Imaging and spectroscopy of DENIS-P J104814-395606

Ralph Neuhaeuser, Eike Guenther, Joao Alves, Nicolas Grosso, Christoph Leinert, Thorsten Ratzka, Thomas Ott, Markus Mugrauer, Fernando Comeron, Andreas Eckart, Wolfgang Brandner

We obtained deep H- and K-band images of DENIS-P J104814-395606 using

SofI and the speckle camera SHARP-I at the ESO-3.5m-NTT as well as QUIRC

at the Mauna Kea 2.2m telescope between December 2000 and June 2001. The

target was recently discovered as nearby M9-dwarf among DENIS sources

(Delfosse et al. 2001). We detect parallactic motion on our images and

determine the distance to be 4.6 pm 0.3 pc, more precise than previously

known. From the available colors, the distance, and the spectral type,

we conclude from theoretical models that the star has a mass of ~0.075

to 0.09 M_sun and an age of ~1 to 2 Gyrs. We also obtained H- and K-band

spectra of this star with ISAAC at the VLT. A faint companion candidate

is detected 6 arc sec NNW of the star, which is 6.4 pm 0.5 mag fainter

in H. However, according to another image taken several month later, the

companion candidate is not co-moving with the M9-dwarf. Instead, it is a

non-moving background object. Limits for undetected companion candidates

are such that we can exclude any stellar companions outside of ~0.25 arc

sec (1 AU), any brown dwarf companions (above the deuterium burning mass

limit) outside of ~2 arc sec (9 AU), and also any companion down to ~40

M_jup with \ge 0.15 arc sec (0.7 AU) separation, all calculated for an

age of 2 Gyrs. Our observations show that direct imaging of sub-stellar

companions near the deuterium burning mass limit in orbit around nearby

ultra-cool dwarfs is possible, even with separations that are smaller

than the semi-major axis of the outermost planet in our solar system,

namely a few tens of AU.

Department of Astrophysics
Publication date
Austrian Fields of Science 2012
103004 Astrophysics
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