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Swift/UVOT Observations of type Ia Supernova ASASSN-15rq show it to be UV-bright

ATel #8213; Peter J. Brown (Mitchell Institute, Texas A&M University) & Peter Milne (U Arizona)
on 25 Oct 2015; 03:52 UT
Credential Certification: Peter J. Brown (grbpeter@yahoo.com)

Subjects: Optical, Ultra-Violet, Supernovae, Transient

We report on observations with Swift's Ultraviolet/Optical Telescope (UVOT) of supernova ASASSN-15rq (Brimacombe et al. 2015, ATEL#8202) classified as a Ia before maximum (Lyman et al. 2015, ATEL#8206). Swift observations began 2015-10-24 09:07:42 UT. The following UVOT magnitudes were measured: v = 15.74 +/- 0.07 (79 s exposure time), b = 15.55 +/- 0.05 (157 s), u = 14.80 +/- 0.05 (157 s), uvw1 = 15.90 +/- 0.07 (315 s), uvm2 = 17.16 +/- 0.07 (1777 s), and uvw2 = 17.14 +/- 0.09 (418 s). These magnitudes are reduced using the method outlined for the Swift Optical Ultraviolet Supernova Archive (SOUSA; Brown et al 2014, Ap&SS, 354, 89, arXiv:1407.3808) on the Swift/UVOT Vega-based photometric system (Poole et al. 2008, Breeveld et al. 2011).

The UV-optical colors are quite blue and the UV magnitudes quite bright for a SN Ia at z=0.025 (Lyman et al. 2015), similar to super-Chandrasekhar candidate SNe Ia (Brown et al. 2014). The PESSTO optical spectrum (Lyman et al. 2015), however, looks more like the high velocity SN 2004dt (Altavilla et al. 2007) which was also UV bright (Wang et al. 2012, Brown 2014).

Swift Supernovae