Early Results from VLT-SPHERE: Long-Slit Spectroscopy of 2MASS 0122-2439B, a Young Companion Near the Deuterium Burning Limit
Bowler, Brendan P.
Aller, Kimberley M.
The Astrophysical Journal Letters
American Astronomical Society
© 2015. The American Astronomical Society. All rights reserved.
We present 0.95–1.80 µm spectroscopy of the ∼12–27 MJup companion orbiting the faint (R∼13.6), young (∼120Myr) M-dwarf 2MASS J01225093–2439505 (“2M0122–2439B”) at 1.′′5 separation (50 AU). Our coronagraphic long-slit spectroscopy was obtained with the new high contrast imaging platform VLT-SPHERE during Science Verification. The unique long-slit capability of SPHERE enables spectral resolution an order of magnitude higher than other extreme AO exoplanet imaging instruments. With a low mass, cool temperature, and very red colors, 2M0122–2439 B occupies a particularly important region of the substellar color-magnitude diagram by bridging the warm directly imaged hot planets with late-M/early-L spectral types (e.g. β Pic b and ROXs 42Bb) and the cooler, dusty objects near the L/T transition (HR 8799bcde and 2MASS 1207b). We fit BT-Settl atmospheric models to our R≈350 spectrum and find Teff=1600±100 K and log(g)=4.5±0.5 dex. Visual analysis of our 2M0122–2439 B spectrum suggests a spectral type L3-L4, and we resolve shallow J-band alkali lines, confirming its low gravity and youth. Specifically, we use the Allers & Liu (2013) spectral indices to quantitatively measure the strength of the FeH, VO, KI, spectral features, as well as the overall H-band shape. Using these indices, along with the visual spectral type analysis, we classify 2M0122–2439 B as an intermediate gravity (int-g) object with spectral type L3.7±1.0.
National Science Foundation Graduate Research Fellowship
STFC Ernest Rutherford Fellowship
Ernest Rutherford grant
Marie Curie CIG grant
Royal Society award
European Research Council
Accepted to ApJ Letters, 8 pages, 4 figures, some minor typographical issues were fixed
The Astrophysical Journal Letters, 2015, Volume 805, Number 1
FP7/2007-2013 grant agreement No. 247060