arXiv subjects

Jacqueline Faherty

Publications and source records attributed to Jacqueline Faherty.

40 records · Page 3Linked to original sources

arXiv2016

Searching for Binary Y dwarfs with the Gemini Multi-Conjugate Adaptive Optics System (GeMS)

The NASA Wide-field Infrared Survey Explorer (WISE) has discovered almost all the known members of the new class of Y-type brown dwarfs. Most of these Y dwarfs have been identified as isolated objects in the field. It is known that binaries with L- and T-type brown dwarf primaries are less prevalent than either M-dwarf or solar-type primaries, they tend to have smaller separations and are more frequently detected in near-equal mass configurations. The binary statistics for Y-type brown dwarfs, however, are sparse, and so it is unclear if the same trends that hold for L- and T-type brown dwarfs also hold for Y-type ones. In addition, the detection of binary companions to very cool Y dwarfs may well be the best means available for discovering even colder objects. We present results for binary properties of a sample of five WISE Y dwarfs with the Gemini Multi-Conjugate Adaptive Optics System (GeMS). We find no evidence for binary companions in these data, which suggests these systems are not equal-luminosity (or equal-mass) binaries with separations larger than ~ 0.5-1.9 AU. For equal-mass binaries at an age of 5 Gyr, we find that the binary binding energies ruled out by our observations (i.e. 10^42 erg) are consistent with those observed in previous studies of hotter ultra-cool dwarfs.

astro-ph.SR↗

arXiv2015

Fundamental Parameters and Spectral Energy Distributions of Young and Field Age Objects with Masses Spanning the Stellar to Planetary Regime

We combine optical, near-infrared and mid-infrared spectra and photometry to construct expanded spectral energy distributions (SEDs) for 145 field age (\textgreater 500 Myr) and 53 young (lower age estimate \textless 500 Myr) ultracool dwarfs (M6-T9). This range of spectral types includes very low mass stars, brown dwarfs, and planetary mass objects, providing fundamental parameters across both the hydrogen and deuterium burning minimum masses for the largest sample assembled to date. A subsample of 29 objects have well constrained ages as probable members of a nearby young moving group (NYMG). We use 182 parallaxes and 16 kinematic distances to determine precise bolometric luminosities ($L_\text{bol}$) and radius estimates from evolutionary models give semi-empirical effective temperatures ($T_\text{eff}$) for the full range of young and field age late-M, L and T dwarfs. We construct age-sensitive relationships of luminosity, temperature and absolute magnitude as functions of spectral type and absolute magnitude to disentangle the effects of degenerate physical parameters such as $T_\text{eff}$, surface gravity, and clouds on spectral morphology. We report bolometric corrections in $J$ for both field age and young objects and find differences of up to a magnitude for late-L dwarfs. Our correction in $Ks$ shows a larger dispersion but not necessarily a different relationship for young and field age sequences. We also characterize the NIR-MIR reddening of low gravity L dwarfs and identify a systematically cooler $T_\text{eff}$ of up to 300K from field age objects of the same spectral type and 400K cooler from field age objects of the same $M_H$ magnitude.

astro-ph.SR↗

arXiv2015

BANYAN. VI. Discovery of a companion at the brown dwarf/planet-mass limit to a Tucana-Horologium M dwarf

We report the discovery of a substellar companion to 2MASS J02192210-3925225, a young M6 $γ$ candidate member of the Tucana-Horologium association (30 - 40 Myr). This L4 $γ$ companion has been discovered with seeing-limited direct imaging observations; at a 4" separation (160AU) and a modest contrast ratio, it joins the very short list of young low-mass companions amenable to study without the aid of adaptive optics, enabling its characterization with a much wider suite of instruments than is possible for companions uncovered by high-contrast imaging surveys. With a model-dependent mass of 12-15MJup, it straddles the boundary between the planet and brown dwarf mass regimes. We present near-infrared spectroscopy of this companion and compare it to various similar objects uncovered in the last few years. The J0219-3925 system falls in a sparsely populated part of the host mass versus mass ratio diagram for binaries; the dearth of known similar companions may be due to observational biases in previous low-mass companion searches.

astro-ph.SR↗

arXiv2013

Bayesian analysis to identify very low-mass members of nearby young stellar kinematic groups

We describe our all-sky survey for >M4 candidate members to nearby, young associations from the 2MASS and WISE catalogs using bayesian inference. We report the first results, including 38 highly probable candidates showing spectroscopic signs of low-gravity (and thus youth). The latest of these objects would correspond to a 11 - 13 MJup object, around the limit of the planetary regime.

astro-ph.SR↗