The coolest ‘stars’ are free-floating planets

V. Joergens, M. Bonnefoy, Y. Liu, A. Bayo, S. Wolf

(Submitted on 29 Jul 2014)

We show that the coolest known object that is probably formed in a star-like mode is a free-floating planet. We discovered recently that the free-floating planetary mass object OTS,44 (M9.5, ~12 Jupiter masses, age ~2 Myr) has significant accretion and a substantial disk. This demonstrates that the processes that characterize the canonical star-like mode of formation apply to isolated objects down to a few Jupiter masses. We detected in VLT/SINFONI spectra that OTS44 has strong, broad, and variable Paschen beta emission. This is the first evidence for active accretion of a free-floating planet.

The object allows us to study accretion and disk physics at the extreme and can be seen as free-floating analog of accreting planets that orbit stars. Our analysis of OTS44 shows that the mass-accretion rate decreases continuously from stars of several solar masses down to free-floating planets. We determined, furthermore, the disk mass (10 Earth masses) and further disk properties of OTS44 through modeling its SED including Herschel far-IR data. We find that objects between 14 and 0.01 solar masses have the same ratio of the disk-to-central-mass of about 1%.

Our results suggest that OTS44 is formed like a star and that the increasing number of young free-floating planets and ultra-cool T and Y field dwarfs are the low-mass extension of the stellar population.

Comments:

Proceeding of 18th Cambridge Workshop on Cool Stars, Stellar Systems, and the Sun, held in Flagstaff (AZ) on June 9-13, 2014, ed. by G. van Belle & H. Harris

Subjects:

Solar and Stellar Astrophysics (astro-ph.SR)

Cite as:

arXiv:1407.7864 [astro-ph.SR] (or arXiv:1407.7864v1 [astro-ph.SR] for this version)

Submission history

From: Viki Joergens 

[v1] Tue, 29 Jul 2014 20:00:26 GMT (3689kb,D)