We present ultraviolet , 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 \pm 0.001 ) , with detailed optical and ultraviolet ( 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 M _ { g } = -21.8 \pm 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 a SLSN , reaching a non- K -corrected M _ { uvm 2 } \simeq - 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 \pm 0.2 ms and a magnetic field of B = 1.9 \pm 0.2 \times 10 ^ { 14 } G for the magnetar .
The estimated ejecta mass is between 8 and 16 \mathrm { M } _ { \odot } and the kinetic energy between 1.3 and 2.5 \times 10 ^ { 52 } 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 .