%APursiainen, M%AGutiérrez, C%AWiseman, P%AChildress, M%ASmith, M%AFrohmaier, C%AAngus, C%ACastro Segura, N%AKelsey, L%ASullivan, M%AGalbany, L%ANugent, P%ABassett, B%ABrout, D%ACarollo, D%AD’Andrea, C%ADavis, T%AFoley, R%AGrayling, M%AHinton, S%AInserra, C%AKessler, R%ALewis, G%ALidman, C%AMacaulay, E%AMarch, M%AMöller, A%AMüller, T%AScolnic, D%ASommer, N%ASwann, E%AThomas, B%ATucker, B%AVincenzi, M%AAbbott, T%AAllam, S%AAnnis, J%AAvila, S%ABertin, E%ABrooks, D%ABuckley-Geer, E%ABurke, D%ACarnero Rosell, A%ACarrasco Kind, M%Ada Costa, L%ADe Vicente, J%ADesai, S%ADiehl, H%ADoel, P%AEifler, T%AEverett, S%AFlaugher, B%AFrieman, J%AGarcía-Bellido, J%AGaztanaga, E%AGerdes, D%AGruen, D%AGruendl, R%AGschwend, J%AGutierrez, G%AHollowood, D%AHonscheid, K%AJames, D%AKim, A%AKrause, E%AKuehn, K%AMaia, M%AMarshall, J%AMenanteau, F%AMiquel, R%AOgando, R%APalmese, A%APaz-Chinchón, F%APlazas, A%ARoodman, A%ASanchez, E%AScarpine, V%ASchubnell, M%ASerrano, S%ASevilla-Noarbe, I%ASuchyta, E%ASwanson, M%ATarle, G%AWester, W%BJournal Name: Monthly Notices of the Royal Astronomical Society; Journal Volume: 494; Journal Issue: 4 %D2020%I %JJournal Name: Monthly Notices of the Royal Astronomical Society; Journal Volume: 494; Journal Issue: 4 %K %MOSTI ID: 10170346 %PMedium: X %TThe mystery of photometric twins DES17X1boj and DES16E2bjy %XABSTRACT We present an analysis of DES17X1boj and DES16E2bjy, two peculiar transients discovered by the Dark Energy Survey (DES). They exhibit nearly identical double-peaked light curves that reach very different maximum luminosities (Mr = −15.4 and −17.9, respectively). The light-curve evolution of these events is highly atypical and has not been reported before. The transients are found in different host environments: DES17X1boj was found near the nucleus of a spiral galaxy, while DES16E2bjy is located in the outskirts of a passive red galaxy. Early photometric data are well fitted with a blackbody and the resulting moderate photospheric expansion velocities (1800  km s−1 for DES17X1boj and 4800  km s−1 for DES16E2bjy) suggest an explosive or eruptive origin. Additionally, a feature identified as high-velocity Ca ii absorption ($v$ ≈ 9400 km s−1) in the near-peak spectrum of DES17X1boj may imply that it is a supernova. While similar light-curve evolution suggests a similar physical origin for these two transients, we are not able to identify or characterize the progenitors. %0Journal Article