Near-infrared Accretion Signatures from the Circumbinary Planetary Mass Companion Delorme 1 (AB)b

Abstract

Accretion signatures from bound brown dwarf and protoplanetary companions provide evidence for ongoing planet formation, and accreting substellar objects have enabled new avenues to study the astrophysical mechanisms controlling formation and accretion processes. Delorme 1 (AB)b, a ~30-45 Myr circumbinary planetary mass companion, was recently discovered to exhibit strong H$\alpha$ emission. This suggests ongoing accretion from a circumplanetary disk, somewhat surprising given canonical gas disk dispersal timescales of 5-10 Myr. Here, we present the first NIR detection of accretion from the companion in Pa$\beta$, Pa$\gamma$, and Br$\gamma$ emission lines from SOAR/TripleSpec 4.1, confirming and further informing its accreting nature. The companion shows strong line emission, with $L_{line}\approx 1-6\times 10^{-8}{L}_{\odot }$ across lines and epochs, while the binary host system shows no NIR hydrogen line emission ($L_{line}<0.32-11\times 10^{-7}{L}_{\odot }$). Observed NIR hydrogen line ratios are more consistent with a planetary accretion shock than with local line excitation models commonly used to interpret stellar magnetospheric accretion. Using planetary accretion shock models, we derive mass accretion rate estimates of ${\dot{M}}_{\mathrm{pla}}\sim 3$-$4\times 10^{-8}{M}_{\mathrm{J}}$ yr${}^{-1}$, somewhat higher than expected under the standard star formation paradigm. Delorme 1 (AB)b's high accretion rate is perhaps more consistent with formation via disk fragmentation. Delorme 1 (AB)b is the first protoplanet candidate with clear (S/N$\sim$5) NIR hydrogen line emission.

Accepted for publication in ApJL

References in corpus (16)

• Two accreting protoplanets around the young star PDS 70
• X-Shooter spectroscopy of young stellar objects in Lupus: Accretion properties of class II and transitional objects
• UV excess measures of accretion onto young very low-mass stars and brown dwarfs
• A Circumplanetary Disk Around PDS70c
• Probing T Tauri Accretion and Outflow with 1 Micron Spectroscopy
• The Hawaii Infrared Parallax Program. II. Young Ultracool Field Dwarfs
• BANYAN. V. A Systematic All-Sky Survey for New Very Late-Type Low-Mass Stars and Brown Dwarfs in Nearby Young Moving Groups
• The CARMENES search for exoplanets around M dwarfs. Activity indicators at visible and near-infrared wavelengths
• The properties of discs around planets and brown dwarfs as evidence for disc fragmentation
• Emission Line Variability of the Accreting Young Brown Dwarf 2MASSW J1207334-393254: From Hours to Years
• Peter Pan Disks: Long-lived Accretion Disks Around Young M Stars
• Comparison of planetary Hα-emission models: A new correlation with accretion luminosity
• Strong H$\alpha$ emission and signs of accretion in a circumbinary planetary mass companion from MUSE
• Accreting protoplanets: Spectral signatures and magnitude of gas and dust extinction at H alpha
• Physical Conditions of Accreting Gas in T Tauri Star Systems
• A Census of the Circumstellar Disk Populations in the Sco-Cen Complex

Cited by in corpus (21)

• Rotation Periods, Inclinations, and Obliquities of Cool Stars Hosting Directly Imaged Substellar Companions: Spin-Orbit Misalignments are Common
• JWST/NIRSpec Observations of the Planetary Mass Companion TWA 27B
• Emission line variability of young 10-30 Mjup companions : I. The case of GQ Lup b and GSC 06214-00210 b
• The Giant Accreting Protoplanet Survey (GAPlanetS) -- Results from a Six Year Campaign to Image Accreting Protoplanets
• Resolved near-UV hydrogen emission lines at 40-Myr super-Jovian protoplanet Delorme 1 (AB)b: Indications of magnetospheric accretion
• The Planetary Accretion Shock. III. Smoothing-free 2.5D simulations and calculation of H alpha emission
• Evidence for Variable Accretion onto PDS 70 c and Implications for Protoplanet Detections
• Revisiting the Helium and Hydrogen Accretion Indicators at TWA 27B: Weak Mass Flow at Near-Freefall Velocity
• Exoplanet accretion monitoring spectroscopic survey (ENTROPY) I. Evidence for magnetospheric accretion in the young isolated planetary-mass object 2MASS J11151597+1937266
• Analyzing JWST/NIRSpec Hydrogen Line Detections at TWA 27B: Constraining Accretion Properties and Geometry
• Planetary line-to-accretion luminosity scaling relations: Extrapolating to higher-order hydrogen lines
• ExoplaNeT accRetion mOnitoring sPectroscopic surveY (ENTROPY) - II. Time series of Balmer line profiles of Delorme 1(AB)b
• The planetary-mass-limit VLT/SINFONI library: Spectral extraction and atmospheric characterization via forward modeling
• Searching for Protoplanets around MWC 758 and MWC 480 in Br-$\gamma$ using Kernel Phase and SCExAO/CHARIS
• On the potential origin of the circumbinary planet Delorme 1 (AB)b
• New members of the Lupus I cloud based on Gaia astrometry Physical and accretion properties from X-Shooter spectra
• Occurrence rates of accreting companions from a new method for computing emission-line survey sensitivity: application to the H-alpha Giant Accreting Protoplanet Survey
• Planet migration in massive circumbinary discs
• Stellar halo subtraction alternative for accreting companions' characterization with integral field spectroscopy: Analytical and on-sky demonstration on the PDS70, HTLup, and YSES1 systems
• Semianalytical Accretion-Tracer Emission: Forming Planets Are Intrinsically Faint
• Atmospheric Signatures of Common Envelope Evolution in White Dwarf Planets