Detection of H$_2$ in the TWA 7 System: A Probable Circumstellar Origin

Kavli Affiliate: Gregory Herczeg

| First 5 Authors: Laura Flagg, Christopher Johns-Krull, Kevin France, Gregory Herczeg, Joan Najita

| Summary:

Using HST-COS FUV spectra, we have discovered warm molecular hydrogen in the
TWA 7 system. TWA 7, a $sim$9 Myr old M2.5 star, has a cold debris disk and
has previously shown no signs of accretion. Molecular hydrogen is expected to
be extremely rare in a debris disk. While molecular hydrogen can be produced in
star spots or the lower chromospheres of cool stars such as TWA 7, fluxes from
progressions that get pumped by the wings of Ly$alpha$ indicate that this
molecular hydrogen could be circumstellar and thus that TWA 7 is accreting at
very low levels and may retain a reservoir of gas in the near circumstellar

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