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Deep infrared imaging and spectroscopy of the nearby late M-dwarf DENIS-P J104814-395606
We obtained deep H- and K-band images of DENIS-P J104814-395606 usingSofI and the speckle camera SHARP-I at the ESO-3.5m-NTT as well as QUIRCat the Mauna Kea 2.2m telescope between December 2000 and June 2001. Thetarget was recently discovered as nearby M9-dwarf among DENIS sources(Delfosse et al. 2001). We detect parallactic motion on our images anddetermine the distance to be 4.6 +/- 0.3 pc, more precise thanpreviously known. From the available colors, the distance, and thespectral type, we conclude from theoretical models that the star has amass of ~ 0.075 to 0.09 Msun and an age of ~ 1 to 2 Gyrs.We also obtained H- and K-band spectra of this star with ISAAC at theVLT. A faint companion candidate is detected 6'' NNW of thestar, which is 6.4 +/- 0.5 mag fainter in H. However, according toanother image taken several month later, the companion candidate is notco-moving with the M9-dwarf. Instead, it is a non-moving backgroundobject. Limits for undetected companion candidates are such that we canexclude any stellar companions outside of ~ 0.25'' (1 AU),any brown dwarf companions (above the deuterium burning mass limit)outside of ~ 2'' (9 AU), and also any companion down to ~40 M_jup with >= 0.15'' (0.7 AU) separation, allcalculated for an age of 2 Gyrs. Our observations show that directimaging of sub-stellar companions near the deuterium burning mass limitin orbit around nearby ultra-cool dwarfs is possible, even withseparations that are smaller than the semi-major axis of the outermostplanet in our solar system, namely a few tens of AU.
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