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Discovery and Classification of the z=1.86 SLSNe: DES15E2mlf

ATel #8460; Y.-C. Pan, R. J. Foley (University of Illinois), L. Galbany, S. Gonzalez-Gaitan, F. Forster, M. Hamuy (Universidad de Chile), J. L. Prieto (Universidad Diego Portales), F. Yuan, B. E. Tucker (Australian National University), C. Lidman (Australian Astronomical Observatory), P. Martini (Ohio State University), Julia Gshwend (Observatorio Nacional / LIneA), A. Moller, B. Zhang (Australian National University), S. Desai, K. Paech (Ludwig Maximilians University, Munich), R. C. Smith (NOAO/CTIO), M. Schubnell (University of Michigan), R. Kessler, J. Lasker, D. Scolnic (University of Chicago), D. J. Brout, L. Gladney, M. Sako, R. C. Wolf (University of Pennsylvania), P. J. Brown, K. Krisciunas, N. Suntzeff (Texas A&M University), R. Nichol, A. Papadopoulos (University of Portsmouth), M. Childress, C. D'Andrea, S. Prajs, M. Smith, M. Sullivan (University of Southampton), R. Maartens (University of the Western Cape), R. Gupta, E. Kovacs, S. Kuhlmann, H. Spinka (Argonne National Laboratory), E. Ahn, D. A. Finley, J. Frieman, J. Marriner, W. Wester (Fermilab), G. Aldering, A. G. Kim, R. C. Thomas (Lawrence Berkeley National Laboratory), K. Barbary, J. S. Bloom, D. Goldstein, P. Nugent, S. Perlmutter (Lawrence Berkeley National Laboratory + University of California, Berkeley), R. Casas, F. J. Castander (ICE, IEEC/CSIC, Barcelona)
on 23 Dec 2015; 22:59 UT
Distributed as an Instant Email Notice Supernovae
Credential Certification: Mathew Smith (matsmith2@gmail.com)

Subjects: Optical, Supernovae

We report the spectroscopic classification of DES15E2mlf as a superluminous supernova (SLSN) discovered by the Dark Energy Survey (ATEL #4668). DES15E2mlf was discovered on 7 November 2015 at R.A. = 00:41:33.40, Decl = -43:27:17.2 with r = 24.1 mag. We obtained spectra using GMOS on Gemini-South (520-990nm) on 06 December 2015 which indicated a redshift of z = 1.86 from Mg II 2800 absorption. The SN peaked at r = 22.4 mag, which corresponds to M = -22.4 mag at z = 1.86. Further observations were obtained with the AAOmega Spectrograph (Saunders et al. 2004, SPIE, 5492, 389) and the 2dF fibre positioner at the Anglo-Australian Telescope (AAT) on 12 & 14th December 2015 and using GMOS on Gemini-South (380-990nm) on 15 December 2015, the latter of which confirm DES15E2mlf to be a SLSN at z = 1.86 at maximum light, spectroscopically similar to SNLS-06D4eu. While our spectra do not cover hydrogen features and thus cannot rule out DES15E2mlf as a SLSN-II, it is most similar, spectroscopically, to other SLSNe-I. Object classification was performed using superfit (Howell et al, 2005, ApJ, 634, 119), the details of which are reported in the table below.

Name       | RA (J2000)| Dec (J2000)|Discovery  |Discovery|Spectrum                                               |Redshift| Type | Phase |Notes 
           |           |            |Date (UT)  |Mag (r)  |Date (UT)                                              |        |      |       | 
DES15E2mlf |00:41:33.40|-43:27:17.2 |2015 Nov 07|  24.1   |2015 Dec 06 and 15 (Gemini-S), 2015 Dec 12 and 14 (AAT)|  1.86  | SLSN |  max  |a,b 
a). Redshift from galaxy emission features	 
b). DES15E2mlf has (g,r,i,z)=(23.3,22.7,22.5,22.7) on 16 Dec 2015 and is rising in i&z. Further spectroscopic observations where possible are encouraged.