Peter Pan Disks: Long-lived Accretion Disks Around Young M Stars

Abstract

WISEA J080822.18-644357.3, an M star in the Carina association, exhibits extreme infrared excess and accretion activity at an age greater than the expected accretion disk lifetime. We consider J0808 as the prototypical example of a class of M star accretion disks at ages $\gtrsim 20$ Myr, which we call ``Peter Pan'' disks, since they apparently refuse to grow up. We present four new Peter Pan disk candidates identified via the Disk Detective citizen science project, coupled with \textit{Gaia} astrometry. We find that WISEA J044634.16-262756.1 and WISEA J094900.65-713803.1 both exhibit significant infrared excess after accounting for nearby stars within the 2MASS beams. The J0446 system has $>95\%$ likelihood of Columba membership. The J0949 system shows $>95\%$ likelihood of Carina membership. We present new GMOS optical spectra of all four objects, showing possible accretion signatures on all four stars. We present ground-based and \textit{TESS} lightcurves of J0808 and 2MASS J0501-4337, including a large flare and aperiodic dipping activity on J0808, and strong periodicity on J0501. We find Pa$\beta$ and Br$\gamma$ emission indicating ongoing accretion in near-IR spectroscopy of J0808. Using observed characteristics of these systems, we discuss mechanisms that lead to accretion disks at ages $\gtrsim 20$ Myr, and find that these objects most plausibly represent long-lived CO-poor primordial disks, or ``hybrid'' disks, exhibiting both debris- and primordial-disk features. The question remains: why have gas-rich disks persisted so long around these particular stars?

25 pages, 17 figures. Accepted for publication in the Astrophysical Journal

References in corpus (18)

• The NumPy array: a structure for efficient numerical computation
• New evolutionary models for pre-main sequence and main sequence low-mass stars down to the hydrogen-burning limit
• Kepler Flares I. Active and Inactive M dwarfs
• unWISE: unblurred coadds of the WISE imaging
• Kepler Flares II: The Temporal Morphology of White-Light Flares on GJ 1243
• Formation and Evolution of Planetary Systems (FEPS): Properties of Debris Dust around Solar-type Stars
• Abundant Circumstellar Silica Dust and SiO Gas Created by a Giant Hypervelocity Collision in the ~12 Myr HD172555 System
• Young Nearby Loose Associations
• Molecular gas in debris disks around young A-type stars
• All-sky Co-moving Recovery Of Nearby Young Members. (ACRONYM) II: The Beta Pictoris Moving Group
• ACRONYM III: Radial Velocities for 336 Candidate Young Low-Mass Stars in the Solar Neighborhood, Including 78 Newly Confirmed Young Moving Group Members
• BANYAN. VIII. New Low-Mass Stars and Brown Dwarfs with Candidate Circumstellar Disks
• A New M Dwarf Debris Disk Candidate in a Young Moving Group Discovered with Disk Detective
• Disk Detective: Discovery of New Circumstellar Disk Candidates through Citizen Science
• First Detection of Hydrogen in the β Pictoris Gas Disk
• New M dwarf debris disk candidates in NGC 2547
• Evidence for accretion in a nearby, young brown dwarf
• The Nearby, Young, Chi1 Fornacis Cluster: Membership, Age, and an Extraordinary Ensemble of Dusty Debris Disks

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