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A new redshift value for SN2018ilu from narrow Halpha emission

ATel #12286; R. Cartier (CTIO)
on 12 Dec 2018; 02:55 UT
Distributed as an Instant Email Notice Supernovae
Credential Certification: Regis Cartier (rgcartier@gmail.com)

Subjects: Optical, Supernovae

We report a new redshift value of 0.0179 ± 0.0003 for SN2018ilu, this redshift was obtained from narrow and spatially extended Halpha emission coincident with the position of the host of SN2018ilu. The observations we were performed on the night of 2018 November 30 at the 4.1-m SOAR telescope equipped with the Goodman High Throughput Spectrograph using the 400 lines/mm grating, and a slit width of 1.0 arc second. From the 2D spectrum, we find that the peak of the Halpha emission is located 9.87 arc seconds to the north-west of the SN position, at a projected distance of about 3.6 kpc at the redshift of the SN. The previous value reported by Berton et al. 2018 in ATel #12216 was obtained by fitting spectral templates to the classification spectrum, the template method yields more uncertain redshift values, particularly at early phases when the spectral diversity is large. The value reported here makes more consistent the spectral and photometric evolution of SN2018ilu with a bright but normal SN Ia.