VELOcities of CEpheids (VELOCE) III. Reconstructing radial velocity curves of classical Cepheids
Year: 2026
Type: article
Abstract: We present a novel framework for accurately reconstructing radial velocity (RV) curves of classical Cepheids (Cepheids) from sparsely sampled time-series data suitable for application in large spectroscopic surveys. Our framework provides a prior for the principal components of the RV curves, established based on high-precision measurements from the VELOcities of CEpheids (ěloce) project. Template RV curves of Cepheids can be readily extracted from our results. We demonstrate the ability of our framework to estimate unbiased pulsation-averaged velocities, v_γ, to within 20--30, ≃,10--15, whereas the precision on v_γ continues to improve. We fitted existing time-series RV data of Cepheids in the Large and Small Magellanic Clouds (LMC and SMC, respectively) using this framework, obtaining typical root-mean-square errors of 0.5--2.0,̨ms. The typical total uncertainty on v_γ achieved for the SMC Cepheids is ∼ 0.84,̨ms, providing sensitivity to spectroscopic binaries (SBs). We identified eight single-lined SB systems, two of which are new detections in the LMC and one in the SMC. This yields a single-lined SB fraction of ∼ 25% and 27% in the two galaxies, similar to the Milky Way's SB fraction of 29%, established as part of ěloce. Despite their relatively small number, LMC Cepheids reproduce the known line-of-sight component of the LMC's large-scale rotation, which differs in the extremes by more than 80,̨ms. The kinematics of the SMC are more complex and not sufficiently sampled by the available Cepheids. Our framework is designed to yield accurate v_γ and P2P values for Cepheids observed by large spectroscopic surveys, such as 4MOST, SDSS-V, and others, and will unlock new insights into the kinematics and multiplicity of evolved intermediate-mass stellar populations. and peak-to-peak amplitudes, P2P, to within ∼ 1.1%. By subsampling the initial dataset, we show that v_γ and P2P can be determined to within ∼ 500, . The precision on P2P stabilizes beyond N_ and ∼ 4%, respectively, using as few as three observations drawn at random pulsation phases, with the phase of minimum radius fitted rather than assumed. As expected, the precision on both v_γ and P2P improves markedly with the number of observations, N_ RV RV
Source: Astronomy and Astrophysics
Authors: Giordano Viviani, Richard I. Anderson
Language: English
Subfield: Astronomy and Astrophysics
Field: Physics and Astronomy
Domain: Physical Sciences
Open Access status: gold
Estimated APC paid: $1,865
OpenAlex ID: W7223081834