Stars that pass too close to a super-massive black hole may be disrupted by strong tidal forces .
OGLE16aaa is one such tidal disruption event ( TDE ) which rapidly brightened and peaked in the optical/UV bands in early 2016 and subsequently decayed over the rest of the year .
OGLE16aaa was detected in an XMM-Newton X-ray observation on June 9 , 2016 with a flux slightly below the Swift/XRT upper limits obtained during the optical light curve peak .
Between June 16–21 , 2016 , Swift/XRT also detected OGLE16aaa and based on the stacked spectrum , we could infer that the X-ray luminosity had jumped up by more than a factor of ten in just one week .
No brightening signal was seen in the simultaneous optical/UV data to cause the X-ray luminosity to exceed the optical/UV one .
A further XMM-Newton observation on November 30 , 2016 showed that almost a year after the optical/UV peak , the X-ray emission was still at an elevated level , while the optical/UV flux decay had already leveled off to values comparable to those of the host galaxy .
In all X-ray observations , the spectra were nicely modeled with a 50–70 eV thermal component with no intrinsic absorption , with a weak X-ray tail seen only in the November 30 XMM-Newton observation .
The late-time X-ray behavior of OGLE16aaa strongly resembles the tidal disruption events ASASSN-15oi and AT2019azh .
We were able to pinpoint the time delay between the initial optical TDE onset and the X-ray brightening to 182 \pm 5 days , which may possibly represent the timescale between the initial circularization of the disrupted star around the super-massive black hole and the subsequent delayed accretion .
Alternatively , the delayed X-ray brightening could be related to a rapid clearing of a thick envelope that covers the central X-ray engine during the first six months .