Gamma-Ray Bursts Observed with the Spectrometer SPI Onboard INTEGRAL

The spectrometer SPI is one of the main detectors of ESA's INTEGRAL mission. The instrument offers two interesting and valuable capabilities for the detection of the prompt emission of Gamma-ray bursts. Within a field of view of 16 degrees, SPI is able to localize Gamma-ray bursts with an accuracy of 10 arcmin. The large anticoincidence shield, ACS, consisting of 512 kg of BGO crystals, detects Gamma-ray bursts quasi omnidirectionally above ~70 keV. Burst alerts from SPI/ACS are distributed to the interested community via the INTEGRAL Burst Alert System. The ACS data have been implemented into the 3rd Interplanetary Network and have proven valuable for the localization of bursts using the triangulation method. During the first 8 months of the mission approximately one Gamma-ray burst per month was localized within the field of fiew of SPI and 145 Gamma-ray burst candidates were detected by the ACS from which 40 % have been confirmed by other instruments.Comment: 4 pages, 2 figures, to appear in the Proceedings of the Conference "30 Years of GRB Discovery", Santa Fe, New Mexico, USA, September 8-12, 200

Bronze Age Tell Communities in Context

Practice – The Social, Space, and Materiality forms the second part of Bronze Age Tell Communities in Context: An exploration into culture, society, and the study of European prehistory. It studies Bronze Age tells and our approaches towards an understanding of this fascinating way of life, drawing on the material remains of long-term architectural stability and references back to ancestral place. While the first volume challenged Neo-Diffusionist models of the influence of Mediterranean palatial centres on the development of tell communities in the Carpathians and an attendant focus on social stratification, the second part sets out an alternative theoretical approach, which foregrounds architecture and the social use of space. Unlike the reductionist macro perspective of mainstream social modelling, inspired by aspects of practice theory outlined in this book, the account given seeks to allow for what is truly remarkable about these sites, and what we can infer from them about the way of life they once framed and enabled. The stability seen on tells, and their apparent lack of change on a macro scale, are specific features of the social field, in a given region and for a specific period of time. Both stability and change are contingent upon specific historical contexts, including traditional practices, their material setting and human intentionality. They are not an inherent, given property of this or that ‘type’ of society or social structure. For our tells, it is argued here, underneath the specific manifestation of sociality maintained, we clearly do see social practices and corresponding material arrangements being negotiated and adjusted. Echoing the argument laid out in the first part of this study, it is suggested that archaeology should take an interest in such processes on the micro scale, rather than succumb to the temptation of neat macro history and great narratives existing aloof from the material remains of past lives

Gamma-Ray Burst Detection with INTEGRAL/SPI

The spectrometer SPI, one of the two main instruments of the INTEGRAL spacecraft, has strong capabilities in the Field of Gamma-Ray Burst (GRB) detections. In its 16 degree Field of view (FoV) SPI is able to trigger and to localize GRBs. With its large anticoincidence shield (ACS) of 512 kg of BGO crystals SPI is able to detect GRBs quasi omnidirectionally with a very high sensitivity. The ACS GRB alerts will provide GRB arrival times with high accuracy but with no or very rough positional information. The expected GRB detection rate in SPI's FoV will be one per month and for the ACS around 300 per year. At MPE two SPI software contributions to the real-time INTEGRAL burst-alert system (IBAS) at the INTEGRAL science data centre ISDC have been developed. The SPI-ACS branch of IBAS will produce burst alerts and light-curves with 50 ms resolution. It is planned to use ACS burst alerts in the 3rd interplanetary network. The SPI-FoV branch of IBAS is currently under development at MPE. The system is using the energy and timing information of single and multiple events detected by the Germanium-camera of SPI. Using the imaging algorithm developed at the University of Birmingham the system is expected to locate strong bursts with an accuracy of better than 1 degree.Comment: 11 pages, 5 figure

High-Energy Calibration of a BGO detector of the GLAST Burst Monitor

The understanding of the instrumental response of the GLAST Burst Monitor BGO detectors at energies above the energy range which is accessible by common laboratory radiation sources (< 4.43 MeV), is important, especially for the later cross-calibration with the LAT response in the overlap region between ~ 20 MeV to 30 MeV. In November 2006 the high-energy calibration of the GBM-BGO spare detector was performed at the small Van-de-Graaff accelerator at SLAC. High-energy gamma-rays from excited 8Be* (14.6 MeV and 17.5 MeV) and 16O* (6.1 MeV) were generated through (p,gamma)-reactions by irradiating a LiF-target. For the calibration at lower energies radioactive sources were used. The results, including spectra, the energy/channel-relation and the dependence of energy resolution are presented.Comment: 2 pages, 1 figure; to appear in the Proc. of the First Int. GLAST Symp. (Stanford, Feb. 5-8, 2007), eds. S.Ritz, P.F.Michelson, and C.Meegan, AIP Conf. Pro

Limits on the GeV Emission from Gamma-Ray Bursts

The Large Area Telescope (LAT) on board of the Fermi satellite detected emission above 30 MeV only in a small fraction of the long gamma-ray bursts (GRBs) detected by the Fermi Gamma-ray Burst Monitor (GBM) at 8 keV - 10 MeV. Those bursts that were detected by the LAT were among the brightest GBM bursts. We examine a sample of the most luminous GBM bursts with no LAT detection and obtain upper limits on their high energy fluence. We find an average upper limit of LAT/GBM fluence ratio of 0.13 for GeV fluence during $T_{90}$ and an average upper limit ratio of 0.45 for GeV fluence during the first 600 seconds after the trigger. These ratios strongly constrain various emission models and in particular rule out SSC models for the prompt emission. In about a third of both LAT detected and LAT non-detected bursts, we find that the extrapolation of the MeV range Band spectrum to the GeV range is larger than the observed GeV fluence (or its upper limit). While this excess is not highly significant for any specific burst, the overall excess in a large fraction of the bursts suggests a decline in the high energy spectral slope in at least some of these bursts. Possibly an evidence for the long sought after pair creation limit.Comment: Accepted for publication in MNRA

The first giant flare from SGR 1806-20: observations with the INTEGRAL SPI Anti-Coincidence Shield

A giant flare from the Soft Gamma-ray Repeater SGR 1806-20 has been detected by several satellites on 2004 December 27. This tremendous outburst, the first one observed from this source, was a hundred times more powerful than the two previous giant flares from SGR 0525-66 and SGR 1900+14. We report the results obtained for this event with the Anticoincidence Shield of the SPI spectrometer on board the INTEGRAL satellite, which provides a high-statistics light curve at E>~80 keV. The flare started with a very strong pulse, which saturated the detector for ~0.7 s, and whose backscattered radiation from the Moon was detected 2.8 s later. This was followed by a ~400 s long tail modulated at the neutron star rotation period of 7.56 s. The tail fluence corresponds to an energy in photons above 3 keV of 1.6x10^44 (d/15 kpc)^2 erg. This is of the same order of the energy emitted in the pulsating tails of the two giant flares seen from other soft repeaters, despite the hundredfold larger overall emitted energy of the SGR 1806-20 giant flare. Long lasting (~1 hour) hard X-ray emission, decaying in time as t^-0.85, and likely associated to the SGR 1806-20 giant flare afterglow has also been detected.Comment: revised version - Accepted for publication on The Astrophysical Journal Letter

Searching for Needles in Haystacks - Using the Fermi/GBM to find GRB gamma-rays with the Fermi/LAT Detector

From the launch of the Fermi Gamma-ray Space Telescope to July 9, 2010, the Gamma-ray Burst Monitor (GBM) has detected 497 probable GRB events. Twenty-two of these satisfy the simultaneous requirements of an estimated burst direction within 52^\circ of the Fermi Large Area Telescope (LAT) boresight and a low energy fluence exceeding 5 $\mu$erg/cm^2. Using matched filter techniques, the spatially correlated Fermi/LAT photon data above 100 MeV have been examined for evidence of bursts that have so far evaded detection at these energies. High energy emission is detected with great confidence for one event, GRB 090228A. Since the LAT has significantly better angular resolution than the GBM, real-time application of these methods could open the door to optical identification and richer characterization of a larger fraction of the relatively rare GRBs that include high energy emission.Comment: 4 pages, 3 figures, 2 tables, accepted for publication in ApJ Letters, minor revision

The sharpness of gamma-ray burst prompt emission spectra

We aim to obtain a measure of the curvature of time-resolved spectra that can be compared directly to theory. This tests the ability of models such as synchrotron emission to explain the peaks or breaks of GBM prompt emission spectra. We take the burst sample from the official Fermi GBM GRB time-resolved spectral catalog. We re-fit all spectra with a measured peak or break energy in the catalog best-fit models in various energy ranges, which cover the curvature around the spectral peak or break, resulting in a total of 1,113 spectra being analysed. We compute the sharpness angles under the peak or break of the triangle constructed under the model fit curves and compare to the values obtained from various representative emission models: blackbody, single-electron synchrotron, synchrotron emission from a Maxwellian or power-law electron distribution. We find that 35% of the time-resolved spectra are inconsistent with the single-electron synchrotron function, and 91% are inconsistent with the Maxwellian synchrotron function. The single temperature, single emission time and location blackbody function is found to be sharper than all the spectra. No general evolutionary trend of the sharpness angle is observed, neither per burst nor for the whole population. It is found that the limiting case, a single temperature Maxwellian synchrotron function, can only contribute up to $58^{+23}_{-18}$% of the peak flux. Our results show that even the sharpest but non-realistic case, the single-electron synchrotron function, cannot explain a large fraction of the observed GRB prompt spectra. Because of the fact that any combination of physically possible synchrotron spectra added together will always further broaden the spectrum, emission mechanisms other than optically thin synchrotron radiation are likely required in a full explanation of the spectral peaks or breaks of the GRB prompt emission phase.Comment: 16 pages, 13 figures, 2 tables, accepted for publication in A&

Integral results on GRB030320: a long gamma-ray burst detected at the edge of the field of view

GRB030320 is the 5th Gamma-ray burst (GRB) detected by INTEGRAL in the field of view (FoV). It is so far the GRB with the largest off-axis angle with respect to the INTEGRAL pointing direction, near to the edge of the FoV of both main instruments, IBIS and SPI. Nevertheless, it was possible to determine its position and to extract spectra and fluxes. The GRB nature of the event was confirmed by an IPN triangulation. It is a ~ 60 s long GRB with two prominent peaks separated by ~ 35 s. The spectral shape of the GRB is best represented by a single power law with a photon index Gamma ~ 1.7. The peak flux in the 20 - 200 keV band is determined to ~ 5.7 photons cm-2 s-1 and the GRB fluence to 1.1 x 10-5 erg cm-2. Analysing the spectral evolution of the GRB, a ``hard-to-soft'' behaviour emerges. A search for an optical counterpart has been carried out, but none was found.Comment: 5 pages, 3 figures. Accepted for publication in A&AL (INTEGRAL issue

Økologisk mat på sykehjem. Med hvilken hensikt og til hvilken nytte?

Bakgrunn og formål: Økologisk mat og landbruk er et stadig tilbakevendende tema i debatter om helse og miljø. Forbruker interessen er økende og i henhold til Soria Moria- erklæringen er det nasjonale målet at 15 prosent av matproduksjonen og matforbruket skal være økologisk i 2020. For å imøtekomme dette målet blir økt forbruk av økologiske produkter i offentlige storhusholdninger trukket frem som en viktig strategi. Et parallelt prosjekt underordnet det nasjonale målet har vært ”økoløft i kommuner”. Sykehjemmet som jeg i denne studien har undersøkt ligger i økokommunen Tingvoll i Møre og Romsdal. Som et resultat av dette valgte sykehjemmets kjøkken å legge om til økologisk mat. Formålet med denne studien er å få en helhetlig forståelse av hvordan omleggingsprosessen ble gjennomført, basert på ulike informanters perspektiver. Dette med fokus på organisering, samarbeid, utfordringer samt nytteverdien av prosjektet for de ulike interessentene. Metode og utvalg: Metoden baserer seg på en kvalitativ casestudie, der semistrukturerte intervjuer er benyttet i datainnsamlingen. Det ble gjennomført intervjuer med 13 informanter med ulik tilknytning til omleggingsprosjektet. Analysen av intervjuene baserer seg på en tematisert analytisk tilnærming. Funn: Studien viser kompleksiteten rundt et omleggingsprosjekt. Omleggingsprosjektet startet i 2008 og per januar 2013 kunne sykehuset erklære seg som den første offentlige institusjonen som har mottatt Debios serveringsmerket i Sølv, hvilket betyr at minimum 50 prosent av maten som kjøpes er økologisk målt ved innkjøpsverdi. Underveis har organisatoriske, praktiske og relasjonelle utfordringer preget de ansattes hverdag. Mangelfull informasjon om prosjektets mål og hensikt var gjennomgående i mine funn. Et interessant funn var at informantene som var godt informert og hadde utviklet en eierskapsfølelse til prosjektet stort sett hadde veldig positive holdninger til økologisk mat og også videreførte kunnskapen ervervet på jobben til privatlivet. Selv om holdningene til økologisk mat blant personalet er noe sprikende, er det generelt en enighet om at omleggingen er av betydning for beboerne. Konklusjon: Fortsatt er det en rekke flaskehalser for virksomheter som ønsker å legge om til et økologisk mattilbud. Et begrenset tilbud av produkter og mangel på produkter som er tilpasset storhusholdninger er en av årsakene til dette. Men også denne studien viste at omleggingsprosjekter ofte fører med seg langt flere positive effekter, enn ”bare” det å servere økologisk mat. For å oppnå en omlegging hele institusjonen har et ”eierskap” til, trengs det informasjon og kunnskap om økologisk mat, kommunikasjon på tvers av avdelingene samt engasjerte og motiverte ansatte som er villige til å ta på seg ansvaret for en krevende prosessMaster i samfunnsernærin