Measuring Radial Velocities of Low Mass Eclipsing Binaries
:
2011-04
Abstract
Due to the complex nature of the spectra of low-mass M type stars, it
is difficult to determine their metallicities and temperatures
directly. By studying eclipsing binary pairs comprising one F, G, or
K type star with an M type star, we are able to use what we know about
the primary star to learn more about the secondary star. Measuring
the orbital reflex motion of the primary star, together with the
eclipse light curve of the M star as it transits the primary star,
allows us to determine the mass, radius, temperature, and metallicity
of the M star.
We studied 23 low mass eclipsing binaries (EBLMs) previously
discovered by SuperWASP photometry. We obtained spectra using the
Cerro Tololo Inter-American Observatory (CTIO) SMARTS 1.5-meter
echelle spectrograph between June 2009 and January 2011. Each EBLM
target was typically observed ~8 times over this time period. The
spectra were processed using standard astronomical software, and a
cross-correlation method was used to measure the radial velocity of
the target star at each observed epoch.
Radial velocities were successfully determined for 21 of the 23 EBLM
target objects. Orbital periods, radial velocity amplitudes, and
eccentricities for these EBLMs could be determined from these radial
velocities together with the preexisting light curves. Using these
values and by assuming a mass for the primary star, we will be able to
calculate the masses of the secondary M type star in each EBLM system.
