The Giant Accreting Protoplanet Survey (GAPlanetS)

We are entering an exciting era where it is becoming possible to directly observe the assembly of giant planets. We present a trio of recent results from the Giant Accreting Protoplanet Survey (GAPlanetS), a five year visible light high contrast imaging campaign targeting the fifteen brightest Southern Hemisphere transitional disks with the Magellan Adaptive Optics System. The GAPlanetS survey leveraged the reduced contrast between accreting protoplanets and their host stars at the wavelength of the H-alpha accretion emission line to detect accreting companions at separations of 0.1-0.25” from their host stars. These measurements confirmed the existence of companions inside the cleared gaps and cavities of their host disks, and enabled estimates of their mass accretion rates. In the first result, we report new astrometry and photometric H-alpha variability measurements for the HD142527B stellar companion. We find that its accretion rate is variable on daily to yearly timescales and that it may be responsible for sculpting the very wide (~100AU) gap in the HD142527 circumstellar disk, despite it’s close current separation (~13au). In the second result, we present and validate a new methodology for optimizing parameters of the computationally intensive KLIP alorithm for recovery of directly imaged exoplanets. We demonstrate that selection of KLIP parameters for GAPlanetS datasets based on optimization of false planet signals injected into continuum (642nm) images results in high fidelity detections of, and SNR improvements in, known companions at H-alpha (656nm). In the final result, we present detection limits for all of the GAPlanetS datasets, using this KLIP optimization technique to achieve maximum contrast. These results and techniques from GAPlanetS will be critical in planning for next generation accreting protoplanet surveys, including with the new MagAO-X system.