NOAO >   Observing Info >   Approved Programs >   2017A-0311

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Program Information for 2017A-0311


PI: Barbara Castanheira, Baylor University, barbara_endl@baylor.edu
Address: Physics Department, Baylor University One Bear Place 97316, Waco, TX 76798 USA

CoI: Keaton Bell, U. of Texas, Austin
CoI: Donald E Winget, U. of Texas, Austin

Title: Photometry of Extremely Low Mass White Dwarf Candidates

Abstract: White dwarfs with $log g <7.0$ 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. ELMs can present photometric variations due to pulsations and/or eclipses, as well as ellipsoidal variations and Doppler beaming. Out of the 88 known ELMs, six are known eclipsing and six are known pulsators (Gianninas et al. 2015). Besides the $sim 1000$,s g-modes common to other classes of white dwarf pulsators, some also show $sim 100$,s p-mode pulsations. In the SDSS DR12 catalog, we found a few thousand stars with $5.0 < log g < 7.0$, what means they are potentially ELM white dwarfs. The goal of this proposal is to confirm this hypothesis by looking for pulsations and eclipses characteristic to this new class of object. Increasing the ELMs sample would help constrain the number of close binaries in the Galaxy. 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 larger than 500,km/s.

Program Type: Standard/Galactic

Scheduled Nights:
Run 1 (2017A):  SOAR/SOI -- 2n on Feb 12 - Feb 13 2017
Run 2 (2017A):  SOAR/Goodman -- 1n on Mar 08 2017


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NOAO >   Observing Info >   Approved Programs >   2017A-0311

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