Paper: astro-ph/0601440
Date: Thu, 19 Jan 2006 17:19:52 GMT (25kb)

Title: Discovery of the Closest Brown Dwarf to the Sun? A Methane Rich Brown
Dwarf around the Nearby M8.5 Star SCR 1845

Authors: B.A. Biller, M. Kasper, L.M. Close, W. Brandner, and S. Kellner

Comments: 5 pages, 3 figures. Submitted to the Astrophysical Journal. Some
figures are currently omitted and will be supplied with the final, accepted
version
\\
We present VLT/NACO SDI images of the very nearby star SCR 1845-6357
(hereafter SCR 1845). SCR 1845 is a recently discovered (Hambly et al. 2004)
M8.5 star just 3.5 pc from the sun (Deacon et al. 2005). Using the capabilities
of the unique SDI device, we discovered a substellar companion to SCR 1845 at a
separation of 4 AU (1.170"+-0.003'' on the sky, PA=170.20 degrees +- 0.13
degrees) and a Delta F1(1.575 um) of 3.57+-0.057 mag. This substellar companion
has an H magnitude of 13.3{+0.24}{-0.21}, and an absolute H magnitude of
15.5{+0.30}{-0.20}. The unique Simultaneous Differential Imager (SDI) consists
of 3 narrowband filters placed around the 1.6 um methane absorption feature
characteristic of T-dwarfs (Teff < 1200 K). The flux of the substellar
companion drops by a factor of 2.7+-0.1 between the SDI F1(1.575 um) filter and
the SDI F3(1.625 um) filter, consistent with strong methane absorption in a
substellar companion. We estimate a spectral type of T6+-1 for the companion
based on the strength of the break. The chances that this object is a
background T dwarf are vanishing small -- and there is no isolated background
T-dwarf anywhere near these coordinates in the field according to 2MASS. Thus,
it is a bound companion, hereafter SCR 1845-6357B. For an age range of 100 Myr
- 10 Gyr and spectral type range of T5-T7, we find a mass range of 8.5 - 60
MJup for SCR 1845B from the Baraffe et al. (2003) COND models. This is likely
the closest brown dwarf to the Sun (in the 16th closest stellar system to the
sun.

\\ ( http://arXiv.org/abs/astro-ph/0601440 , 25kb)

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\\

Paper: astro-ph/0601441
Date: Thu, 19 Jan 2006 17:21:54 GMT (25kb)

Title: Discovery of the Closest Brown Dwarf to the Sun? A Methane Rich Brown
Dwarf around the Nearby M8.5 Star SCR 1845-6357

Authors: B.A. Biller, M. Kasper, L.M. Close, W. Brandner, and S. Kellner

Comments: 5 pages, 3 figures. Submitted to the Astrophysical Journal. Some
figures are currently omitted and will be supplied with the final, accepted
version
\\
We present VLT/NACO SDI images of the very nearby star SCR 1845-6357
(hereafter SCR 1845). SCR 1845 is a recently discovered (Hambly et al. 2004)
M8.5 star just 3.5 pc from the sun (Deacon et al. 2005). Using the capabilities
of the unique SDI device, we discovered a substellar companion to SCR 1845 at a
separation of 4 AU (1.170"+-0.003'' on the sky, PA=170.20 degrees +- 0.13
degrees) and a Delta F1(1.575 um) of 3.57+-0.057 mag. This substellar companion
has an H magnitude of 13.3{+0.24}{-0.21}, and an absolute H magnitude of
15.5{+0.30}{-0.20}. The unique Simultaneous Differential Imager (SDI) consists
of 3 narrowband filters placed around the 1.6 um methane absorption feature
characteristic of T-dwarfs (Teff < 1200 K). The flux of the substellar
companion drops by a factor of 2.7+-0.1 between the SDI F1(1.575 um) filter and
the SDI F3(1.625 um) filter, consistent with strong methane absorption in a
substellar companion. We estimate a spectral type of T6+-1 for the companion
based on the strength of the break. The chances that this object is a
background T dwarf are vanishing small -- and there is no isolated background
T-dwarf anywhere near these coordinates in the field according to 2MASS. Thus,
it is a bound companion, hereafter SCR 1845-6357B. For an age range of 100 Myr
- 10 Gyr and spectral type range of T5-T7, we find a mass range of 8.5 - 60
MJup for SCR 1845B from the Baraffe et al. (2003) COND models. This is likely
the closest brown dwarf to the Sun (in the 16th closest stellar system to the
sun.

\\ ( http://arXiv.org/abs/astro-ph/0601441 , 25kb)