35 research outputs found
Insights into the high-energy γ-ray emission of Markarian 501 from extensive multifrequency observations in the Fermi era
We report on the γ-ray activity of the blazar Mrk 501 during the first 480 days of Fermi operation. We find that the average Large Area Telescope (LAT) γ-ray spectrum of Mrk 501 can be well described by a single power-law function with a photon index of 1.78 ± 0.03. While we observe relatively mild flux variations with the Fermi-LAT (within less than a factor of two), we detect remarkable spectral variability where the hardest observed spectral index within the LAT energy range is 1.52 ± 0.14, and the softest one is 2.51 ± 0.20. These unexpected spectral changes do not correlate with the measured flux variations above 0.3 GeV. In this paper, we also present the first results from the 4.5 month long multifrequency campaign (2009 March 15-August 1) on Mrk 501, which included the Very Long Baseline Array (VLBA), Swift, RXTE, MAGIC, and VERITAS, the F-GAMMA, GASP-WEBT, and other collaborations and instruments which provided excellent temporal and energy coverage of the source throughout the entire campaign. The extensive radio to TeV data set from this campaign provides us with the most detailed spectral energy distribution yet collected for this source during its relatively low activity. The average spectral energy distribution of Mrk 501 is well described by the standard one-zone synchrotron self-Compton (SSC) model. In the framework of this model, we find that the dominant emission region is characterized by a size ≲0.1 pc (comparable within a factor of few to the size of the partially resolved VLBA core at 15-43 GHz), and that the total jet power (≃1044 erg s-1) constitutes only a small fraction (∼10-3) of the Eddington luminosity. The energy distribution of the freshly accelerated radiating electrons required to fit the time-averaged data has a broken power-law form in the energy range 0.3 GeV-10 TeV, with spectral indices 2.2 and 2.7 below and above the break energy of 20 GeV. We argue that such a form is consistent with a scenario in which the bulk of the energy dissipation within the dominant emission zone of Mrk 501 is due to relativistic, proton-mediated shocks. We find that the ultrarelativistic electrons and mildly relativistic protons within the blazar zone, if comparable in number, are in approximate energy equipartition, with their energy dominating the jet magnetic field energy by about two orders of magnitude. © 2011. The American Astronomical Society
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Päällystemerkinnät ja niiden rekisteröinti Oulun kaupungissa
Oulun kaupungissa on ollut kehittämistarpeita päällystemerkintöihin liittyen. Yksi opinnäytetyön tavoitteista oli luoda kaupungille päällystemerkintäperiaatteet, joista selviää, mitä merkintöjä tehdään millekin katuluokalle. Koska Oulussa tehdään suurin osa päällystemerkinnöistä maalamalla, toinen tavoite oli selvittää, minkälaisia vuosikustannuksia kestävämmät merkintämateriaalit aiheuttavat. Lisäksi kaupungilla oli tarve päällystemerkintärekisterille, josta saisi tietoa päällystemerkintöjen sijainneista ja lukumääristä. Kolmantena tavoitteena oli tehdä esiselvitys siitä, millä periaatteilla päällystemerkintärekisteriä kannattaa lähteä luomaan.
Työssä tutkittiin eri päällystemerkintämateriaalien ominaisuuksia ja selvitettiin aikaisempien tutkimustulosten sekä kyselytutkimuksen avulla, miten eri materiaalit kestävät kulutusta eri liikennemäärillä. Tulosten perusteella laskettiin merkintämateriaaleista aiheutuvia vuosikustannuksia. Päällystemerkintäperiaatteita varten laadittiin katuluokitus sekä ohjeet siitä, miten päällystemerkinnät tehdään eri luokan kaduille. Lisäksi tutkittiin Tekla Civil Basicin soveltumista päällystemerkintärekisterin työkaluksi esimerkkitapausten perusteella.
Päällystemerkintäperiaatteet tulevat helpottamaan jokakesäisiä kunnossapidon merkintätöitä Oulussa. Tutkimustulosten perusteella saatiin selville, että 1,5 mm:n vahvuinen spraymerkintä on vuosikustannuksiltaan kaikista edullisin. Päällystemerkintärekisterin luonti Tekla Civil Basicilla on teknisesti mahdollista.One purpose of this thesis was to develop principles for pavement markings in order to find out what kind of markings to use in different classes of streets. Most of the pavement markings in the city of Oulu are painted and there was a need for a research of the annual costs for other pavement marking materials. The city of Oulu had also a need for a register of pavement markings that could provide information about the locations and counts of the markings. Another purpose was to research the principles for creating the register.
In this thesis the properties of different marking materials were examined. Additionally, it was found out how long the materials would last in different amounts of traffic. The research was made with the help of earlier investigations and a survey. The annual costs of the pavement markings were calculated from the results. Before composing the pavement marking principles, the streets had to be classified. In addition, it was studied, based on some example cases, how suitable tool Tekla Civil Basic would be for the pavement marking register.
The pavement marking principles will facilitate the yearly maintenance work with pavement markings in the city of Oulu. Based on the results it was found out that markings made from 1.5 mm thick spray has the lowest annual costs. It was also found out that it is technically possible to create the pavement markings register with Tekla Civil Basic