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arXiv · 2209.13924

A White Dwarf-Main Sequence Binary Unveiled by Time-Domain Observations from LAMOST and TESS

Ling-Lin Zheng·Wei-Min Gu·Mouyuan Sun·Zhixiang Zhang·Tuan Yi·Jianfeng Wu·Junfeng Wang·Jin-Bo Fu·Sen-Yu Qi·Fan Yang·Song Wang·Liang Wang·Zhongrui Bai·Haotong Zhang·Chun-Qian Li·Jian-Rong Shi·Weikai Zong·Yu Bai·Jifeng Liu
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Abstract

We report a single-lined white dwarf-main sequence binary system, LAMOST J172900.17+652952.8, which is discovered by LAMOST's medium resolution time-domain surveys. The radial velocity semi-amplitude and orbital period of the optical visible star are measured by using the Palomar 200-inch telescope follow-up observations and the light curves from TESS. Thus the mass function of the invisible candidate white dwarf is derived, $f(M_{\rm{2}}) = 0.120\,\pm\,0.003\,M_{\odot}$. The mass of the visible star is measured based on the spectral energy distribution fitting, $M_{\mathrm{1}}$ = $0.81^{+0.07}_{-0.06}\,M_{\odot}$. Hence, the mass of its invisible companion is $M_{\rm{2}}\,\gtrsim\,0.63\,M_{\odot}$. The companion ought to be a compact object rather than a main-sequence star owing to the mass ratio $q = M_{\rm{2}} / M_{\rm 1} \gtrsim 0.78$ and the single-lined spectra. The compact object is likely to be a white dwarf except for small inclination angle, $i\,\lesssim\,40^{\circ}$. By using the GALEX NUV flux, the effective temperature of the white dwarf candidate is constrained as $T_{\rm eff}^{\rm WD}\,\lesssim\,12000-13500$ K. It is difficult to detect white dwarfs which are outshone by their bright companions via single-epoch optical spectroscopic surveys. Therefore, the optical time-domain surveys can play an important role in unveiling invisible white dwarfs and other compact objects in binaries.

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Ling-Lin Zheng, Wei-Min Gu, Mouyuan Sun, Zhixiang Zhang, Tuan Yi, Jianfeng Wu, Junfeng Wang, Jin-Bo Fu, Sen-Yu Qi, Fan Yang, Song Wang, Liang Wang, Zhongrui Bai, Haotong Zhang, Chun-Qian Li, Jian-Rong Shi, Weikai Zong, Yu Bai, Jifeng Liu. 2022-09-28. A White Dwarf-Main Sequence Binary Unveiled by Time-Domain Observations from LAMOST and TESS. https://doi.org/10.3847/1538-4357%2Fac853f

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