ARCSAT ID NUMBER: AS08

DESCRIPTIVE TITLE: Monitoring long-term orbital period variations and
transient events in bright Cataclysmic Variables

PI: Paula Szkody

OBSERVER(S): Zhibin Dai

UNCERTIFIED/UNTRAINED OBSERVERS: 

COLLABORATORS: Zhibin Dai
 
CONTACT INFORMATION: 
Zhibin Dai
E-mail: zhibin_dai@ynao.ac.cn
off: (86) 871-67339079
Res:
Cell: (86) 18988418816

TIME REQUESTED: 
Priority order        time               moon phase  
       1.             May 2 - 8              dark
       2.             May 30 - June 5        dark
       3.             June 27 - July 3       dark


INSTRUMENT: FlareCam

FILTERS: SDSS ugriz

COMMENTS:

BRIEF SCIENCE JUSTIFICATION: 

Considering that cataclysmic variables (CVs) are famous for
high-amplitude and rapid photometric variations within an orbital
cycle, ARCSAT is ideal to study these features in bright CVs. Besides
dwarf novae with short orbital periods, Nova-like variables including
SW Sex-type CVs with high accretion rates and Intermediate polars
(systems with magnetic white dwarfs) with long orbital periods, are
also critical to unravel accretion phenomena related to CV formation
and evolution. The parameters of CVs located on the high edge of the
period gap (at 3-4 hrs) are especially important for tests of the
current standard evolution theory of CVs. Although some of them have
been previously studied, many newfound CVs with orbital periods in
this range lack detailed investigation. We attempt to remedy this
situation by accomplishing high time resolution photometry for the
bright targets. Using literature searches, we found that there are
over 200 CVs with magnitudes less than 18 on the upper edge of the
period gap. Many of these objects are observable from May to
July. Moreover, among these, the eclipsing systems comprise nearly 30
percent. By modelling the complete light curves, their basic physical
and geometric parameters can be constrained. Additionally, we also
expect to detect and study many more transient events in Nova-like
stars since their permanent outburst state allows for high accretion
rate effects.

In the summer and winter quarters of 2014, we obtained good results
from ARCSAT, including eight SW Sex type nova-likes; four SU UMa type
dwarf novae; two polars and one U Gem type dwarf nova (EX Dra). Of
these CVs, several targets need further follow-up. In particular, the
reduced light curve of EX Dra shows a good eclipse profile and small
quasi-oscillations outside eclipse. According to our previous
experience, we hope to continue our program and achieve better results
in the following quarter by adjusting some observation parameters.