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BP Velorum, V392 Carinae and V752 Centauri

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BP Velorum, V392 Carinae and V752 Centauri Analysis of three close eclipsing binary systems: BP Velorum, V392 Carinae and V752 Centauri A thesis submitted in partial fulfilment of the requirements for the degree of Master of Science Hana Josephine Schumacher 2008 Department of Physics and Astronomy, University of Canterbury, Private Bag 4800, Christchurch, New Zealand Abstract This thesis reports photometric and spectroscopic studies of three close binary systems; BP Velorum, V392 Carinae and V752 Centauri. BP Velorum, a W UMa-type binary, was observed photometrically in February 2007. The light curves in four filters were fitted simultaneously with a model generated in the eclipsing binary modeling software package PHOEBE. The best model was one with a cool star spot on the secondary larger component. The light curves showed additional cycle-to- cycle variations near the times of maximum light which may indicate the presence of star spots that vary in strength and/or location on a time scale comparable with the orbital period, (P = 0d.265). The system was confirmed to belong to the W-type subgroup of W UMa binaries for which the deeper primary minimum is due to an occultation. V392 Carinae, a detached binary with an orbital period of 3d.147, was observed pho- tometrically by Michael Snowden in 1997. These observations were reduced and com- bined with the published light curve from Debernardi and North (2001). High resolution spectroscopic images were taken using the University of Canterbury’s HERCULES spec- trograph. The radial velocities measured from these observations were combined with velocities from Debernardi and North (2001). The radial velocity and light curves were fit simultaneously, confirming that V392 Car is a detached system of two main sequence A stars with a mass-ratio of 0.95. The derived systematic velocity is consistent with V392 Car being a member of the open cluster NGC 2516. The W UMa-type binary V752 Centauri was observed photometrically and spectro- scopically during 2007. The high resolution spectra displayed weak sharp lined features superimposed over the strong broad lined spectrum expected from the 0d.370 contact bi- nary. Fourier methods were used to separate the broad and sharp spectral features and radial velocities for each were measured by cross-correlation. A fit to the photometry and radial velocities for the contact binary implied a system of two late F stars with a mass-ratio of 3.38 in an over-contact configuration. The derived systematic velocity ( 13.8kms−1), has changed significantly from the 1972 value (29.2kms−1). The third − (sharp lined) component’s radial velocities were measured and found to have a period of 5d.147, semi-amplitude of 43.4kms−1 and systematic velocity of 7.3kms−1. The likely − configuration of the entire system is that of a contact binary in a long period orbit about a lower mass detached binary. V752 Cen is thus a triple lined spectroscopic quadruple. Contents 1 Introduction 1 1.1 Binary Systems of Stars: Historicaloverview ............................... 1 1.2 EclipsingBinaryStars ............................. 2 1.3 Classification of Close Binary Systems: The Roche Model . .... 3 1.4 WUMa-typeBinaries ............................. 7 1.5 Motivationforthiswork . 8 2 Observations 10 2.1 Photometry ................................... 10 2.2 Spectroscopy .................................. 11 2.2.1 HERCULES............................... 11 3 Reductions and Software 13 3.1 Photometry ................................... 13 3.1.1 MIRAAL................................ 13 3.1.2 ReducingPhotometricImages . 13 3.1.3 Heliocentric Correction . 15 3.2 Reduction of the Spectroscopic Images . 15 3.3 PreparationoftheSpectra . 16 3.4 Cross-correlationoftheSpectra . 16 3.5 TheSpectroscopicOrbitalSolution . 18 3.6 PHysicsOfEclipsingBinariEs . 19 iii 4 BP Velorum 20 4.1 PreviousModel ................................. 20 4.2 PreparationoftheLightCurves . 21 4.3 ModelingwithPHOEBE............................ 23 4.3.1 UnspottedModel ............................ 24 4.3.2 SpottedModel ............................. 25 4.4 Solution ..................................... 27 5 V392 Carinae 31 5.1 Photometry ................................... 32 5.1.1 PhotometricDataPreparation. 32 5.1.2 PhotometricModel . 33 5.2 Spectroscopy .................................. 35 5.2.1 Spectroscopic Data Preparation . 35 5.2.2 Radial Velocity Measurements . 36 5.3 OrbitalAnalysis................................. 39 5.4 ModelingwithPHOEBE............................ 39 5.5 ComparisonwithPreviousModel . 42 6 V752 Centauri 44 6.1 Photometry ................................... 45 6.1.1 PhotometricDataPreparation. 45 6.1.2 PhotometricModel . 46 6.2 Spectroscopy .................................. 49 6.2.1 Radial Velocity Measurements . 49 6.3 OrbitalAnalysis................................. 53 6.4 PHOEBE .................................... 54 6.4.1 Model with initial mass-ratio q = 3.15 ................ 55 6.5 ThirdComponent................................ 58 6.5.1 DeterminingthePeriod. 58 6.5.2 V752 Centauri: A triple system? . 59 iv 7 Summary 63 7.1 BPVelorum................................... 63 7.2 V392Carinae .................................. 63 7.3 V752Centauri.................................. 64 7.4 Futurework................................... 65 References 66 Acknowledgements 69 A MATLAB code 70 B Photometry Measurements 86 C Radial Velocity Measurements 151 v List of Figures 1.1 The orbital plane of the objects as seen from the Earth. ........... 2 1.2 A schematic diagram of the Lagrangian points in the Roche model. .... 4 1.3 Configurations of close binary stars given by the Roche Model. ....... 6 4.1 Goodness of fit parameter figure taken from Lapasset et al. (1996). 21 4.2 BP Vel (O-C) residuals. ............................ 23 4.3 Goodness of fit parameter determined using models produced by PHOEBE. 24 4.4 The unspotted WD model in BV RI filters. .................. 25 4.5 The spotted WD model in BV RI filters. ................... 26 4.6 3-D plots of the surface of BP Velorum (with spot). ............. 26 4.7 The light curves of BP Vel in the Visual filter. ................ 29 4.8 The light curves of BP Vel in the Red filter. ................. 29 5.1 The light curve of V392 Car in Stromgren B filter. .............. 33 5.2 The light curve of V392 car in Stromgren Y filter. ............. 33 5.3 The V-light curve in GENEVA filter of V392 Car. .............. 34 5.4 3-D plots of the surface of V392 Car. ..................... 34 5.5 The combined spectrum of V392 Car. ..................... 35 5.6 The strong Hβ absorption line from fig 5.5. ................. 36 5.7 The cross-correlation function for V392 Car coming into an eclipse. 37 5.8 The cross-correlation function of V392 Car near a time of maximum sepa- ration. ...................................... 38 5.9 The Radial Velocity curves from both components of V392 Car including the measurements from Debernardi and North (2001). ............ 38 vi 5.10 The Radial Velocity curves from both components of V392 Car fitted with the model generated in PHOEBE. ....................... 40 6.1 The unspotted WD model in BV RI filters. .................. 47 6.2 The spotted WD model in BV RI filters. ................... 48 6.3 3-D plots of the surface of V752 Cen (with spot). .............. 48 6.4 Spectrum of V752 Cen near a time of eclipse. ................ 51 6.5 A CCF profile of V752 Cen: the contact binary near a time of eclipse. 52 6.6 A CCF profile of V752 Cen: the contact binary near a time of maximum separation. .................................... 52 6.7 The sine fit using least squares optimization for V752 Cen. ......... 53 6.8 PHOEBE’s model radial velocity curves with the measured velocities from V752 Cen. ................................... 56 6.9 An example of the CCF of the third component of V752 Cen. ....... 58 6.10 The sine fit using least squares optimization for the third component’s total velocities in MATLAB. ............................. 59 6.11 Schematic diagrams showing the possible geometric configurations of the complete V752 system. ............................. 60 6.12 Spectrum of V752 Cen near a time of maximum light from the contact binary. 62 vii List of Tables 1.1 The details of the three stars analysed in this thesis. ............. 9 2.1 The resolution of HERCULES fibre positions ................. 11 2.2 The dates of the observing runs completed for this research. ........ 12 4.1 Photometric Solutions for BP Velorum from Lapasset et al. (1996). 22 4.2 Star spot parameters from Lapasset et al. (1996). .............. 22 4.3 Star spot parameters determined with PHOEBE. .............. 27 4.4 Photometric Solution for BP Velorum determined from our model gener- ated using PHOEBE. .............................. 28 5.1 The orbital elements of V392 Car. ....................... 39 5.2 The absolute parameters of V392 Car. .................... 40 5.3 Solution of V392 Car determined from PHOEBE. .............. 41 5.4 The physical parameters of V392 Car determined by Debernardi and North (2001) ...................................... 42 5.5 The orbital parameters of V392 Car taken from Debernardi and North (2001). 43 6.1 The derived parameters of V752 Cen taken from Barone et al. (1993). 45 6.2 The orbital elements of V752 Cen ....................... 54 6.3 Star spot parameters for V752 Cen. ..................... 55 6.4 The solution to the spotted and unspotted models from PHOEBE. ..... 57 B.1 The photometric measurements of BP Velorum. ............... 86 B.2 The photometric measurements of V752 Centauri. .............101
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