An Imaging Search for Post-Main-Sequence Planets of Sirius B

TL;DR

This study uses high-contrast imaging to search for post-main-sequence planets around Sirius B, setting new mass sensitivity limits and demonstrating the technique's effectiveness for nearby white dwarfs.

Contribution

It provides the first deep imaging constraints on planetary companions around Sirius B, achieving sub-Jupiter mass sensitivities at close separations.

Findings

No companions detected around Sirius B.

Achieved sensitivity to planets as small as 0.7-1.2 Jupiter masses beyond 1 AU.

Demonstrated the potential of high-contrast imaging for studying nearby white dwarfs.

Abstract

We present deep imaging of Sirius B, the closest and brightest white dwarf, to constrain post-main-sequence planetary evolution in the Sirius system. We use Keck/NIRC2 in L'-band (3.776 $\mu$m) across three epochs in 2020 using the technique of angular differential imaging. Our observations are speckle-limited out to 1 AU and background-limited beyond. The 5$\sigma$ detection limits from our best performing epoch are 17 to 20.4 L' absolute magnitude. We consider multiple planetary formation pathways in the context of Sirius B's evolution to derive mass sensitivity limits, and achieve sub-Jupiter sensitivities at sub-AU separations, reaching 1.6 $\mathrm{M_J}$ to 2.4 $\mathrm{M_J}$ at 0.5 AU down to a sensitivity of 0.7 $\mathrm{M_J}$ to 1.2 $\mathrm{M_J}$ at >1 AU. Consistent with previous results, we do not detect any companions around Sirius B. Our strong detection limits demonstrate the potential of using high-contrast imaging to characterize nearby white dwarfs.