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Swift UVOT Observations of SN2018evt

ATel #12355; Peter J. Brown (Texas A&M)
on 3 Jan 2019; 23:04 UT
Credential Certification: Peter J. Brown (grbpeter@yahoo.com)

Subjects: Supernovae, Transient

SN2018evt/ASASSN-18ro was discovered by ASAS-SN (Brimacombe et al. 2018, ATEL\#11976) and classified as a 91T-like SN Ia by ePESSTO (Stein et al. 2018, ATEL\#11947). Dong et al. (2018, ATEL\#12325) noted a sustained optical luminosity in the four months after discovery, prompting a request for observations with the Ultra-Violet/Optical Telescope (UVOT; Roming et al. 2005) on the Neil Gehrels Swift Observatory (Gehrels et al. 2004). Swift/UVOT observations began 2019-01-02 01:45:25 (UT). The following magnitudes were measured using aperture photometry: uvw2=18.3, uvm2=18.3, uvw1=17.4, u=16.7, b=17.0, v=16.3, with a photometric uncertainty of 0.1 mag. These measurements use the zeropoints from Breeveld et al. (2011) and are not corrected for galaxy contamination or extinction. Assuming a distance modulus of 35.4 for MCG-01-35-011 (based on a redshift of z=0.02497100 from Theureau et al. 2005 and the bulk galaxy flow model of Mould et al. 2000 used by the NASA Extragalactic Database), this corresponds to absolute magnitudes of uvw2=-17.1, uvm2=-17.1, uvw1=-18.0, u=-18.7, b=-18.4, v=-19.1. The UV magnitudes are comparable to a type Ia supernova at maximum light (Brown et al. 2010).