Exoplanet accretion monitoring spectroscopic survey (ENTROPY) I. Evidence for magnetospheric accretion in the young isolated planetary-mass object 2MASS J11151597+1937266

Gayathri Viswanath; Simon C. Ringqvist; Dorian Demars; Markus Janson; Mickaël Bonnefoy; Yuhiko Aoyama; Gabriel-Dominique Marleau; Catherine Dougados; Judit Szulágyi; Thanawuth Thanathibodee

doi:10.1051/0004-6361/202450881

arXiv · 2409.12187

Exoplanet accretion monitoring spectroscopic survey (ENTROPY) I. Evidence for magnetospheric accretion in the young isolated planetary-mass object 2MASS J11151597+1937266

Gayathri Viswanath·Simon C. Ringqvist·Dorian Demars·Markus Janson·Mickaël Bonnefoy·Yuhiko Aoyama·Gabriel-Dominique Marleau·Catherine Dougados·Judit Szulágyi·Thanawuth Thanathibodee

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Abstract

Accretion among planets is a poorly understood phenomenon, due to lack of both observational and theoretical studies. Detection of emission lines from accreting gas giants facilitate detailed investigations into this process. This work presents a detailed analysis of Balmer lines from one of the few known young, planetary-mass objects with observed emission, the isolated L2 dwarf 2MASS J11151597+1937266 with a mass 7-21 Mj and age 5-45 Myr, located at 45+-2 pc. We obtained the first high-resolution (R~50,000) spectrum of the target with VLT/UVES, a spectrograph in the near-UV to visible wavelengths (3200-6800 AA). We report resolved H3-H6 and He I (5875.6 AA) emission in the spectrum. Based on the asymmetric line profiles of H3 and H4, 10% width of H3 (199+-1 km/s), tentative He I 6678 AA emission and indications of a disk from MIR excess, we confirm ongoing accretion at this object. Using the Gaia update of the parallax, we revise its temperature to 1816+-63 K and radius to 1.5+-0.1 Rj. Analysis of observed H I profiles using 1D planet-surface shock model implies a pre-shock gas velocity of v0=120(+80,-40) km/s and a pre-shock density of log(n0/cm^-3)=14(+0,-5). Pre-shock velocity points to a mass of 6(+8,-4) Mj for the target. Combining the H I line luminosities and planetary Lline-Lacc scaling relations, we derive a mass accretion rate of 1.4(+2.8,-0.9)x10^-8 Mj/yr.

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Gayathri Viswanath, Simon C. Ringqvist, Dorian Demars, Markus Janson, Mickaël Bonnefoy, Yuhiko Aoyama, Gabriel-Dominique Marleau, Catherine Dougados, Judit Szulágyi, Thanawuth Thanathibodee. 2024-09-18. Exoplanet accretion monitoring spectroscopic survey (ENTROPY) I. Evidence for magnetospheric accretion in the young isolated planetary-mass object 2MASS J11151597+1937266. https://doi.org/10.1051/0004-6361/202450881

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