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Abstract Brown dwarfs bridge the gap between stars and planets, providing valuable insight into both planetary and stellar-formation mechanisms. Yet the census of transiting brown-dwarf companions, in particular around M-dwarf stars, remains incomplete. We report the discovery of two transiting brown dwarfs around low-mass hosts using a combination of space- and ground-based photometry along with near-infrared radial velocities. We characterize TOI-5389Ab ( ) and TOI-5610b ( ), two moderately massive brown dwarfs orbiting early M-dwarf hosts (Teff = 3569 ± 59 K and 3618 ± 59 K, respectively). For TOI-5389Ab, the best fitting parameters are periodP = 10.40046 ± 0.00002 days, radius RJ, and low eccentricity . In particular, this constitutes one of the most extreme substellar-stellar companion-to-host mass ratios ofq= 0.150. For TOI-5610b, the best-fitting parameters are periodP = 7.95346 ± 0.00002 days, radius RJ, and moderate eccentricity . Both targets are expected to have shallow, but potentially observable, occultations: ≲500 ppm in the JohnsonKband. A statistical analysis of M-dwarf/BD systems reveals for the first time that those at short orbital periods (P < 13 days) exhibit a dearth of 13MJ < MBD < 40MJcompanions (q < 0.1) compared to those at slightly wider separations.
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Predicting Cloud Conditions in Substellar Mass Objects Using Ultracool Dwarf Companions
Abstract We present results from conducting a theoretical chemical analysis of a sample of benchmark companion brown dwarfs whose primary star is of type F, G, or K. We summarize the entire known sample of these types of companion systems, termed “compositional benchmarks,” that are present in the literature or recently published as key systems of study in order to best understand brown dwarf chemistry and condensate formation. Via mass balance and stoichiometric calculations, we predict a median brown dwarf atmospheric oxygen sink of by utilizing published stellar abundances in the local solar neighborhood. Additionally, we predict a silicate condensation sequence such that atmospheres with bulk Mg/Si ≲0.9 will form enstatite (MgSiO3) and quartz (SiO2) clouds, and atmospheres with bulk Mg/Si ≳0.9 will form enstatite and forsterite (Mg2SiO4) clouds. The implications of these results on C/O ratio trends in substellar-mass objects and the utility of these predictions in future modeling work are discussed.
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- PAR ID:
- 10493211
- Publisher / Repository:
- DOI PREFIX: 10.3847
- Date Published:
- Journal Name:
- The Astrophysical Journal
- Volume:
- 963
- Issue:
- 1
- ISSN:
- 0004-637X
- Format(s):
- Medium: X Size: Article No. 67
- Size(s):
- Article No. 67
- Sponsoring Org:
- National Science Foundation
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