Exoplanetology: Exoplanets & Exomoons

Evidence for Variable Accretion Onto PDS 70 c and Implications for Protoplanet Detections

By Keith Cowing

Status Report

astro-ph.EP

February 21, 2025

Filed under astro-ph.EP, exoplanet, imaging, PDS 70, PDS 70 b, PDS 70 c, Protoplanet, Protoplanetary Disk

Evidence for Variable Accretion Onto PDS 70 c and Implications for Protoplanet Detections — Primary-subtracted images of PDS 70 in 2020 (left) and 2024 (right). North is up and East is to the left. Color scales of the two panels are identical. The expected positions of PDS 70 b and c are marked. The white dashed line marks the inner edge of PDS 70’s outer disk in infrared scattered light. PDS 70 b is detected in both epochs and demonstrates a significant orbital motion. PDS 70 c is only detected in Epoch 2024. The apparent brightness variations in PDS 70 b and c do not accurately represent the planets’ intrinsic variability, as high-contrast imaging post-processing introduces flux loss. For a comprehensive analysis of the evidence for variability, refer to Section 3.3. astro-ph.EP

Understanding the processes of planet formation and accretion in young systems is essential to unraveling the initial conditions of planetary systems.

The PDS 70 system, which hosts two directly imaged protoplanets, provides a unique laboratory for studying these phenomena, particularly through H-alpha emission a commonly used accretion tracer. We present multi-epoch observations and examine the variability in accretion signatures within this system, focusing on PDS 70 b and c.

Using Hubble Space Telescope narrowband H-alpha imaging from 2020 and 2024, we achieve high signal-to-noise ratio detections of these planets and reveal significant changes in H-alpha flux. For PDS 70 c, the H-alpha flux more than doubled between 2020 and 2024. The trend is consistent with the one identified in recently published MagAO-X data, further confirming that PDS 70 c has become significantly brighter in H between 2023 March and 2024 May.

The observed variability suggests dynamic accretion processes, possibly modulated by circumplanetary disk properties or transient accretion bursts. High-amplitude variability in PDS 70 c motivates simultaneous monitoring of multiple accretion tracers to probe the mechanisms of mass growth of gas giant planets.

We quantify the impact of variability on the detectability of protoplanets in imaging surveys and emphasize the need for continued and regular monitoring to accurately assess the occurrence and characteristics of young, forming planets.

Yifan Zhou, Brendan P. Bowler, Aniket Sanghi, Gabriel-Dominique Marleau, Shinsuke Takasao, Yuhiko Aoyama, Yasuhiro Hasegawa, Thanawuth Thanathibodee, Taichi Uyama, Jun Hashimoto, Kevin Wagner, Nuria Calvet, Dorian Demars, Ya-Lin Wu, Lauren I. Biddle, Sebastiaan Haffert, Marta L. Bryan

Comments: See Figure 1 for new HST/WFC3 detections of PDS 70 b and c, Figures 2 and 3 for confirming the H-alpha variability of PDS 70 c. Published on ApJ Letters
Subjects: Earth and Planetary Astrophysics (astro-ph.EP)
Cite as: arXiv:2502.14024 [astro-ph.EP] (or arXiv:2502.14024v1 [astro-ph.EP] for this version)
https://doi.org/10.48550/arXiv.2502.14024
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Related DOI:
https://doi.org/10.3847/2041-8213/adb134
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Submission history
From: Yifan Zhou
[v1] Wed, 19 Feb 2025 19:00:00 UTC (679 KB)
https://arxiv.org/abs/2502.14024
Astrobiology,

Keith Cowing

Explorers Club Fellow, ex-NASA Space Station Payload manager/space biologist, Away Teams, Journalist, Lapsed climber, Synaesthete, Na’Vi-Jedi-Freman-Buddhist-mix, ASL, Devon Island and Everest Base Camp veteran, (he/him) 🖖🏻

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