The Locations of Gamma-Ray Bursts Measured by COMPTEL

The COMPTEL instrument on the Compton Gamma Ray Observatory is used to measure the locations of gamma-ray bursts through direct imaging of MeV photons. In a comprehensive search, we have detected and localized 29 bursts observed between 1991 April 19 and 1995 May 31. The average location accuracy of these events is 1.25\arcdeg (1$\sigma$), including a systematic error of \sim0.5\arcdeg, which is verified through comparison with Interplanetary Network (IPN) timing annuli. The combination of COMPTEL and IPN measurements results in locations for 26 of the bursts with an average ``error box'' area of only $\sim$0.3 deg$^2$ (1$\sigma$). We find that the angular distribution of COMPTEL burst locations is consistent with large-scale isotropy and that there is no statistically significant evidence of small-angle auto-correlations. We conclude that there is no compelling evidence for burst repetition since no more than two of the events (or $\sim$7% of the 29 bursts) could possibly have come from the same source. We also find that there is no significant correlation between the burst locations and either Abell clusters of galaxies or radio-quiet quasars. Agreement between individual COMPTEL locations and IPN annuli places a lower limit of $\sim$100~AU (95% confidence) on the distance to the stronger bursts.Comment: Accepted for publication in the Astrophysical Journal, 1998 Jan. 1, Vol. 492. 33 pages, 9 figures, 5 table

X- and gamma-ray observations of the 15 November 1991 Solar Flare

This work expands the current understanding of the 15 November 1991 Solar Flare. The flare was a well observed event in radio to gamma-rays and is the first flare to be extensively studied with the benefit of detailed soft and hard X-ray images. In this work, we add data from all four instruments on the Compton Gamma Ray Observatory. Using these data we determined that the accelerated electron spectrum above 170 keV is best fit with a power law with a spectral index of −4.6, while the accelerated proton spectrum above 0.6 MeV is fit with a power law of spectral index −4.5. From this we computed lower limits for the energy content of these particles of∼1023 ergs (electrons) and ∼1027 ergs (ions above 0.6 MeV). These particles do not have enough energy to produce the white-light emission observed from this event. We computed a time constant of 26+20−15 s for the 2.223 MeV neutron capture line, which is consistent at the 2σ level with the lowest values of ∼70 s found for other flares. The mechanism for this short capture time may be better understood after analyses of high energy EGRET data that show potential evidence for pion emission near ∼100 MeV

Characteristics of long-duration inhibitory postsynaptic potentials in rat neocortical neurons in vitro

1. The characteristics of long-duration inhibitory postsynaptic potentials (l-IPSPs) which are evoked in rat frontal neocortical neurons by local electrical stimulation were investigated with intracellular recordings from anin vitro slice preparation. 2. Stimulation with suprathreshold intensities evoked l-IPSPs with typical durations of 600–900 msec at resting membrane potential. Conductance increases of 15–60% were measured at the peak amplitude of l-IPSPs (150–250 msec poststimulus). 3. The duration of the conductance increases during l-IPSPs displayed a significant voltage dependence, decreasing as the membrance potential was depolarized and increasing with hyperpolarization. 4. The reversal potential of l-IPSPs is significantly altered by reductions in the extracellular potassium concentration. Therefore it is concluded that l-IPSPs in rat neocortical neurons are generated by the activation of a potassium conductance. 5. l-IPSPs exhibit stimulation fatigue. Stimulation with a frequency of 1 Hz produces a complete fatigue of the conductance increases during l-IPSPs after approximately 20 consecutive stimuli. Recovery from this fatigue requires minutes. 6. l-IPSPs are not blocked by bicuculline but are blocked by baclofen

Trace identities and their semiclassical implications

The compatibility of the semiclassical quantization of area-preserving maps with some exact identities which follow from the unitarity of the quantum evolution operator is discussed. The quantum identities involve relations between traces of powers of the evolution operator. For classically {\it integrable} maps, the semiclassical approximation is shown to be compatible with the trace identities. This is done by the identification of stationary phase manifolds which give the main contributions to the result. The same technique is not applicable for {\it chaotic} maps, and the compatibility of the semiclassical theory in this case remains unsettled. The compatibility of the semiclassical quantization with the trace identities demonstrates the crucial importance of non-diagonal contributions.Comment: LaTeX - IOP styl

Sexual harassment and eating disorders in female elite athletes - A controlled study

The aims were to examine the percentage of female elite athletes and controls reporting sexual harassment and abuse (SHAB), and whether a higher percentage of female athletes with eating disorders (ED) had experienced SHAB. A questionnaire was administered to the total population of female elite athletes (n=660) and controls (n=780) aged 15-39 years. SHAB were measured through 11 questions, ranging from light to severe SHAB. In addition, questions about dietary-, menstrual- and training history and the Eating Disorder Inventory were included. The response rate was 88% for athletes and 71% for controls. Athletes (n=121) and controls (n=81) classified as “at risk” for ED and non-ED controls participated in a clinical interview. A higher percentage of controls, compared with athletes reported experiences of SHAB in general (59% vs. 51%, p<0.001). A lower percentage of athletes had experienced SHAB in sports than outside sport (28% vs.39%, p<0.001). A higher percentage of ED athletes than non-ED athletes had experienced SHAB (66% vs.48%) (p<0.01), both inside sport and outside sport. In spite of the fact that a higher percentage of controls compared with athletes had experienced SHAB, it is necessary to formulate clear guidelines, set up educational workshops and implement intervention programs for both ED and SHAB in sport

First results of the BATSE/COMPTEL/NMSU rapid burst response campaign

The Imaging Compton Telescope (COMPTEL) on board the Compton Gamma Ray Observatory regularly observes gamma‐ray bursts which occur inside the instrument’s ∼1 sr field‐of‐view. COMPTEL images bursts in the 0.75–30 MeV energy range with a typical location accuracy of 1–3 degrees, depending on burst strength, position, duration, and spectrum. COMPTEL’s imaging capability has been exploited in order to search for fading gamma‐ray burst counterparts at other wavelengths through the establishment of a BATSE/COMPTEL/NMSU rapid burst response campaign. This campaign utilizes near real‐time identification and preliminary burst location by BATSE, accelerated COMPTEL imaging, and a world‐wide network of observers to search COMPTEL error boxes as quickly as possible. Timely, deep searches for lingering counterpart emission of several bursts per year are the realized goal of this campaign. During its first year of operation, the rapid response program has been successfully applied to two strong bursts: GRB 930131 and GRB 930309. These bursts were imaged in record time only hours after their occurrence. Subsequently, several observations were made at radio and optical observatories world‐wide

Initial results from COMPTEL—an overview

COMPTEL is presently completing the first full sky survey in MeV gamma‐ray astronomy (0.7 to 30 MeV). An overview of initial results from the survey is given: among these are the observations of the Crab and Vela pulsars with unprecedented accuracy, the observation of the black hole candidates Cyg X‐1 and Nova Persei 1992, an analysis of the diffuse Galactic continuum emission from the Galactic center region, the broad scale distribution of the 1.8 MeV line from radioactive 2 6Al, upper limits on gamma‐ray line emission from SN 1991T, observations of the three quasars 3C273, 3C279 and PKS 0528+134 and the radio galaxy Cen A, measurements of energy spectra, time histories and locations of a number of cosmic gamma‐ray bursts, and gamma‐ray and neutron emission from solar flares

Gamma‐ray burst studies by COMPTEL during its first year of operation

During the first year of Compton GRO operations, more than 20 cosmic gamma‐ray burst‐detected by the BATSE instrument ‐ occurred inside the 1 sr field of view of the imaging gamma‐ray telescope COMPTEL. Using COMPTEL’s primary mode of operation (the telescope mode) direct images (with ∼1° GRB location accuracy) and event spectra (0.7 MeV – 30 MeV) with spectral resolution better than 10% FWHM have been obtained. In its secondary mode of burst operations, COMPTEL has recorded time resolved spectra (0.1 MeV – 10 MeV) from its large NaI detectors. This paper summarises the results on cosmic GRB sources obtained by COMPTEL during its first year of operation

Observations of GRB 990123 by the Compton Gamma-Ray Observatory

GRB 990123 was the first burst from which simultaneous optical, X-ray and gamma-ray emission was detected; its afterglow has been followed by an extensive set of radio, optical and X-ray observations. We have studied the gamma-ray burst itself as observed by the CGRO detectors. We find that gamma-ray fluxes are not correlated with the simultaneous optical observations, and the gamma-ray spectra cannot be extrapolated simply to the optical fluxes. The burst is well fit by the standard four-parameter GRB function, with the exception that excess emission compared to this function is observed below ~15 keV during some time intervals. The burst is characterized by the typical hard-to-soft and hardness-intensity correlation spectral evolution patterns. The energy of the peak of the nu f_nu spectrum, E_p, reaches an unusually high value during the first intensity spike, 1470 +/- 110 keV, and then falls to \~300 keV during the tail of the burst. The high-energy spectrum above ~MeV is consistent with a power law with a photon index of about -3. By fluence, GRB 990123 is brighter than all but 0.4% of the GRBs observed with BATSE, clearly placing it on the -3/2 power-law portion of the intensity distribution. However, the redshift measured for the afterglow is inconsistent with the Euclidean interpretation of the -3/2 power-law. Using the redshift value of >= 1.61 and assuming isotropic emission, the gamma-ray fluence exceeds 10E54 ergs.Comment: Submitted to The Astrophysical Journal. 16 pages including 4 figure

Preliminary Report on Stone Breakage and Lesion Size Produced by a New Extracorporeal Electrohydraulic (Sparker Array) Discharge Device

Objective To determine if an innovative extracorporeal electrohydraulic shock wave device (sparker array) can effectively fracture artificial stones in vitro and in vivo, and if sparker array treatment produces a renal lesion in our pig model of lithotripsy injury. Results of these experiments will be used to help evaluate the suitability of this device as a clinical lithotripter. Methods Utracal-30 artificial stones were placed in a holder at the focus of the sparker array and treated with 600 shock waves (21.6 kV, 60 shocks/min). Stone fragments were collected, dried and weighed to determine stone breakage. In vivo stone breakage entailed implanting stones into pigs. These stones were treated with 600 or 1200 shock waves and the fragments collected for analysis. Lesion analysis consisted of treating the left kidney of pigs with 1200 or 2400 shock waves and quantitating the hemorrhagic lesion. Results In vitro, 71±2% of each artificial stone was fractured to < 2 mm in size. In vivo stone breakage averaged 63%. Renal injury analysis revealed that only 1 out of 7 kidneys showed evidence of hemorrhagic injury in the treated area. Conclusions The sparker array consistently comminuted artificial stones demonstrating its ability to fracture stones like other lithotripters. Also, the sparker array caused little to no renal injury at the settings used in this study. These findings suggest further research is warranted to determine the potential of this device as a clinical lithotripter