Stellar Flyby Analysis for Spiral Arm Hosts with Gaia DR3
Scattered-light imaging studies have detected nearly two dozen spiral arm systems in circumstellar disks, yet the formation mechanisms for most of them are still under debate. Although existing studies can use motion measurements to distinguish leading mechanisms such as planet–disk interaction and disk self-gravity, close-in stellar flybys can induce short-lived spirals and even excite arm-driving planets into highly eccentric orbits. With unprecedented stellar location and proper-motion measurements from Gaia Data Release 3 (DR3), here we study for known spiral arm systems their flyby history with their stellar neighbors by formulating an analytical on-sky flyby framework. For stellar neighbors currently located within 10 pc of the spiral hosts, we restrict the flyby time to within the past 10⁴ yr and the flyby distance to within 10 times the disk extent in scattered light. Among a total of 12,570 neighbors that are identified in Gaia DR3 for 20 spiral systems, we do not identify credible flyby candidates for isolated systems. Our analysis suggests that a close-in recent flyby is not the dominant formation mechanism for isolated spiral systems in scattered light.
We thank the anonymous referees who provided comments and made this paper more rigorous. We thank Myriam Benisty, Gregory Herczeg, Andrew Winter, Xuesong Wang, and Bo Zhang for useful discussions. T.F. and L.S. are supported by the National Key R&D Program of China No. 2017YFA0402600, and NSFC grant Nos. 11890692, 12133008, and 12221003. T.F. and L.S. acknowledge science research grants from the China Manned Space Project with No. CMS-CSST-2021-A04. This project has received funding from the European Research Council under the European Union's Horizon 2020 research and innovation program (PROTOPLANETS, grant agreement No. 101002188). R.D. acknowledges financial support provided by the Natural Sciences and Engineering Research Council of Canada through a Discovery Grant, as well as by the Alfred P. Sloan Foundation through a Sloan Research Fellowship. L.S., B.B.R., R.D., and X.Z. acknowledge the 2022 Protoplanetary Disks and Planet Formation summer school hosted at the China Center of Advanced Science and Technology (CCAST) for discussions. The spiral arm gallery images are based on observations collected at the European Organisation for Astronomical Research in the Southern Hemisphere under ESO program 0104.C-0157(B) for AB Aur, 099.C-0685(A) for AS 205, 098.C-0760(B) for CQ Tau, 0102.C-0453(A) for DR Tau, 097.C-0536(A) for DZ Cha, 1100.C-0481(Q) for EM* SR 21, 60.A-9800(S) for HD 34282, 1104.C-0415(A) for HD 34700, 096.C-0248(B) for HD 100453, 096.C-0248(B) for HD 100546, 099.C-0601(A) for HD 142527, 097.C-0902(A) for HD 143006, 098.C-0760(B) for LkHa 330, 60.A-9389(A) for MWC 758, 095.C-0273(A) for SAO 206462, 198.C-0209(F) for TWA 7, 1104.C-0415(G) for V599 Ori, 0102.C-0778(A) for V1247 Ori, 1100.C-0481(R) for Wa Oph 6, and 098.C-0486(A) for WW Cha. This work has made use of data from the European Space Agency mission Gaia (https://www.cosmos.esa.int/gaia), processed by the Gaia Data Processing and Analysis Consortium (DPAC; https://www.cosmos.esa.int/web/gaia/dpac/consortium). Funding for the DPAC has been provided by national institutions, in particular the institutions participating in the Gaia Multilateral Agreement.