Drums in the Deep: constraining the orbit and photometric variability of the chasm-carving M-dwarf HD 142527B

Cavities and gaps in circumstellar disks are predicted to be sites of planet formation. The HD 142527 system hosts the widest cavity of the observed transition disk population (~140AU, Avenhaus et al. 2014, Yamaguchi et al. 2020), but it remains unclear what mechanism has carved the gap (a single companion? photoevaporation? a multiplanet system?) . The M-dwarf companion HD 142527B, at ~13AU (Biller et al. 2012), is expected to contribute substantially to the size of the cavity, but the extent to which its motion alone can explain the disk morphology is under debate (Price et al 2018). Models show that additional widely separated giant planets within the cavity can replicate the disk structure (Casassus 2012), but these planets remain undetected. With multi-epoch Hα and continuum detections of HD 142527B from the visible light Magellan Adaptive Optics camera VisAO, we present monitoring of orbital motion and photometric variability of HD142527B over 5 years. We use a python implementation of Karhounen-Lourve Image Processing (pyKLIP) to forward model the companion, and a Bayesian MCMC method to sample the position of the embedded, accreting companion to constrain the astrometry to milli-arcsecond accuracy. We demonstrate the construction of a library of potential orbit fits to the astrometry using the orbitize! tool (Blunt 2020). Constraining the orbit of the companion will indicate the extent to which the morphology of the disk can be explained by the M-dwarf companion alone, and the data inform broader questions regarding the orbital dynamics and accretion variability of companions embedded within transitional disks.