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Spectral classification of nuclear transient OGLE18be as SN Ia at z=0.151

ATel #11316; M. Gromadzki, L. Wyrzykowski (Warsaw Observatory), F. Bufano (INAF Catania), M. Berton (Uni Padova), C. Vogl (MPA), A. Floers, S. Taubenberger, J. Anderson (ESO), L. Galbany (Pittsburgh), S. Schulze, O. Yaron, I. Manulis (Weizmann), C. Inserra (Southampton), E. Kankare, K. Maguire, S. J. Smartt, D. Young, K. W. Smith (QUB)
on 18 Feb 2018; 00:11 UT
Credential Certification: Lukasz Wyrzykowski (wyrzykow@astrouw.edu.pl)

Subjects: Optical, Supernovae, Transient

OGLE18be/SN2018be nuclear transient was discovered by the OGLE-IV Transient Search System (http://ogle.astrouw.edu.pl/ogle4/transients/ Wyrzykowski et al. 2014, Acta Astronomica 64, 197) on 2018-01-06. Classification spectrum was obtained on on 2018-01-16 using NTT/EFOSC2 (ePESSTO, ATel #11192). Its quality did not allow for precise classification and redshift estimation. The spectrum was in fair agreement with strongly reddened Type I SNe. SNID found matches with various SNe type I at z~0.01 to 0.04 (ATEL #11192).

We obtained an additional spectrum of OGLE18be on 2018-02-01 using the FOcal Reducer/low dispersion Spectrograph 2 (FORS2) on the Very Large Telescope (VLT). The spectrum contains mostly the light from the host galaxy and reminds a Luminous Red Galaxy with apparent absorption line Ca II H & K, Hbeta and HeI at redshift z=0.151.

The VLT/FORS spectrum was used to remove the host contribution from the earlier NTT/EFOSC2 spectrum. The spectroscopic classification on the differential spectrum with SNID code (Blondin & Tonry 2007, ApJ, 666, 1024) showed the transient was consistent with SN Type Ia at maximum, in good agreement with OGLE I-band light curve shape.

We thank ESO and VLT staff for the observations. VLT/FORS2 ToO observations were carried under ESO programme 0100.B-0503(A), PI: Gromadzki.