Glaciation on the Arctic Slope of the Brooks Range, Northern Alaska

Reconstructs glacial history of the area (approx. 68-69 30 N, 147-162 W) on the basis of observations during 1944-1953 of the nature and extent of glacial deposits in the central part of the Range between Shainin and Itkillik Lakes and in the southern part of the Foothills Province from the Shaviovik River west to Etivluk River. Distribution is mapped and characteristics described of deposits from six glaciations for which a tentative chronological sequence is established: Anaktuvuk and Sagavanirktok of Pre-Wisconsin age; Itkillik and Echooka of Early Wisonsin; Alapah Mountain of Late Wisconsin; and Fan Mountain of Recent age. Terrace deposits and Pleistone alluviations are mentioned

The Factory and the Beehive. IV. A Comprehensive Study of the Rotation X-Ray Activity Relation in Praesepe and the Hyades

X-ray observations of low-mass stars in open clusters are critical to understanding the dependence of magnetic activity on stellar properties and their evolution. Praesepe and the Hyades, two of the nearest, most-studied open clusters, are among the best available laboratories for examining the dependence of magnetic activity on rotation for stars with masses 21 M . We present an updated study of the rotation-X-ray activity relation in the two clusters. We updated membership catalogs that combine pre-Gaia catalogs with new catalogs based on Gaia Data Release 2. The resulting catalogs are the most inclusive ones for both clusters: 1739 Praesepe and 1315 Hyades stars. We collected X-ray detections for cluster members, for which we analyzed, re-analyzed, or collated data from ROSAT, the Chandra X-ray Observatory, the Neil Gehrels Swift Observatory, and XMM-Newton. We have detections for 326 Praesepe and 462 Hyades members, of which 273 and 164, respectively, have rotation periods - an increase of 6× relative to what was previously available. We find that at ≈700 Myr, only M dwarfs remain saturated in X-rays, with only tentative evidence for supersaturation. We also find a tight relation between the Rossby number and fractional X-ray luminosity L X/L bol in unsaturated single members, suggesting a power-law index between -3.2 and -3.9. Lastly, we find no difference in the coronal parameters between binary and single members. These results provide essential insight into the relative efficiency of magnetic heating of the stars' atmospheres, thereby informing the development of robust age-rotation-activity relations