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Within-Season Changes in the Periodsand Light Curves of W UMa Binaries
Russ Genet Orion Observatory
Tom Smith Dark Ridge Observatory
Dirk Terrell Southwest Research Institute
The 94th Spr9ing Meeting of the AAVSOMarch 25-26, 2005, Las Cruces, New Mexico
Presented at
Acknowledgment for support fromErick Sturm and Ray Weymann
•Common envelope with mass and luminosity transfer between the two stars
•Convective (W UMa) and Radiative Envelopes
•Tend to have period and light curve variability
Overcontact Binaries
W UMa Systems
OC Systems with convective envelopes are the W UMa systems
Early-type Systems
OC Systems with radiative envelopes do exist, e.g. TU Mus
Planets?
W UMa systems have several characteristics that make them favorable for the development of habitable planetary systems.
Light Curve Variability
Inexpensive Equipment• Meade 10” LX200
• SBIG ST-7XE CCD
• UBVRCIC Filter Set
The Wilson-Devinney Program• First published in 1971 by Bob Wilson and Ed Devinney
• Still being developed. New version uses filter bandpasses rather than effective wavelengths. Adds Kurucz atmospheres.
• Uses modified Roche model to compute figures of the stars. Can model stars with eccentric orbits and non-synchronous rotation.
• Can do light curves, radial velocity curves and spectral line profiles. Unpublished versions have added ability to model polarization curves, fluorescence and X-ray pulses.
• Consists of two programs:
• LC computes light curves given a set of parameters
• DC fits light curves to observations using the method of differential corrections
Program Objectives
Looking for subtle changes in light curve shapes and eclipse timing
* Within season * Between seasons
Light curve shape changes could be due to
* Starspots * Bright steaming * Observational errors
Eclipse timing changes could be due to
* AML * Applegate * Micro MT episodes * Third bodies *Obs error
Program Approach
Make lots of observations
Worry precision, both timing and photometric
Taylor analysis to the situation
Learn and refine
Make Lots of Observations
Total Dedication Multiple Observatories
Binaries * Few * Short period * North * Strategy
Maximize Observing Time * Nightly (airmass) * Seasonal (dew)
Semi-Automation * Observations * Reduction * Analysis
Binary DRO Orion Total
V523 Cas 31 15 46 RW Com 18 8 26V400 Lyr 7 10 17TZ Boo 18 13 31V1191 Cyg 22 39 61GM Dra 14 3 17
Totals 110 88 198
~Obs/Night x640 x320
~Total Obs 70K + 28K = 98K
Pilot Season Observations
RW Com (20040508) Rc (JD:2453134)
10.400
10.500
10.600
10.700
10.800
10.900
11.000
11.100
11.200
11.300
11.400
Julian Date
Inst
rum
ent
Mag
nit
ud
e
-0.400
-0.300
-0.200
-0.100
0.000
0.100
0.200
0.300
0.400
0.500
0.600
C-K
Ph
oto
met
ry
C-V(meas) + C Known
C-K
V400Lyr (20040808) Rc
2.800
2.900
3.000
3.100
3.200
3.300
3.400
3.500
3.600
3.700
3.800
3.900
4.000
JD: 2453226
Inst
rum
ent
Mag
nit
ud
e
-0.970
-0.870
-0.770
-0.670
-0.570
-0.470
-0.370
-0.270
-0.170
-0.070
0.030
0.130
0.230
0.330
0.430
0.530
0.630
C-K
C-V(meas) + C Known
C-K
V523Cas (20040912) Rc
0.200
0.300
0.400
0.500
0.600
0.700
0.800
0.900
1.000
1.100
1.200
1.300
1.400
HJD: 2453261
Inst
rum
ent
Mag
nit
ud
e
-0.270
-0.170
-0.070
0.030
0.130
0.230
0.330
0.430
0.530
0.630
0.730
0.830
0.930
C-K
C-V(meas) + C Known
C-K
Make Lots of Observations
Total Dedication Multiple Observatories
Binaries * Few * Short period * North * Strategy
Maximize Observing Time * Nightly (airmass) * Seasonal (dew)
Semi-Automation * Observations * Reduction * Analysis
Worry Precision
Timing Precision Clock / time recorded Shutter Barycentric correction
Photometric Precision Model (Howell + Young) Brightness (program & comps) Same position / instrument Flats, transformations Guiding, defocus, dither
Aperture Experiment
Erick Sturm Cal Poly
Taylor Analysis
Light Curve Shapes Parametric / nonparametric Simple statistics / entire curves Smoothing / point by point Single nights / grouped nights
Eclipse Timing Errors (internal / external) Minimize seasonal scatter Interactions / Cuts Part curve / whole curve Hertzsprung method Sliding whole-curve fits Master curves / Tsesevich Seasonal ephemeredes
Hertzsprung Method
Folded Data Results
8.931
8.932
8.933
8.934
8.935
8.936
8.937
8.938
8.939
8.94
0.86 0.88 0.9 0.92 0.94 0.96 0.98
Miliphase
Relat
ive M
agni
tude
Series1
O-C Combined Data OO and DRO
-30.00
-25.00
-20.00
-15.00
-10.00
-5.00
0.00
5.00
10.00
15.00
20.00
25.00
0 100 200 300 400 500 600
Orbital Cycles
O-C
(S
eco
nd
s)
=
O-C Combined Data OO and DRO
-30.00
-20.00
-10.00
0.00
10.00
20.00
0 100 200 300 400 500 600
Orbital Cycles
O-C
(S
eco
nd
s)
=
Number of Points 32Standard Deviation 4.3 secStd Error of Mean 0.8 sec
Learn and Refine
Lots of Observations Aperture Simultaneous color bands More complete automation Precision Aperture Simultaneous color bands Various refinements
Analysis
Feedback
MTT
Multiple Tube Telescopes
B
V
R I
U BV
c
R
I
Four Shooter Five Banger
c
Two-Channel Dichroic
Four Color
Observations this past season 98K
Observations this coming season8 months * 20 obs/month * 2 observatories = 320 nights320 (Orion) +640 (Dark Ridge) = 1000 obs/night320 nights * 1000 obs / night = 320K ObsSay 180K obs 2005 seasonIf 3 binaries, then 60K obs/binary
10” to 20” x 41 filt to 2 filt x 2
14” to 20” x21 filt to 2 filt x 2
2.5 K obs/night eachTotal of 5K obs/night320 nights/season1.6Meg obs/seasonIf 3 binaries, then533K obs/binary/season
Potential Throughput
32 nights = 15K observationsYielded 0.8 sec SD
533K obs possible 2 ea .5-m 2 flts533K/15K = 34.7Sqrt 34.7 = 5.8
0.8/5.8 = 0.14 sec
If ensemble *2 then Sqrt 2 factor0.14/Sqrt2 = 0.1 sec
If 4 instead of 20.1/Sqrt2 = 0.07 sec
Potential Precision
Learn and Refine
Lots of Observations Aperture Simultaneous color bands More complete automation Precision Aperture Simultaneous color bands Various refinements
Analysis
Feedback
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