While the majority of massive stars have a stellar companion, most pulsars appear to be isolated. Taken at face value, this suggests that most massive binaries break apart due to strong natal kicks received in supernova explosions. However, the observed binary fraction can still be subject to strong selection effects, as monitoring of newly discovered pulsars is rarely carried out for long enough to conclusively rule out multiplicity. Here, we use the second Gaia Data Release (DR2) to search for companions to 1534 rotation-powered pulsars with positions known to better than 0.5 arcseconds. We find 22 matches to known pulsars, including one not reported elsewhere, and 8 new possible companions to young pulsars. We examine the photometric and kinematic properties of these systems and provide empirical relations for identifying Gaia sources with potential millisecond pulsar companions. Our results confirm that the observed multiplicity fraction is small. However, we show that the number of binaries below the sensitivity of Gaia and radio timing in our sample could still be significantly higher. We constrain the binary fraction of young pulsars to be $f_{\rm young}^{\rm true}\leq 5.3(8.3)\%$ under realistic(conservative) assumptions for the binary properties and current sensitivity thresholds. For massive stars ($\geq 10$ M$_{\odot}$) in particular, we find $f_{\rm OB}^{\rm true}\leq 3.7\%$ which sets a firm independent upper limit on the galactic neutron-star merger rate, $\leq 7.2\times 10^{-4}$ yr$^{-1}$. Ongoing and future projects such as the CHIME/pulsar program, MeerTime, HIRAX and ultimately the SKA, will significantly improve these constraints in the future.
Modelling the Future of Gaia Neutron Star-Main Sequence Binaries: From Eccentric Orbits to Millisecond Pulsar-White Dwarfs
Northwestern University（西北大学）；NSF-Simons AI Institute for the Sky (SkAI)（NSF-Simons 天空人工智能研究所）；University of California, San Diego（加州大学圣地亚哥分校）；California Institute of Technology（加州理工学院）
A Census of Pulsars in Possible Association with Galactic Open Clusters
School of Physics and Technology, Wuhan University（武汉大学物理科学与技术学院）；Department of Physics, Faculty of Arts and Sciences, Beijing Normal University（北京师范大学文理学院物理系）；Advanced Institute of Natural Sciences, Beijing Normal University（北京师范大学前沿科学中心）；Institute for Gravitational Wave Astronomy, Henan Academy of Sciences（河南省科学院引力波天文研究院）；Shanghai Astronomical Observatory, Chinese Academy of Sciences（中国科学院上海天文台）；Institute for Frontier in Astronomy and Astrophysics, Beijing Normal University（北京师范大学天文与空间科学学院）
California Institute of Technology（加州理工学院）；University of California, Los Angeles（加州大学洛杉矶分校）；Mani L. Bhaumik Institute for Theoretical Physics（马尼·L·巴乌米克理论物理研究所）
