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We present the characterization of the low-gravity M6 dwarf 2MASS J0619-2903previously identified as an unusual field object based on its strong IR excessand variable near-IR spectrum. Multiple epochs of low-resolution (R~150)near-IR spectra show large-amplitude (~0.1-0.5 mag) continuum variations ontimescales of days to 12 years, unlike the small-amplitude variability typicalfor field ultracool dwarfs. The variations between epochs are well-modeled aschanges in the relative extinction ($\Delta{A_V}\approx2$ mag). Likewise,Pan-STARRS optical photometry varies on timescales as long as 11 years (andpossibly as short as an hour) and implies similar amplitude $A_V$ changes.NEOWISE mid-IR light curves also suggest changes on 6-month timescales, withamplitudes consistent with the optical/near-IR extinction variations. However,near-IR spectra, near-IR photometry, and optical photometry obtained in thepast year indicate the source can also be stable on hourly and monthlytimescales. From comparison to objects of similar spectral type, the totalextinction of 2MASS J0619-2903 seems to be $A_V\approx4-6$ mag, with perhapsepochs of lower extinction. Gaia EDR3 finds that 2MASS J0619-2903 has awide-separation (1.2' = 10450 AU) stellar companion, with an isochronal age of$31^{+22}_{-10}$ Myr and a mass of $0.30^{+0.04}_{-0.03}$ Msun. Adopting thiscompanion's age and EDR3 distance (145.2$\pm$0.6 pc), we estimate a mass of0.11-0.17 Msun for 2MASS J0619-2903. Altogether, 2MASS J0619-2903 appears topossess an unusually long-lived primordial circumstellar disk, perhaps makingit a more obscured analog to the "Peter Pan" disks found around a few M dwarfsin nearby young moving groups.

On The Unusual Variability of 2MASS J06195260-2903592: A Long-Lived Disk around a Young Ultracool Dwarf