ROUGH DRAFT authorea.com/99858

# TYC 8241 2652 1 and the case of the disappearing disk: no smoking gun yet $\star$$\star$footnotetext: Based on observations made with ESO telescopes at the Paranal Observatory (ESO program IDs 090.C-0697(A), 090.C-0904(A), and 095.C-0438(A)) and on observations obtained with XMM-Newton, an ESA science mission with instruments and contributions directly funded by ESA Member States and NASA.

TYC 8241 2652 1 is a young star that showed a strong mid-infrared (mid-IR, 8-25 $$\mu$$m) excess in all observations before 2008 consistent with a dusty disk. Between 2008 and 2010 the mid-IR luminosity of this system dropped dramatically by at least a factor of 30 suggesting a loss of dust mass of an order of magnitude or more. So far there is no conclusive explanation for this observational fact; possibilities include removal of disk material by stellar activity processes, a collisional cascade that rapidly grinds dust of all sizes down to where radiative blowout is effective, or a run-away accretion event spurred by the presence of gaseous material in the disk. We present new X-ray observations, optical spectroscopy, near-IR interferometry, and mid-IR photometry of this system to constrain its parameters and identify the cause of the dust mass loss.

In X-rays TYC 8241 2652 1 has all properties expected from a young star: Its luminosity is in the saturation regime and the abundance pattern shows enhancement of O/Fe. The photospheric H$$\alpha$$ line is filled with a weak emission feature, indicating chromospheric activity consistent the observed level of coronal emission. Interferometry does not detect a companion and sets upper limits on the companion mass of 0.2, 0.35, 0.1 and 0.05 $$M_{\odot}$$ at a distance of 0.1-4 AU, 4-6 AU, 6-11 AU, and 11-34 AU, respectively. Our mid-IR measurements, the first of the system since 2012, are consistent with the depleted dust level seen after 2009.

The new data confirms that stellar activity is unlikely to destroy the dust in the disk and shows that scenarios where either TYC 8241 2652 1 heats the disk of a binary companion or a potential companion heats the disk of TYC 8241 2652 1 are higly unlikely.