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Abstract Companions embedded in the cavities of transitional circumstellar disks have been observed to exhibit excess luminosity at H α , an indication that they are actively accreting. We report 5 yr (2013–2018) of monitoring of the position and H α 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 H α 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 H α 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 H α 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.
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Near-infrared Accretion Signatures from the Circumbinary Planetary-mass Companion Delorme 1 (AB)b*
Abstract Accretion signatures from bound brown dwarf and protoplanetary companions provide evidence for ongoing planet formation, and accreting substellar objects have enabled new avenues to study the astrophysical mechanisms controlling the formation and accretion processes. Delorme 1 (AB)b, a ∼30–45 Myr circumbinary planetary-mass companion, was recently discovered to exhibit strong H α emission. This suggests ongoing accretion from a circumplanetary disk, somewhat surprising given canonical gas disk dispersal timescales of 5–10 Myr. Here, we present the first NIR detection of accretion from the companion in Pa β , Pa γ , and Br γ emission lines from SOAR/TripleSpec 4.1, confirming and further informing its accreting nature. The companion shows strong line emission, with L line ≈ 1–6 × 10 −8 L ⊙ across lines and epochs, while the binary host system shows no NIR hydrogen line emission ( L line < 0.32–11 × 10 −7 L ⊙ ). Observed NIR hydrogen line ratios are more consistent with a planetary accretion shock than with local line excitation models commonly used to interpret stellar magnetospheric accretion. Using planetary accretion shock models, we derive mass accretion rate estimates of M ̇ pla ∼ 3 –4 × 10 −8 M J yr −1 , somewhat higher than expected under the standard star formation paradigm. Delorme 1 (AB)b’s high accretion rate is perhaps more consistent with formation via disk fragmentation. Delorme 1 (AB)b is the first protoplanet candidate with clear (signal-to-noise ratio ∼5) NIR hydrogen line emission.
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- Award ID(s):
- 2009816
- PAR ID:
- 10352984
- Date Published:
- Journal Name:
- The Astrophysical Journal Letters
- Volume:
- 935
- Issue:
- 1
- ISSN:
- 2041-8205
- Page Range / eLocation ID:
- L18
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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- Free Publicly Accessible Full Text
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Accepted Manuscript
- Journal Article:
- https://doi.org/10.3847/2041-8213/ac85ef
