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

TL;DR

This study searches for quiescent compact objects in wide-orbit binaries using LAMOST multi-epoch spectroscopic data, identifying 74 candidates with robust orbital solutions and highlighting the importance of long-term monitoring.

Contribution

It introduces a method combining multi-epoch LAMOST data and orbital analysis to identify compact objects in wide binaries, expanding the search capabilities with extended time baselines.

Findings

Identified 74 binary candidates with potential compact objects.

Classified 4 strong compact object candidates with main-sequence companions.

Cross-matched 16 sources with Gaia DR3, confirming orbital solutions.

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.