Catálogo de publicaciones - revistas

<jats:title>Abstract</jats:title> <jats:p>We analyze <jats:italic>K2</jats:italic> light curves for 132 low-mass (1 <jats:italic>M</jats:italic> <jats:sub>⊙</jats:sub> ≳ <jats:italic>M</jats:italic> <jats:sub>*</jats:sub> ≳ 0.1 <jats:italic>M</jats:italic> <jats:sub>⊙</jats:sub>) members of the 600–800 Myr old Hyades cluster and measure rotation periods (<jats:inline-formula> <jats:tex-math> <?CDATA ${P}_{\mathrm{rot}}$?> </jats:tex-math> <jats:inline-graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="apjab2468ieqn1.gif" xlink:type="simple" /> </jats:inline-formula>) for 116 of these stars. These include 93 stars with no prior <jats:inline-formula> <jats:tex-math> <?CDATA ${P}_{\mathrm{rot}}$?> </jats:tex-math> <jats:inline-graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="apjab2468ieqn2.gif" xlink:type="simple" /> </jats:inline-formula> measurements; the total number of Hyads with a known <jats:inline-formula> <jats:tex-math> <?CDATA ${P}_{\mathrm{rot}}$?> </jats:tex-math> <jats:inline-graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="apjab2468ieqn3.gif" xlink:type="simple" /> </jats:inline-formula> is now 232. We then combine literature binary data with <jats:italic>Gaia</jats:italic> DR2 photometry and astrometry to select single-star sequences in the Hyades and its roughly coeval Praesepe open cluster and derive a new reddening value of <jats:italic>A</jats:italic> <jats:sub> <jats:italic>V</jats:italic> </jats:sub> = 0.035 ± 0.011 for Praesepe. Comparing the effective temperature–<jats:inline-formula> <jats:tex-math> <?CDATA ${P}_{\mathrm{rot}}$?> </jats:tex-math> <jats:inline-graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="apjab2468ieqn4.gif" xlink:type="simple" /> </jats:inline-formula> distributions for the Hyades and Praesepe, we find that solar-type Hyads rotate, on average, 0.4 day slower than their Praesepe counterparts. This <jats:inline-formula> <jats:tex-math> <?CDATA ${P}_{\mathrm{rot}}$?> </jats:tex-math> <jats:inline-graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="apjab2468ieqn5.gif" xlink:type="simple" /> </jats:inline-formula> difference indicates that the Hyades is slightly older than Praesepe: we apply a new gyrochronology model tuned with Praesepe and the Sun and find an age difference between the two clusters of 57 Myr. However, this <jats:inline-formula> <jats:tex-math> <?CDATA ${P}_{\mathrm{rot}}$?> </jats:tex-math> <jats:inline-graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="apjab2468ieqn6.gif" xlink:type="simple" /> </jats:inline-formula> difference decreases and eventually disappears for lower-mass stars. This provides further evidence for stalling in the rotational evolution of these stars and highlights the need for more detailed analysis of angular momentum evolution for stars of different masses and ages.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>We examine the different element abundances exhibited by the closed loop solar corona and the slow speed solar wind. Both are subject to the first ionization potential (FIP) effect, the enhancement in coronal abundance of elements with FIP below 10 eV (e.g., Mg, Si, Fe) with respect to high-FIP elements (e.g., O, Ne, Ar), but with subtle differences. Intermediate elements, S, P, and C, with FIP just above 10 eV, behave as high-FIP elements in closed loops, but are fractionated more like low-FIP elements in the solar wind. On the basis of FIP fractionation by the ponderomotive force in the chromosphere, we discuss fractionation scenarios where this difference might originate. Fractionation low in the chromosphere where hydrogen is neutral enhances the S, P, and C abundances. This arises with nonresonant waves, which are ubiquitous in open field regions, and is also stronger with torsional Alfvén waves, as opposed to shear (i.e., planar) waves. We discuss the bearing these findings have on models of interchange reconnection as the source of the slow speed solar wind. The outflowing solar wind must ultimately be a mixture of the plasma in the originally open and closed fields, and the proportions and degree of mixing should depend on details of the reconnection process. We also describe novel diagnostics in ultraviolet and extreme ultraviolet spectroscopy now available with these new insights, with the prospect of investigating slow speed solar wind origins and the contribution of interchange reconnection by remote sensing.</jats:p>