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2MASSI J1315309-264951: An L Dwarf with Strong and Variable H-alpha Emission

Patrick B. Hall
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Abstract

2MASSI J1315309-264951 is an L3 dwarf with strong H-alpha emission discovered in the course of a color-selected survey for active galactic nuclei using the Two-Micron All-Sky Survey (2MASS). The strength of its H-alpha emission decreased by about a factor of two between two epochs separated by 137 days. This is the first time that variable H-alpha emission has been reported in an L dwarf, and is probably the first observation of an H-alpha flare in an L dwarf. The value of log(L_Halpha/L_bol)>-4.17 observed at the discovery epoch is larger than that of any other L dwarf but comparable to that of 2MASSI J1237392+652615, the only reported T dwarf with H-alpha emission. The observed variability indicates that the H-alpha emission of 2MASSI J1315309-264951 is powered either by magnetic fields or by accretion in a binary system. Spectroscopic or narrow-band H-alpha monitoring of L and T dwarfs on timescales of hours to days would be the most useful step toward a better understanding of their H-alpha emission mechanism(s).

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Patrick B. Hall. 2001-12-11. 2MASSI J1315309-264951: An L Dwarf with Strong and Variable H-alpha Emission. https://doi.org/10.1086/339020

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