A Large X-ray Flare from a Single Weak-lined T Tauri Star TWA-7 Detected with MAXI GSC

Abstract

We present a large X-ray flare from a nearby weak-lined T Tauri star TWA-7 detected with the Gas Slit Camera (GSC) on the Monitor of All-sky X-ray Image (MAXI). The GSC captured X-ray flaring from TWA-7 with a flux of $3\times 10^{-9}$ ergs cm${}^{-2}$ s${}^{-1}$ in 2--20 keV band during the scan transit starting at UT 2010-09-07 18:24:30.The estimated X-ray luminosity at the scan in the energy band is 3$\times 10^{32}$ ergs s${}^{-1}$,indicating that the event is among the largest X-ray flares fromT Tauri stars.Since MAXI GSC monitors a target only during a scan transit of about a minute per 92 min orbital cycle, the luminosity at the flare peak might have been higher than that detected. At the scan transit, we observed a high X-ray-to-bolometric luminosity ratio, log $L_{\mathrm{X}}/L_{\mathrm{bol}}$ = $-0.1_{-0.3}^{+0.2}$; i.e., the X-ray luminosity is comparable to the bolometric luminosity. Since TWA-7 has neither an accreting disk nor a binary companion, the observed event implies that none of those are essential to generate such big flares in T Tauri stars.

4 pages, 2 figures, 1 table accepted for publication in PASJ

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• Variations in emission from episodic plasmoid ejecta around black holes
• The RS CVn type star GT Mus shows most energetic X-ray flares throughout the 2010s
• SRG/eROSITA prospects for detection of GRB afterglows
• Detection of coherent low-frequency radio bursts from weak-line TTauri stars
• Nearby Young Stars and Young Moving Groups