Abstract

For the first time, BVI_c observations of the Cepheid V811 Oph were obtained by using a new 60‑cm telescope at the Caucasus Mountain Observatory, Sternberg Astronomical Institute, Moscow State University (SAI MSU). An \(O{-}C\) diagram covering a time span of 124 years was plotted using photometry from old photographic and modern sky surveys. The diagram has a parabola shape, which made it possible to determine for the first time the quadratic elements of the brightness variations. Furthermore, it made it possible to calculate the rate of an evolutionary decrease in the period of V811 Oph \(dP{\text{/}}dt = - 0.00375( \pm 0.00177)\) s/year, which is consistent with the theoretical calculation results for the second intersection of the instability strip if this Cepheid is a classical one. The pulsation stability test proposed by Lombard and Koen confirmed the actual decrease in the period.

中文翻译：

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英属维尔京群岛c观测和搜寻造父变星V811 Oph时期的进化变异

摘要

在莫斯科国立大学斯特恩伯格天文研究所高加索山脉天文台（SAI MSU）使用新的60厘米望远镜首次获得了造父变星V811 Oph的BVI _c观测值。使用旧的摄影和现代天空调查中的测光法绘制了涵盖124年时间的\（O {-} C \）图。该图具有抛物线形状，这使得首次确定亮度变化的二次元素成为可能。此外，可以计算出V811 Oph期间的进化下降率\（dP {\ text {/}} dt =-0.00375（\ pm 0.00177）\）s / year，如果该造父变星是经典星云，则与不稳定带第二个交点的理论计算结果一致。Lombard和Koen提出的脉动稳定性测试证实了这一时期的实际下降。