Keck Laser Guide Star Adaptive Optics Monitoring of the M8+L7 Binary LHS 2397aAB: First Dynamical Mass Benchmark at the L/T Transition

Details Keck Laser Guide Star Adaptive Optics Monitoring of the M8+L7 Binary LHS 2397aAB: First Dynamical Mass Benchmark at the L/T Transition Keck Laser Guide Star Adaptive Optics Monitoring of the M8+L7 Binary LHS 2397aAB: First Dynamical Mass Benchmark at the L/T Transition

2009-04-17

arxiv.org/abs/0904.2573v1

Astrophys.J.699:168-185,2009

Astronomy and Astrophysics

Astrophysics

Solar and Stellar Astrophysics

ApJ, in press

Scientific paper

10.1088/0004-637X/699/1/168

We present Keck LGS AO imaging and aperture masking observations of the M8+L7 binary LHS 2397aAB. Together with archival HST, Gemini-North, and VLT data, our observations span 11.8 years of the binary's 14.2-year orbital period. We determine a total dynamical mass of 0.146+/-0.014 MSun (153+/-15 MJup). Using the combined observational constraints of the total mass and individual luminosities, the Tucson (Lyon) evolutionary models give an age for the system of 1.6 Gyr (1.8 Gyr), consistent with its space motion. We also use these models to determine the mass ratio, giving individual masses of 0.0839+/-0.0011 MSun (0.0848+/-0.0011 MSun) for LHS 2397aA and 0.061+/-0.013 MSun (0.060+/-0.010 MSun) for LHS 2397aB. Because LHS 2397aB is very close to the theoretical mass-limit of lithium burning, measuring its lithium depletion would uniquely test substellar models. We estimate a spectral type of L7+/-1 for LHS 2397aB, making it the first L/T transition object with a dynamical mass determination. This enables a precise estimate of its effective temperature from Tucson (Lyon) models of 1460+/-40 K (1440+/-40 K), which is 200 K higher than estimates for young late-L companions but consistent with older late-L field dwarfs, supporting the idea that the temperature of the L/T transition is surface gravity dependent. Comparing our temperature estimate for LHS 2397aB to those derived from spectral synthesis modeling for similar objects reveals consistency between evolutionary and atmospheric models at the L/T transition, despite the currently limited understanding of this phase of substellar evolution. Future dynamical masses for L/T binaries spanning a range of surface gravity and age will provide the next critical tests of substellar models at the L/T transition.

Affiliated with

Also associated with

No associations

Rating

Keck Laser Guide Star Adaptive Optics Monitoring of the M8+L7 Binary LHS 2397aAB: First Dynamical Mass Benchmark at the L/T Transition does not yet have a rating. At this time, there are no reviews or comments for this scientific paper.

If you have personal experience with Keck Laser Guide Star Adaptive Optics Monitoring of the M8+L7 Binary LHS 2397aAB: First Dynamical Mass Benchmark at the L/T Transition, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Keck Laser Guide Star Adaptive Optics Monitoring of the M8+L7 Binary LHS 2397aAB: First Dynamical Mass Benchmark at the L/T Transition will most certainly appreciate the feedback.

Rate now

Comments { 0 }

Profile ID: LFWR-SCP-O-140494