Kazan Federal University Digital Repository

Statistical equilibrium of Sr II in the atmospheres of F and G stars

Show simple item record

dc.contributor.author Belyakova E.
dc.contributor.author Mashonkina L.
dc.date.accessioned 2018-09-17T21:10:07Z
dc.date.available 2018-09-17T21:10:07Z
dc.date.issued 1997
dc.identifier.issn 1063-7729
dc.identifier.uri https://dspace.kpfu.ru/xmlui/handle/net/134615
dc.description.abstract The statistical equilibrium of Sr II in the atmospheres of stars with T eff = 5500-6500 K, logg = 1.0-4.5, and [M/H] from 0 to -3 has been analyzed for the first time. For Sr II, the pumping of excited states by chains of radiative bound-bound (b-b) transitions starting from the ground level and the subsequent photoionization from these states underlie the mechanism of departures from LTE. As a result, the upper excited levels and the Sr III continuum are overpopulated relative to the equilibrium state, the population of the ground 5s level is essentially constant, and the 5p level is depopulated when the b-b transitions are strong (in stars with [M/H] = 0 and -1) and is overpopulated when the b-b transitions from it are unable to remove the pumping produced by the resonance 5s-5p transition (stars with [M/H] = -2 and -3). As a consequence, the subordinate lines that arise during the transitions from the 5p level weaken compared to the LTE case over the entire range of the parameters, while the resonance lines strengthen for [M/H] = 0 and -1 and weakened for [M/H] = -2 and -3. In stars with normal heavy-element abundances, the departures from LTE for all Sr II lines except for the infrared triplet in the 4d-5p transition (λ10400 Å) are small: the non-LTE corrections to the strontium abundance do not exceed 0.05 dex. In metal-deficient stars, the departures from LTE increase with decreasing [M/H], with rising T eff, and with decreasing logg. For the resonance lines, the correction reverses its sign and becomes positive for [M/H] ≤ -2; its value may reach 0.4 dex for main-sequence stars and 0.8-1.2 dex for supergiants. This may be the key to explaining the observed deficiency of s-process elements relative to α-process elements in stars of the Galactic halo.
dc.relation.ispartofseries Astronomy Reports
dc.title Statistical equilibrium of Sr II in the atmospheres of F and G stars
dc.type Article
dc.relation.ispartofseries-issue 4
dc.relation.ispartofseries-volume 41
dc.collection Публикации сотрудников КФУ
dc.relation.startpage 530
dc.source.id SCOPUS10637729-1997-41-4-SID0031487132


Files in this item

This item appears in the following Collection(s)

  • Публикации сотрудников КФУ Scopus [24551]
    Коллекция содержит публикации сотрудников Казанского федерального (до 2010 года Казанского государственного) университета, проиндексированные в БД Scopus, начиная с 1970г.

Show simple item record

Search DSpace


Advanced Search

Browse

My Account

Statistics