Variability in a Young, L/T Transition Planetary-Mass Object

Beth A. Biller, Johanna Vos, Mariangela Bonavita, Esther Buenzli, Claire Baxter, Ian J. M. Crossfield, Katelyn Allers, Michael C. Liu, Mickaël Bonnefoy, Niall Deacon, Wolfgang Brandner, Joshua E. Schlieder, Trent Dupuy, Taisiya Kopytova, Elena Manjavacas, France Allard, Derek Homeier, Thomas Henning

Research output: Contribution to journalArticlepeer-review


As part of our ongoing NTT SoFI survey for variability in young free-floating planets and low mass brown dwarfs, we detect significant variability in the young, free-floating planetary mass object PSO J318.5-22, likely due to rotational modulation of inhomogeneous cloud cover. A member of the 23$\pm$3 Myr $\beta$ Pic moving group, PSO J318.5-22 has T$_\mathrm{eff}$ = 1160$^{+30}_{-40}$ K and a mass estimate of 8.3$\pm$0.5 M$_{Jup}$ for a 23$\pm$3 Myr age. PSO J318.5-22 is intermediate in mass between 51 Eri b and $\beta$ Pic b, the two known exoplanet companions in the $\beta$ Pic moving group. With variability amplitudes from 7-10$\%$ in J$_{S}$ at two separate epochs over 3-5 hour observations, we constrain the rotational period of this object to $>$5 hours. In K$_{S}$, we marginally detect a variability trend of up to 3$\%$ over a 3 hour observation. This is the first detection of weather on an extrasolar planetary mass object. Among L dwarfs surveyed at high-photometric precision ($
Original languageEnglish
JournalAstrophysical Journal
Publication statusPublished - 30 Oct 2015


  • astro-ph.EP


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