Improved Orbital Constraints and Hα Photometric Monitoring of the Directly Imaged Protoplanet Analog HD 142527 B

Abstract

Companions embedded in the cavities of transitional circumstellar disks have been observed to exhibit excess luminosity at Hα, an indication that they are actively accreting. We report 5 yr (2013–2018) of monitoring of the position and Hα excess luminosity of the embedded, accreting low-mass stellar companion HD 142527 B from the MagAO/VisAO instrument. We use pyklip, a Python implementation of the Karhunen–Loeve Image Processing algorithm, to detect the companion. Using pyklip forward modeling, we constrain the relative astrometry to 1–2 mas precision and achieve sufficient photometric precision (±0.2 mag, 3% error) to detect changes in the Hα contrast of the companion over time. In order to accurately determine the relative astrometry of the companion, we conduct an astrometric calibration of the MagAO/VisAO camera against 20 yr of Keck/NIRC2 images of the Trapezium cluster. We demonstrate agreement of our VisAO astrometry with other published positions for HD 142527 B, and use orbitize! to generate a posterior distribution of orbits fit to the relative astrometry of HD 142527 B. Our data suggest that the companion is close to periastron passage, on an orbit significantly misaligned with respect to both the wide circumbinary disk and the recently observed inner disk encircling HD 142527 A. We translate observed Hα contrasts for HD 142527 B into mass accretion rate estimates on the order of 4–9 × 10−10 M ⊙ yr−1. Photometric variation in the Hα excess of the companion suggests that the accretion rate onto the companion is variable. This work represents a significant step toward observing accretion-driven variability onto protoplanets, such as PDS 70 b&c.

ISPY: NACO Imaging Survey for Planets around Young stars

“…An accreting stellar companion is located within the cavity (Biller et al 2012;Close et al 2014) at ∼ 0 . 063 (Cugno et al 2019a;Balmer et al 2022) on an orbit misaligned with the outer disk (Lacour et al 2016;Balmer et al 2022). Being so close to its host, HD142527 B falls at a separation smaller than the angular resolution of our NaCo observations (λ/D ≈ 0 .…”

The Giant Accreting Protoplanet Survey (GAPlanetS): Optimization Techniques for Robust Detections of Protoplanets

“…This was not the case for the GAPlanetS data collected on 2017 February 10, for which the companion was undetectable at signal-to-noise ratio (S/N) greater than 3 using any KLIP parameters. This is likely due to the limited rotation of this data set (16°.1) and the companion's tight separation (44.29 ± 2.57 mas; Balmer et al 2022).…”

“…This work focuses on the transitional disk system HD 142527, which has a known -+ M 0.26 0.14 0.16  (Claudi et al 2019) companion (Close et al 2008;Biller et al 2012, HD 142527 B) at separations ranging from 12.38 to 22.89 au (Balmer et al 2022). In particular, we are interested in HD 142527 epochs where the companion is detectable with a range of KLIP parameters.…”

“…The properties of the data sets used are described in Table 1. Astrometry and photometry of the HD 142527 B companion from these data sets are discussed in detail in Balmer et al (2022).…”

“…To this end, we injected planetary signals into the raw continuum image sequences (culled according to the chosen "data quality" cuts). The continuum images were chosen in order to reduce the influence of the companion on the results, though we note that it is recoverable at moderate S/N (S/N = 2-6; Balmer et al 2022) in continuum wavelengths. In the case of HD 142527, we injected planets away from the companion to mitigate its effects, which are then limited to an inflation of the noise statistics at the companion's separation.…”