New Links between Pulsation and Stellar History

TL;DR

This paper explores the formation and history of Cepheid stars through multi-method observations, including space and ground-based studies, revealing new insights into their companions and orbital characteristics.

Contribution

It introduces a multi-approach study combining space telescopes and ground observations to investigate Cepheid formation, companions, and orbital parameters.

Findings

Identification of possible stellar companions to Cepheids.

Confirmation of young low-mass companions via X-ray observations.

Refined orbital parameters for V350 Sgr.

Abstract

New instrumentation is providing new insights into intermediate mass pulsating Cepheids, particularly about their formation and history. Three approaches are discussed, using space (Hubble and Chandra) and ground-based studies (radial velocities). First, we are conducting a survey of Cepheids with the Hubble Space Telescope Wide Field Camera 3 (WFC3) to identify possible resolved companions (for example Eta Aql) and thus provide constraints on star formation. Followup X-ray observations (Chandra and XMM-Newton) can confirm whether possible low mass companions are young enough to be physical companions of Cepheids. In a related study of intermediate mass stars, Chandra X-ray observations of late B stars in Tr 16 have been used to determine the fraction which have X-ray active low mass companions. Finally, the Tennessee State Automatic Spectroscopic Telescope AST and the Moscow University group have obtained velocities of a number of Cepheids. As an example, the orbit of V350 Sgr has been redetermined, providing a new level of accuracy to the orbital velocity amplitude, which is needed for mass determination.