Gamma-Ray Spectra & Variability of the Crab Nebula Emission Observed by BATSE

We report ~ 600 days of BATSE earth-occultation observations of the total gamma-ray (30 keV to 1.7 MeV) emission from the Crab nebula, between 1991 May 24 (TJD 8400) and 1994 October 2 (TJD 9627). Lightcurves from 35-100, 100-200, 200-300, 300-400, 400-700, and 700-1000 keV, show that positive fluxes were detected by BATSE in each of these six energy bands at significances of approximately 31, 20, 9.2, 4.5, 2.6, and 1.3 sigma respectively per day. We also observed significant flux and spectral variations in the 35-300 keV energy region, with time scales of days to weeks. The spectra below 300 keV, averaged over typical CGRO viewing periods of 6-13 days, can be well described by a broken power law with average indices of ~ 2.1 and ~ 2.4 varying around a spectral break at ~ 100 keV. Above 300 keV, the long-term averaged spectra, averaged over three 400 d periods (TJD 8400-8800, 8800-9200, and 9200-9628, respectively) are well represented by the same power law with index of ~ 2.34 up to ~ 670 keV, plus a hard spectral component extending from ~ 670 keV to ~ 1.7 MeV, with a spectral index of ~ 1.75. The latter component could be related to a complex structure observed by COMPTEL in the 0.7-3 MeV range. Above 3 MeV, the extrapolation of the power-law continuum determined by the low-energy BATSE spectrum is consistent with fluxes measured by COMPTEL in the 3-25 MeV range, and by EGRET from 30-50 MeV. We interpret these results as synchrotron emission produced by the interaction of particles ejected from the pulsar with the field in different dynamical regions of the nebula system, as observed recently by HST, XMM-Newton, and Chandra.Comment: To be published in the November 20, 2003, Vol 598 issue of the Astrophysical Journa

Recent results from COMPTEL observations of Cygnus X‐1

The COMPTEL experiment on the Compton Gamma‐Ray Observatory (CGRO) has now observed Cyg X‐1 on four separate occasions during phase 1 and phase 2 of its orbital mission (April, 1991 to August, 1993). Here we report on the results of the latest analysis of these data, which provide a spectrum extending to energies greater than 2 MeV. A spectral analysis of these data, in the context of a classical Comptonization model, indicates an electron temperature much higher than previous hard X‐ray measurements would suggest (200 keV vs 60–80 keV). This implies either some limitations in the standard Comptonization model and/or the need to incorporate a reflected component in the hard X‐ray spectrum. Although significant variability near 1 MeV has been observed, there is no evidence for any ‘MeV excess.

Pengaruh Intensitas Membaca Berita Tentang Ganjar Pranowo di Surat Kabar Daerah dan Interaksi dengan Kelompok Rujukan terhadap Tingkat Kepercayaan Masyarakat Mengenai Kinerja Gubernur

Sejak 23 Agustus 2013, masyarakat Jawa Tengah resmi dipimpin oleh Ganjar Pranowo USAi beliau memenangi pemilihan gubernur. Namun, survei menunjukkan keraguan masyarakat terhadap kinerja gubernur setelah empat bulan masa kepemimpinannya berlangsung. Surat kabar daerah dipandang berkontribusi dalam menentukan tingkat kepercayaan masyarakat karena kerap mengekspos dinamika kepemimpinan Ganjar Pranowo. Tingkat kepercayaan masyarakat dapat pula terbentuk saat mereka berbincang tentang kinerja gubernur bersama keluarga dan teman.Penelitian ini merupakan penelitian kuantitatif dengan tipe eskplanatori, yang bertujuan untuk mengetahui pengaruh intensitas membaca berita tentang Ganjar Pranowo di surat kabar daerah dan interaksi dengan kelompok rujukan terhadap tingkat kepercayaan masyarakat mengenai kinerja gubernur. Teori yang digunakan dalam penelitian ini adalah Teori Efek Media Massa dan Teori Kelompok Rujukan. Jumlah populasi sebanyak 7311 orang merupakan penduduk berusia 17-60 tahun di Kelurahan Sumurboto, Semarang. Menggunakan teknik multistage random sampling, diambil sampel sebanyak 99 orang. Data primer dianalisis menggunakan uji validitas, uji reliabilitas, uji asumsi klasik, dan regresi linier sederhana dengan bantuan program SPSS.Perhitungan statistik menunjukkan persamaan regresi linier sederhana antara intensitas membaca berita tentang Ganjar Pranowo di surat kabar daerah terhadap tingkat kepercayaan masyarakat mengenai kinerja gubernur adalah Y= 39.517+0.419X1dengan nilai signifikansi 0.000 < 0.01. Sementara, persamaan regresi linier sederhana antara interaksi dengan kelompok rujukan terhadap tingkat kepercayaan masyarakat mengenai kinerja gubernur adalah Y=36.340+0.234X2 dengan nilai signifikansi 0.001 < 0.01. Berdasarkan kedua persamaan tersebut dapat diketahui bahwa terdapat pengaruh positif yang sangat signifikan secara parsial antar variabel-variabel X terhadap variabel Y, namun pengaruhnya sangat kecil.Surat kabar daerah hendaknya memegang teguh komitmen untuk melaksanakan praktik jurnalisme bertanggung jawab dengan menjaga obyektivitas berita. Humas Pemprov disarankan untuk aktif mempublikasikan informasi mengenai kinerja gubernur dalam merealisasikan program-program pro rakyat dan berbagai kebijakan yang dirumuskan. Hal ini bertujuan untuk memberikan pengetahuan dan meningkatkan kepercayaan masyarakat. Masyarakat seharusnya menjadi pembaca yang kritis

The first COMPTEL Source Catalogue

The imaging Compton telescope COMPTEL aboard NASA's Compton Gamma-Ray Observatory has opened the MeV gamma-ray band as a new window to astronomy. COMPTEL provided the first complete all-sky survey in the energy range 0.75 to 30 MeV. The catalogue, presented here, is largely restricted to published results. It contains firm as well as marginal detections of continuum and line emitting sources and presents upper limits for various types of objects. The numbers of the most significant detections are 32 for steady sources and 31 for gamma-ray bursters. Among the continuum sources, detected so far, are spin-down pulsars, stellar black-hole candidates, supernova remnants, interstellar clouds, nuclei of active galaxies, gamma-ray bursters, and the Sun during solar flares. Line detections have been made in the light of the 1.809 MeV 26Al line, the 1.157 MeV 44Ti line, the 847 and 1238 keV 56Co lines, and the neutron capture line at 2.223 MeV. For the identification of galactic sources, a modelling of the diffuse galactic emission is essential. Such a modelling at this time does not yet exist at the required degree of accuracy. Therefore, a second COMPTEL source catalogue will be produced after a detailed and accurate modelling of the diffuse interstellar emission has become possible.Comment: 50 pages including 4 figures; accepted for publication in A&A Supplement

BATSE Observations of the Piccinotti Sample of AGN

BATSE Earth occultation data have been used to search for emission in the 20-100 keV band from all sources in the Piccinotti sample, which represents to date the only complete 2-10 keV survey of the extragalactic sky down to a limiting flux of 3.1 x 10^(-11) erg cm^(-2)$ s^(-1). Nearly four years of observations have been analyzed to reach a 5sigma sensitivity level of about 7.8x 10^(-11) erg cm^(-2) s^(-1) in the band considered. Of the 36 sources in the sample, 14 have been detected above 5sigma confidence level while marginal detection (3<sigma<5) can be claimed for 13 sources; for 9 objects 2sigma upper limits are reported. Comparison of BATSE results with data at higher energies is used to estimate the robustness of our data analysis: while the detection level of each source is reliable, the flux measurement maybe overestimated in some sources by as much as 35%, probably due to incomplete data cleaning. Comparison of BATSE fluxes with X-ray fluxes, obtained in the 2-10 keV range and averaged over years, indicates that a canonical power law of photon index 1.7 gives a good description of the broad band spectra of bright AGNs and that spectral breaks preferentially occur above 100 keV.Comment: 18 pages, 1 figure. Accepted for publication on Apj

COMPTEL images locations of gamma‐ray bursts

The γ‐ray telescope COMPTEL onboard GRO has so far located 6 gamma‐ray bursts which occurred in its ∼1 sr field of view. The positions of the sources were derived by the maximum‐entropy method. Systematic and statistical uncertainties for the four strongest bursts are approximately 1° to 2° and can be reduced in future analysis

Analysis of lead oxide (PbO) layers for direct conversion X-ray detection

Lead oxide (PbO) is a candidate direct conversion material for medical X-ray applications. We produced various samples and detectors with thick PbO layers. X-ray performance data such as dark current, charge generation yield and temporal behavior were evaluated on small samples. The influence of the metal contacts was studied in detail. We also covered large a-Si thin-film transistor (TFT)-plates with PbO. Imaging results from a large detector with an active area of 18 cm × 20 cm are presented. The detector has 960 × 1080 pixels with a pixel pitch of 184 ?m. The modulation transfer function at the Nyquist frequency of 2.72 linepairs/mm is 50%. Finally, a full size X-ray image is presented