Query : 2010A&A...516A..37S

2010A&A...516A..37S - Astronomy and Astrophysics, volume 516, A37-37 (2010/6-2)

2MASS J03105986+1648155AB - a new binary at the L/T transition.


Abstract (from CDS):

The transition from the L to the T spectral type of brown dwarfs is marked by a very rapid transition phase, remarkable brightening in the J-band, and higher binary frequency. Despite being an active area of inquiry, this transition region still remains one of the most poorly understood phases of brown dwarf evolution. We resolved the L dwarf 2MASS J03105986+1648155 for the first time into two almost equally bright components straddling the L/T transition. Since such a coeval system with common age and composition provides crucial information on this special transition phase, we monitored the system over ∼3 years to derive first orbital parameters and dynamical mass estimates, as well as a spectral type determination. We obtained resolved high angular resolution, near-IR images with both HST and the adaptive optics instrument NACO at the VLT, including the laser guide star system PARSEC. Based on two epochs of astrometric data, we derive a minimum semi-major axis of 5.2±0.8AU. The assumption of a face-on circular orbit yields an orbital period of 72±4 years and a total system mass of ∼30-60MJup. This places the masses of the individual components of the system at the lower end of the mass regime of brown dwarfs. The achieved photometry allowed a first spectral type determination of L9±1 for each component. In addition, this seems to be only the fifth resolved L/T transition binary with a flux reversal. While ultimate explanations for this effect are still lacking, the 2MASS J03105986+1648155 system adds an important benchmark object for improving our understanding of this remarkable evolutionary phase of brown dwarfs. Additionally, the observational results of 2MASS J03105986+1648155AB derived with the new PARSEC AO system at the VLT show the importance of this technical capability. The updated AO system allows us to significantly extend the sample of brown dwarfs observable with high resolution from the ground, hence to reveal more of their physical properties.

Abstract Copyright:

Journal keyword(s): brown dwarfs - stars: individual: 2MASS J03105986+1648155AB - stars: fundamental parameters - binaries: visual - techniques: high angular resolution

Simbad objects: 10

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Number of rows : 10
N Identifier Otype ICRS (J2000)
ICRS (J2000)
Mag U Mag B Mag V Mag R Mag I Sp type #ref
1850 - 2023
1 2MASSW J0310599+164816 BD* 03 10 59.86560 +16 48 15.5988           L8V 47 0
2 2MASSI J0423485-041403 BD* 04 23 48.5763811987 -04 14 03.246502948           L6.5+T2 120 0
3 2MASSI J0825196+211552 BD* 08 25 19.6125672818 +21 15 51.549358145       21.97 19.22 L7.5V 114 0
4 2MASS J10210969-0304197 BD* 10 21 09.69240 -03 04 19.7904           T1+T4 73 0
5 2MASS J12074717+0244249 BD* 12 07 47.17296 +02 44 24.9576           L6.5+T2.5 63 0
6 2MASS J14044948-3159330 BD* 14 04 49.48416 -31 59 33.0576           T1+T5 32 1
7 * eta CrB C BD* 15 23 22.63488 +30 14 56.2092           L8V 100 1
8 2MASS J15341711+1615463 BD* 15 34 17.11008 +16 15 46.3680           T1.5+T5.5 21 0
9 2MASSW J1728114+394859 BD* 17 28 11.50056 +39 48 59.3100           L5+L6.5 56 0
10 * eps Ind B BD* 22 04 10.5951812451 -56 46 58.239102418     24.12 20.8 15.60 T1V+T6V 153 1

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