paper

The Unusual Late-Time Evolution of the Tidal Disruption Event ASASSN-15oi

arXiv:1804.00006 · doi:10.1093/mnras/sty2273

Abstract

We present late-time optical spectroscopy and X-ray, UV, and optical photometry of the nearby ( Mpc, ) tidal disruption event (TDE) ASASSN-15oi. The optical spectra span 450 days after discovery and show little remaining transient emission or evolution after roughly 3 months. In contrast, the Swift and XMM-Newton observations indicate the presence of evolving X-ray emission and lingering thermal UV emission that is still present 600 days after discovery. The thermal component of the X-ray emission shows a unique, slow brightening by roughly an order of magnitude to become the dominant source of emission from the TDE at later times, while the hard component of the X-ray emission remains weak and relatively constant throughout the flare. The TDE radiated ergs across all wavelengths, and the UV and optical emission is consistent with a power law decline and potentially indicative of a late-time shift in the power-law index that could be caused by a transition in the dominant emission mechanism.

arXiv comment16 pages, 9 figures, 4 tables. Updated to reflect changes made in the published version

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