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<article xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xmlns:ali="http://www.niso.org/schemas/ali/1.0/" article-type="research-article" dtd-version="1.2" xml:lang="en"><front><journal-meta><journal-id journal-id-type="publisher-id">Astronomy Reports</journal-id><journal-title-group><journal-title xml:lang="en">Astronomy Reports</journal-title><trans-title-group xml:lang="ru"><trans-title>Астрономический журнал</trans-title></trans-title-group></journal-title-group><issn publication-format="print">0004-6299</issn><issn publication-format="electronic">3034-5170</issn><publisher><publisher-name xml:lang="en">The Russian Academy of Sciences</publisher-name></publisher></journal-meta><article-meta><article-id pub-id-type="publisher-id">691027</article-id><article-id pub-id-type="doi">10.31857/S0004629925080042</article-id><article-id pub-id-type="edn">qikszt</article-id><article-categories><subj-group subj-group-type="toc-heading" xml:lang="en"><subject>Articles</subject></subj-group><subj-group subj-group-type="toc-heading" xml:lang="ru"><subject>СТАТЬИ</subject></subj-group><subj-group subj-group-type="article-type"><subject>Research Article</subject></subj-group></article-categories><title-group><article-title xml:lang="en">Absolute parameters and apsidal rotation of the eclipsing system V501 Mon</article-title><trans-title-group xml:lang="ru"><trans-title>Абсолютные параметры и апсидальное вращение затменной системы V501 Mon</trans-title></trans-title-group></title-group><contrib-group><contrib contrib-type="author"><name-alternatives><name xml:lang="en"><surname>Volkova</surname><given-names>A. S.</given-names></name><name xml:lang="ru"><surname>Волкова</surname><given-names>А. С.</given-names></name></name-alternatives><email>kravts@yandex.ru</email><xref ref-type="aff" rid="aff1"/><xref ref-type="aff" rid="aff2"/></contrib><contrib contrib-type="author"><name-alternatives><name xml:lang="en"><surname>Volkov</surname><given-names>I. M.</given-names></name><name xml:lang="ru"><surname>Волков</surname><given-names>И. М.</given-names></name></name-alternatives><email>hwp@yandex.ru</email><xref ref-type="aff" rid="aff1"/><xref ref-type="aff" rid="aff2"/></contrib></contrib-group><aff-alternatives id="aff1"><aff><institution xml:lang="en">Lomonosov Moscow State University</institution></aff><aff><institution xml:lang="ru">Московский государственный университет им. М. В. Ломоносова</institution></aff></aff-alternatives><aff-alternatives id="aff2"><aff><institution xml:lang="en">Sternberg Astronomical Institute, Moscow, Russia</institution></aff><aff><institution xml:lang="ru">Государственный астрономический институт им. П. К. Штернберга, Москва, Россия</institution></aff></aff-alternatives><pub-date date-type="pub" iso-8601-date="2025-08-15" publication-format="electronic"><day>15</day><month>08</month><year>2025</year></pub-date><volume>102</volume><issue>8</issue><issue-title xml:lang="en">VOL 102, NO8 (2025)</issue-title><issue-title xml:lang="ru">ТОМ 102, №8 (2025)</issue-title><fpage>683</fpage><lpage>706</lpage><history><date date-type="received" iso-8601-date="2025-09-21"><day>21</day><month>09</month><year>2025</year></date></history><permissions><copyright-statement xml:lang="en">Copyright ©; 2025, Russian Academy of Sciences</copyright-statement><copyright-statement xml:lang="ru">Copyright ©; 2025, Российская академия наук</copyright-statement><copyright-year>2025</copyright-year><copyright-holder xml:lang="en">Russian Academy of Sciences</copyright-holder><copyright-holder xml:lang="ru">Российская академия наук</copyright-holder><ali:free_to_read xmlns:ali="http://www.niso.org/schemas/ali/1.0/" start_date="2026-08-15"/></permissions><self-uri xlink:href="https://journals.eco-vector.com/0004-6299/article/view/691027">https://journals.eco-vector.com/0004-6299/article/view/691027</self-uri><abstract xml:lang="en"><p>Our photoelectric measurements over the past 30 years and a new solution of the radial velocity curve of the eclipsing star with an elliptical orbit V501 Mon (A8 + F2) allowed us to determine with high accuracy all the main parameters of the system: T1 = 7380 ± 60 K, M1 = 1.66 ± 0.03 M☉, R1 = 1.90 ± 0.02 R☉, T2 = 6920 ± 30 K, M2 = 1.47 ± 0.02 M☉, R2 = 1.58 ± 0.01 R☉. The photometric parallax determined in the study coincides with the Gaia value π = 0.00103″ within the error limits. For the first time, the apsidal rotation velocity ω̇_obs = 0.022°/year was accurately measured, which, within the error limits, matches the theoretical value: ω̇_theor = 0.024°/year, 70 % of this value being a relativistic contribution. The system possibly satisfies the condition of synchronism between rotational and orbital angular momenta. The age of the stars was determined to be 0.95 billion years. The main component is probably a pulsating variable star of the δ Scuti type (DSCT).</p></abstract><trans-abstract xml:lang="ru"><p>Наши фотоэлектрические измерения в течение последних 30 лет и новое решение кривой лучевых скоростей затменной звезды с эллиптической орбитой V501 Mon (A8 + F2) позволили определить с высокой точностью все основные параметры системы: T1 = 7380 ± 60 K, M1 = 1.66 ± 0.03 M☉, R1 = 1.90 ± 0.02 R☉, T2 = 6920 ± 30 K, M2 = 1.47 ± 0.02 M☉, R2 = 1.58 ± 0.01 R☉. Определенный в исследовании фотометрический параллакс в пределах ошибок равен значению Gaia π = 0.00103″. Впервые точно измерена скорость апсидального вращения ω̇_obs = 0.022°/год, которая в пределах ошибок совпала с теоретическим значением: ω̇_theor = 0.024°/год, 70 % этой величины являются релятивистским вкладом. В системе возможно выполняется условие синхронизма между вращательными и орбитальным моментами. Возраст звезд составляет 0.95 млрд лет. Главный компонент, вероятно, является пульсирующей переменной звездой типа δ Щита (DSCT).</p></trans-abstract><kwd-group xml:lang="en"><kwd>eclipsing binary stars</kwd><kwd>fundamental parameters of stars</kwd><kwd>individual stars (V501 Mon)</kwd><kwd>photometric observations</kwd></kwd-group><kwd-group xml:lang="ru"><kwd>двойные затменные звезды</kwd><kwd>фундаментальные параметры звезд</kwd><kwd>индивидуальные звезды (V501 Mon)</kwd><kwd>фотометрия звезд</kwd></kwd-group><funding-group/></article-meta></front><body></body><back><ref-list><ref id="B1"><label>1.</label><mixed-citation>A.A. Wachmann, Astron. Abhandlungen der Hamburger Sternwarte 7(7), 341 (1966).</mixed-citation></ref><ref id="B2"><label>2.</label><mixed-citation>G. Torres, C.H. Sandberg Lacy, K. Pavlovski, F.C. Fekel, and M.W. Muterspaugh, Astron. J. 150(5), id. 154 (2015).</mixed-citation></ref><ref id="B3"><label>3.</label><mixed-citation>H. Bossen and P. 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