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Variability of young stars [Elektronische Ressource] / von Claus-Michael Scheyda

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VARIABILITY OF YOUNG STARS DISSERTATION ZUR ERLANGUNG DES GRADES DOKTOR DER NATURWISSENSCHAFTEN FAKULTÄT FÜR PHYSIK UND ASTRONOMIE RUHR-UNIVERSITÄT BOCHUM VON CLAUS-MICHAEL SCHEYDA BOCHUM BOCHUM 2010 1. Gutachter: Prof. Dr. Rolf Chini; Bochum 2. Gutachter: Prof. Dr. Ralph Neuhäuser; Jena Datum der Disputation: 17.09.2010 VARIABILITY OF YOUNG STARS PHD THESIS FACULTY OF PHYSICS AND ASTRONOMY RUHR-UNIVERSITY BOCHUM CLAUS-MICHAEL SCHEYDA BOCHUM BOCHUM 2010 First referee: Prof. Dr. Rolf Chini; Bochum Second referee: Prof. Dr. Ralph Neuhäuser; Jena Date of defense: 09/17/2010 For my father TABLE OF CONTENTS Chapter I – Introduction & Overview ............................................................................................... 1 1.1 Star Formation .............................................................................................................. 1 1.2 Variable Young Stellar Objects ............... 2 1.2.1 TTauri Stars ..................................................................................................... 2 1.2.2 HAeBe Stars ..... 2 1.3 The Omega Nebula ...................................................................................................... 3 1.4 This Thesis ...................................................................................................................... 4 Chapter II – Observation & Data Reduction .................. 5 2.1 Observations ............................

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Ajouté le 01 janvier 2010
Nombre de lectures 25
Langue Deutsch
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VARIABILITY
OF
YOUNG STARS
DISSERTATION
ZUR ERLANGUNG DES GRADES
DOKTOR DER NATURWISSENSCHAFTEN
FAKULTÄT FÜR PHYSIK UND ASTRONOMIE
RUHR-UNIVERSITÄT BOCHUM
VON
CLAUS-MICHAEL SCHEYDA
BOCHUM
BOCHUM 2010 1. Gutachter: Prof. Dr. Rolf Chini; Bochum
2. Gutachter: Prof. Dr. Ralph Neuhäuser; Jena
Datum der Disputation: 17.09.2010
VARIABILITY
OF
YOUNG STARS
PHD THESIS
FACULTY OF PHYSICS AND ASTRONOMY
RUHR-UNIVERSITY BOCHUM
CLAUS-MICHAEL SCHEYDA
BOCHUM
BOCHUM 2010 First referee: Prof. Dr. Rolf Chini; Bochum
Second referee: Prof. Dr. Ralph Neuhäuser; Jena
Date of defense: 09/17/2010

For my father TABLE OF CONTENTS
Chapter I – Introduction & Overview ............................................................................................... 1
1.1 Star Formation .............................................................................................................. 1
1.2 Variable Young Stellar Objects ............... 2
1.2.1 TTauri Stars ..................................................................................................... 2
1.2.2 HAeBe Stars ..... 2
1.3 The Omega Nebula ...................................................................................................... 3
1.4 This Thesis ...................................................................................................................... 4
Chapter II – Observation & Data Reduction .................. 5
2.1 Observations ................................................................................................ 5
2.1.1 Sutherland, South Africa............. 5
2.1.2 Calar Alto, Spain ............................................................................................. 8
2.2 Data Reduction ............................................................................................................ 11
2.2.1 IRSF Data ........ 12
2.2.2 Calar Alto Data .............................................................................................. 12
Chapter III – Data Analysis ................................................................................................................. 15
3.1 Image Subtraction: ISIS ........................... 16
3.1.1 ISIS Operation Overview .......................................................................... 16
3.1.2 ISIS Analysis Steps ...................... 17
3.2 Calibration: IRAF & 2MASS .................................................................................... 24
3.3 Lightcurve Analysis ................................................................................................... 26
Chapter IV – Results & Interpretation ........................... 29
4.1 Types of Young Variables ....................................................................................... 29
4.1.1 Low Mass Young Variables ...................................................................... 29
4.1.2 Intermediate Mass Young Variables .................................................... 35
4.1.3 Other Types of Variables .......................................... 36
4.2 Statistics & Lightcurves ........................................................................................... 37
4.2.1 Statistics Summary ..................... 37
4.2.2 Template Lightcurves ................................................................................ 48
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4.3 Analysis-Diagrams over Time .............................................................................. 55
4.3.1 Color-Color Diagrams ............... 55
4.3.2 Color-Magnitude Diagrams .................................................................... 57
4.4 Comparison to Other Studies ............... 61
4.4.1 IR-Excess and CO-Features ..................................................................... 62
4.4.2 X-Ray Emission ............................................................ 65
4.4.3 Polarization ................................................................... 65
Chapter V – Summary & Outlook ..................................... 69
5.1 Variability as a Tracer for Star Formation ...................................................... 69
5.2 The IRIS Project ......................................................................... 70
Chapter VI – Acknowledgements .................................... 71


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LIST OF FIGURES
Figure I—1: Three color composite of M 17 at optical wavelengths .................................. 3

Figure II—1: The South African Astronomical Observatory .................................................. 6
Figure II—2: Transmissioncurve IRSF J, H, and Ks ..................................... 6
Figure II—3: Schematics of the IRSF SIRIUS-camera ................................ 7
Figure II—4: The Astronomical Center at Calar Alto and the 3.5m telescope ................ 9
Figure II—5: The OMEGA2000 camera mounted on the telescope..... 9
Figure II—6: Erroneous flux subtraction on CAHA image .................................................... 14

Figure III—1: Flow chart displaying ISIS analysis steps ........................ 18
Figure III—2: Erroneous background computation using tiles on CAHA image ......... 19
Figure III—3: Comparison variability image to reference image ....................................... 21
Figure III—4: Noise on the variability image ............................................. 22
Figure III—5: 2MASS reference stars used in this study ....................................................... 25
Figure III—6: Template Gri-plot ...................................................................... 27

Figure IV—1: V-band variability over time diagram of a typical Classical TTauri ...... 30
Figure IV—2: V-band magnitude vs. phase diagram pical Weak-line TTauri .. 31
Figure IV—3: Doppler imaging illustrative of star-spots on a Weak-line TTauri........ 32
Figure IV—4: Template lightcurves of FU Orionis outbursts .............................................. 33
Figure IV—5: V-band photometry of EX Lupi ............................................. 34
Figure IV—6: Small-scale HAeBe variability ............... 35
Figure IV—7: Lightcurve and color-variation of UX Orionis ................................................ 36
Figure IV—8: IRSF field of view superposed on CAHA field of view................................. 38
Figure IV—9: Variable stars per magnitude – combined K .................. 39
Figure IV—10: Rotational period comparison (incl. IR-excess stars) .............................. 41
Figure IV—11: Variable stars per magnitude – JHK (M 17 core) ....................................... 41
Figure IV—12: Average variability depending on reference magnitude ........................ 42
Figure IV—13: Distribution of variability amplitudes ............................................................ 44
Figure IV—14: Distribution of variability periods ................................... 44
Figure IV—15: Time between observations ............................................... 45
Figure IV—16: Variables distribution for inner and outer M 17 ........ 46
Figure IV—17: Variability period comparison inner and outer M17 ............................... 47
Figure IV—18: Variability amplitude comparison inner and outer M17 ........................ 47
Figure IV—19: Comparison of CAHA and IRSF lightcurves of star lc150 ....................... 52
Figure IV—20: ComparisonHA and IRSF lightcurve of star lc395 ......................... 52
Figure IV—21: Comparison of lightcurves in three filters .................................................... 53
Figure IV—22: Comparison of lightcurves derived from IRSF J, H, K, and CAHA K .... 54
Figure IV—23: Two color diagram – (J-H) vs. (H-K) ................................................................ 56
Figure IV—24: Two color diagram – (J-H) vs. (H-K) with color variations .................... 56
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Figure IV—25: Color-magnitude diagram – J vs. (H-K) .......................................................... 58
Figure IV—26: Color-magniiagram – K vs. (H-K) ........................ 58
Figure IV—27: Color-magnitude diagram – K vs. (B-K) ......................... 60
Figure IV—28: Detection conformity comparison to other studies – overall ................. 61
Figure IV—29: Detection conformity comparison to other studies – per magnitude . 62
Figure IV—30: Comparison of variability amplitude with archival data ....................... 63
Figure IV—31: Distribution of variable stars showing IR-excess...................................... 64
Figure IV—32: Distribution of variable stars showing CO-bands ..... 64
Figure IV—33: Distribution of variable stars showing X-ray emission .......................... 66
Figure IV—34: Distribution of variable stars showing polarization ................................ 66

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