1,046 research outputs found
GRBs in the Era of Swift and Fermi
Utilizing both Swift and Fermi to study GRBs provides us with a unique broad spectral and temporal window into both prompt emission and afterglow studies. Swift has provided key information from GRB follow-up of LAT detected bursts) that has led to ground-based redshift measurements and afterglow broadband light curves and SEDs. We study the X-ray and optical afterglows of Fermi-LAT detected bursts in the context of the hundreds of GRBs discovered by Swift over the last 7 years) in order to better understand the origin of the high-energy gamma-rays. We also briefly describe the efforts to best facilitate joint Swift-Fermi observations. These initial results demonstrate the synergy between Swift and Fermi) and hint at the many interesting discoveries to come
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Locked In: the Silent Siege of Dubrovnik by the Tourism Industry
This thesis argues that Yugoslavia and an independent Croatia used Dubrovnik's cultural heritage to define and substantiate themselves as they emerged from political upheaval, disrupted economies, and nascent institutional foundations and thus firmly embedded the tourism industry within their political economies as more than an economic tool. Through the tourism industry, the cultural heritage of Dubrovnik played a fundamental role, symbolically and economically, in their process of nation building. As an emblematic site of historic and national significance, Dubrovnik represented the freedom and wealth of culture that both Yugoslavia and Croatia as new unsteady political institutions sought to evoke. Within bolstering the tourism industry, Yugoslavia and Croatia cultivated Dubrovnik's path dependency in the sector, which resulted in its contemporary "lock-in" and mono-economy. This study of Dubrovnik will elucidate the role of path dependency in shaping Dubrovnik's economy, political actors, and social fabric, while portraying the extent that tourism has pervaded throughout all spectrums of society and distorted its local heritage. Thus, I seek to answer the following questions: How did the State's focus on the tourism industry as an economic and political engine engender Dubrovnik's path dependency in the sector? How does Dubrovnik's lock-in the tourism industry represent the State's failure to regulate the industry? How does a lock-in the tourism industry facilitate the erosion of a site's cultural heritage? Using Dubrovnik as a case study to answer these questions, this research will evaluate path dependency's potential use as an ex-ante planning and preservation tool to predict if a state is advancing towards an irreconcilable lock-in and how to intervene if it does. Path dependency makes meaningful intervention all the more difficult, because it increasingly diminishes the agency of political actors to switch paths. Therefore, as will be demonstrated, planners need to increase means for effective participatory planning to counter a potential lack of political will that can prevent developing alternative, more optimal paths
Fermi-LAT Gamma-ray Bursts and Insight from Swift
A new revolution in GRB observation and theory has begun over the last 3 years since the launch of the Fermi gamma-ray space telescope. The new window into high energy gamma-rays opened by the Fermi-LAT is providing insight into prompt emission mechanisms and possibly also afterglow physics. The LAT detected GRBs appear to be a new unique subset of extremely energetic and bright bursts. In this talk I will discuss the context and recent discoveries from these LAT GRBs and the large database of broadband observations collected by Swift over the last 7 years and how through comparisons between the Swift, GBM, and LAT GRB samples, we can learn about the unique characteristics and relationships between each population
Fermi-LAT Gamma-Ray Bursts and Insights from Swift
A new revolution in Gamma-ray Burst (GRB) observations and theory has begun over the last two years since the launch of the Fermi Gamma-ray Space Telescope. The new window into high energy gamma-rays opened by the Fermi-Large Area Telescope (LAT) is providing insight into prompt emission mechanisms and possibly also afterglow physics. The LAT detected GRBs appear to be a new unique subset of extremely energetic and bright bursts compared to the large sample detected by Swift over the last 6 years. In this talk, I will discuss the context and recent discoveries from these LAT GRBs and the large database of broadband observations collected by the Swift X-ray Telescope (XRT) and UV/Optical Telescope (UVOT). Through comparisons between the GRBs detected by Swift-BAT, G8M, and LAT, we can learn about the unique characteristics, physical differences, and the relationships between each population. These population characteristics provide insight into the different physical parameters that contribute to the diversity of observational GRB properties
A Correlation Between the Intrinsic Brightness and Average Decay Rate of Gamma-ray Burst X-ray Afterglow Light Curves
We present a correlation between the average temporal decay
({\alpha}X,avg,>200s) and early-time luminosity (LX,200s) of X-ray afterglows
of gamma-ray bursts as observed by Swift-XRT. Both quantities are measured
relative to a rest frame time of 200 s after the {\gamma}-ray trigger. The
luminosity average decay correlation does not depend on specific temporal
behavior and contains one scale independent quantity minimizing the role of
selection effects. This is a complementary correlation to that discovered by
Oates et al. (2012) in the optical light curves observed by Swift-UVOT. The
correlation indicates that on average, more luminous X-ray afterglows decay
faster than less luminous ones, indicating some relative mechanism for energy
dissipation. The X-ray and optical correlations are entirely consistent once
corrections are applied and contamination is removed. We explore the possible
biases introduced by different light curve morphologies and observational
selection effects, and how either geometrical effects or intrinsic properties
of the central engine and jet could explain the observed correlation.Comment: Accepted for Publication in ApJ; 16 pages, 15 figures, 2 table
Fermi and Swift Gamma-Ray Burst Afterglow Population Studies
The new and extreme population of GRBs detected by Fermi-LAT shows several new features in high energy gamma-rays that are providing interesting and unexpected clues into GRB prompt and afterglow emission mechanisms. Over the last 6 years, it has been Swift that has provided the robust data set of UV/optical and X-ray afterglow observations that opened many windows into components of GRB emission structure. The relationship between the LAT GRBs and the well studied, fainter, less energetic GRBs detected by Swift-BAT is only beginning to be explored by multi-wavelength studies. We explore the large sample of GRBs detected by BAT only, BAT and Fermi-GBM, and GBM and LAT, focusing on these samples separately in order to search for statistically significant differences between the populations, using only those GRBs with measured redshifts in order to physically characterize these objects. We disentangle which differences are instrumental selection effects versus intrinsic properties, in order to better understand the nature of the special characteristics of the LAT bursts
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