WASP-69b’s Escaping Envelope Is Confined to a Tail Extending at Least 7 R<sub>p</sub>
Dakotah Tyler, Erik A. Petigura, Antonija Oklopčić, Trevor J. David
Abstract
Abstract Studying the escaping atmospheres of highly irradiated exoplanets is critical for understanding the physical mechanisms that shape the demographics of close-in planets. A number of planetary outflows have been observed as excess H/He absorption during/after transit. Such an outflow has been observed for WASP-69b by multiple groups that disagree on the geometry and velocity structure of the outflow. Here, we report the detection of this planet’s outflow using Keck/NIRSPEC for the first time. We observed the outflow 1.28 hr after egress until the target set, demonstrating the outflow extends at least 5.8 × 10 5 km or 7.5 R p This detection is significantly longer than previous observations, which report an outflow extending ∼2.2 planet radii just 1 yr prior. The outflow is blueshifted by −23 km s −1 in the planetary rest frame. We estimate a current mass-loss rate of 1 M ⊕ Gyr −1 . Our observations are most consistent with an outflow that is strongly sculpted by ram pressure from the stellar wind. However, potential variability in the outflow could be due to time-varying interactions with the stellar wind or differences in instrumental precision.