ﻻ يوجد ملخص باللغة العربية
We present i and z photometry for 25 T dwarfs and one L dwarf. Combined with published photometry, the data show that the i - z, z - Y and z - J colors of T dwarfs are very red, and continue to increase through to the late-type T dwarfs, with a hint of a saturation for the latest types with T_eff ~ 600 K. We present new 0.7-1.0 um and 2.8-4.2 um spectra for the very late-type T dwarf UGPS J072227.51-054031.2, as well as improved astrometry for this dwarf. Examination of the spectral energy distribution using the new and published data, with Saumon & Marley models, shows that the dwarf has T_eff = 505 +/- 10 K, a mass of 3-11 M_Jupiter and an age between 60 Myr and 1 Gyr. This young age is consistent with the thin disk kinematics of the dwarf. The mass range overlaps with that usually considered to be planetary, despite this being an unbound object discovered in the field near the Sun. This apparently young rapid rotator is also undergoing vigorous atmospheric mixing, as determined by the IRAC and WISE-2 4.5 um photometry and the Saumon & Marley models. The optical spectrum for this 500 K object shows clearly detected lines of the neutral alkalis Cs and Rb, which are emitted from deep atmospheric layers with temperatures of 900-1200 K.
We present {lambda}/{Delta}{lambda} ~ 6000 near-infrared spectroscopy of the nearby T9 dwarf, UGPS J072227.51-054031.2, obtained during the commissioning of the Folded-Port Infrared Echellette Spectrograph on the Baade Magellan telescope at Las Campa
Mid-infrared data, including Spitzer warm-IRAC [3.6] and [4.5] photometry, is critical for understanding the cold population of brown dwarfs now being found, objects which have more in common with planets than stars. As effective temperature (T_eff)
With a spectral type of T10, UGPS J072227.51-054031.2 is one of the coolest objects known to date in the solar neighborhood. Multiple systems are relatively common among early and mid-T dwarfs. We search for faint and close companions around UGPSJ072
With the discovery of Y dwarfs by the WISE mission, the population of field brown dwarfs now extends to objects with temperatures comparable to those of Solar System planets. To investigate the atmospheres of these newly identified brown dwarfs, we h
We present the discovery of three late type (>T4) brown dwarfs, including a probable Y dwarf, in the WFC3 Infrared Spectroscopic Parallels (WISP) Survey. We use the G141 grism spectra to determine the spectral types of the dwarfs and derive distance