Article
Gaia16apd – a link between fast and slowly declining type I superluminous supernovae
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Organisations
- (1) University of Turku, grid.1374.1
- (2) California Institute of Technology, grid.20861.3d
- (3) Stockholm University, grid.10548.38
- (4) University College Dublin, grid.7886.1
- (5) University of Cambridge, grid.5335.0
- (6) Ege University, grid.8302.9
- (7) Osservatorio Astronomico di Padova, grid.436939.2
- (8) University of Barcelona, grid.5841.8
- (9) University of Sheffield, grid.11835.3e
- (10) Florida State University, grid.255986.5
- (11) Autonomous University of Barcelona, grid.7080.f
- (12) Institut d'Estudis Espacials de Catalunya, grid.435450.3
- (13) Queen's University Belfast, grid.4777.3
- (14) University of Wrocław, grid.8505.8
- (15) Aarhus University, grid.7048.b, AU
- (16) Instituto de Astrofísica de Canarias, grid.17423.33
- (17) University of Warsaw, grid.12847.38
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Description
We present ultraviolet (UV), optical and infrared photometry and optical spectroscopy of the type Ic superluminous supernova (SLSN) Gaia16apd (=SN 2016eay), covering its evolution from 26 d before the g-band peak to 234.1 d after the peak. Gaia16apd was followed as a part of the NOT Unbiased Transient Survey (NUTS). It is one of the closest SLSNe known (z = 0.102 ± 0.001), with detailed optical and UV observations covering the peak. Gaia16apd is a spectroscopically typical type Ic SLSN, exhibiting the characteristic blue early spectra with O ii absorption, and reaches a peak Mg = −21.8 ± 0.1 mag. However, photometrically it exhibits an evolution intermediate between the fast and slowly declining type Ic SLSNe, with an early evolution closer to the fast-declining events. Together with LSQ12dlf, another SLSN with similar properties, it demonstrates a possible continuum between fast and slowly declining events. It is unusually UV-bright even for an SLSN, reaching a non-K-corrected Muvm2 ≃ −23.3 mag, the only other type Ic SLSN with similar UV brightness being SN 2010gx. Assuming that Gaia16apd was powered by magnetar spin-down, we derive a period of P = 1.9 ± 0.2 ms and a magnetic field of B = 1.9 ± 0.2 × 1014 G for the magnetar. The estimated ejecta mass is between 8 and 16 M⊙, and the kinetic energy between 1.3 and 2.5 × 1052 erg, depending on opacity and assuming that the entire ejecta is swept up into a thin shell. Despite the early photometric differences, the spectra at late times are similar to slowly declining type Ic SLSNe, implying that the two subclasses originate from similar progenitors.