Hubble Space Telescope Spectroscopy of Brown Dwarfs Discovered with the Wide-field Infrared Survey Explorer
We present a sample of brown dwarfs identified with the Wide-field Infrared Survey Explorer (WISE) for which we have obtained Hubble Space Telescope (HST) Wide Field Camera 3 (WFC3) near-infrared grism spectroscopy. The sample (22 in total) was observed with the G141 grism covering 1.10–1.70 μm, while 15 were also observed with the G102 grism, which covers 0.90–1.10 μm. The additional wavelength coverage provided by the G102 grism allows us to (1) search for spectroscopic features predicted to emerge at low effective temperatures (e.g.,ammonia bands) and (2) construct a smooth spectral sequence across the T/Y boundary. We find no evidence of absorption due to ammonia in the G102 spectra. Six of these brown dwarfs are new discoveries, three of which are found to have spectral types of T8 or T9. The remaining three, WISE J082507.35+280548.5 (Y0.5), WISE J120604.38+840110.6 (Y0), and WISE J235402.77+024015.0 (Y1), are the 19th, 20th, and 21st spectroscopically confirmed Y dwarfs to date. We also present HST grism spectroscopy and reevaluate the spectral types of five brown dwarfs for which spectral types have been determined previously using other instruments.
© 2015 American Astronomical Society. Received 2014 October 2; accepted 2015 February 18; published 2015 May 6. We wish to thank Caroline Morley and Didier Saumon for useful discussions regarding low-temperature models. This publication makes use of data products from the Wide-field Infrared Survey Explorer, which is a joint project of the University of California, Los Angeles, and the Jet Propulsion Laboratory/California Institute of Technology, and NEOWISE, which is a project of the Jet Propulsion Laboratory/California Institute of Technology. WISE and NEOWISE are funded by the National Aeronautics and Space Administration. This research has benefitted from the M, L, T, and Y dwarf compendium housed at dwarfarchives.org. This research has benefitted from the SpeX Prism Spectral Libraries, maintained by Adam Burgasser at http://pono.ucsd.edu/~adam/browndwarfs/spexprism. HST acknowledgement needed. We thank the STSCI help desk for useful discussions and resolution suggestions regarding WFC3 IR photometry. The authors wish to thank Caroline Morley for providing spectroscopic models via the webpage http://ucolick.org/~cmorley/cmorley/Models.html.
Published - 0004-637X_804_2_92.pdf
Submitted - 1502.05365v1.pdf