A new benchmark T8-9 brown dwarf and a couple of new mid-T dwarfs from the UKIDSS DR5 LAS - Astrophysics > Solar and Stellar AstrophysicsReport as inadecuate




A new benchmark T8-9 brown dwarf and a couple of new mid-T dwarfs from the UKIDSS DR5 LAS - Astrophysics > Solar and Stellar Astrophysics - Download this document for free, or read online. Document in PDF available to download.

Abstract: Benchmark brown dwarfs are those objects for which fiducial constraints areavailable, including effective temperature, parallax, age, metallicity. Wesearched for new cool brown dwarfs in 186 sq.deg. of the new area covered bythe data release DR5+ of the UKIDSS Large Area Survey. Follow-up optical andnear-infrared broad-band photometry, and methane imaging of four promisingcandidates, revealed three objects with distinct methane absorption, typical ofmid- to late-T dwarfs, and one possibly T4 dwarf. The latest-type object,classified as T8-9, shares its large proper motion with Ross 458 BD+13o2618,an active M0.5 binary which is 102- away, forming a hierarchical low-massstar+brown dwarf system. Ross 458C has an absolute J-band magnitude of 16.4,and seems overluminous, particularly in the K band, compared to similar fieldbrown dwarfs. We estimate the age of the system to be less than 1 Gyr, and itsmass to be as low as 14 Jupiter masses for the age of 1 Gyr. At 11.4 pc, thisnew late T benchmark dwarf is a promising target to constrain the evolutionaryand atmospheric models of very low-mass brown dwarfs. We present proper motionmeasurements for our targets and for 13 known brown dwarfs. Two brown dwarfshave velocities typical of the thick disk and may be old brown dwarfs.



Author: B. Goldman, S. Marsat, T. Henning, C. Clemens, J. Greiner

Source: https://arxiv.org/







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