The TRENDS High-Contrast Imaging Survey. VII. Discovery of a Nearby Sirius-like White Dwarf System (HD 169889)

TL;DR

This paper reports the discovery of a nearby white dwarf companion orbiting a G9 V star, using long-term radial velocity monitoring and high-contrast imaging, revealing a Sirius-like binary system.

Contribution

It presents the first direct imaging and dynamical mass constraint of a white dwarf companion to a nearby star, expanding the known population of such systems.

Findings

White dwarf companion at 28 au detected via imaging

Radial velocity data shows a linear acceleration indicating a massive companion

Dynamical mass constraint of at least 0.369 solar masses

Abstract

Monitoring the long-term radial velocity (RV) and acceleration of nearby stars has proven an effective method for directly detecting binary and substellar companions. Some fraction of nearby RV trend systems are expected to be comprised of compact objects that likewise induce a systemic Doppler signal. In this paper, we report the discovery of a white dwarf companion found to orbit the nearby ($\pi = 28.297 \pm 0.066$ mas) G9 V star HD 169889. High-contrast imaging observations using NIRC2 at Keck and LMIRCam at the LBT uncover the ($\Delta H = 9.76 \pm 0.16$, $\Delta L' = 9.60 \pm 0.03$) companion at an angular separation of 0.8'' (28 au). Thirteen years of precise Doppler observations reveal a steep linear acceleration in RV time series and place a dynamical constraint on the companion mass of $M \geq 0.369 \pm 0.010 M_{\odot}$. This "Sirius-like" system adds to the census of white dwarf companions suspected to be missing in the solar neighborhood.