Swift/UVOT Observations of SN2016adj in NGC5128

ATel #8662; Peter J. Brown, Nancy J. Landez, Britton A. Beeny (Texas A&M University)
on 9 Feb 2016; 23:04 UT
Credential Certification: Peter J. Brown (grbpeter@yahoo.com)

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We report on observations with Swift's Ultraviolet/Optical Telescope (UVOT) of SN 2016adj (Marples et al. 2016, ATEL#8651). Swift observations began 2016 Feb 8 17:24:44 and concluded 2016 Feb 9 12:49:03 UT, consisting of multiple snapshots on different orbits. By comparison with pre-explosion images from July/August 2013, the transient is visible as a new source in the v-band images but not clearly visible in bluer filters. Even when utilizing a faster readout time to lessen the effects of coincidence loss, the bright underlying galaxy flux and nearby star make the optical magnitudes unreliable. SN 2016adj is marginally detected in coadded images in the uvw1 filter at the 3 sigma level with uvw1=18.7 +/- 0.4 (371 s exposure). However we caution this may be influenced by the nearby star or purely due to the optical tail of the uvw1 filter (see e.g. Brown et al. 2015 for the shifting of the effective wavelength due to reddening). The source is not significantly detected in the mid-ultraviolet down to 3 sigma limits of uvm2 > 20.1 (4864 s total coadded exposure time) and uvw2 > 19.1 (340 s). The photometry was reduced using the method outlined for the Swift Optical Ultraviolet Supernova Archive (SOUSA; Brown et al 2014, Ap&SS, 354, 89, arXiv:1407.3808), including subtraction of the underlying galaxy count rates and using the Swift/UVOT Vega-based photometric zeropoints (Poole et al. 2008, Breeveld et al. 2011).

The non-detections in the ultraviolet are consistent with the apparently reddened nature of the source (Kiyota et al. 2016, ATEL#8654; Yi et al. 2016, ATEL#8655; Stitzinger et al. 2016, ATEL#8657).

We wish to thank the Swift operations team for their excellent response to this nearby supernova and helpful discussions with the ASASSN and BOSS teams.

Before and After UVOT Image