ARCSAT ID NUMBER: AS04

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

PI: Tiffany Clements (Pewett) (GSU)

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

UNCERTIFIED/UNTRAINED OBSERVERS:

COLLABORATORS:
 
CONTACT INFORMATION: Tiffany Clements (Pewett), pewett@astro.gsu.edu,
(419)460-0072

TIME REQUESTED: 
We request one week for the Q2 semester.
Any of the following four weeks are best. 

1. APR 25-MAY1
2. MAY 9-15
3. MAY 23-29
4. JUN 06-12



INSTRUMENT: SurveyCam

FILTERS: Johnson-Cousins VRI

COMMENTS:
Any moon phase is good.

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
temperatures differ by a factor of 16 in luminosity in the V
band. This implies that red dwarfs with identical V-K colors differ in
radius by a factor of four. It is our goal to determine 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 continue observing northern nearby (within 25
pc) 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
4 to 5 hours with the longest exposures being 300s, which will allow
us to observe two stars each night.  We request a week closer to April or May for the longer nights so we can observe more targets in a given evening. We do not require photometric
conditions, nor a completely dark sky as we are doing relative
photometry.  So far we have successfully observed 47 stars with ARCSAT
and the initial results for 13 fully reduced fields indicate that we
can routinely reach a one standard deviation level in variability of
~3.5 millimags.  These data will complement our spectroscopy efforts
on the APO 3.5m to measure metallicities and other properties,
astrometric work to measure space velocities to probe age
characteristics, and our program at CTIO to sample southern stars. Our
goal is to obtain astrometric, photometric, and spectroscopic sets of
data on a minimum of 100 stars (and preferably closer to 200); thus far we have obtained short-term
variability for 88 stars (41 from Chile, 47 using ARCSAT).  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.

Our nights will be shared with those of CoI Silverstein's proposed
photometric observations. During photometric conditions, her
observations will be done, while observations for this project will be
done during the remaining lower quality nights.