ARCSAT ID NUMBER: AS08

DESCRIPTIVE TITLE: Short Term Variability for Stars of Similar Temperatures but Different Luminosities

PI: Tiffany Pewett

OBSERVER(S): Tiffany Pewett (GSU), Michele Silverstein (GSU), Todd Henry (GSU)

UNCERTIFIED/UNTRAINED OBSERVERS:

COLLABORATORS: Wei-Chun Jao (GSU)
 
CONTACT INFORMATION: Tiffany Pewett, pewett@astro.gsu.edu, 419-460-0072

TIME REQUESTED: 

1. January 12 - January 18
2. November 10 - November 16
3. December 15 - December 21

One week is requested to observe ~14 stars for photometric variability.

INSTRUMENT: SurveyCam

FILTERS: Johnson Cousins V

COMMENTS: 

BRIEF SCIENCE JUSTIFICATION: The Main Sequence (MS) can span more than
three magnitudes in Mv for spectral types M0V to M5V, indicating
that stars of similar temperature differ by a factor of 16 in
luminosity.  This implies that red dwarfs with identical V-K colors
may differ in radius by a factor of four ... but why?

For her PhD thesis work, the PI is using various methods to uncover
the underlying causes of this widening of the MS.  Here we propose to
use the ARCSAT 0.5m to observe northern nearby (within 25pc) M dwarf stars with
accurate parallaxes and excellent photometry (hence, the MS positions
are not in question) to obtain short-term variability data that can
provide insight into the surface magnetic field activity of these
stars.  We will regularly observe a target for up to 5 hours with the
longest exposures being 300s, which will allow us to observe two stars
each night.  We do not require photometric conditions or a completely
dark sky as we are doing relative photometry.  We will defocus the
telescope as needed to obtain about one million total counts without
saturating, allowing us to sample stellar light curves to ~1 millimag precision.
Thus, we will be able to confirm magnitude changes due to flare
activity on the order of ~5 mmags.  These data will complement our
spectroscopy efforts on the APO 3.5m to measure metallicities,
astrometric work to measure space velocities to probe age
characteristics, and programs at CTIO to sample southern stars.  Our
goal is to obtain astrometric, photometric, and spectroscopic sets of
data on a minimum of 100 stars.  The ARCSAT monitoring is an important piece of the
thesis work that will allow us to understand the role of magnetic
activity in the width of the low mass MS.