Discovery with ZTF and the Liverpool and GTC telescopes of the superluminous supernova SN 2020ank (ZTF20aahbfmf, ATLAS20dzr)

ATel #13489; F. Poidevin (IAC & ULL), R. Marques-Chaves (CAB), I. Perez-Fournon, C. Jimenez Angel, R. Shirley (IAC & ULL), S. Geier (GRANTECAN & IAC), Y. Shu (IoA), S. Rodney, J. Roberts-Pierel (Univ. of South Carolina), A. Bolton (NSF's OIR Lab), S. Chakrabarti, P. Craig, and B. Alamiri (RIT)
on 16 Feb 2020; 02:56 UT
Distributed as an Instant Email Notice Supernovae
Credential Certification: Ismael Perez-Fournon (ipf@iac.es)

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We report the discovery of the superluminous supernova SN 2020ank based on spectroscopic observations with SPRAT on the Liverpool Telescope (LT) and OSIRIS on the Gran Telescopio Canarias (GTC) of the ZTF transient ZTF20aahbfmf, also detected by ATLAS (ATLAS20dzr), by the project Supernova and Gravitational Lenses Follow up (SGLF). ZTF20aahbfmf was selected by us as a good supernova candidate using the public ZTF alerts, processed by the Lasair, ANTARES, ALeRCE, and MARS brokers. We reported the discovery to TNS (Poidevin et al., TNS Astronomical Transient Report No. 59581 [2020TNSTR.234....1P]) based on the first ZTF detections on 2020-01-19 and 2020-01-23 UT, with the first detection g = 20.909 +/- 0.295 on 2020-01-19 09:15:13 UT. LT SPRAT spectra were obtained on the nights of 2020-01-30, 2020-02-01, and 2020-02-10 UT. Faint broad features on a blue continuum in the SPRAT spectra combined with the lack of a host galaxy in SDSS, PanSTARRS-1, and DESI Legacy Imaging surveys suggested that AT 2020ank is a superluminous supernova. We triggered GTC OSIRIS long-slit spectroscopy, that was carried out on the night of 2020-02-13 UT, and reported to TNS the classification as an SLSN-I at z = 0.22 (Poidevin et al., TNS Classification Report No. 6122 [2020TNSCR.500....1P]). The features in the GTC OSIRIS spectrum are similar to those seen in other SLSN-I close to maximum light. At the time of our TNS classification report on 2020-02-14 18:28:38 UT the last absolute ZTF magnitudes, after correction for galactic extinction, were Mg = -21.61, and Mr = -21.47. The ZTF light curve (available at, e.g. https://lasair.roe.ac.uk/object/ZTF20aahbfmf/) shows that SN 2020ank is now close to maximum light, with g = 18.428 +/- 0.060 on 2020-02-15 04:59:21 UT and r = 18.535 +/- 0.081 on 2020-02-15 05:35:24 UT. The ZTF mean coordinates of SN 2020ank are RA = 08:16:14.653, Dec = 04:19:26.88. We encourage photometric and spectroscopic follow up of SN 2020ank.

Based on observations made with the Gran Telescopio Canarias (GTC) and the Liverpool Telescope, installed at the Spanish Observatorio del Roque de los Muchachos of the Instituto de Astrofisica de Canarias, in the island of La Palma. The Liverpool Telescope is operated by Liverpool John Moores University with financial support from the UK Science and Technology Facilities Council. We are very grateful to the Liverpool Telescope and GTC staff for the operations of these facilities and to the GTC staff for the prompt completion of Target of Opportunity observations. The imaging data were provided by the Zwicky Transient Facility (https://www.ztf.caltech.edu) and processed through the Lasair (https://lasair.roe.ac.uk), ALeRCE (https://alerce.online), ANTARES (https://antares.noao.edu), and MARS (https://mars.lco.global) brokers.