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No X-ray detection of Superluminous Supernova ASASSN-15lh by Swift during the UV re-brightening

ATel #8089; Raffaella Margutti (NYU)
on 24 Sep 2015; 06:55 UT
Credential Certification: Raffaella Margutti (rmargutti@cfa.harvard.edu)

Subjects: X-ray, Supernovae

Referred to by ATel #: 8216

ASASSN-15lh/2015L is the most luminous SN ever detected (Dong 2015). Recent observations by the Swift satellite (PI Brown, Holoien, Quimby, Dong) revealed a late-time re-brightening of the supernova at UV wavelengths (Brown, Atel #8086).

We analyzed the Swift-XRT data collected during the UV re-brightening, finding no evidence for detectable X-ray emission at the supernova site. In particular, by using data collected between September 12, 2015 and September 19, 2015 (exposure time of 17 ks) we estimate a 3-sigma count-rate upper limit of ~1d-3 c/s (0.3-10 keV), which corresponds to a flux limit F<5d-14 erg/s/cm2 for an assumed power-law spectrum with index Gamma=2 (L<8d42 erg/s at the distance of ASASSN-15lh).