Probing Compact Objects in Wide-Orbit Binaries with Joint LAMOST LRS and MRS

Abstract

Wide-orbit binaries serve as crucial laboratories for understanding stellar evolution and identifying quiescent compact objects. In this work, we search for compact objects in wide-orbit binaries by merging the LAMOST multi-epoch catalogs from LRS and MRS in the 12th data release. We specifically focus on sources with at least 20 observation epochs that clearly exhibit long-term radial velocity (RV) variations while remaining essentially stationary over short time scales. By constraining the mass function with Lomb-Scargle periods and RV ranges, we identified 74 single-lined spectroscopic binary candidates harboring potential compact objects with robust orbital solutions. These systems exhibit orbital periods ranging from 10 to 1000 days, with semi-amplitudes of velocity $K_1 \lesssim 50$ ${\rm km\,s^{-1}}$ and mass functions $f(M_2)$ between 0.03 and 0.94 $M_{\odot}$. Combining $f(M_2)$ with SED-derived stellar parameters, we identify four strong compact object candidates with main-sequence companions (Class A), 9 systems likely consisting of either compact objects with giant/subgiant companions or mass-inverted Algol-type binaries (Class B), and 61 candidates with relatively lower mass ratios (Class C). Cross-matching with the \textit{Gaia} DR3 \texttt{nss\_two\_star\_orbit} catalog yields 16 sources, all of which exhibit orbital solutions consistent with our results. This study demonstrates the essential role of long-term spectroscopic monitoring in searching for compact objects in wide-orbit binaries and validating orbital solutions. The strategy of leveraging extended time baselines will be increasingly effective as spectroscopic databases continue to grow, enabling the systematic discovery of compact objects in wide orbits across the Galaxy.