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 Unpublished versions have added ability to model polarization curves, fluorescence and X-ray pulses.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