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Projeto Observacional para 2016B - SO2016B-002
Autor: Ingrid Pelisoli
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, followed by companions 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 their companions is 0.76 solar masses, and the median orbital period is 5.4 h, so they present large radial velocity variations in short periods of time. In our SDSS DR12 catalog (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, several with velocities above 500 km/s.