This thesis reports the discovery of relativistic stellar explosions outside of the gamma ray band, using optical time domain surveys. It is well known that some massive stars end their lives with the formation of a compact object (a neutron star or black hole) that launches a relativistic jet detectable from earth as a burst of gamma rays. It has long been suspected, however, that gamma ray bursts are only the tip of the iceberg in a broad landscape of relativistic explosions, and so the results presented in this thesis represent a major breakthrough. Highlights of this thesis include: characterization of the first major new class of relativistic explosions in a decade; the discovery of abrupt end-of-life mass-loss in a surprisingly diverse range of stars; and the routine discovery of afterglow emission and several events that may represent baryonically dirty jets or jets viewed slightly off axis. These discoveries necessitated the solution of difficult technical challenges such as the identification of rare and fleeting “needles” in a vast haystack of time-varying phenomena in the night sky, and responding to discoveries within hours to obtain data across the electromagnetic spectrum from X-rays to radio wavelengths.
Author(s): Anna Y. Q. Ho
Series: Springer Theses
Publisher: Springer
Year: 2022
Language: English
Pages: 315
City: Cham
Supervisor's Foreword
Acknowledgments
Parts of This Thesis Have Been Published in the Following Journal Articles
Contents
1 Introduction and Summary
1.1 Landscape Overview
The GRB View
The Ic-BL SN View
Radio Unification Efforts
1.2 Summary of Thesis
References
Part I Afterglows at Cosmological Distances
2 ZTF20aajnksq (AT2020blt): A Fast Optical Transient at z 2.9 With No Detected Gamma-Ray Burst Counterpart
2.1 Introduction
2.2 Observations
ZTF Discovery
Follow-up Observations
Optical Imaging
Optical Spectroscopy
X-Ray Observations
Radio Observations
Search for Associated GRB
2.3 Comparison to GRB Afterglows
Optical Light Curve
Spectral Energy Distribution
Radio Light Curve
2.4 Interpretation
A Slightly Off-Axis GRB
A Dirty Fireball
2.5 Summary and Conclusions
References
3 iPTF Archival Search for Fast Optical Transients
3.1 Introduction
3.2 Data and Candidate Selection
3.3 Properties of the iPTF M-dwarf Flares
3.4 Rate of Relativistic Fast Optical Transients in iPTF
3.5 Conclusions
3.6 Appendix
References
Part II Low-Luminosity Gamma-Ray Bursts
4 SN2020bvc: A Broad-Lined Type Ic Supernova with a Double-Peaked Optical Light Curve and a Luminous X-ray and Radio Counterpart
4.1 Introduction
4.2 Observations
ZTF Detection and Classification
Host Galaxy
Optical Photometry
Spectroscopy
UV and X-Ray Observations
Submillimeter and Radio Observations
Search for a Gamma-Ray Burst
4.3 Light Curve Analysis
Comparisons to Other Ic-BL SNe
Blackbody Fits
4.4 Spectroscopic Properties
Spectroscopic Evolution and Comparisons
Velocity Estimates from Fe II Features
4.5 Modeling the Light Curve
Nickel Decay
Shock-Cooling
4.6 Modeling the Fast Ejecta
Radio Emission
X-Ray Emission
4.7 Early ZTF Light Curves of Nearby Ic-BL SNe
4.8 Summary and Discussion
4.9 Appendix
Photometry Table
Details: Mass and Radius of the Extended Material
Details: Properties of the Forward Shock
Inverse Compton Scattering
References
Part III Ic-BL Supernovae
Reference
5 The Broad-Lined Ic Supernova ZTF18aaqjovh (SN2018bvw): An Optically Discovered Engine-Driven Supernova Candidate with Luminous Radio Emission
5.1 Introduction
5.2 Observations
Zwicky Transient Facility Discovery
Spectral Classification
Radio Observations
X-Ray Observations
Search for Gamma-Rays
5.3 Analysis and Discussion
Modeling the Optical Light Curve
Properties of the Fastest (Radio-Emitting) Ejecta
Modeling the Radio to X-Ray SED
Gamma-Ray Burst
5.4 Summary and Conclusions
References
6 Evidence for Late-Stage Eruptive Mass Loss in the Progenitor to SN2018gep, a Broad-Lined Ic Supernova: Pre-explosion Emission and a Rapidly Rising Luminous Transient
6.1 Introduction
6.2 Observations
Zwicky Transient Facility Discovery
Photometry
Spectroscopy
Search for Pre-discovery Emission
Radio Follow-up
X-ray Follow-Up
Search for Prompt Gamma-Ray Emission
Host Galaxy Data
6.3 Basic Properties of the Explosion and Its Host Galaxy
Physical Evolution from Blackbody Fits
Spectral Evolution and Velocity Measurements
Comparisons to Early Spectra in the Literature
Origin of the ``W'' Feature
Photospheric Velocity from Ic-BL Spectra
Properties of the Host Galaxy
6.4 Interpretation
Radioactive Decay
Interaction with Extended Material
6.5 Comparison to Unclassified Rapidly Evolving Transients at High Redshift
6.6 Summary and Future Work
6.7 Appendix
UV and Optical Photometry
UV and Optical Spectroscopy
Atomic Data for Spectral Modeling
Data for Measuring Host Properties
References
Part IV A New Class of Energetic Stellar Explosions in a Dense Medium
7 AT2018cow: A Luminous Millimeter Transient
7.1 Introduction
The Transient Millimeter Sky
AT2018cow
7.2 Observations
Radio and Submillimeter Observations
The Submillimeter Array (SMA)
The Australia Telescope Compact Array (ATCA)
The Atacama Large Millimeter/Submillimeter Array (ALMA)
X-Ray Observations
Swift/XRT
NuSTAR
7.3 Basic Properties of the Shock
Light Curve
Modeling the Radio to Submillimeter SED
7.4 Implications of Shock Properties
AT2018cow in Velocity–Energy Space and a Discussion of Epsilons
A Luminous Millimeter Transient in a Dense Environment
Novel Features of the Synchrotron Model Parameters
7.5 Origin of the X-ray Emission and Emergence of a Compact Source
7.6 Conclusions and Outlook
7.7 Appendix
ALMA Band 9 Calibration
Full SMA Light Curves
Selection of Peak Frequency and Peak Luminosity for Other Transients
References
8 The Koala: A Fast Blue Optical Transient with Luminous Radio Emission from a Starburst Dwarf Galaxy at z=0.27
8.1 Introduction
8.2 Discovery and Basic Analysis
Optical
Photometry
Spectroscopy and Host-Galaxy Properties
Radio Observations
8.3 Comparison with Extragalactic Explosions
Optical Light Curve and Spectrum
Radio Light Curve
A Starburst Host Galaxy
8.4 Interpretation
Modeling the Optical Light Curve
Modeling the Radio Light Curve
Progenitor Systems and a Search for an Associated Gamma-ray Burst
8.5 Rate Estimate
8.6 Prospects for Detecting X-Ray Emission
8.7 Summary and Conclusions
8.8 Appendix
Light Curve Measurements
References
9 Other Contributions
9.1 ZTF19abvizsw: A Cosmological Afterglow with No Detected Gamma-Ray Burst
9.2 How Much CSM Is Sufficient to Choke a Jet?
9.3 Radio Observations of Ic-BL SNe Discovered by ZTF
References
10 Summary and the Future
