H$\alpha$ and He I absorption in HAT-P-32 b observed with CARMENES -- Detection of Roche lobe overflow and mass loss

TL;DR

This study detects Roche lobe overflow and atmospheric mass loss in HAT-P-32 b through high-resolution spectroscopy, X-ray observations, and hydrodynamic modeling, revealing complex atmospheric dynamics and significant planetary mass loss.

Contribution

It presents the first combined high-resolution spectral and X-ray analysis of HAT-P-32 b, demonstrating Roche lobe overflow and detailed atmospheric escape mechanisms.

Findings

Detection of time-dependent Halpha and He I absorption signals.

Mass-loss rate estimated at about 1e13 g/s.

Observation of early ingress and redshifted absorption components.

Abstract

We analyze two high-resolution spectral transit time series of the hot Jupiter HAT-P-32 b obtained with the CARMENES spectrograph. Our new XMM-Newton X-ray observations of the system show that the fast-rotating F-type host star exhibits a high X-ray luminosity of 2.3e29~erg/s (5-100 A), corresponding to a flux of 6.9e4 erg/cm**2/s at the planetary orbit, which results in an energy-limited escape estimate of about 1e13 g/s for the planetary mass-loss rate. The spectral time series show significant, time-dependent absorption in the Halpha and He I triplet lines with maximum depths of about 3.3% and 5.3%. The mid-transit absorption signals in the Halpha and He I lines are consistent with results from one-dimensional hydrodynamic modeling, which also yields mass-loss rates on the order of 1e13 g/s. We observe an early ingress of a redshifted component of the transmission signal, which extends into a redshifted absorption component, persisting until about the middle of the optical transit. While a super-rotating wind can explain redshifted ingress absorption, we find that an up-orbit stream, transporting planetary mass in the direction of the star, also provides a plausible explanation for the pre-transit signal. This makes HAT-P-32 a benchmark system for exploring atmospheric dynamics via transmission spectroscopy.