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A Survey for Hα Emission from Late L Dwarfs and T Dwarfs

Pineda, J. Sebastian and Hallinan, Gregg and Kirkpatrick, J. Davy and Cotter, Garret and Kao, Melodie M. and Mooley, Kunal (2016) A Survey for Hα Emission from Late L Dwarfs and T Dwarfs. Astrophysical Journal, 826 (1). Art. No. 73. ISSN 0004-637X. https://resolver.caltech.edu/CaltechAUTHORS:20160916-152943959

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Abstract

Recently, studies of brown dwarfs have demonstrated that they possess strong magnetic fields and have the potential to produce radio and optical auroral emissions powered by magnetospheric currents. This emission provides the only window on magnetic fields in the coolest brown dwarfs and identifying additional benchmark objects is key to constraining dynamo theory in this regime. To this end, we conducted a new red optical (6300–9700 Å) survey with the Keck telescopes looking for Hα emission from a sample of late L dwarfs and T dwarfs. Our survey gathered optical spectra for 29 targets, 18 of which did not have previous optical spectra in the literature, greatly expanding the number of moderate-resolution (R ~ 2000) spectra available at these spectral types. Combining our sample with previous surveys, we confirm an Hα detection rate of 9.2±^(3.5)_(2.1)% for L and T dwarfs in the optical spectral range of L4–T8. This detection rate is consistent with the recently measured detection rate for auroral radio emission from Kao et al., suggesting that geometrical selection effects due to the beaming of the radio emission are small or absent. We also provide the first detection of Hα emission from 2MASS 0036+1821, previously notable as the only electron cyclotron maser radio source without a confirmed detection of Hα emission. Finally, we also establish optical standards for spectral types T3 and T4, filling in the previous gap between T2 and T5.


Item Type:Article
Related URLs:
URLURL TypeDescription
http://dx.doi.org/10.3847/0004-637X/826/1/73DOIArticle
http://iopscience.iop.org/article/10.3847/0004-637X/826/1/73/metaPublisherArticle
https://arxiv.org/abs/1604.03941arXivDiscussion Paper
ORCID:
AuthorORCID
Pineda, J. Sebastian0000-0002-4489-0135
Kao, Melodie M.0000-0001-5125-1414
Additional Information:© 2016 The American Astronomical Society. Received 2015 November 5; accepted 2016 April 7; published 2016 July 22. The data presented herein were obtained at the W. M. Keck Observatory, which is operated as a scientific partnership among the California Institute of Technology, the University of California and the National Aeronautics and Space Administration. The Observatory was made possible by the generous financial support of the W. M. Keck Foundation. The authors wish to recognize and acknowledge the very significant cultural role and reverence that the summit of Mauna Kea has always had within the indigenous Hawaiian community. We are most fortunate to have the opportunity to conduct observations from this mountain. The authors would like to thank the anonymous referee for helpful comments strengthening this contribution. J.S.P. would like to thank Yi Cao for assistance in DEIMOS data reduction. J.S.P. was supported by a grant from the National Science Foundation Graduate Research Fellowship under grant No. (DGE-11444469). This research has benefitted from the M, L, T, and Y dwarf compendium housed at DwarfArchives.org. This research has benefitted from the Ultracool RIZzo Spectral Library maintained by Jonathan Gagné and Kelle Cruz. This researched has benefitted from the Database of Ultracool Parallaxes maintained by Trent Dupuy. PyRAF is a product of the Space Telescope Science Institute, which is operated by AURA for NASA. PyFITS is a product of the Space Telescope Science Institute, which is operated by AURA for NASA. The data presented herein were obtained at the W. M. Keck Observatory, which is operated as a scientific partnership among the California Institute of Technology, the University of California, and the National Aeronautics and Space Administration. The Observatory was made possible by the generous financial support of the W. M. Keck Foundation. This publication makes use of data products from the Two Micron All Sky Survey, which is a joint project of the University of Massachusetts and the Infrared Processing and Analysis Center/California Institute of Technology, funded by the National Aeronautics and Space Administration and the National Science Foundation.
Group:Infrared Processing and Analysis Center (IPAC)
Funders:
Funding AgencyGrant Number
NSF Graduate Research FellowshipDGE-1144469
W. M. Keck FoundationUNSPECIFIED
NASAUNSPECIFIED
NSFUNSPECIFIED
Subject Keywords:brown dwarfs – stars: activity – stars: low-mass
Issue or Number:1
Record Number:CaltechAUTHORS:20160916-152943959
Persistent URL:https://resolver.caltech.edu/CaltechAUTHORS:20160916-152943959
Official Citation:J. Sebastian Pineda et al 2016 ApJ 826 73
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:70408
Collection:CaltechAUTHORS
Deposited By: Tony Diaz
Deposited On:20 Sep 2016 01:56
Last Modified:03 Oct 2019 10:30

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