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Projeto Observacional para 2017A - SO2017A-002
Título: Time Resolved Spectroscopy of the Lowest Mass White Dwarfs
Resumo: White dwarfs with log(g) lower than 7.0 are called Extremely Low Mass white dwarfs (ELMs). They were first found as companions to pulsars, then to other white dwarfs and main sequence stars (The ELM Survey: 2010 to 2016), and can only be formed in interacting binaries in the age of the Universe. Out of the 88 known ELMs, 76 are confirmed binaries. The mean mass of the ELMs is 0.22 Msun, and of their companions, 0.76 Msun, with a median orbital period of 5.4 h, presenting large radial velocity variations in short timescales. In our SDSS DR12 catalogue (Kepler et al. 2016), we found a few thousand stars in the effective temperature and surface gravity ranges attributed to ELMs, but they need their binarity confirmed to be called ELMs. Increasing the ELMs sample would help constrain the number of close binaries in the Galaxy. Interestingly, if they turn out to be A stars with an overestimated log g, the distance modulus would put these young stars in the halo.