Understanding the extreme luminosity of DES14X2fna

Grayling, M.; Gutiérrez, C. P.; Sullivan, M.; Wiseman, P.; Vincenzi, M.; González-Gaitán, S.; Tucker, B. E.; Galbany, L.; Kelsey, L.; Lidman, C.; Swann, E.; Smith, M.; Frohmaier, C.; Carollo, D.; Glazebrook, K.; Lewis, G. F.; Möller, A.; Hinton, S. R.; Uddin, S. A.; Abbott, T. M. C.; Aguena, M.; Avila, S.; Bertin, E.; Bhargava, S.; Brooks, D.; Carnero Rosell, A.; Carrasco Kind, M.; Carretero, J.; Costanzi, M.; Da Costa, L. N.; De Vicente, J.; Desai, S.; Diehl, H. T.; Doel, P.; Everett, S.; Ferrero, I.; Fosalba, P.; Frieman, J.; García-Bellido, J.; Gaztanaga, E.; Gruen, D.; Gruendl, R. A.; Gschwend, J.; Gutierrez, G.; Hoyle, B.; Kuehn, K.; Kuropatkin, N.; Lima, M.; Maccrann, N.; Marshall, J. L.; Martini, P.; Miquel, R.; Morgan, R.; Palmese, A.; Paz-Chinchón, F.; Plazas, A. A.; Romer, A. K.; Sánchez, C.; Sanchez, E.; Scarpine, V.; Serrano, S.; Sevilla-Noarbe, I.; Soares-Santos, M.; Suchyta, E.; Tarle, G.; Thomas, D.; To, C.; Varga, T. N.; Walker, A. R.; Wilkinson, R. D. (DES Collaboration)

doi:10.1093/mnras/stab1478

We present DES14X2fna, a high-luminosity, fast-declining Type IIb supernova (SN IIb) at redshift z = 0.0453, detected by the Dark Energy Survey (DES). DES14X2fna is an unusual member of its class, with a light curve showing a broad, luminous peak reaching M-r similar or equal to -19.3 mag 20 d after explosion. This object does not show a linear decline tail in the light curve until similar or equal to 60 d after explosion, after which it declines very rapidly (4.30 +/- 0.10 mag 100 d(-1) in the r band). By fitting semi-analytic models to the photometry of DES14X2fna, we find that its light curve cannot be explained by a standard Ni-56 decay model as this is unable to fit the peak and fast tail decline observed. Inclusion of either interaction with surrounding circumstellar material or a rapidly-rotating neutron star (magnetar) significantly increases the quality of the model fit. We also investigate the possibility for an object similar to DES14X2fna to act as a contaminant in photometric samples of SNe Ia for cosmology, finding that a similar simulated object is misclassified by a recurrent neural network (RNN)-based photometric classifier as an SN Ia in similar to 1.1-2.4 percent of cases in DES, depending on the probability threshold used for a positive classification.

Understanding the extreme luminosity of DES14X2fna / Grayling, M.; Gutiérrez, C. P.; Sullivan, M.; Wiseman, P.; Vincenzi, M.; González-Gaitán, S.; Tucker, B. E.; Galbany, L.; Kelsey, L.; Lidman, C.; Swann, E.; Smith, M.; Frohmaier, C.; Carollo, D.; Glazebrook, K.; Lewis, G. F.; Möller, A.; Hinton, S. R.; Uddin, S. A.; Abbott, T. M. C.; Aguena, M.; Avila, S.; Bertin, E.; Bhargava, S.; Brooks, D.; Carnero Rosell, A.; Carrasco Kind, M.; Carretero, J.; Costanzi, M.; da Costa, L. N.; De Vicente, J.; Desai, S.; Diehl, H. T.; Doel, P.; Everett, S.; Ferrero, I.; Fosalba, P.; Frieman, J.; García-Bellido, J.; Gaztanaga, E.; Gruen, D.; Gruendl, R. A.; Gschwend, J.; Gutierrez, G.; Hoyle, B.; Kuehn, K.; Kuropatkin, N.; Lima, M.; Maccrann, N.; Marshall, J. L.; Martini, P.; Miquel, R.; Morgan, R.; Palmese, A.; Paz-Chinchón, F.; Plazas, A. A.; Romer, A. K.; Sánchez, C.; Sanchez, E.; Scarpine, V.; Serrano, S.; Sevilla-Noarbe, I.; Soares-Santos, M.; Suchyta, E.; Tarle, G.; Thomas, D.; To, C.; Varga, T. N.; Walker, A. R.; Wilkinson, R. D. (DES Collaboration). - In: MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY. - ISSN 0035-8711. - 505:3(2021), pp. 3950-3967. [10.1093/mnras/stab1478]