A massive white dwarf or low-mass neutron star discovered by LAMOST

TL;DR

This paper reports the discovery of a close binary system containing a potential massive white dwarf or neutron star, using LAMOST and TESS data, with implications for stellar evolution and supernova progenitors.

Contribution

It is the first identification of a binary with an unseen compact object of this mass range using combined spectroscopic and photometric data.

Findings

Mass of the unseen object is approximately 1.34 solar masses.

No additional spectral features or X-ray/radio signals detected from the compact object.

The system could evolve into a Type Ia supernova or a neutron star depending on the nature of the compact object.

Abstract

We report the discovery of a close binary J0606+2132 (Gaia DR3 3423365496448406272) with $P_{\rm obs}=2.77$ days containing a possible massive white dwarf or a neutron star using the LAMOST spectroscopic data. By a joint fitting of the radial velocity from LAMOST and the light curve from TESS, we derived a circular Keplerian orbit with an inclination of $i=$81.31$^{\circ}$$^{+6.26^{\circ}}_{-7.85^{\circ}}$, which is consistent with that derived from $v{\rm sin}I$. Together with the mass of the visible star, we derived the mass of the invisible object to be 1.34$^{+0.35}_{-0.40} M_{\odot}$. Spectral disentangling with the LAMOST medium-resolution spectra shows no absorption feature from an additional component, suggesting the presence of a compact object. No X-ray or radio pulsed signal is detected from ROSAT and FAST archive observations. J0606+2132 could evolve into either a Type Ia supernova or a neutron star through accretion-induced collapse if it is a white dwarf, or into an intermediate-mass X-ray binary if it is a neutron star.