Dramatic X-ray brightening of tidal disruption flare AT2019ehz
ATel #12813; S. Gezari (UMd), S. van Velzen (UMd and NYU), D. A. Perley (LJMU), T. Hung (UCSC), S. B. Cenko (GSFC), S. Frederick (UMd), C. Ward (UMd), M. Graham (Caltech), S. R. Kulkarni (Caltech)
on 28 May 2019; 18:09 UT
Credential Certification: Suvi Gezari (suvi@astro.umd.edu)
Subjects: Optical, Ultra-Violet, X-ray, Request for Observations, Tidal Disruption Event
We report the dramatic X-ray brightening of tidal disruption flare AT2019ehz (ATEL #12789) from Neil Gehrels Swift telescope observations (PI: Gezari). The Swift XRT flux increased from 0.005 +/- 0.002 cts/sec on 2019 May 17 to 0.117 +/- 0.008 cts/sec on 2019 May 25, with all the counts in the soft band (0.3-1.5 keV). In contrast, the Swift UVOT UV flux is following the decline rate of the optical flux measured by ZTF (ZTF19aarioci) and optical monitoring observations from the Liverpool Telescope, fading by 0.25 mag in the uvw2 band from 17.62 +/- 0.05 to 17.87 +/- 0.09 mag, and maintaining a blue UV-optical color of uvw2-g = -0.37 mag a week after its optical peak.
The dramatic X-ray brightening of this tidal disruption event (TDE) by a factor of 25 in one week is unusual, and the current bright X-ray flux of ~2.5e-12 ergs/cm^2/s should enable more detailed timing and spectroscopic X-ray analysis. VLA observations have been triggered, and we have an 18 ksec observation with XMM scheduled for 2019 May 30. Swift monitoring observations have been approved with a cadence of 5 days for 30 days. We strongly encourage further observations in the X-rays, as well as optical spectroscopy.
