Two white dwarfs in ultrashort binaries with detached, eclipsing, likely substellar companions detected by K2

SGP acknowledges the support of the Leverhulme Trust. The research leading to these results has received funding from the European Research Council under the European Union's Seventh Framework Programme (FP/2007-2013)/ERC Grant Agreement numbers 340040 (HiPERCAM) and 320964 (WDTracer), as well as the European Union's Horizon 2020 Research and Innovation Programme/ERC Grant Agreement number 677706 (WD3D). ULTRACAM, and TRM, VSD and SPL are supported by the Science and Technology Facilities Council (STFC) under grants ST/L000733 and ST/M001350. DAHB is supported by the National Research Foundation of South Africa. Support for this work was provided by NASA through Hubble Fellowship grant #HST-HF2-51357.001-A, by NASA K2 Cycle 4 Grant NNX17AE92G, as well as NSF grants AST-1413001 and AST-1312983. This work has made use of data obtained at the Thai National Observatory on Doi Inthanon, operated by NARIT; the Southern Astrophysical Research (SOAR) telescope, which is a joint project of the Ministério da Ciência, Tecnologia, e Inovação da República Federativa do Brasil, the U.S. National Optical Astronomy Observatory, the University of North Carolina at Chapel Hill and the Michigan State University; and the McDonald Observatory of the University of Texas at Austin; as well as the SALT, through DDT programme 2016-2-DDT-006, where the assistance of Marissa Kotze is acknowledged. Data for this paper have been obtained under the International Time Programme of the CCI (International Scientific Committee of the Observatorios de Canarias of the IAC) with the GTC operated on the island of La Palma in the Observatorio del Teide/Roque de los Muchachos.