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Multi-messenger emission from gamma-ray bursts
KTH, School of Engineering Sciences (SCI), Physics, Particle and Astroparticle Physics. Oskar Klein Ctr Cosmoparticle Phys, SE-10691 Stockholm, Sweden..
2020 (English)Licentiate thesis, comprehensive summary (Other academic)
Abstract [en]

Multi-messenger astronomy is a very hot topic in the astrophysical community. A messenger is something that carries information. Different astrophysical messenger types are photons, cosmic rays, neutrinos, and gravitational waves. They all carry unique and complementary information to one another. The idea with multi-messenger astronomy is that the more different types of messengers one can obtain from the same event, the more complete the physical picture becomes.

In this thesis I study the multi-messenger emission from gamma-ray bursts (GRBs), the most luminous events known in the Universe. Specifically, I study the connection of GRBs to extremely energetic particles called ultra-high-energy cosmic rays (UHECRs). UHECRs have unknown origin despite extensive research. GRBs have long been one of the best candidates for the acceleration of these particles but a firm connection is yet to be made. In Paper I and Paper II, we study the possible GRB-UHECR connection by looking at the electromagnetic radiation from electrons that would also be accelerated together with the UHECR. My conclusion is that the signal from these electrons does not match current GRB observation, disfavoring that a majority of UHECRs comes from GRBs.

Abstract [sv]

”Multi-messenger astronomy” (mångbudbärarastronomi, fri översättning) är ett väldigt aktuellt område inom astrofysiken just nu. En meddelare är någonting som bär på information. Olika meddelartyper inom astrofysiken är fotoner, kosmisk strålning, neutriner och gravitations vågor. Dessa har alla unik och olika typ av information som kompletterar varandra. Idén bakom multi-meddelare-astronomi är att ju fler olika meddelartyper vi kan upptäcka från samma event, desto mer komplett blir vår fysikaliska tolkning.

I denna avhandling studerar jag multi-meddelare emission från gammablixtar (GRBs), de mest ljusstarka företeelser vi känner till i Universum. Mer specifikt, så studerar jag kopplingen mellan GRBs och ultraenergetisk kosmisk strålning (UHECRs). Ursprunget till UHECRs är fortfarande okänt trots långt pågående forskning. GRBs har länge varit en av de mest lovande accelerationskandidaterna men än så länge finns inga fasta bevis. I Paper I och Paper II studerar vi den möjliga GRB-UHECR kopplingen genom att studera den elektromagnetiska strålningen från elektronerna som även de skulle bli accelererade tillsammans med UHECRs. Min slutsats är att strålningen från elektronerna inte matchar observationer från GRBs, vilket talar emot att en majoritet av UHECRs kommer från GRBs.

Place, publisher, year, edition, pages
KTH Royal Institute of Technology, 2020. , p. 53
Series
TRITA-SCI-FOU ; 2020:20
Keywords [en]
astrophysics, gamma-ray bursts, cosmic rays
National Category
Astronomy, Astrophysics and Cosmology
Research subject
Physics, Atomic, Subatomic and Astrophysics
Identifiers
URN: urn:nbn:se:kth:diva-273383ISBN: 978-91-7873-560-0 (print)OAI: oai:DiVA.org:kth-273383DiVA, id: diva2:1430516
Presentation
2020-06-10, Via Zoom: https://kth-se.zoom.us/j/65393939824, Du som saknar dator/datorvana kan kontakta fryde@kth.se för information, Stockholm, 15:15 (English)
Opponent
Supervisors
Available from: 2020-05-19 Created: 2020-05-15 Last updated: 2020-06-05Bibliographically approved
List of papers
1. The Limited Contribution of Low- and High-luminosity Gamma-Ray Bursts to Ultra-high-energy Cosmic Rays
Open this publication in new window or tab >>The Limited Contribution of Low- and High-luminosity Gamma-Ray Bursts to Ultra-high-energy Cosmic Rays
2019 (English)In: Astrophysical Journal, ISSN 0004-637X, E-ISSN 1538-4357, Vol. 876, no 2, article id 93Article in journal (Refereed) Published
Abstract [en]

The acceleration site for ultra-high-energy cosmic rays (UHECRs) is still an open question despite extended research. In this paper, we reconsider the prompt phase of gamma-ray bursts (GRBs) as a possible candidate for this acceleration and constrain the maximum proton energy in optically thin synchrotron and photospheric models, using properties of the prompt photon spectra. We find that neither of the models favors acceleration of protons to 10(20) eV in high-luminosity bursts. We repeat the calculations for low-luminosity GRBs (llGRBs) considering both protons and completely stripped iron and find that the highest obtainable energies are < 10(19) eV and < 10(20) eV for protons and iron respectively, regardless of the model. We conclude therefore that for our fiducial parameters, GRBs, including low-luminosity bursts, contribute little to nothing to the UHECRs observed. We further constrain the conditions necessary for an association between UHECRs and llGRBs and find that iron can be accelerated to 1020 eV in photospheric models, given very efficient acceleration and/or a small fractional energy given to a small fraction of accelerated electrons. This will necessarily result in high prompt optical fluxes, and the detection of such a signal could therefore be an indication of successful UHECR acceleration at the source.

Place, publisher, year, edition, pages
IOP PUBLISHING LTD, 2019
Keywords
cosmic rays, gamma-ray burst: general
National Category
Physical Sciences
Identifiers
urn:nbn:se:kth:diva-252607 (URN)10.3847/1538-4357/ab153c (DOI)000467460700004 ()2-s2.0-85067286419 (Scopus ID)
Note

QC 20190610

Available from: 2019-06-10 Created: 2019-06-10 Last updated: 2020-05-15Bibliographically approved
2. Constraining Low-luminosity Gamma-Ray Bursts as Ultra-high-energy Cosmic Ray Sources Using GRB 060218 as a Proxy
Open this publication in new window or tab >>Constraining Low-luminosity Gamma-Ray Bursts as Ultra-high-energy Cosmic Ray Sources Using GRB 060218 as a Proxy
Show others...
(English)Manuscript (preprint) (Other academic)
Abstract [en]

We study the connection between low-luminosity gamma-ray bursts (llGRBs) and ultra-high-energy cosmic rays using the canonical low-luminosity GRB 060218 as a proxy. We focus on the consequen- tial synchrotron emission from electrons that are co-accelerated in the UHECR acceleration region, comparing this emission to observations. Both the prompt and afterglow phases are considered. For the prompt phase, we find that bright optical-UV emission is inevitable if the co-accelerated electrons are instantaneously injected into a power-law distribution. To enable acceleration of UHECRs while accommodating the optical-UV emission, it is necessary to keep the electrons from fast cooling (e.g., via reheating). Yet, the energetics of such models are independently constrained from our analysis of the afterglow. For the afterglow phase, we consider mildly relativistic outflows with bulk Lorentz factor $\Gamma \gtrsim 2$. Using thermal synchrotron radiation, we show that the initial kinetic energy of the afterglow blast wave of GRB 060218 was 10 times lower than the minimum energy required to satisfy the observed flux of UHECRs. Indeed, a blast wave with sufficient energy and where electrons carry 10–20% of the energy as suggested by particle-in-cell simulations, would typically overshoot the available radio data at ∼ 3 days by more than an order of magnitude. If GRB 060218 is representative of the llGRB population as a whole, then our results show that their relativistic afterglows are unlikely to be the dominant sources of UHECRs. It also implies that for the prompt phase to be the main origin of UHECRs, a majority of the energy would need to escape as cosmic rays, neutrinos, or radiation before the onset of the afterglow, independent of the prompt emission mechanism. More generally, our study demonstrates that synchrotron emission from thermal electrons is a powerful diagnostic of the physics of mildly relativistic shocks.

Keywords
gamma-ray bursts, cosmic rays
National Category
Astronomy, Astrophysics and Cosmology
Research subject
Physics, Atomic, Subatomic and Astrophysics
Identifiers
urn:nbn:se:kth:diva-273347 (URN)
Note

QC 20200518

Available from: 2020-05-14 Created: 2020-05-14 Last updated: 2020-05-18Bibliographically approved

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