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The C/N ratio from FUV spectroscopy as a constraint upon the past evolution of HS0218+3229

Toloza, Odette and Gäensicke, Boris T. and Guzmán-Rincon, Laura M. and Marsh, Tom R. and Szkody, Paula and Schreiber, Matthias R. and de Martino, Domitilla and Zorotovic, Monica and El-Badry, Kareem and Koester, Detlev and Lagos, Felipe (2022) The C/N ratio from FUV spectroscopy as a constraint upon the past evolution of HS0218+3229. . (Unpublished)

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Some white dwarfs accreting from non-degenerate companions show anomalous carbon and nitrogen abundances in the photospheres of their stellar components which have been postulated to be descendants of supersoft X-ray binaries. Therefore the carbon-to-nitrogen ratio can provide constraints upon their past evolution. We fit far ultraviolet spectroscopy of the cataclysmic variable HS0218+3229 taken with the Cosmic Origins Spectrograph using Markov Chain Monte Carlo. While some parameters depend upon the amount of reddening, the carbon-to-nitrogen ratio is about one tenth of the Solar value (log C/N = −0.53^(+0.13)_(−0.14) and −0.58^(+0.16)_(−0.15) for almost no reddening and E(B-V) = 0.065, respectively, which are consistent within the uncertainties). We also provide estimates of the silicon and aluminum abundances, and upper limits for iron and oxygen. Using the measured parameters of HS0218+3229 we reconstruct its past using evolutionary simulations with MESA. We implemented Gaussian process fits to the MESA grid in order to determiner the most likely initial binary configuration of HS0218+3229. We found that an initial mass of the donor of M_(donor;i) = 0.90−0.98, M_⊙ and an initial orbital period of P_(orb;i) = 2.88 days (P_(orb;i) = 3.12−3.16 days) for an assumed white dwarf mass of M_(WD) = 0.83 M_⊙ (M_(WD) = 0.60 M_⊙) are needed to replicate the measured parameters. These configurations imply that the system did not go through a phase of quasi-steady hydrogen-burning on the white dwarf's surface. However, it could have experienced a phase of thermal timescale mass transfer in the past if the initial mass ratio was ≥1.5. We predict that HS0218+3229 will evolve into a CV with a period below the ≃80\,min period minimum for normal CVs, displaying helium and hydrogen in its spectrum.

Item Type:Report or Paper (Discussion Paper)
Related URLs:
URLURL TypeDescription Paper
Toloza, Odette0000-0002-2398-719X
Gäensicke, Boris T.0000-0002-2761-3005
Marsh, Tom R.0000-0002-2498-7589
Szkody, Paula0000-0003-4373-7777
Schreiber, Matthias R.0000-0003-3903-8009
de Martino, Domitilla0000-0002-5069-4202
Zorotovic, Monica0000-0002-4526-0469
El-Badry, Kareem0000-0002-6871-1752
Koester, Detlev0000-0002-6164-6978
Additional Information:OT was supported by a FONDECYT project 321038 and a Leverhulme Trust Research Project Grant. MRS and MZ were also supported by FONDECYT (grant 1221059). The code from (Toonen et al. 2020) was adapted for Figure 15. We thank Patrick Godon for their helpful insights on the discussion. DdM is supported by INAF-ASI grants I/037/12/0 and 2017-14-H.0 and INAF/PRIN and "Main Streams" programmes. This project has received funding from the European Research Council (ERC) under the European Union’s Horizon 2020 research and innovation programme (Grant agreement No. 101020057). DATA AVAILABILITY. The data and numerical tools used in this article can be obtained upon request to the corresponding author and after agreeing to the terms of use.
Funding AgencyGrant Number
Fondo Nacional de Desarrollo Científico y Tecnológico (FONDECYT)321038
Leverhulme TrustUNSPECIFIED
Fondo Nacional de Desarrollo Científico y Tecnológico (FONDECYT)1221059
Agenzia Spaziale Italiana (ASI)I/037/12/0
Agenzia Spaziale Italiana (ASI)2017-14-H.0
Istituto Nazionale di Astrofisica (INAF)UNSPECIFIED
European Research Council (ERC)101020057
Record Number:CaltechAUTHORS:20230130-184114442
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Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:118973
Deposited By: George Porter
Deposited On:31 Jan 2023 13:49
Last Modified:02 Jun 2023 01:29

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