The SPOTS Models: A Grid of Theoretical Stellar Evolution Tracks and Isochrones for Testing the Effects of Starspots on Structure and Colors

Abstract

One-dimensional stellar evolution models have been successful at representing the structure and evolution of stars in diverse astrophysical contexts, but complications have been noted in the context of young, magnetically active stars, as well as close binary stars with significant tidal interactions. Numerous puzzles are associated with pre-main sequence and active main-sequence stars, relating to their radii, their colors, certain elemental abundances, and the coevality of young clusters, among others. A promising explanation for these puzzles is the distorting effects of magnetic activity and starspots on the structure of active stars. To assist the community in evaluating this hypothesis, we present the Stellar Parameters Of Tracks with Starspots (SPOTS) models, a grid of solar-metallicity stellar evolutionary tracks and isochrones which include a treatment of the structural effects of starspots. The models range from 0.1-1.3M and from spot-less to a surface covering fraction of 85%, and are evolved from the pre-main sequence to the red giant branch (or 15 Gyr). We also produce two-temperature synthetic colors for our models using empirically-calibrated color tables. We describe the physical ingredients included in the SPOTS models and compare their predictions to other modern evolution codes. Finally, we apply these models to several open questions in the field of active stars, including the radii of young eclipsing binaries, the color scale of pre-main sequence stars, and the existence of sub-subgiants, demonstrating that our models can explain many peculiar features of active stars.

Stellar Rotation in the Gaia Era: Revised Open Clusters’ Sequences

“…As other studies suggest, these differences could arise due to the known radius inflation problem in cool dwarfs (e.g., Torres & Ribas 2002;Clausen et al 2009;Torres et al 2010;Kraus et al 2011;Somers & Stassun 2017;Jackson et al 2018Jackson et al , 2019. Accounting for the underlying physical process that causes this in the models is beyond the scope of this paper, but we refer interested readers to the works by Somers & Pinsonneault (2015) and Somers et al (2020). Regardless, while evidently not perfect, Figure 8 shows a good overall agreement of the data with models across the HR diagram for all the clusters.…”

Eclipsing Binaries in the Open Cluster Ruprecht 147. I. EPIC 219394517

“…Star spots are thought to elicit a similar response (Chabrier et al 2007;Somers & Pinsonneault 2015). Although most publicly available "standard" models of stellar evolution do not account for these effects, a few efforts in this direction to include non-standard physics have been made, with promising results (e.g., D'Antona et al 2000;MacDonald & Mullan 2009Feiden & Chaboyer 2013Somers & Pinsonneault 2015;Somers et al 2020). Of the small number of detailed comparisons of eclipsing binary observations against these non-standard models that have been made, almost all have involved active M dwarfs.…”

Light Elements in the Universe

“…The difference in lithium between slow and fast rotators is much smaller than what is seen in the older Pleiades, but it suggests that non standard physics is already active during the PMS of low-mass stars. Several possible explanations were proposed by Bouvier et al (2016), among which planet ingestion, the effect of the accretion history, early angular momentum evolution, or magnetic fields and activity that would result in enhanced radii and reduced Li burning, as originally proposed by Somers and Pinsonneault (2014) and Somers and Pinsonneault (2015) (see also Somers et al, 2020, for a very recent update). More specifically, rotation and magnetism have since long been identified as non standard processes that may also affect the structure of young stars and hence Li depletion (Spruit and Weiss 1986;Martin and Claret, 1996;Ventura et al, 1998;Mendes et al, 1999;D'Antona et al, 2000;Feiden and Chaboyer, 2013;Spada et al, 2018) and the new data sets indeed confirm that this is the case and in principle allow constraints to be put on the models.…”