Intrinsic and Cosmological Signatures in Gamma-Ray Burst Time Profiles: Time Dilation

The time profiles of many gamma-ray bursts consist of distinct pulses, which offers the possibility of characterizing the temporal structure of these bursts using a relatively small set of pulse shape parameters. We have used a pulse decomposition procedure to analyze the Time-to-Spill (TTS) data for all bursts observed by BATSE up through trigger number 2000, in all energy channels for which TTS data is available. We obtain amplitude, rise and decay timescales, a pulse shape parameter, and the fluences of individual pulses in all of the bursts. We investigate the correlations between brightness measures (amplitude and fluence) and timescale measures (pulse width and separation) which may result from cosmological time dilation of bursts, or from intrinsic properties of burst sources or from selection effects. The effects of selection biases are evaluated through simulations. The correlations between these parameters among pulses within individual bursts give a measure of the intrinsic effects while the correlations among bursts could result both from intrinsic and cosmological effects. We find that timescales tend to be shorter in bursts with higher peak fluxes, as expected from cosmological time dilation effects, but also find that there are non-cosmological effects contributing to this inverse correlation. We find that timescales tend to be longer in bursts with higher total fluences, contrary to what is expected from cosmological effects. We also find that peak fluxes and total fluences of bursts are uncorrelated, indicating that they cannot both be good distance indicators for bursts.Comment: 39 pages, 17 figures composed of 30 EPS files. Submitted to Astrophysical Journal. PostScript and PDF with un-bitmapped figures available at http://www.slac.stanford.edu/pubs/slacpubs/8000/slac-pub-8365.html . Accompanies astro-ph/000221

Properties of Gamma-Ray Burst Time Profiles Using Pulse Decomposition Analysis

The time profiles of many gamma-ray bursts consist of distinct pulses, which offers the possibility of characterizing the temporal structure of these bursts using a relatively small set of pulse shape parameters. This pulse decomposition analysis has previously been performed on a small sample of bright long bursts using binned data from BATSE, which comes in several data types, and on a sample of short bursts using the BATSE Time-Tagged Event (TTE) data type. We have developed an interactive pulse-fitting program using the phenomenological pulse model of Norris, et al. and a maximum-likelihood fitting routine. We have used this program to analyze the Time-to-Spill (TTS) data for all bursts observed by BATSE up through trigger number 2000, in all energy channels for which TTS data is available. We present statistical information on the attributes of pulses comprising these bursts, including relations between pulse characteristics in different energy channels and the evolution of pulse characteristics through the course of a burst. We carry out simulations to determine the biases that our procedures may introduce. We find that pulses tend to have shorter rise times than decay times, and tend to be narrower and peak earlier at higher energies. We also find that pulse brightness, pulse width, and pulse hardness ratios do not evolve monotonically within bursts, but that the ratios of pulse rise times to decay times tend to decrease with time within bursts.Comment: 40 pages, 19 figures. Submitted to Astrophysical Journal. PostScript and PDF with un-bitmapped figures available at http://www.slac.stanford.edu/pubs/slacpubs/8000/slac-pub-8364.html . Accompanying paper astro-ph/0002218 available at http://www.slac.stanford.edu/pubs/slacpubs/8000/slac-pub-8365.htm

Investigating High Field Gravity using Astrophysical Techniques

The purpose of these lectures is to introduce particle physicists to astrophysical techniques. These techniques can help us understand certain phenomena important to particle physics that are currently impossible to address using standard particle physics experimental techniques. As the subject matter is vast, compromises are necessary in order to convey the central ideas to the reader. Many general references are included for those who want to learn more. The paragraphs below elaborate on the structure of these lectures. I hope this discussion will clarify my motivation and make the lectures easier to follow. The lectures begin with a brief review of more theoretical ideas. First, elements of general relativity are reviewed, concentrating on those aspects that are needed to understand compact stellar objects (white dwarf stars, neutron stars, and black holes). I then review the equations of state of these objects, concentrating on the simplest standard models from astrophysics. After these mathematical preliminaries, Sec. 2(c) discusses 'The End State of Stars'. Most of this section also uses the simplest standard models. However, as these lectures are for particle physicists, I also discuss some of the more recent approaches to the equation of state of very dense compact objects. These particle-physics-motivated equations of state can dramatically change how we view the formation of black holes. Section 3 focuses on the properties of the objects that we want to characterize and measure. X-ray binary systems and Active Galactic Nuclei (AGN) are stressed because the lectures center on understanding very dense stellar objects, black hole candidates (BHCs), and their accompanying high gravitational fields. The use of x-ray timing and gamma-ray experiments is also introduced in this section. Sections 4 and 5 review information from x-ray and gamma-ray experiments. These sections also discuss the current state of the art in x-ray and gamma-ray satellite experiments and plans for future experiments

Full pf shell study of A = 47 and A = 49 nuclei

Complete diagonalizations in the pf major shell, lead to very good agreement with the experimental data (level schemes, transitions rates, and static moments) for the A=47 and A=49 isotopes of Ca, Sc, Ti, V, Cr, and Mn. Gamow-Teller and M1 strength functions are calculated. The necessary monopole modifications to the realistic interactions are shown to be critically tested by the spectroscopic factors for one particle transfer from 48Ca, reproduced in detail by the calculations. The collective behaviour of 47Ti, and of the mirror pairs 47V-47Cr and 49Cr-49Mn is found to follow at low spins the particle plus rotor model. It is then analysed in terms of the approximate quasi-SU(3) symmetry, for which some new results are given.Comment: 30 Pages, RevTeX and epsf.sty, 23 figures included. Postscript version available at http://www.ft.uam.es/~gabriel/a47-49.ps.g

Detecting Dark Matter annihilation lines with Fermi

Dark matter constitutes one of the most intriguing but so far unresolved issues in physics today. In many extensions of the Standard Model the existence of a stable Weakly Interacting Massive Particle (WIMP) is predicted. The WIMP is an excellent dark matter particle candidate and one of the most interesting scenarios include an annihilation of two WIMPs into two gamma-rays. If the WIMPs are assumed to be non-relativistic, the resulting photons will both have an energy equal to the mass of the WIMP and manifest themselves as a monochromatic spectral line in the energy spectrum. This type of signal would represent a 'smoking gun' for dark matter, since no other known astrophysical process should be able to produce it. In these proceedings we give an overview of the different approaches to a search for dark matter lines that the Fermi-LAT collaboration is pursuing and the various challenges involved

A redshift - observation-time relation for gamma-ray bursts: evidence of a distinct sub-luminous population

We show how the redshift and peak-flux distributions of gamma-ray bursts (GRBs) have an observation time dependence that can be used to discriminate between different burst populations. We demonstrate how observation time relations can be derived from the standard integral distributions and that they can differentiate between GRB populations detected by both the BATSE and \emph{Swift} satellites. Using \emph{Swift} data we show that a redshift--observation-time relation (log\,$Z$\,--\,log\,$T$) is consistent with both a peak-flux\,--\,observation time relation (log\,$P$\,--\,log\,$T$) and a standard log\,$N$\,--\,log\,$P$ brightness distribution. As the method depends only on rarer small-$z$ events, it is invariant to high-$z$ selection effects. We use the log\,$Z$\,--\,log\,$T$ relation to show that sub-luminous GRBs are a distinct population occurring at a higher rate of order $150^{+180}_{-90} \mathrm{Gpc}^{-3}\mathrm{yr}^{-1}$. Our analysis suggests that GRB 060505 -- a relatively nearby GRB observed without any associated supernova -- is consistent with a sub-luminous population of bursts. Finally, we suggest that our relations can be used as a consistency test for some of the proposed GRB spectral energy correlations.Comment: Accepted by MNRA

Characterisation of feline renal cortical fibroblast cultures and their transcriptional response to transforming growth factor beta 1

Chronic kidney disease (CKD) is common in geriatric cats, and the most prevalent pathology is chronic tubulointerstitial inflammation and fibrosis. The cell type predominantly responsible for the production of extra-cellular matrix in renal fibrosis is the myofibroblast, and fibroblast to myofibroblast differentiation is probably a crucial event. The cytokine TGF-β1 is reportedly the most important regulator of myofibroblastic differentiation in other species. The aim of this study was to isolate and characterise renal fibroblasts from cadaverous kidney tissue of cats with and without CKD, and to investigate the transcriptional response to TGF-β1