1.
The
CRTS
light
curves
of
269
CVs
from
the
Sloan
Digital
Sky
Survey
(SDSS)
were
analysed
using
Python
by
ploDng
their
light
curves.
From
the
light
curves
the
CVs
could
be
characterised
to
determine
whether
they
were
polar,
eclipsing,
nova-­‐like
or
detached
systems.
The
spectra
available
from
SDSS
also
allowed
for
a
further
analysis
of
the
CVs
by
examining
characterisJc
lines
of
the
spectra.
[3]
The
orbital
period
was
found
by
two
data
analysis
techniques:
phase
dispersion
minimizaJon
(PDM)
and
least-­‐squared
spectral
analysis
(LSSA)
.
Both
methods
allowed
data
to
be
folded
on
a
trial
period
of
which,
if
the
data
were
periodic,
it
would
produce
a
light
curve
with
sinusoidal
variaJons
(Fig
3).
The
two
analysis
techniques
could
then
be
compared
to
find
the
beVer
method
of
selecJng
and
obtaining
the
orbital
period.
2.
Method
A
large
variaJon
of
CVs
were
analysed
from
the
data
set
from
CRTS.
This
variaJon
was
mostly
due
to
the
accreJon
disk,
making
it
harder
to
resolve
eclipses
in
the
light
curves
and
to
fold
on
a
target
period.
However,
the
analysis
of
the
269
light
curves
allowed
for
many
of
them
to
be
characterised
as
well
as
a
handful
of
orbital
periods
to
be
obtained.
Cataclysmic
variables
(CVs)
are
binary
stars
that
vary
in
their
brightness
in
short
Jme
periods
of
a
few
hours.
CVs
consists
of
a
very
bright
white
dwarf
and
an
orbiJng
red
dwarf.
As
the
red
dwarf
orbits
around
the
white
dwarf
periodically,
some
eclipses
can
be
seen
in
their
light
curve
by
decreases
in
its
brightness.
Another
feature
of
CVs
are
bright
outbursts
(Fig
2)
that
can
frequently
occur
due
to
thermal
instability
in
the
accreJon
disks
thus
allowing
for
CVs
to
be
detected
by
CRTS.[1]
The
Catalina
real
Jme
transient
survey
(CRTS)
covers
33000
deg2
of
the
sky
exploring
transient
objects
using
data
from
3
telescopes.
The
survey
has
been
running
for
almost
7
years,
enough
Jme
to
produce
reliable
light
curves.[2]
By
establishing
parameters
such
as
orbital
periods
and
their
stellar
masses,
a
more
in
depth
understanding
of
their
evoluJon
can
be
formed.
The
most
accurate
measurements
come
from
eclipsing
systems.
1.
IntroducJon
Eclipsing
Cataclysmic
Variables
from
CRTS
Melissa
Liow
m.liow@warwick.ac.uk
Supervisors:
Elmé
Breedt
and
Boris
Gänsicke
Astronomy
Group,
Department
of
Physics
• 249
CVs
had
complete
data
available
to
produce
light
curves.
30
CVs
had
their
periods
recovered
of
which
there
were
found
to
be
20
dwarf
novae,
6
nova-­‐like,
3
polar
CVs
and
1
detached
system.
• From
the
30
CVs
9
new
periods
were
obtained.
• 8
CVs
were
found
to
be
eclipsing.
• PDM
was
found
to
be
the
beVer
method
of
finding
the
orbital
periods
and
was
more
accurate,
obtaining
7
periods
that
agreed
with
previous
results.
3.
Results
4.
Conclusion
References:
[1]
Drake,
A.J.
et
al.
First
Results
from
the
Catalina
Real-­‐Jme
Transient
Survey
(2009).
[2]
SDSS
data
release
10,
www.sdss3.org,
last
accessed
23/08/14.
[3]
C
Hellier,
Cataclysmic
variable
–
How
and
why
they
vary,
Springer
science
&
Business
media
(2001)
Fig
1.
The
spaJal
distribuJon
of
269
CVs
detected
by
SDSS.
Fig
3.
a,
b,
c,
d.
(top
leg,
clockwise)
a)
A
detached
system
with
a
period
of
6.7hrs.
The
variaJon
is
due
to
one
side
of
the
red
dwarf
being
heated
by
the
hot
white
dwarf.
b)
An
AM
Her
(polar)
CV
with
a
period
of
1.75hrs.
Polars
do
not
have
accreJon
disks
as
the
magneJc
field
of
the
white
dwarf
controls
the
flow
of
material.
c)
A
dwarf
nova
CV
with
a
period
of
2.77hrs
and
many
outbursts
seen
in
its
light
curve.
d)
A
deeply
eclipsing
CV
with
a
period
of
3.14hrs.
Fig
2.
The
light
curve
(leg)
of
an
eclipsing
CV
(known
as
DV
UMa)
with
two
outbursts
of
low
magnitude.
The
folded
light
curve
(right)
shows
the
system
eclipsing
at
a
period
of
2.06hrs.