Milagrito: a TeV air-shower array

Milagrito, a large, covered water-Cherenkov detector, was the world's first air-shower-particle detector sensitive to cosmic gamma rays below 1 TeV. It served as a prototype for the Milagro detector and operated from February 1997 to May 1998. This paper gives a description of Milagrito, a summary of the operating experience, and early results that demonstrate the capabilities of this technique.Comment: 38 pages including 24 figure

On the sensitivity of the HAWC observatory to gamma-ray bursts

We present the sensitivity of HAWC to Gamma Ray Bursts (GRBs). HAWC is a very high-energy gamma-ray observatory currently under construction in Mexico at an altitude of 4100 m. It will observe atmospheric air showers via the water Cherenkov method. HAWC will consist of 300 large water tanks instrumented with 4 photomultipliers each. HAWC has two data acquisition (DAQ) systems. The main DAQ system reads out coincident signals in the tanks and reconstructs the direction and energy of individual atmospheric showers. The scaler DAQ counts the hits in each photomultiplier tube (PMT) in the detector and searches for a statistical excess over the noise of all PMTs. We show that HAWC has a realistic opportunity to observe the high-energy power law components of GRBs that extend at least up to 30 GeV, as it has been observed by Fermi LAT. The two DAQ systems have an energy threshold that is low enough to observe events similar to GRB 090510 and GRB 090902b with the characteristics observed by Fermi LAT. HAWC will provide information about the high-energy spectra of GRBs which in turn could help to understanding about e-pair attenuation in GRB jets, extragalactic background light absorption, as well as establishing the highest energy to which GRBs accelerate particles

DEVELOPMENT of the MODEL of GALACTIC INTERSTELLAR EMISSION for STANDARD POINT-SOURCE ANALYSIS of FERMI LARGE AREA TELESCOPE DATA

Most of the celestial \u3b3 rays detected by the Large Area Telescope (LAT) on board the Fermi Gamma-ray Space Telescope originate from the interstellar medium when energetic cosmic rays interact with interstellar nucleons and photons. Conventional point-source and extended-source studies rely on the modeling of this diffuse emission for accurate characterization. Here, we describe the development of the Galactic Interstellar Emission Model (GIEM), which is the standard adopted by the LAT Collaboration and is publicly available. This model is based on a linear combination of maps for interstellar gas column density in Galactocentric annuli and for the inverse-Compton emission produced in the Galaxy. In the GIEM, we also include large-scale structures like Loop I and the Fermi bubbles. The measured gas emissivity spectra confirm that the cosmic-ray proton density decreases with Galactocentric distance beyond 5 kpc from the Galactic Center. The measurements also suggest a softening of the proton spectrum with Galactocentric distance. We observe that the Fermi bubbles have boundaries with a shape similar to a catenary at latitudes below 20\ub0 and we observe an enhanced emission toward their base extending in the north and south Galactic directions and located within \u2dc4\ub0 of the Galactic Center

The On-orbit Calibrations for the Fermi Large Area Telescope

The Large Area Telescope (LAT) on--board the Fermi Gamma ray Space Telescope began its on--orbit operations on June 23, 2008. Calibrations, defined in a generic sense, correspond to synchronization of trigger signals, optimization of delays for latching data, determination of detector thresholds, gains and responses, evaluation of the perimeter of the South Atlantic Anomaly (SAA), measurements of live time, of absolute time, and internal and spacecraft boresight alignments. Here we describe on orbit calibration results obtained using known astrophysical sources, galactic cosmic rays, and charge injection into the front-end electronics of each detector. Instrument response functions will be described in a separate publication. This paper demonstrates the stability of calibrations and describes minor changes observed since launch. These results have been used to calibrate the LAT datasets to be publicly released in August 2009.Comment: 60 pages, 34 figures, submitted to Astroparticle Physic

Pengaruh Pemberian Ketotifen terhadap Jumlah Sel Fibroblas dan Kepadatan Sel Kolagen pada Luka Insisi Tikus Wistar

Ingga Hadian, S-501202027. PENGARUH PEMBERIAN KETOTIFEN TERHADAP JUMLAH SEL FIBROBLAS DAN KEPADATAN SEL KOLAGEN PADA LUKA INSISI TIKUS WISTAR. Pembimbing I : DR. Untung Alfianto, dr, Sp.Bs, Pembimbing II : dr. Ardana Tri Arianto. Msi. Med. Sp.An-KNA. Program studi Magister Kedokteran Keluarga, Minat Utama Ilmu Biomedik, Fakultas Kedokteran Universitas Sebelas Maret, Surakarta, 2016. Latar Belakang : Sel mast merupakan salah satu yang berperan dalam proses inflamasi pada penyembuhan luka. Sel mast dikaitkan dengan kejadian luka kronis, sehingga sel mast diduga ikut memelihara proses inflamasi secara berlebihan. Hambatan pada degranulasi sel mast diharapkan akan mempercepat penyembuhan luka yang ditandai dengan meningkatnya jumlah sel fibroblas dan kepadatan sel kolagen. Ketotifen mampu mengurangi dreganulasi sel Mast dan mengurangi pelepasan Histamin, protease sel Mast, myeloperoxidase, leukotriens, PAF dan bermacam-macam Prostaglandin. Ketotifen juga menghambat agregasi polimorfonuklear serta mengurangi respon inflamasi dan mempercepat migrasi fibroblas di fase proliferasi. Tujuan :Mengetahui perbedaan jumlah sel fibroblas dan kepadatan sel kolagen pada tikus wistar yang diberikan Ketotifen oral dosis 0.3 mg/kg dibandingkan plasebo pada penyembuhan luka insisi tikus wistar. Metode : Penelitian ini termasuk true eksperimental laboratorik dengan desain Randomized Controlled Trial yang menggunakan tikus wistar sebagai obyek penelitian. 14 tikus Wistar dibagi dalam 2 kelompok, masing masing kelompok terdiri atas 7 tikus Wistar. Kelompok 1 merupakan kelompok kontrol yang dilakukan insisi sepanjang 2cm pada kulit punggung tikus dan diberikan plasebo per oral selama 6 hari. Kelompok 2 merupakan kelompok perlakuan yang dilakukan insisi sepanjang 2cm pada kulit punggung tikus dan diberikan Ketotifen 0,3 mg/kgBB per oral setiap 12 jam selama 6 hari. Analisis data untuk membandingkan rerata antar kedua kelompok yaitu kelompok perlakuan dan kelompok kontrol menggunakan uji independent samples t-test, dengan tingkat kemaknaan p < 0,05 (dikatakan bermakna secara statistik). Hasil : Pada kelompok kontrol didapatkan rerata persentase kepadatan sel kolagen sebesar 26,05 %, sedangkan pada kelompok Ketotifen didapatkan rerata persentase kepadatan sel kolagen sebesar 36,13 %. Untuk jumlah sel fibroblas pada kelompok kontrol didapatkan rerata sebesar 423 per lapang pandang, sedangkan pada kelompok Ketotifen didapatkan rerata sebesar 555,43 per lapang pandang. Kesimpulan : Ketotifen mempercepat penyembuhan luka ditandai dengan peningkatan sel fibroblas dan sel kolagen. Kata Kunci : Sel Mast, Ketotifen, Sel fibroblas, Serabut Kolagen. ABSTRACT Ingga Hadian, S-501202027. EFFECTS OF KETOTIFEN ON FIBROBLAST CELL COUNT AND COLLAGEN DENSITY ON INCISED WISTAR RATS. DR. Untung Alfianto, dr., Sp.BS, dr. Ardana Tri Arianto, Msi, Med, Sp.An-KNA. Background: Mast cells have a pivotal role in every healing process that involves inflammation of the cells, usually in wounds of chronic nature. If the degranulation process of the mast cells are inhibited, the healing process of the wound will accelerate, indicated by a raise in fibroblast cells and collagen density. Ketotifen are shown to inhibit the degranulation process and decreasing the release of histamin, mast cells proteases, myeloperoxidases, leukotriens, PAF, and various prostaglandins. Ketotifen can also inhibit the aggregation of polymorphonuclear cells, increasing the rate of fibroblast migration in the proliferation phase. This study was aimed to identify the effects of ketotifen on fibroblast cell count and collagen density tested on a wistar rats model. Methods: This study was a true laboratoric experimental study with randomized controlled trial using wistar rats model as objects. 14 rats were divided into two groups, each group contained seven rats. The first group was the control group, where the rats were incised 2 cm above the back skin, and were given per oral placebo for 6 days. The second group were given the same treatment, only the rats were given ketotifen 0.3 mg/kg per oral, every 12 hours lasting 6 days. The data were then collected and tested with independent sample t-test, with p value less than 0,05 is statistically significant. Results: In the control group, the mean percentage of the thickest collagen density were marked at 26.05%, whereas in the treatment group collagen density were marked at 36.13%. The mean fibroblast cell count were marked at 423 and 555.43 each viewing field, on the control group and the treatment group respectively. Conclusion: Ketotifen can accelerate the healing process, marked by the significant increase in collagen density and fibroblast cell count. Keywords: mast cells, ketotifen, fibroblast cells, collagen fibers

The spectral energy distribution of fermi bright blazars

We have conducted a detailed investigation of the broadband spectral properties of the γ-ray selected blazars of the Fermi LAT Bright AGN Sample (LBAS). By combining our accurately estimated Fermi γ-ray spectra with Swift, radio, infra-red, optical, and other hard X-ray/γ-ray data, collected within 3 months of the LBAS data taking period, we were able to assemble high-quality and quasi-simultaneous spectral energy distributions (SED) for 48 LBAS blazars. The SED of these γ-ray sources is similar to that of blazars discovered at other wavelengths, clearly showing, in the usual log ν-log ν Fν representation, the typical broadband spectral signatures normally attributed to a combination of low-energy synchrotron radiation followed by inverse Compton emission of one or more components. We have used these SED to characterize the peak intensity of both the low- and the high-energy components. The results have been used to derive empirical relationships that estimate the position of the two peaks from the broadband colors (i.e., the radio to optical, αro, and optical to X-ray, αox, spectral slopes) and from the γ-ray spectral index. Our data show that the synchrotron peak frequency (νSpeak) is positioned between 1012.5 and 1014.5 Hz in broad-lined flat spectrum radio quasars (FSRQs) and between 10 13 and 1017 Hz in featureless BL Lacertae objects. We find that the γ-ray spectral slope is strongly correlated with the synchrotron peak energy and with the X-ray spectral index, as expected at first order in synchrotron-inverse Compton scenarios. However, simple homogeneous, one-zone, synchrotron self-Compton (SSC) models cannot explain most of our SED, especially in the case of FSRQs and low energy peaked (LBL) BL Lacs. More complex models involving external Compton radiation or multiple SSC components are required to reproduce the overall SED and the observed spectral variability. While more than 50% of known radio bright high energy peaked (HBL) BL Lacs are detected in the LBAS sample, only less than 13% of known bright FSRQs and LBL BL Lacs are included. This suggests that the latter sources, as a class, may be much fainter γ-ray emitters than LBAS blazars, and could in fact radiate close to the expectations of simple SSC models. We categorized all our sources according to a new physical classification scheme based on the generally accepted paradigm for Active Galactic Nuclei and on the results of this SED study. Since the LAT detector is more sensitive to flat spectrum γ-ray sources, the correlation between νSpeak and γ-ray spectral index strongly favors the detection of high energy peaked blazars, thus explaining the Fermi overabundance of this type of sources compared to radio and EGRET samples. This selection effect is similar to that experienced in the soft X-ray band where HBL BL Lacs are the dominant type of blazars. © 2010 The American Astronomical Society

Multi-wavelength observations of blazar AO 0235+164 in the 2008-2009 flaring state

The blazar AO 0235+164 (z = 0.94) has been one of the most active objects observed by Fermi Large Area Telescope (LAT) since its launch in Summer 2008. In addition to the continuous coverage by Fermi, contemporaneous observations were carried out from the radio to γ-ray bands between 2008 September and 2009 February. In this paper, we summarize the rich multi-wavelength data collected during the campaign (including F-GAMMA, GASP-WEBT, Kanata, OVRO, RXTE, SMARTS, Swift, and other instruments), examine the cross-correlation between the light curves measured in the different energy bands, and interpret the resulting spectral energy distributions in the context of well-known blazar emission models. We find that the γ-ray activity is well correlated with a series of near-IR/optical flares, accompanied by an increase in the optical polarization degree. On the other hand, the X-ray light curve shows a distinct 20 day high state of unusually soft spectrum, which does not match the extrapolation of the optical/UV synchrotron spectrum. We tentatively interpret this feature as the bulk Compton emission by cold electrons contained in the jet, which requires an accretion disk corona with an effective covering factor of 19% at a distance of 100 R g. We model the broadband spectra with a leptonic model with external radiation dominated by the infrared emission from the dusty torus. © 2012. The American Astronomical Society. All rights reserved

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

Observational evidence for magnetars powering GRBs

The core‐collapse of a massive star may lead either to a black hole or a, possibly unstable, rapidly‐rotating magnetar. A magnetar provides an potential additional source of rotational energy which is available to power emission during the burst. If the energy reservoir is used up the magnetar may then suffer gravitational collapse ending the emission period. We have carried out a systematic search for the signature of a spinning‐down magnetar in the long GRBs observed by the Swift satellite up to the end of 2008. We find 10 GRBs that have a feature—which we call an “internal plateau”—in their light curves that can be associated with the injection of energy into the jet by a magnetar. The duration and intensity of the internal plateau provides constraints on the initial spin period and magnetic field of the magnetar. The derived magnetic fields are large compared to those of long‐lived galactic magnetars, but are within the most extreme values predicted for magnetars

GBM Capabilities for Multi-Messenger Time-Domain Astronomy

Owing to its wide sky coverage and broad energy range, the Fermi Gamma-ray Burst Monitor (GBM) is an excellent observer of the transient hard X-ray sky. GBM detects about 240 triggered Gamma-Ray Bursts (GRBs) per year, including over 30 which also trigger the Swift Burst Alert Telescope (BAT). The number of GRBs seen in common with Swift is smaller than expected from the overlap in sky coverage because GBM is not as sensitive as the BAT and the GBM GRB population is thus skewed to the brighter, closer bursts. This population includes about 45 short GRBs per year, giving GBM an excellent opportunity to observe the electromagnetic counterpart to any gravitational wave candidate resulting from the merger of compact binary members. The same characteristics make GBM an ideal partner for neutrino searches from nearby GRBs, and for the elusive Very-High Energy (VHE) counterparts to GRBs. With the deployment of the next-generation gravitational-wave detectors (Advanced LIGO/VIRGO) and VHE experiments (CTA and HAWC) potentially within the lifetime of the Fermi Gamma-ray Space Telescope, the prospects for breakthrough observations are good