Magellan Adaptive Optics Imaging of PDS 70: Measuring the Mass Accretion Rate of a Young Giant Planet within a Gapped Disk

By K. Wagner, K. Follette, L. Close, D. Apai, A. Gibbs, M. Keppler, A. Müller, Th. Henning, M. Kasper, Ya-Lin Wu and 4 more. Astrophysical Journal Letters, 2018

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PDS 70b is a recently discovered and directly imaged exoplanet within the wide (≳40 au) cavity around PDS 70. Ongoing accretion onto the central star suggests that accretion onto PDS 70b may also be ongoing. We present the first high-contrast images at Hα (656 nm) and nearby continuum (643 nm) of PDS 70 utilizing the MagAO system. The combination of these filters allows for the accretion rate of the young planet to be inferred, as hot infalling hydrogen gas will emit strongly at Hα over the optical continuum. We detected a source in Hα at the position of PDS 70b on two sequential nights in 2018 May, for which we establish a false positive probability of <0.1%. We conclude that PDS 70b is a young, actively accreting planet. We utilize the Hα line luminosity to derive a mass accretion rate of M˙=10−8±1 M Jup yr−1, where the large uncertainty is primarily due to the unknown amount of optical extinction from the circumstellar and circumplanetary disks. PDS 70b represents the second case of an accreting planet interior to a disk gap, and is among the early examples of a planet observed during its formation.

Subfields: Astronomy and Astrophysics, Instrumentation

View Paper: https://www.semanticscholar.org/paper/2eae69e06d4b05b3116752b294e7752f74fc0bbc

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Citations in the corpus

Discovery of a planetary-mass companion within the gap of the transition disk around PDS 70 (2018, background): “The H2 − L′ colour is as red as the >50 Myr old, very dusty companion to 2 PDS 70 has also recently been observed by MagAO, revealing a potential detection of Hα emission at the expected location of PDS 70b (Wagner et al. 2018).”
SPHERE: the exoplanet imager for the Very Large Telescope (2019, background): “An important science niche of such a system would be the detection of accreting young objects that present strong Hα emission, for instance LkCa 15 (Sallum et al. 2015) or PDS 70 (Wagner et al. 2018).”