分类： 天文学 >> 天文学 提交时间： 2023-02-19
摘要： We present a detailed analysis of an eclipsing double-lined binary FX UMa based on TESS photometry and newly acquired spectroscopic observations. The radial velocities and atmospheric parameters for each component star are obtained from the SONG high-resolution spectra. Combined with the radial-velocity measurements, our light-curve modeling yields absolute masses and radii of the two components. The Fourier amplitude spectrum of the residual light curve reveals a total of 103 frequencies with signal-to-noise ratio (S/N) > 4, including 12 independent frequencies, 17 multiples of the orbital frequency (Nforb), and 74 combination frequencies. Ten Nforb peaks with S/N > 10 have very high amplitudes and are likely due to tidally excited oscillations (TEOs). The remaining Nforb peaks (4 < S/N < 10) may be originated from the imperfect removal, or they are actually real TEOs. Four anharmonic frequencies can pair up and sum to give exact harmonics of the orbital frequency, suggesting the existence of non-linear tidal processes in the eccentric binary system FX UMa. Eight independent frequencies in the range of 20 to 32 day$^{-1}$ are typical low-order pressure modes of delta Scuti pulsators.
分类： 天文学 >> 天文学 提交时间： 2023-02-19
Stephanie Monty
David Yong
Anna F. Marino
Amanda I. Karakas
Madeleine McKenzie
Frank Grundahl
Aldo Mura-Guzmán
摘要： The view of globular clusters (GCs) as simple systems continues to unravel, revealing complex objects hosting multiple chemical peculiarities. Using differential abundance analysis, we probe the chemistry of the Type I GC, NGC 288 and the Type II GC, NGC 362 at the 2\% level for the first time. We measure 20 elements and find differential measurement uncertainties on the order 0.01-0.02 dex in both clusters. The smallest uncertainties are measured for Fe I in both clusters, with an average uncertainty of $\sim$0.013 dex. Dispersion in the abundances of Na, Al, Ti I, Ni, Fe I, Y, Zr, Ba and Nd are recovered in NGC 288, none of which can be explained by a spread in He. This is the first time, to our knowledge, a statistically significant spread in $s$-process elements and a potential spread in metallicity has been detected in NGC 288. In NGC 362, we find significant dispersion in the same elements as NGC 288, with the addition of Co, Cu, Zn, Sr, La, Ce, and Eu. Two distinct groups are recovered in NGC 362, separated by 0.3 dex in average differential $s$-process abundances. Given strong correlations between Al and several $s$-process elements, and a significant correlation between Mg and Si, we propose that the $s$-process rich group is younger. This agrees with asymptotic giant branch star (AGB) enrichment between generations, if there is overlap between low- and intermediate-mass AGBs. In our scenario, the older population is dominated by the $r$-process with a $\Delta^{\mathrm{La}}-\Delta^{\mathrm{Eu}}$ ratio of $-0.16\pm0.06$. We propose that the $r$-process dominance and dispersion found in NGC 362 are primordial.
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