ARCSAT ID NUMBER: AS04

DESCRIPTIVE TITLE: Census of Variable stars in the UMi dwarf
spheroidal galaxy.

PI: Karen Kinemuchi

OBSERVER(S): Karen Kinemuchi

UNCERTIFIED/UNTRAINED OBSERVERS: Karen Kinemuchi

COLLABORATORS: Recruiting collaborators at the moment!
 
CONTACT INFORMATION: Karen Kinemuchi:  (email): kinemuchi@apo.nmsu.edu
or kkinemuchi@gmail.com  (phone): 352-514-5013

TIME REQUESTED: 
June 2-8  and/or  June 23-29 and/or July 7-13 (see comment)

INSTRUMENT: SurveyCam

FILTERS: Broadband Johnson BVRI (preferred) or Sloan gri

COMMENTS: 
For the week of July 7-13, I will be onsite for the observations due
to my 2.5m duties.  I will arrange with my observing partner (Dmitry
Bizyaev) on the overlap nights to facilitate work on both telescopes.
With the timing so soon to monsoon season, the likelihood of obtaining
data is low, but still worth a try. 

BRIEF SCIENCE JUSTIFICATION:  

The classical dwarf spheroidal galaxy Ursa Minor contains a large
number of variable stars, particularly of the RR Lyrae and anomalous
Cepheid types.  I propose to do an updated census of variable stars of
the dwarf galaxy.  A previous census included data points from
photographic plates (22 epochs) and a number of CCD observations
(38 epochs) (Nemec et al. 1988).  The ARCSAT telescope and the SurveyCam are ideally
suited for this project: the camera has a large enough field of view
to get the entire galaxy and the telescope scheduling allows for good
phase coverage for variable stars.  We expect the exposure times to be
on the order of 600-900 seconds in order to reach the horizontal
branch of UMi (V~19.5) (Bellazzini et al. 2002). 

The goal will be to produce an updated catalog of variable stars,
their (re)classification, new period determinations (or discovery of
period modulations), and a list of new ephermerides for the
pulsators.  The photometry will be done with DAOPHOT, much like the
Nemec study, and the analysis of the RR Lyrae population will be
similar to the work done with the Draco dwarf spheroidal galaxy
(Kinemuchi et al. 2008).  With enough data points (minimum of 40 epochs), we will determine
photometric metallicities using the Jurcsik & Kovacs (1996) method via
Fourier decomposition parameters.  We will provide an analysis of the
RR Lyrae variable star population, as well a discussion of other
variables discovered in this census.  We hope to also update the
number of anomalous Cepheids associated with this dwarf galaxy
(anomalous Cepheids are preferentially found in dwarf spheroidal
galaxies).  These Cepheids provide another independent method of
deriving distances to the galaxy, but are less understood than their
Pop I and II cousins.

REFERENCES:
Bellazzini, M., et al. 2001, AJ, 124, 3222
Jurcsik, J. & Kovacs, G., 1996, A&A 312, 111
Kinemuchi, K. et al. 2008, AJ 136, 1921 
Nemec, J., Wehlau, A., & Mendes de Oliveira, C., 1988, AJ, 96, 528