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Within-Season Changes in the Periods and Light Curves of W UMa Binaries

Within-Season Changes in the Periods and Light Curves of W UMa Binaries. Russ Genet Orion Observatory Tom Smith Dark Ridge Observatory Dirk Terrell Southwest Research Institute. Acknowledgment for support from Erick Sturm and Ray Weymann. Presented at.

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Within-Season Changes in the Periods and Light Curves of W UMa Binaries

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  1. Within-Season Changes in the Periods and Light Curves of W UMa Binaries Russ Genet Orion Observatory Tom Smith Dark Ridge Observatory Dirk Terrell Southwest Research Institute Acknowledgment for support from Erick Sturm and Ray Weymann Presented at The 94th Spr9ing Meeting of the AAVSO March 25-26, 2005, Las Cruces, New Mexico

  2. Overcontact Binaries • 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

  3. W UMa Systems OC Systems with convective envelopes are the W UMa systems

  4. Early-type Systems OC Systems with radiative envelopes do exist, e.g. TU Mus

  5. Planets? W UMa systems have several characteristics that make them favorable for the development of habitable planetary systems.

  6. Light Curve Variability

  7. Inexpensive Equipment • Meade 10” LX200 • SBIG ST-7XE CCD • UBVRCIC Filter Set

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 Unpublished versions have added ability to model polarization curves, fluorescence and X-ray pulses.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

  9. 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

  10. Program Approach Make lots of observations Worry precision, both timing and photometric Taylor analysis to the situation Learn and refine

  11. 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

  12. Pilot Season Observations Binary DRO Orion Total V523 Cas 31 15 46 RW Com 18 8 26 V400 Lyr 7 10 17 TZ Boo 18 13 31 V1191 Cyg 22 39 61 GM Dra 14 3 17 Totals 110 88 198 ~Obs/Night x640x320 ~Total Obs 70K + 28K = 98K

  13. 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

  14. 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

  15. Aperture Experiment

  16. Erick Sturm Cal Poly

  17. 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

  18. Hertzsprung Method

  19. Number of Points 32 Standard Deviation 4.3 sec Std Error of Mean 0.8 sec

  20. Learn and Refine Lots of Observations Aperture Simultaneous color bands More complete automation Precision Aperture Simultaneous color bands Various refinements Analysis Feedback

  21. MTT Multiple Tube Telescopes U B V B c c V I I R R Five Banger Four Shooter

  22. Two-Channel Dichroic

  23. Four Color

  24. Potential Throughput Observations this past season 98K Observations this coming season 8 months * 20 obs/month * 2 observatories = 320 nights 320 (Orion) +640 (Dark Ridge) = 1000 obs/night 320 nights * 1000 obs / night = 320K Obs Say 180K obs 2005 season If 3 binaries, then 60K obs/binary 10” to 20” x 4 1 filt to 2 filt x 2 14” to 20” x2 1 filt to 2 filt x 2 2.5 K obs/night each Total of 5K obs/night 320 nights/season 1.6Meg obs/season If 3 binaries, then 533K obs/binary/season

  25. Potential Precision 32 nights = 15K observations Yielded 0.8 sec SD 533K obs possible 2 ea .5-m 2 flts 533K/15K = 34.7 Sqrt 34.7 = 5.8 0.8/5.8 = 0.14 sec If ensemble *2 then Sqrt 2 factor 0.14/Sqrt2 = 0.1 sec If 4 instead of 2 0.1/Sqrt2 = 0.07 sec

  26. 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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