B-TYPEECLIPSINGBINARYSTARSIN THEBOCHUMGALACTICDISKSURVEY DISSERTATION zur Erlangung des Grades „Doktor der Naturwissenschaften“ an der Fakultät für Physik und Astronomie der Ruhr-Universität Bochum von LENAMARIAKADERHANDT aus Herdecke Bochum, 2016 gutachter: Prof. Dr. Rolf Chini, Ruhr-Universität Bochum PD Dr. Horst Fichtner, Ruhr-Universität Bochum Disputation: 15.12.2016 Lena Maria Kaderhandt: B-type Eclipsing Binary Stars in the Bochum Galactic Disk Survey, c 2016 To my parents and my grandmother Maria ABSTRACT This thesis investigates eclipsing binary stars (EBs) of spectral type B in the Bochum Galactic Disk Survey (GDS). In order to place the B-type EBs in the context of other types of variable stars, both in terms of spectral and variability class, a general census of variable stars contained in the GDS was conducted first. By cross-matching the list of 64149 GDS variable sources with existing databases it was found that ∼90% of the catalogue matched stars were not known to be variable before. Of the known variable sources, 50.8% have not been classified yet, the others consist mostly of EBs (22.5%) and pulsating stars (22.8%). The variable stars with known spectral types are predominantly of type B (993 or 30.8%) and M (1001 or 31.1%). It was found that the majority of B stars with known variability type are EBs (229 or 23.1%) and that the fraction of EBs decreases to later spectral types. A brief survey of other variability types in spectral class B is also given. 237 B-type EBs – 167 known, 63 new and 7 of different catalogue classification – from the sample of automatically classified light curves provided by C. Fein were selected for further analysis. Amplitudes and lower limits for orbital eccentricities were calculated, yielding minimum eccentricities of up to ∼ 0.45. The new EBs were preliminarily grouped into contact classes, containing 16 contact (EC), 22 semi-detached (ESD) and 25 detached (ED) systems with periods from 0.32 d to 7.7 d in the EC, 0.7 d to 13 d in the ESD and 1.3 d to 25 d in the ED category. Flux amplitudes between 0.06 and 0.2 were found for the EC systems, indicating either low inclinations or their really being ellipsoidal variables. For half of the systems the brightness amplitudes are larger than 0.1 mag, which is in favour of their being EBs. Flux amplitude ratios are always close to 1. In the ESD and ED categories we find potentially larger inclinations, flux amplitudes reaching up to 0.4 and 0.3, respectively. The flux amplitude ratios imply significant temperature differences for many of the systems in both of these categories. Preliminary conclusions regarding the physical parameters of the new systems are provided along with suggestions for further studies. For the known EBs, catalogue periods were compared with our periods, finding agree- ment for the largest part. In one case we could improve on the catalogue period, in two more cases we provide a valid alternative where future measurements have to decide on the correct value. v PUBLICATIONS Some results and figures have been published previously by the author in Kaderhandt et al. 2015: Kaderhandt, L.; Barr Domínguez, A; Chini, R.; Hackstein, M.; Haas, M.; Pozo Nuñez, F.; Murphy, M: Variable stars in the Bochum Galactic Disk Survey. In: Astronomische Nachrichten, 336 (2015), September, S. 677. http://dx.doi.org/10.1002/asna.201512201. – DOI 10.1002/asna.201512201 vii CONTENTS 1 INTRODUCTION 1 2 OBSERVATIONS AND DATA REDUCTION 5 3 VARIABLESTARSINTHEGDS-ANOVERVIEW 9 3.1 Source identification 9 3.2 Classification of variable stars 10 3.3 Spectral types and variability 12 3.4 Amplitudes 16 4 B S TA R S 19 4.1 Eclipsing binaries 34 4.1.1 New eclipsing binary candidates 49 4.1.2 EB candidates with different catalogue classification 69 4.1.3 Known eclipsing binaries 75 5 S U M M A RY A N D O U T L O O K 79 A A P P E N D I X A - TA B L E S 81 A.1 Amplitudes and eccentricities 81 A.2 Calculated spectral types 90 B APPENDIX B - CONCEPTS AND METHODS 95 B.1 Orbital elements 95 B.2 Newton’s method 97 B.3 Calculation of intrinsic star colours 98 B I B L I O G R A P H Y 101 ix LISTOFFIGURES Figure 1 Magnitudes of GDS variables in r0 (blue) and i0 (red). 6 Figure 2 i0 versus r0 magnitudes of all GDS variables. 7 Figure 3 Distribution of the known variables over variability types. 11 Figure 4 Distribution of variable stars over spectral types. 12 Figure 5 Distribution of the main variability types over spectral types. 14 Figure 6 Left: i0 vs. r0 magnitudes of all stars with known spectral type, right: the same without classes M, S, C and N. 16 Figure 7 Amplitude distribution for all sources in r0 (blue) and i0 (red). 17 Figure 8 i0 vs. r0 amplitudes plotted separately for all known variables and for each category. Note that axis scales have been adapted for each category. 18 Figure 9 Distribution of the B stars over variability types. 19 Figure 10 Light curve of DW CMa, blue=r0, red=i0, black=nearby constant comparison star for each filter. 20 Figure 11 Light curve of V640 Car, colour scheme as in Figure 10. 21 Figure 12 r0 light curve of HD 90834 folded with P = 231 d. 22 Figure 13 Light curve of IRAS 07377-2523, colour scheme as in Figure 10. 23 Figure 14 Light curve of HU CMa, colour scheme as in Figure 10. 24 Figure 15 r0 light curve of TYC 8977-2816-1, folded with P = 3.40701 d. 26 Figure 16 r0 light curve of V426 Car, folded with P = 7.5375 d. 26 Figure 17 r0 light curve of V754 Mon, folded with P = 1.505 d. 27 Figure 18 r0 light curve of HD 65743, folded with P = 1.84372 d. 28 Figure 19 Light curve of V735 Car, folded with P = 3.145 d. Blue=r0, red=i0. 29 Figure 20 Light curve of HD 141926, colour scheme as in Figure 10. 30 Figure 21 Top: Light curve of HD 330950 in r0. Bottom: Light curve of HD 330950 in i0. Nearby constant comparison source in black. 31 Figure 22 Sloan filter curves. r0 is in red, i0 in purple. 32 Figure 23 Amplitudes of Be stars in i0 vs. r0. 33 Figure 24 Schematic EB configurations and corresponding typical light curves. 36 x List of Figures xi Figure 25 Minima timing. 37 Figure 26 Eclipse geometry (based on Smith 1995). 38 Figure 27 Dependence of eccentricity on phase difference. 41 Figure 28 Top: Distribution of calculated mean minimum eccentricites with a bin size of 0.01, bottom: mean eccentricity vs. period with log- arithmic period axis. 42 0 Figure 29 r light curve of BN Cir, P = 4.4098 d, emin = 0.45. 43 0 Figure 30 r light curve of V674 Car, P = 19.811 d, emin = 0.31. 44 0 Figure 31 r light curve of HD 306096, P = 5.38322 d, emin = 0.3. 45 Figure 32 Periods of the EB sample, bin size 0.5 d. 46 Figure 33 Colour-colour diagram for all 192 EBs where UBV measure- ments were available. The intrinsic colours of the main sequence are plotted in colour with violet=O, blue=B, cyan=A, green=F, yellow=G, orange=K, red=M. Also shown is an extinction vector for spectral type B0 and a visual extinction of Av = 2 mag. 48 Figure 34 Period distribution for the EC (top), ESD (middle) and ED sys- tems (bottom), bin size 0.5 d. 50 Figure 35 Minimum eccentricity versus period for the new EB candidates; black=EC, red=ESD, blue=ED. 51 Figure 36 Flux-normalised r0 light curve of CD-24 5898A, P = 7.66801 d. 52 Figure 37 Flux-normalised r0 light curve of HD 300814, P = 3.39773 d 53 Figure 38 Flux-normalised r0 light curve of CCDM J06493-0239AB, P = 1.33653 d. 54 Figure 39 Flux-normalised r0 light curve of TYC 4799-714-1, P = 6.32693 d. 55 Figure 40 Flux-normalised r0 light curve of TYC 8959-350-1, P = 5.38739 d. 56 Figure 41 Flux-normalised r0 light curve of 2MASS J06401339-0114484, P = 4.17805 d. 57 Figure 42 Flux-normalised r0 light curve of BD-17 5191s, P = 0.395328 d 57 Figure 43 Flux-normalised r0 light curve of HD 328533, P = 4.65906 d. 59 Figure 44 Flux-normalised i0 light curve of HD 150723, P = 4.70469 d. 60 Figure 45 Flux-normalised r0 light curve of CPD-59 2618, P = 0.97187 d. 62 Figure 46 Flux-normalised r0 light curve of [ICS99 A], P = 3.48027 d. 62 Figure 47 Flux-normalised r0 light curve of HD 168862, P = 4.44639 d. 64 Figure 48 Flux-normalised r0 light curve of HD 60366, P = 4.27526 d. 65 xii List of Figures Figure 49 Flux-normalised r0 light curve of CPD-26 2634, P = 5.47088 d. 66 Figure 50 Flux-normalised r0 light curve of HD 53542, P = 2.38978 d. 67 Figure 51 Flux-normalised r0 light curve of HD 295887, P = 4.69846 d. 67 Figure 52 Flux-normalised r0 light curve of CD-59 5583, P = 8.70544 d. 69 Figure 53 Flux-normalised r0 light curve of HD 295557, P = 9.55283 d.