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The Many Facets of Cosmic Explosions

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The Many Facets of Cosmic Explosions The Many Facets of Cosmic Explosions Alicia Margarita Soderberg DISSERTATION.COM Boca Raton The Many Facets of Cosmic Explosions Copyright © 2007 Alicia Margarita Soderberg All rights reserved. Dissertation.com Boca Raton, Florida USA • 2007 ISBN: 1-58112- 377-9 13-ISBN: 978-1-58112-377-7 The Many Facets of Cosmic Explosions Thesis by Alicia Margarita Soderberg Advisor Shrinivas R. Kulkarni In Partial Fulfillment of the Requirements for the Degree of Doctor of Philosophy California Institute of Technology Pasadena, California 2007 (Defended May 18, 2007) ii iii c 2007 Alicia Margarita Soderberg All rights Reserved iv v Acknowledgements Arriving at Caltech in 2002, I anticipated five years of challenging and rewarding experiences - I have not been disappointed. Working with Professor Shri Kulkarni is a unique opportunity that has been both motivational and maturing. Not only did Shri encourage my independence and dedication, he also showed me (through successes and some infrequent failures) the ingredients that make up a fantastic ad- visor. To future Caltech graduate students, I cannot recommend a better or more unique Ph.D. advisor, and I will always consider Shri as a mentor, a colleague, and a friend. The results presented in this thesis would not have been possible without the support of my col- laborators. Most notable is Dale Frail, who mirrors Shri’s enthusiasm and scientific drive, and has an uncanny knack of steering students in the scientific paths that maximize their success. Next, I thank Roger Chevalier for his mentorship and guidance in the study of radio supernovae. Among the Caltech GRB group, I thank Derek Fox, Edo Berger, Brad Cenko, and Paul Price for their dedication. I also thank Re’em Sari, Doug Leonard, Udi Nakar, and Avishay Gal-Yam for fruitful discussions, and my office mates (Dawn Erb, Naveen Reddy, Joanna Brown, and Brian Cameron) for daily companionship. Finally, I thank Ed Fenimore for first introducing me to the fascinating study of gamma-ray bursts, and Enrico Ramirez-Ruiz for mentorship at the IoA in Cambridge. I am indebted to the people at the VLA and AOC for their continued support; in particular I thank Joan Wrobel and Barry Clark for their generous allocation of VLA time towards this thesis effort. Along this line, I also thank the CXO team (most notably, Harvey Tannenbaum) and the staff at Palomar and Keck Observatories. I am also indebted to the NSF Graduate Research Fellowship Program and the NASA Graduate Student Research Program for financial support throughout the duration of this five-year thesis effort. Finally, none of this would have been possible without the support of Edo and my parents, Nancy and Jon, who have each pushed me to be independent and successful from day one. vi vii The Many Facets of Cosmic Explosions by Alicia Margarita Soderberg In Partial Fulfillment of the Requirements for the Degree of Doctor of Philosophy Abstract Over the past few years, long-duration γ-ray bursts (GRBs), including the subclass of X-ray flashes (XRFs), have been revealed to be a rare variety of Type Ibc supernova (SN Ibc). While all these events result from the death of massive stars, the electromagnetic luminosities of GRBs and XRFs exceed those of ordinary Type Ibc SNe by many orders of magnitude. The observed diversity of stellar death corresponds to large variations in the energy, velocity, and geometry of the explosion ejecta. Using multi-wavelength (radio, optical, X-ray) observations of the nearest GRBs, XRFs, and SNe Ibc, I show that GRBs and XRFs couple at least 1048 erg to relativistic material while SNe Ibc typically couple ∼ < 1047 erg to their fastest (albeit non-relativistic) outflows. Specifically, I find that less than 3% of local ∼ SNe Ibc show any evidence for association with a GRB or XRF. Interestingly, this dichotomy is not echoed by the properties of their optical SN emission, dominated by the radioactive decay of Nickel-56; I find that GRBs, XRFs, and SNe Ibc show significant overlap in their optical peak luminosity and photospheric velocities. Recently, I identified a new class of GRBs and XRFs that are under-luminous in comparison with the statistical sample of GRBs. Owing to their faint high-energy emission, these sub-energetic bursts are only detectable nearby (z < 0.1) and are likely 10 times more common than ∼ cosmological GRBs. In comparison with local SNe Ibc and typical GRBs/XRFs, these explosions are intermediate in terms of both volumetric rate and energetics. Yet the essential physical process that causes a dying star to produce a GRB, XRF, or sub-energetic burst, and not just a SN, remains a crucial open question. Progress requires a detailed understanding of ordinary SNe Ibc which will be facilitated with the launch of wide-field optical surveys in the near future. viii ix Contents 1 Introduction and Summary 1 1.1 Introduction: The Death of Massive Stars . ............. 1 1.1.1 Supernovae .................................... ... 1 1.1.2 Gamma-rayBursts............................... .... 2 1.1.3 GRB 980425/SN 1998bw . .... 3 1.1.4 AGRB-SNConnection ............................. ... 5 1.1.5 X-rayFlashes.................................. .... 5 1.1.6 Off-axisGRBsandSNeIbc . .... 6 1.2 SummaryoftheThesis.............................. ....... 6 1.2.1 The Nature of GRB 980425 and a New Class of GRBs . ....... 6 1.2.2 TheNatureofX-rayFlashes . ...... 8 1.2.3 An Optical View of the GRB-SN Connection . ........ 9 1.2.4 A Large Radio Survey of TypeIbcSupernovae . ......... 10 I The Discovery of a Class of Sub-energetic GRBs 13 2 Constraints on an Off-Axis jet in GRB-SN 1998bw 15 2.1 Introduction.................................... ....... 15 2.2 Observations .................................... ...... 17 2.3 SN 1998bw: Constraining the Off-Axis Jet Model . ............. 17 2.3.1 The ǫ M˙ − /v Degeneracy............................ 18 B − 5 w,3 2.4 Local Type Ibc Supernovae: Further Constraints . ............... 18 2.5 DiscussionandConclusions . .......... 19 3 The Sub-energetic GRB 031203 as a Cosmic Analogue to GRB 980425 23 4 Relativistic Ejecta from XRF 060218 and the Rate of Cosmic Explosions 29 II The Nature of X-ray Flashes 37 5 The First Redshift for an X-ray Flash: XRF 020903 at z=0.25 39 5.1 Introduction.................................... ....... 39 5.2 Observations .................................... ...... 40 5.2.1 Ground-basedPhotometry . ...... 40 5.2.2 Ground-basedSpectroscopy . ........ 41 5.2.3 HubbleSpaceTelescope . ...... 41 5.2.4 Radio Observations of XRF 020903 . ........ 42 5.3 TheAfterglowofXRF020903. ........ 42 x 5.4 Energetics...................................... ...... 43 5.5 Conclusions ..................................... ...... 43 6 A Spectacular Radio Flare from XRF 050416a at 40 Days 51 6.1 Introduction.................................... ....... 52 6.2 Observations .................................... ...... 53 6.2.1 EarlyOpticalObservations . ........ 53 6.2.2 Late-time Observations with HST . ........ 54 6.2.3 Spectroscopic Observations . ......... 54 6.2.4 RadioObservations ............................. ..... 55 6.2.5 X-rayObservations. ...... 55 6.3 Properties of the Early Afterglow . ............ 56 6.3.1 PreliminaryConstraints . ........ 56 6.3.2 ForwardShockBroadbandModel. ....... 57 6.3.3 Collimation of the Ejecta and Viewing Angle . ........... 57 6.4 Properties of the Late-time Afterglow . ............. 58 6.4.1 Off-axisJetEmission. ...... 58 6.4.2 Circumburst Density Variations . .......... 59 6.4.3 EnergyInjection ............................... ..... 59 6.4.4 AnAssociatedSupernova . ...... 60 6.5 HostGalaxyProperties . .. .. .. .. .. .. .. .. ........ 61 6.6 IsXRF050416aaShortBurst? . ........ 62 6.7 DiscussionandConclusions . .......... 63 III An Optical View of the GRB-SN Connection 75 7 An HST Search for Supernovae Accompanying X-ray Flashes 77 7.1 Introduction.................................... ....... 78 7.2 SupernovaLight-curveSynthesis . ............ 79 7.2.1 SN1998bw ...................................... 79 7.2.2 SN1994I....................................... 79 7.2.3 SN2002ap...................................... 79 7.3 Hubble Space Telescope XRF-SN Search . ........... 80 7.3.1 XRF020903..................................... 81 7.3.2 XRF040701..................................... 82 7.3.3 XRF040812..................................... 83 7.3.4 XRF040916..................................... 85 7.4 ASummaryofXRF-SNSearches . ....... 86 7.5 Discussion...................................... ...... 87 8 An HST Study of GRB-SNe 101 8.1 Introduction.................................... ....... 102 8.2 SupernovaLight-curveSynthesis . ............ 102 8.3 Hubble Space Telescope GRB-SN Search . ........... 103 8.3.1 GRB040924..................................... 103 8.3.2 GRB041006..................................... 105 8.4 Discussion...................................... 107 xi IV A Large Radio Survey of Type Ibc Supernovae 121 9 The Radio and X-ray Luminous Type Ibc Supernova 2003L 123 9.1 Introduction.................................... ....... 123 9.2 RadioObservationsofSN2003L . ......... 124 9.2.1 VeryLargeArrayData ............................ 124 9.2.2 Very Long Baseline Array Data . ....... 125 9.3 X-rayObservationswithChandra. ........... 125 9.4 PreliminaryConstraints . .......... 126 9.5 Internal Synchrotron Self-absorption . ............... 127 9.5.1 Hydrodynamical Evolution of the Ejecta . ........... 127 9.5.2 SSAModelFitforSN2003L . 128 9.5.3 PhysicalParameters . 129 9.6 ExternalAbsorption .............................
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