using linear inversions. How about mixed modes, non-linear seismic inversion?
5) How mass transfer affects the stellar oscillations, e.g. mode frequencies and excitation, instability?
6) Mode selection mechanisms in delta Scuti stars are still poorly understood, and the huge number of non-pulsating stars is puzzling.
7) The majority of TESS stars have only one-month of time span observed, how can we exploit the data to study g-modes which usually require a long time-span observation?
8) During the last years several claims of the indirect detection of g-modes in the lowest frequency interval of the solar spectrum have appeared in the literature, but none of them have been definitively confirmed. What is worse, experiments with neutrino detectors have recently provided evidence against the best solar models which fit the assumed detected g-modes. It appears that accurate prediction through theoretical models is still needed as well as new observational techniques.
9) A common description of stellar pulsators in the presence of stochastic noise have been found recently for solar-like and semi-regular variables which might be extended to classical pulsators in the main-sequence.
Image Credit : ESO/L. Calçada link
Our knowledge about stellar interiors and stellar evolution has experienced a revolution during the past decades thanks to the exploitation of ultra-precise space missions like Kepler/K2, CoRoT, SoHO and SDO. The best tool by far that we have to learn about stars is asteroseismology. Discoveries provided by asteroseismology extend to galactic archaeology, exoplanetary systems, and even testing dark matter models. However, more data does not always mean more understanding. Almost 20 years have passed since the communication ‘Unsolved Problems in Stellar Pulsation Physics’ presented by Arthur Cox in Leuven and most of the problems are still open. Although we have learnt a lot from space missions there are long-standing problems which remain unsolved and additional problems have emerged with the new data availability.
The literature is full of positive results and findings but there is a wide empty space for publications providing evidence against the fundamental assumptions of the field. These can be valuable pieces of work that researchers struggle to publish because of the bias towards positive results. This Frontiers Research Topic is to offer researchers a place to publish papers that present a critical point of view and pursue new routes to go beyond the limitations of our current understanding of stars and their interiors.
Every researcher has his/her own Moby Dick, and this volume is intended to collect a bestiary of asteroseismology problems, both theoretical and observational, in the era of space missions. This Research Topic accepts both original and review articles, addressing (but not limited to) the following questions:
1) When rotation is included in the calculation of stellar oscillations, for g-modes, the frequently used Traditional Approximation works fine, even for fast-rotating stars, however, the newly discovered inertial modes would require the 2-D modeling. For p-modes, the perturbative approach only works for slow-rotators, and we really need a 2-D model.
2) How can we deal with the non-linear mode interactions, including e.g., resonance mode coupling, non-linear response of stellar medium/atmosphere, the problem of mode-degeneracy.
3) Some high-amplitude delta Scuti stars have shown phase or period changes along time intervals of a few years as observed by Kepler, is it possible to observe stellar evolution in real-time or maybe there are other unknown processes involved that can explain these changes.
4) Asteroseismic inversion, mostly applied to linear modes and pretty much all are using linear inversions. How about mixed modes, non-linear seismic inversion?
5) How mass transfer affects the stellar oscillations, e.g. mode frequencies and excitation, instability?
6) Mode selection mechanisms in delta Scuti stars are still poorly understood, and the huge number of non-pulsating stars is puzzling.
7) The majority of TESS stars have only one-month of time span observed, how can we exploit the data to study g-modes which usually require a long time-span observation?
8) During the last years several claims of the indirect detection of g-modes in the lowest frequency interval of the solar spectrum have appeared in the literature, but none of them have been definitively confirmed. What is worse, experiments with neutrino detectors have recently provided evidence against the best solar models which fit the assumed detected g-modes. It appears that accurate prediction through theoretical models is still needed as well as new observational techniques.
9) A common description of stellar pulsators in the presence of stochastic noise have been found recently for solar-like and semi-regular variables which might be extended to classical pulsators in the main-sequence.
Image Credit : ESO/L. Calçada link
