Isotopic ratios in the red giant component of the recurrent nova T Coronae Borealis

Autor: Thomas R. Geballe, S. G. Starrfield, U. Munari, Robert D. Gehrz, Ya. V. Pavlenko, A. Evans, Chick E Woodward, Debabrata Banerjee
Jazyk: angličtina
Rok vydání: 2020
Předmět:
ISSN: 0035-8711
Popis: We report the determination of abundances and isotopic ratios for C, O and Si in the photosphere of the red giant component of the recurrent nova T Coronae Borealis from new 2.284--2.402 $\mu$m and 3.985--4.155 $\mu$m spectroscopy. Abundances and isotopic ratios in the photosphere may be affected by (i) processes in the red giant interior which are brought to the surface during dredge-up, (ii) contamination of the red giant, either during the common envelope phase of the binary evolution or by material synthesised in recurrent nova eruptions, or a combination of the two. We find that the abundances of C, O and Si are reasonably consistent with the expected composition of a red giant after first dredge-up, as is the $^{16}$O/$^{17}$O ratio. The $^{28}$Si/$^{29}$Si ratio is found to be $8.6\pm3.0$, and that for $^{28}$Si/$^{30}$Si is $21.5\pm3.0$. The $^{12}$C/$^{13}$C ratio ($10\pm2$) is somewhat lower than expected for first dredge-up. The $^{16}$O/$^{18}$O ratio ($41\pm3$) is highly inconsistent with that expected either from red giant evolution ($\sim550$) or from contamination of the red giant by the products of a nova thermonuclear runaway. In particular the C and O isotopic ratios taken in combination are a puzzle. We urge confirmation of our results using spectroscopy at high resolution. We also encourage a thorough theoretical study of the effects on the secondary star in a recurrent nova system of contamination by ejecta having anomalous abundances and isotopic ratios.
Comment: Accepted for publication in Monthly Notices of the Royal Astronomical Society on August 26th. 11 pages, 10 figures
Databáze: OpenAIRE
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