Uncovering the physics behind the blazar sequence using a realistic model for jet emission

Blazar spectra are one of the most important windows into the physical processes occurring along jets. The spectrum, composed from the different emitting regions along the jet, allows us to constrain the physical conditions in the jet. I present my work modelling blazar spectra using an extended inhomogeneous jet model with an accelerating, magnetically dominated, parabolic base transitioning to a slowly decelerating, conical section motivated by observations, simulations and theory. We set the inner geometry of our multi-zone model using observations of the jet in M87 which transitions from parabolic to conical at 10^5 Schwarzschild radii. This model is able to reproduce quiescent blazar spectra very well across all wavelengths (including radio observations) for a sample of 42 BL Lacs and FSRQs. Using this inhomogeneous model we are able to constrain the location at which the synchrotron emission is brightest in these jets by fitting to the optically thick to thin synchrotron break. We find that the radius of the jet at which the synchrotron emission is brightest (where the jet first approaches equipartition) scales approximately linearly with the jet power. We also find a correlation between the length of the accelerating, parabolic section of the jet and the maximum bulk Lorentz factor. In agreement with previous work we find that BL Lacs are low power blazars whereas FSRQs are high power blazars. Together with our simple jet power-radius relation this leads us to a deeper understanding of the physics underlying the blazar sequence.Comment: 5 pages, 5 figures, to appear in "The Innermost Regions of Relativistic Jets and Their Magnetic Fields" conference proceedings; includes minor change

Synchrotron and inverse-Compton emission from blazar jets - III. Compton-dominant blazars

In this paper we develop the extended jet model of Potter & Cotter to model the simultaneous multi-wavelength spectra of six Compton-dominant blazars. We include an accelerating parabolic base transitioning to a slowly decelerating conical jet with a geometry set by observations of M87 and consistent with simulations and theory. We investigate several jet models and find that the optically thick to thin synchrotron break in the radio spectrum requires the jet to first come into equipartition at large distances along the jet (10^5 Schwarzschild radii), consistent with the observed transition from parabolic to conical in the jet of M87. We confirm this result analytically and calculate the expected frequency core-shift relations for the models under consideration. We find that a parabolic jet transitioning to a ballistic conical jet, which starts in equipartition and becomes more particle dominated at larger distances, fits the multiwavelength data of the six blazars well, whilst an adiabatic equipartition conical section requires very large bulk Lorentz factors to reproduce the Compton-dominance of the blazars. We find that all these blazars require high power, high bulk Lorentz factor jets observed close to the line of sight as we expect from the blazar sequence and consistent with the results from Paper II. The inverse-Compton emission in our fits is due to inverse-Compton scattering of high-redshift CMB photons at large distances along the jet due to the high bulk Lorentz factors of the jets. We postulate a new interpretation of the blazar sequence based on the radius of the transition region of the jet (where the jet is brightest in synchrotron emission) scaling linearly with black hole mass.Comment: 13 pages, 5 figures, accepted for publication in MNRA

A sociophonetic account of morphophonemic variation in Palestinian Arabic

This study presents findings from sociolinguistic fieldwork on Palestinian Arabic conducted in the Gaza Strip. The sample includes 15 speakers who are indigenous residents of Gaza City, representing three age groups and both genders. Linear mixed effects analyses are presented on the vowel raising of the Arabic feminine gender marker; a word final vocalic morpheme. The traditional dialect of Gaza City is reported to realize this morpheme consistently as [a] (Bergsträßer 1915), with all other Levantine city dialects raising the feminine ending to [ɛ, e] or [i] except after back consonants (Al-Wer 2007). Results indicate robust sociophonetic variation in the realization of this vowel across age generations. In comparison to the elderly generation in the sample, younger speakers realize this vowel significantly lower and backer in their casual speech. These results reflect what appears to be a change in progress happening across generations in the traditional dialect of Gaza City as a result of dialect contact happening in the Gaza Strip between speakers of difference varieties of Palestinian Arabic

Do Military Leaflets Save Lives or Just Instill Fear?

Contribution to SAPIENS magazine, pre-pub versio

On depression, anxiety, and looking for the silver lining in short term fieldwork

Special issue from the conference on Discourses on Deat

One Piece of the Puzzle: Notes on the Historic Interdental Fricatives /θ, ð, ðˁ/ in the Arabic Dialect of Gaza City

Although a great deal has been written about the Gaza Strip within the fields of political science, history, and international relations, very little linguistic research has been conducted in the coastal territory. This study aims at filling one gap in the linguistic record of Gaza through an examination of one set of phonemes, the Arabic interdentals /θ, ð, ðˁ/, in the dialect of Gaza City. The results of this study suggest that the present day dialect of Gaza City is largely in line with the earliest report on the realization of the interdentals as reported by Bergsträßer (1915), contrasting data presented in later published work by Salonen (1979, 1980)

Not-so-strange bedfellows: Documentation, description, and sociolinguistics in Gaza

Arabic is often investigated within dialectological frameworks that emerged in the 19th century, though that work now exists alongside decades of variationist sociolinguistic research. The latter method typically produces abundant data, recorded at very high quality, which lend themselves to being transcribed, described and preserved. This paper presents descriptive information on the Arabic dialect of Gaza City that is based on recent sociolinguistic fieldwork conducted in the Gaza Strip with 39 speakers from the wider Gaza City community. These descriptive aspects of the dialect are presented as part of a broader discussion regarding the need for a more holistic integration of sociolinguistics and language description and documentation in work on understudied or endangered varieties of Arabic

Gaza at the margins? Legibility and indeterminacy in the Israel-Palestine conflict

Despite prominent attention to the nature of the state in the social sciences, the place of language in creating and maintaining the state remains an emerging area of research. The analysis that follows investigates indeterminacy and illegibility in messages disseminated by the Israeli military in the Gaza Strip. This analysis highlights the ways in which linguistic indeterminacy is used as a tool by the state in controlling populations at its margins, while investigating the role of language in reproducing the state through the circulation of texts

The Feasibility of Magnetic Reconnection Powered Blazar Flares from Synchrotron Self-Compton Emission

Order of magnitude variability has been observed in the blazar sub-class of Active Galactic Nuclei on minute timescales. These high-energy flares are often difficult to explain with shock acceleration models due to the small size of the inferred emitting region, with recent particle-in-cell (PIC) simulations showing that magnetic reconnection is a promising alternative mechanism. Here, we present a macroscopic emission model physically motivated by PIC simulations, where the energy for particle acceleration originates from the reconnecting magnetic field. We track the radial growth and relative velocity of a reconnecting plasmoid, modelling particle acceleration and radiative losses from synchrotron and synchrotron self-Compton (SSC) emission. To test the viability of magnetic reconnection as the mechanism behind rapid blazar flares we simultaneously fit our model to the observed light-curve and SED from the 2016 TeV flare of BL Lacertae. We find generally that, without considering external photons, reconnecting plasmoids are unable to produce Compton-dominant TeV flares and so cannot reproduce the observations due to overproduction of synchrotron emission. Additionally, problematically large plasmoids, comparable in size to the entire jet radius, are required to emit sufficient SSC gamma-rays to be observable. However, our plasmoid model can reproduce the rapid TeV lightcurve of the flare, demonstrating that reconnection is able to produce rapid, powerful TeV flares on observed timescales. We conclude that while reconnection can produce SSC flares on the correct timescales, the primary source of TeV emission cannot be SSC and the size of plasmoids required may be implausibly large.Comment: Replaced with accepted version. Contains additional figures and considers the effect of a magnetic guide fiel