The Pre-He White Dwarfs in Eclipsing Binaries. V. TIC 399725538
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arXiv
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| Format: | Preprint |
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2026
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| _version_ | 1866910004353695744 |
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| author | Lee, Jae Woo Hong, Kyeongsoo Jeong, Min-Ji Rittipruk, Pakakaew Park, Jang-Ho |
| author_facet | Lee, Jae Woo Hong, Kyeongsoo Jeong, Min-Ji Rittipruk, Pakakaew Park, Jang-Ho |
| contents | We present echelle spectra of TIC 399725538 obtained in Korea and Thailand to investigate the physical properties and evolutionary scenarios of EL CVn-type binaries. The time-series spectra yielded the radial velocities (RVs) of the primary component and its atmospheric parameters, $T_{\rm eff,A}=7194\pm70$ K and $v_{\rm A}\sin i=68\pm9$ km s$^{-1}$. Joint modeling of our RVs and the archival TESS data provided component masses of $M_{\rm A}=1.930\pm0.054$ $M_\odot$ and $M_{\rm B}=0.211\pm0.005$ $M_\odot$, radii of $R_{\rm A}=1.922\pm0.020$ $R_\odot$ and $R_{\rm B}=0.207\pm0.005$ $R_\odot$, and luminosities of $L_{\rm A}=8.87\pm0.39$ $L_\odot$ and $L_{\rm B}=0.546\pm0.034$ $L_\odot$. The surface gravity and distance derived from this modeling are consistent with the model-independent $\log g_{\rm B}$ obtained from the direct observables and with the Gaia distance. The third light of $l_3=0.136\pm0.003$ comes mainly from two neighboring stars, TIC 399725539 and TIC 399725544. Comparison with stellar models indicates that TIC 399725538 A lies within the instability region of $δ$ Sct$-$$γ$ Dor hybrids, whereas its extremely low-mass companion is markedly underluminous compared to theoretical white dwarf (WD) counterparts. Multifrequency analysis of the binary-subtracted residual lights revealed three significant signals, two of which correspond to aliases at two and four times the dominant frequency $f_1=0.0848$ day$^{-1}$. The $f_1$ frequency is likely a $γ$ Dor-type pulsation arising from the brighter A component, though further confirmation is required. Our results demonstrate that TIC 399725538 is a short-period EL CVn system belonging to the thick-disk population, consisting of a main-sequence $γ$ Dor pulsator and a helium-core WD precursor formed through stable mass transfer. |
| format | Preprint |
| id |
arxiv_https___arxiv_org_abs_2601_21142 |
| institution | arXiv |
| publishDate | 2026 |
| record_format | arxiv |
| spellingShingle | The Pre-He White Dwarfs in Eclipsing Binaries. V. TIC 399725538 Lee, Jae Woo Hong, Kyeongsoo Jeong, Min-Ji Rittipruk, Pakakaew Park, Jang-Ho Solar and Stellar Astrophysics We present echelle spectra of TIC 399725538 obtained in Korea and Thailand to investigate the physical properties and evolutionary scenarios of EL CVn-type binaries. The time-series spectra yielded the radial velocities (RVs) of the primary component and its atmospheric parameters, $T_{\rm eff,A}=7194\pm70$ K and $v_{\rm A}\sin i=68\pm9$ km s$^{-1}$. Joint modeling of our RVs and the archival TESS data provided component masses of $M_{\rm A}=1.930\pm0.054$ $M_\odot$ and $M_{\rm B}=0.211\pm0.005$ $M_\odot$, radii of $R_{\rm A}=1.922\pm0.020$ $R_\odot$ and $R_{\rm B}=0.207\pm0.005$ $R_\odot$, and luminosities of $L_{\rm A}=8.87\pm0.39$ $L_\odot$ and $L_{\rm B}=0.546\pm0.034$ $L_\odot$. The surface gravity and distance derived from this modeling are consistent with the model-independent $\log g_{\rm B}$ obtained from the direct observables and with the Gaia distance. The third light of $l_3=0.136\pm0.003$ comes mainly from two neighboring stars, TIC 399725539 and TIC 399725544. Comparison with stellar models indicates that TIC 399725538 A lies within the instability region of $δ$ Sct$-$$γ$ Dor hybrids, whereas its extremely low-mass companion is markedly underluminous compared to theoretical white dwarf (WD) counterparts. Multifrequency analysis of the binary-subtracted residual lights revealed three significant signals, two of which correspond to aliases at two and four times the dominant frequency $f_1=0.0848$ day$^{-1}$. The $f_1$ frequency is likely a $γ$ Dor-type pulsation arising from the brighter A component, though further confirmation is required. Our results demonstrate that TIC 399725538 is a short-period EL CVn system belonging to the thick-disk population, consisting of a main-sequence $γ$ Dor pulsator and a helium-core WD precursor formed through stable mass transfer. |
| title | The Pre-He White Dwarfs in Eclipsing Binaries. V. TIC 399725538 |
| topic | Solar and Stellar Astrophysics |
| url | https://arxiv.org/abs/2601.21142 |