Piercing the Glare: Direct Imaging Search for Planets in the Sirius System

TL;DR

This study used advanced high-contrast imaging to search for a hypothesized third body in the Sirius system, refuting its existence and providing new constraints on potential companions.

Contribution

First direct imaging constraints on the Sirius system that challenge previous astrometric predictions of a third companion.

Findings

No companion detected above 5-sigma in the observed data.

Refutes the existence of Sirius C as previously suggested.

Sets new upper limits on companion masses at various separations.

Abstract

Astrometric monitoring of the Sirius binary system over the past century has yielded several predictions for an unseen third system component, the most recent one suggesting a \leq50 MJup object in a ~6.3-year orbit around Sirius A. Here we present two epochs of high-contrast imaging observations performed with Subaru IRCS and AO188 in the 4.05 \mum narrow-band Br alpha filter. These data surpass previous observations by an order of magnitude in detectable companion mass, allowing us to probe the relevant separation range down to the planetary mass regime (6-12 M_Jup at 1", 2-4 M_Jup at 2", and 1.6 M_Jup beyond 4"). We complement these data with one epoch of M-band observations from MMT/AO Clio, which reach comparable performance. No dataset reveals any companion candidates above the 5-sigma level, allowing us to refute the existence of Sirius C as suggested by the previous astrometric analysis. Furthermore, our Br alpha photometry of Sirius B confirms the lack of an infrared excess beyond the white dwarf's blackbody spectrum.