Early Results from VLT SPHERE: Long-slit Spectroscopy of 2MASS 0122–2439 B, a Young Companion Near the Deuterium Burning Limit

Abstract

We present 0.95–1.80 μm spectroscopy of the ~12–27 M_(Jup) companion orbiting the faint (R ~ 13.6), young (~120 Myr) M-dwarf 2MASS J01225093–2439505 ("2M0122–2439 B") at 1farcs 5 separation (50 AU). Our coronagraphic long-slit spectroscopy was obtained with the new high contrast imaging platform Very Large Telescope Spectro-Polarimetric High-contrast Exoplanet REsearch (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 T_(eff) = 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 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 object with spectral type L3.7 ± 1.0.

Additional Information

© 2015 American Astronomical Society. Received 2015 March 18; accepted 2015 April 24; published 2015 May 19. We thank the anonymous referee for several useful comments. The research of K.M.A. was supported by the National Science Foundation Graduate Research Fellowship under grant No. DGE-1329626. Any opinion, findings, and conclusions or recommendations expressed in this material are those of the authors' and do not necessarily reflect the views of the National Science Foundation. S.K. acknowledges support from an STFC Ernest Rutherford Fellowship ST/J004030/1, Ernest Rutherford grant (ST/K003445/1), and Marie Curie CIG grant (SH-06192). This work is partly supported by Royal Society award WM090065 and the consolidated STFC grant ST/J001627/1. The research leading to these results has received funding from the European Research Council under the European Community's Seventh Framework Programme (FP7/2007-2013 grant agreement No. 247060).

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