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Coronal X-ray emission from an intermediate-age brown dwarf

Yohko Tsuboi·Yoshitomo Maeda·Eric D. Feigelson·Gordon P. Garmire·George Chartas·Koji Mori·Steven H. Pravdo
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Abstract

We report the X-ray detection of the brown dwarf (BD) companion TWA 5B in a $\simeq 12$ Myr old pre-main sequence binary system. We clearly resolve the faint companion (35 photons) separated from the X-ray luminous primary by 2 arcsec in a {\it Chandra} ACIS image. TWA 5B shows a soft X-ray spectrum with a low plasma temperature of only 0.3 keV and a constant flux during the 3 hour observation, of which the characteristics are commonly seen in the solar corona. The X-ray luminosity is 4$\times10^{27}$ erg s$^{-1}$ (0.1--10 keV band) or $\log L_X/L_{bol} = -3.4$. Comparing these properties to both younger and older BDs, we discuss the evolution of the X-ray emission in BDs. During their first few Myr, they exhibit high levels of X-ray activity as seen in higher mass pre-main sequence stars. The level in TWA 5B is still high at $t \simeq 12$ Myr in $\log L_X/L_{bol}$ while $kT$ has already substantially cooled.

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Yohko Tsuboi, Yoshitomo Maeda, Eric D. Feigelson, Gordon P. Garmire, George Chartas, Koji Mori, Steven H. Pravdo. 2003-04-12. Coronal X-ray emission from an intermediate-age brown dwarf. https://doi.org/10.1086/375017

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