%0 Generic %1 jackson2018search %A Jackson, R. J. %A Jeffries, R. D. %A Deliyannis, Constantine P. %A Sun, Qinghui %A Douglas, Stephanie T. %D 2018 %K mdwarf radius %T A search for radius inflation among active M-dwarfs in Praesepe %U http://arxiv.org/abs/1811.11232 %X Rotation periods from Kepler K2 are combined with projected rotation velocities from the WIYN 3.5-m telescope, to determine projected radii for fast-rotating, low-mass ($0.15 M/M_ødot 0.6$) members of the Praesepe cluster. A maximum likelihood analysis that accounts for observational uncertainties, binarity and censored data, yields marginal evidence for radius inflation -- the average radius of these stars is $6\pm4$ per cent larger at a given luminosity than predicted by commonly-used evolutionary models. This over-radius is smaller (at 2-sigma confidence) than was found for similar stars in the younger Pleiades using a similar analysis; any decline appears due to changes occurring in higher mass ($>0.25 M_ødot$) stars. Models incorporating magnetic inhibition of convection predict an over-radius, but do not reproduce this mass dependence unless super-equipartition surface magnetic fields are present at lower masses. Models incorporating flux-blocking by starspots can explain the mass dependence but there is no evidence that spot coverage diminishes between the Pleiades and Praesepe samples to accompany the decline in over-radius. The fastest rotating stars in both Praesepe and the Pleiades are significantly smaller than the slowest rotators for which a projected radius can be measured. This may be a selection effect caused by more efficient angular momentum loss in larger stars leading to their progressive exclusion from the analysed samples. Our analyses assume random spin-axis orientations; any alignment in Praesepe, as suggested by Kovacs (2018), is strongly disfavoured by the broad distribution of projected radii.

@misc{jackson2018search, abstract = {Rotation periods from Kepler K2 are combined with projected rotation velocities from the WIYN 3.5-m telescope, to determine projected radii for fast-rotating, low-mass ($0.15 \leq M/M_{\odot} \leq 0.6$) members of the Praesepe cluster. A maximum likelihood analysis that accounts for observational uncertainties, binarity and censored data, yields marginal evidence for radius inflation -- the average radius of these stars is $6\pm4$ per cent larger at a given luminosity than predicted by commonly-used evolutionary models. This over-radius is smaller (at 2-sigma confidence) than was found for similar stars in the younger Pleiades using a similar analysis; any decline appears due to changes occurring in higher mass ($>0.25 M_{\odot}$) stars. Models incorporating magnetic inhibition of convection predict an over-radius, but do not reproduce this mass dependence unless super-equipartition surface magnetic fields are present at lower masses. Models incorporating flux-blocking by starspots can explain the mass dependence but there is no evidence that spot coverage diminishes between the Pleiades and Praesepe samples to accompany the decline in over-radius. The fastest rotating stars in both Praesepe and the Pleiades are significantly smaller than the slowest rotators for which a projected radius can be measured. This may be a selection effect caused by more efficient angular momentum loss in larger stars leading to their progressive exclusion from the analysed samples. Our analyses assume random spin-axis orientations; any alignment in Praesepe, as suggested by Kovacs (2018), is strongly disfavoured by the broad distribution of projected radii.}, added-at = {2018-11-29T17:10:23.000+0100}, author = {Jackson, R. J. and Jeffries, R. D. and Deliyannis, Constantine P. and Sun, Qinghui and Douglas, Stephanie T.}, biburl = {https://www.bibsonomy.org/bibtex/2f438524da9ece9ad5f1d75d7033d2198/superjenwinters}, description = {A search for radius inflation among active M-dwarfs in Praesepe}, interhash = {c56fc8db928faa134d9298c804c8ece2}, intrahash = {f438524da9ece9ad5f1d75d7033d2198}, keywords = {mdwarf radius}, note = {cite arxiv:1811.11232Comment: Accepted version for publication in MNRAS, 14 pages}, timestamp = {2018-11-29T17:10:23.000+0100}, title = {A search for radius inflation among active M-dwarfs in Praesepe}, url = {http://arxiv.org/abs/1811.11232}, year = 2018 }