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Title: Discovery and Early Evolution of ASASSN-19bt, the First TDE Detected by TESS
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  1. We report on spectroscopic measurements on the4f76s28S7/2∘<#comment/>→<#comment/>4f7(8S∘<#comment/>)6s6p(1P∘<#comment/>)8P9/2transition in neutral europium-151 and europium-153 at 459.4 nm. The center of gravity frequencies for the 151 and 153 isotopes, reported for the first time in this paper, to our knowledge, were found to be 652,389,757.16(34) MHz and 652,386,593.2(5) MHz, respectively. The hyperfine coefficients for the6s6p(1P∘<#comment/>)8P9/2state were found to beA(151)=−<#comment/>228.84(2)MHz,B(151)=226.9(5)MHzandA(153)=−<#comment/>101.87(6)MHz,B(153)=575.4(1.5)MHz, which all agree with previously published results except for A(153), which shows a small discrepancy. The isotope shift is found to be 3163.8(6) MHz, which also has a discrepancy with previously published results.