New high-speed photometry of EH Lib and a binary interpretation of its period change期刊界 All Journals 搜尽天下杂志传播学术成果专业期刊搜索期刊信息化学术搜索

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New high-speed photometry of EH Lib and a binary interpretation of its period change

Institution:	Beijing Observatory China

Abstract:	Six times of maxima of the ultrashort-period cepheid variable EH Librae were measured in 1980 May to June and in 1981 January, with a three-channel photocounting high-speed photoelectric photometer. These, together with all the photoelectric times of maxima over the past 30 years, are used to re-examine the nature of the change of the period. We found that we can fix the times of maxima by the following formula $T_{max} = T_{0} +P_{0} E+ 12 βE^{2} +A sin 2π EP_{0} E_{0}$ where T₀ = HJD 2433438.6088 and P₀ = 0.0884132445 d represent the initial maximum epoch and the pulsation period, β = ?2.8 × 10^?8/yr; A = 0.0015 d, P₀ = 6251 d = 17.1 yr are the semi-amplitude and the period of the sine curve, and E is the number of periods elapsed since T₀, and (E₀ = 70700).If we interpret this 17.1 year periodicity as a modulation of the phase of maximum by binary motion, then the semi-amplitude of the orbital radial velocity variation is K = 2πasini/E₀ = 0.45 km/s and the mass function is $f(m)= m^{3}_{2} sin^{3} i (m_{1} m_{2})^{2} = (a sin i)^{3} E^{2}_{0} =6 x 10^{?5} M_{⊙}$

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