{"id":2262,"date":"2025-05-09T13:05:07","date_gmt":"2025-05-09T12:05:07","guid":{"rendered":"https:\/\/pepsi.aip.de\/?p=2262"},"modified":"2025-06-10T13:33:07","modified_gmt":"2025-06-10T12:33:07","slug":"a-search-for-maunder-minimum-candidate-stars","status":"publish","type":"post","link":"https:\/\/pepsi.aip.de\/?p=2262","title":{"rendered":"A search for Maunder-minimum candidate stars"},"content":{"rendered":"\n
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Stars with very low levels of magnetic activity provide an opportunity for a more quantitative comparison with the Sun during its Maunder minimum. We employ spectra from the RAVE survey in a search for particularly low-activity stars with the goal of identifying candidates for so-called Maunder-minimum stars. Spectra were used to measure the relative flux in the cores of the Ca II infrared-triplet (IRT) lines. Those were converted to absolute emission-line fluxes and were corrected with target fluxes from high-resolution STELLA and ultra-high-resolution PEPSI spectra. Absolute Ca II IRT fluxes for a total of 78 111 RAVE dwarf stars are presented and compared with fluxes of the 123 stars from our high-resolution STELLA+PEPSI sample. RAVE fluxes appear higher than the STELLA and PEPSI fluxes by on average 19% for IRT-1, 21% for IRT-2, and 25% for IRT-3 due to their lower spectral resolution. Our sample also spans a metallicity [Fe\/H] range relative to the Sun of \u22121.5 to +0.5 dex. We confirm the strong dependency of IRT fluxes on metallicity and quantify it to be at most \u00b114% in the B\u2013V range 0.53\u20130.73. Without a metallicity correction, practically all very-low-activity RAVE dwarfs show a super-solar metallicity. After correcting for spectral resolution and for metallicity, we find 13 RAVE stars out of 13 326 (0.1%) that fall well below our empirical lower flux bound from high-resolution versus B\u2013V. For solar B\u2013V, this relates to a photospheric uncorrected radiative loss in the IRT lines of log RIRT<\/sub> = \u22124.13 (\u224820% below the solar-minimum value in late 2016). However, 11 targets turned out to be evolved stars based on their Gaia DR3 parallaxes. Two stars, TIC 352227373 (G2V) and TYC 7560-477-1 (G7V), are our only Maunder-minimum candidates from the present search. Contrary to the initial suggestion from the Mount-Wilson H&K Survey, we conclude that such stars are very rare.<\/p>\n<\/div>\n<\/div>\n<\/div>\n\n\n\n

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Metallicity-corrected RAVE Ca II IRT-1 fluxes (13 326 targets). Crosses are the possible candidate targets. Boldfaced crosses are the two MM candidates, TIC 352227373 (RAVE J191213.1- 760732) and TYC 7560-477-1 (RAVE J025410.6-383603).<\/figcaption><\/figure>\n\n\n\n

Read more: J\u00e4rvinen & Strassmeier 2025, A&A, 698, A93<\/a>; \u00a0arXiv<\/a><\/p>\n\n\n","protected":false},"excerpt":{"rendered":"

Stars with very low levels of magnetic activity provide an opportunity for a more quantitative comparison with the Sun during its Maunder minimum. We employ spectra from the RAVE survey in a search for particularly low-activity stars with the goal of identifying candidates for so-called Maunder-minimum stars. Spectra were used to measure the relative flux … Continue reading A search for Maunder-minimum candidate stars<\/span> →<\/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-2262","post","type-post","status-publish","format-standard","hentry","category-publications"],"_links":{"self":[{"href":"https:\/\/pepsi.aip.de\/index.php?rest_route=\/wp\/v2\/posts\/2262","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=2262"}],"version-history":[{"count":4,"href":"https:\/\/pepsi.aip.de\/index.php?rest_route=\/wp\/v2\/posts\/2262\/revisions"}],"predecessor-version":[{"id":2268,"href":"https:\/\/pepsi.aip.de\/index.php?rest_route=\/wp\/v2\/posts\/2262\/revisions\/2268"}],"wp:attachment":[{"href":"https:\/\/pepsi.aip.de\/index.php?rest_route=%2Fwp%2Fv2%2Fmedia&parent=2262"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/pepsi.aip.de\/index.php?rest_route=%2Fwp%2Fv2%2Fcategories&post=2262"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/pepsi.aip.de\/index.php?rest_route=%2Fwp%2Fv2%2Ftags&post=2262"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}