{"id":2240,"date":"2025-02-10T08:55:18","date_gmt":"2025-02-10T07:55:18","guid":{"rendered":"https:\/\/pepsi.aip.de\/?p=2240"},"modified":"2025-02-11T09:15:50","modified_gmt":"2025-02-11T08:15:50","slug":"testing-the-rossby-paradigm-weakened-magnetic-braking-in-early-k-type-stars","status":"publish","type":"post","link":"https:\/\/pepsi.aip.de\/?p=2240","title":{"rendered":"Testing the Rossby Paradigm: Weakened Magnetic Braking in early K-type Stars"},"content":{"rendered":"\n<p>We present new observational constraints on magnetic braking for an evolutionary sequence of six early K-type stars. To determine the wind braking torque for each of our targets, we combine spectropolarimetric constraints on the large-scale magnetic field, Ly\u03b1&nbsp;or X-ray constraints on the mass-loss rate, as well as uniform estimates of the stellar rotation period, mass, and radius. As identified previously from similar observations of hotter stars, we find that the wind braking torque decreases abruptly by more than an order of magnitude at a critical value of the stellar Rossby number. Given that all of the stars in our sample exhibit clear activity cycles, we suggest that weakened magnetic braking may coincide with the operation of a subcritical stellar dynamo.<\/p>\n\n\n\n<figure id=\"attachment_2239\" aria-describedby=\"caption-attachment-2239\" style=\"width: 1000px\" class=\"wp-caption alignnone\"><a href=\"https:\/\/pepsi.aip.de\/wp-content\/uploads\/2025\/02\/Bild1_hd166620.jpg\"><img loading=\"lazy\" decoding=\"async\" class=\"size-full wp-image-2239\" src=\"https:\/\/pepsi.aip.de\/wp-content\/uploads\/2025\/02\/Bild1_hd166620.jpg\" alt=\"\" width=\"1000\" height=\"959\" srcset=\"https:\/\/pepsi.aip.de\/wp-content\/uploads\/2025\/02\/Bild1_hd166620.jpg 1000w, https:\/\/pepsi.aip.de\/wp-content\/uploads\/2025\/02\/Bild1_hd166620-300x288.jpg 300w, https:\/\/pepsi.aip.de\/wp-content\/uploads\/2025\/02\/Bild1_hd166620-768x737.jpg 768w\" sizes=\"auto, (max-width: 1000px) 100vw, 1000px\" \/><\/a><figcaption id=\"caption-attachment-2239\" class=\"wp-caption-text\">PEPSI Stokes V polarization profile for HD166620 from LBT observations on 2024 July 5. The mean LSD profile is shown as a black line with uncertainties indicated by the gray shaded area.<\/figcaption><\/figure>\n\n\n\n<p>Read more: Metcalfe et al. 2025 <a href=\"https:\/\/ui.adsabs.harvard.edu\/#abs\/2025arXiv250119169M\/abstract\">arXiv<\/a><\/p>\n\n\n","protected":false},"excerpt":{"rendered":"<p>We present new observational constraints on magnetic braking for an evolutionary sequence of six early K-type stars. To determine the wind braking torque for each of our targets, we combine spectropolarimetric constraints on the large-scale magnetic field, Ly\u03b1&nbsp;or X-ray constraints on the mass-loss rate, as well as uniform estimates of the stellar rotation period, mass, &hellip; <a href=\"https:\/\/pepsi.aip.de\/?p=2240\" class=\"more-link\">Continue reading <span class=\"screen-reader-text\">Testing the Rossby Paradigm: Weakened Magnetic Braking in early K-type Stars<\/span> <span class=\"meta-nav\">&rarr;<\/span><\/a><\/p>\n","protected":false},"author":5,"featured_media":0,"comment_status":"closed","ping_status":"","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[11],"tags":[],"class_list":["post-2240","post","type-post","status-publish","format-standard","hentry","category-publications"],"_links":{"self":[{"href":"https:\/\/pepsi.aip.de\/index.php?rest_route=\/wp\/v2\/posts\/2240","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/pepsi.aip.de\/index.php?rest_route=\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/pepsi.aip.de\/index.php?rest_route=\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/pepsi.aip.de\/index.php?rest_route=\/wp\/v2\/users\/5"}],"replies":[{"embeddable":true,"href":"https:\/\/pepsi.aip.de\/index.php?rest_route=%2Fwp%2Fv2%2Fcomments&post=2240"}],"version-history":[{"count":3,"href":"https:\/\/pepsi.aip.de\/index.php?rest_route=\/wp\/v2\/posts\/2240\/revisions"}],"predecessor-version":[{"id":2244,"href":"https:\/\/pepsi.aip.de\/index.php?rest_route=\/wp\/v2\/posts\/2240\/revisions\/2244"}],"wp:attachment":[{"href":"https:\/\/pepsi.aip.de\/index.php?rest_route=%2Fwp%2Fv2%2Fmedia&parent=2240"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/pepsi.aip.de\/index.php?rest_route=%2Fwp%2Fv2%2Fcategories&post=2240"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/pepsi.aip.de\/index.php?rest_route=%2Fwp%2Fv2%2Ftags&post=2240"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}