ExoplaNeT accRetion mOnitoring sPectroscopic surveY (ENTROPY): I. Evidence for magnetospheric accretion in the young isolated planetary-mass object 2MASS J11151597+1937266
OPEN ACCESS
Loading...
Author / Producer
Date
2024-11
Publication Type
Journal Article
ETH Bibliography
yes
Citations
Altmetric
OPEN ACCESS
Data
Rights / License
Abstract
Context: Accretion among planetary mass companions is a poorly understood phenomenon, due to the lack of both observational and theoretical studies. The detection of emission lines from accreting gas giants facilitates detailed investigations into this process.
Aims: This work presents a detailed analysis of Balmer lines from one of the few known young, planetary-mass objects with observed emission, the isolated L2γ dwarf 2MASS J11151597+1937266 with a mass between 7 and 21 M_Jup and an age of 5–45 Myr, located at 45 ± 2 pc.
Methods: We obtained the first high-resolution (R ~ 50 000) spectrum of the target with VLT/UVES, an echelle spectrograph operating in the near-ultraviolet to visible wavelengths (3200–6800 Å).
Results: We report several resolved hydrogen (H I; H3–H6) and helium (He I; λ5875.6) emission lines in the spectrum. Based on the asymmetric line profiles of Hα and Hβ, the 10% width of Hα (199 ± 1 km s⁻¹), tentative He I λ6678 emission, and indications of a disk from mid-infrared 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 RJup. Analysis of observed H I profiles using a 1D planet-surface shock model implies a pre-shock gas velocity, v₀ = 120₋₄₀⁺⁸⁰ km s⁻¹, and a pre-shock density, log(n₀/cm⁻³) = 14₋₅⁺⁰. The pre-shock velocity points to a mass, Mₚ = 6−4⁺⁸ M_Jup, for the target. Combining H I line luminosities (L_line) and planetary L_line−L_acc (accretion luminosity) scaling relations, we derived a mass accretion rate, Ṁacc = 1.4₋₀.₉⁺².⁸ × 10⁻⁸ M_Jup yr⁻¹.
Conclusions: The line-emitting area predicted from the planet-surface shock model is very small (~0.03%), and points to a shock at the base of a magnetospherically induced funnel. The Hα profile exhibits a much stronger flux than predicted by the model that best fits the rest of the H I profiles, indicating that another mechanism than shock emission contributes to the Hα emission. Comparison of line fluxes and Ṁacc from archival moderate-resolution SDSS spectra indicate variable accretion at 2MASS J11151597+1937266.
Permanent link
Publication status
published
External links
Editor
Book title
Journal / series
Volume
691
Pages / Article No.
Publisher
EDP Sciences
Event
Edition / version
Methods
Software
Geographic location
Date collected
Date created
Subject
accretion, accretion disks; line: profiles; techniques: spectroscopic; planets and satellites: individual: 2MASSJ11151597+1937266; brown dwarfs
Organisational unit
09745 - Szulágyi, Judit (ehemalig) / Szulágyi, Judit (former)