Abstract
We report the discovery of a deep, singular eclipse of the bona fide brown dwarf Roque 12, a substellar member of the Pleiades. The eclipse was 0.65mag deep, lasted 1.3h, and was observed with two telescopes simultaneously in October 2002. No further eclipse was recorded, despite continuous monitoring with Kepler/K2 over 70d in 2015. There is tentative (2sigma) evidence for radial velocity variations of 5km/s, over timescales of three months. The best explanation for the eclipse is the presence of a companion on an eccentric orbit. The observations constrain the eccentricity to e>0.5, the period to P>70d, and the mass of the companion to ~0.001-0.04Msol. In principle it is also possible that the eclipse is caused by circum-sub-stellar material. Future data releases by Gaia and later LSST as well as improved radial velocity constraints may be able to unambiguously confirm the presence of the companion. This would turn the system into one of the very few known eclipsing binary brown dwarfs with known age.
Highlights
Stellar variability encodes information about stars and their environment
We report the discovery of a deep, singular eclipse of the bona fide brown dwarf Roque 12, a substellar member of the Pleiades
The unique event seen in October 2002 with two Calar Alto telescopes simultaneously remains to date the only eclipse observed in this object
Summary
Stellar variability encodes information about stars and their environment. Firstly, specific types of variability can be used to infer fundamental properties of stars that are notoriously difficult to determine by other means (luminosity, radius, distance, rotation period). The resolution that can be achieved by modeling variability caused by obscurations is independent of distance and applicable down to very faint stars For brown dwarfs this technique is currently the only hope of mapping the planet-forming zone around them. For all these reasons it is thought of as critical to find rare systems undergoing eclipses, even more so when the primary source of light is a brown dwarf. We report such a system, for which we observed one singular deep and short eclipse in October 2002, an event that is best explained by a sub-stellar/planetary companion on an eccentric orbit, but could in principle be caused by circum-sub-stellar dust
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