Gamma-rays from millisecond pulsars in Globular Clusters

Globular clusters (GCs) with their ages of the order of several billion years contain many final products of evolution of stars such as: neutron stars, white dwarfs and probably also black holes. These compact objects can be at present responsible for the acceleration of particles to relativistic energies. Therefore, gamma-ray emission is expected from GCs as a result of radiation processes occurring either in the inner magnetosperes of millisecond pulsars or in the vicinity of accreting neutron stars and white dwarfs or as a result of interaction of particles leaving the compact objects with the strong radiation field within the GC. Recently, GeV gamma-ray emission has been detected from several GCs by the new satellite observatory Fermi. Also Cherenkov telescopes reported interesting upper limits at the TeV energies which start to constrain the content of GCs. We review the results of these gamma-ray observations in the context of recent scenarios for their origin.Comment: 20 pages, 9 figures, will be published in Astrophysics and Space Science Series (Springer), eds. N. Rea and D.F. Torre

Flavor conversion of cosmic neutrinos from hidden jets

High energy cosmic neutrino fluxes can be produced inside relativistic jets under the envelopes of collapsing stars. In the energy range E ~ (0.3 - 1e5) GeV, flavor conversion of these neutrinos is modified by various matter effects inside the star and the Earth. We present a comprehensive (both analytic and numerical) description of the flavor conversion of these neutrinos which includes: (i) oscillations inside jets, (ii) flavor-to-mass state transitions in an envelope, (iii) loss of coherence on the way to observer, and (iv) oscillations of the mass states inside the Earth. We show that conversion has several new features which are not realized in other objects, in particular interference effects ("L- and H- wiggles") induced by the adiabaticity violation. The neutrino-neutrino scattering inside jet and inelastic neutrino interactions in the envelope may produce some additional features at E > 1e4 GeV. We study dependence of the probabilities and flavor ratios in the matter-affected region on angles theta13 and theta23, on the CP-phase delta, as well as on the initial flavor content and density profile of the star. We show that measurements of the energy dependence of the flavor ratios will, in principle, allow to determine independently the neutrino and astrophysical parameters.Comment: 56 pages, 19 figures. Minor changes. Accepted by JHEP

Predicting Distribution of Aedes Aegypti and Culex Pipiens Complex, Potential Vectors of Rift Valley Fever Virus in Relation to Disease Epidemics in East Africa.

The East African region has experienced several Rift Valley fever (RVF) outbreaks since the 1930s. The objective of this study was to identify distributions of potential disease vectors in relation to disease epidemics. Understanding disease vector potential distributions is a major concern for disease transmission dynamics. DIVERSE ECOLOGICAL NICHE MODELLING TECHNIQUES HAVE BEEN DEVELOPED FOR THIS PURPOSE: we present a maximum entropy (Maxent) approach for estimating distributions of potential RVF vectors in un-sampled areas in East Africa. We modelled the distribution of two species of mosquitoes (Aedes aegypti and Culex pipiens complex) responsible for potential maintenance and amplification of the virus, respectively. Predicted distributions of environmentally suitable areas in East Africa were based on the presence-only occurrence data derived from our entomological study in Ngorongoro District in northern Tanzania. Our model predicted potential suitable areas with high success rates of 90.9% for A. aegypti and 91.6% for C. pipiens complex. Model performance was statistically significantly better than random for both species. Most suitable sites for the two vectors were predicted in central and northwestern Tanzania with previous disease epidemics. Other important risk areas include western Lake Victoria, northern parts of Lake Malawi, and the Rift Valley region of Kenya. Findings from this study show distributions of vectors had biological and epidemiological significance in relation to disease outbreak hotspots, and hence provide guidance for the selection of sampling areas for RVF vectors during inter-epidemic periods

A Spatial Analysis of Rift Valley Fever Virus Seropositivity in Domestic Ruminants in Tanzania

Rift Valley fever (RVF) is an acute arthropod-borne viral zoonotic disease primarily occurring in Africa. Since RVF-like disease was reported in Tanzania in 1930, outbreaks of the disease have been reported mainly from the eastern ecosystem of the Great Rift Valley. This cross-sectional study was carried out to describe the variation in RVF virus (RVFV) seropositivity in domestic ruminants between selected villages in the eastern and western Rift Valley ecosystems in Tanzania, and identify potential risk factors. Three study villages were purposively selected from each of the two Rift Valley ecosystems. Serum samples from randomly selected domestic ruminants (n = 1,435) were tested for the presence of specific immunoglobulin G (IgG) and M (IgM), using RVF enzyme-linked immunosorbent assay methods. Mixed effects logistic regression modelling was used to investigate the association between potential risk factors and RVFV seropositivity. The overall RVFV seroprevalence (n = 1,435) in domestic ruminants was 25.8% and species specific seroprevalence was 29.7%, 27.7% and 22.0% in sheep (n = 148), cattle (n = 756) and goats (n = 531), respectively. The odds of seropositivity were significantly higher in animals sampled from the villages in the eastern than those in the western Rift Valley ecosystem (OR = 1.88, CI: 1.41, 2.51; p<0.001), in animals sampled from villages with soils of good than those with soils of poor water holding capacity (OR = 1.97; 95% CI: 1.58, 3.02; p< 0.001), and in animals which had been introduced than in animals born within the herd (OR = 5.08, CI: 2.74, 9.44; p< 0.001). Compared with animals aged 1-2 years, those aged 3 and 4-5 years had 3.40 (CI: 2.49, 4.64; p< 0.001) and 3.31 (CI: 2.27, 4.82, p< 0.001) times the odds of seropositivity. The findings confirm exposure to RVFV in all the study villages, but with a higher prevalence in the study villages from the eastern Rift Valley ecosystem

ASSESSMENT OF NATURAL RADIOACTIVITY LEVEL AND ASSOCIATED RADIOLOGICAL HAZARDS IN MARINE SEDIMENT SAMPLES COLLECTED FROM ABYAN BEACH, GULF OF ADEN, YEMEN

تمَّ تجميع 23 عينه بقايا بحرية من ساحل ابين على شاطئ خليج عدن لقياس تركيز الراديوم-226، الثوريوم -232 والبوتاسيوم -40 ومعاملات الاخطار الناتجة عنها بأستخدام كاشف الجرمانيوم عالي النقاوة .HPGe اظهرت النتائج ان اعلى تركيز لفعالية نويدة الراديوم-226 وجدت في العينة ٍS11 والذي تساوي &nbsp;(36.300±1.41Bq/kg)بينما اقل قيمة وجدت في العينة S23 والذي تساوي (9.44±0.38Bq/kg) بمعدل تركيزيساوي (16.25±0.53Bq/kg). بينما وجدت اعلى تركيزلفعالية نويدة الثوريوم -232المشعة طبيعيا"في العينة S11 والذي تساوي (95.75±5.88Bq/kg) واقل قيمة وجدت في العينة S12 والذي تساوي (12.94±0.79Bq/kg) بمعدل تركيزيساوي (23.80±1.46Bq/kg). اما اعلى تركيز لفعالية نويدة البوتاسيوم -40 فقد وجدت في العينةS5 والتي تساوي (747.72±64.32Bq/kg) واقل قيمة وجدت في العينة S11 والذي تساوي (296.67±25.52Bq/kg) بمعدل تركيزيساوي (518.54±45.84Bq/kg). تم حساب معاملات الاخطار الاشعاعية الناتجة عن تواجد هذه الانوية الطبيعية في عينات البقايا البحرية المقاسة. اظهرت النتائج ان فعالية المعامل الراديومي (Raeq) تقع في المدى (65.58to196.06Bq/kg) بمعدل يساوي (90.21Bq/kg)، معامل الخطورة الخارجي (Hex) يقع في المدى (0.177 to 0.529) بمعدل يساوي 0.243، معامل الخطورة الداخلي (Hin) يقع في المدى (0.203 to 0.627) بمعدل يساوي 0.287. حسبت معدل الجرعة الممتصة الخارجي Dout ومعدل الجرعة الممتصة الداخلي (Din) ووجدت انها تقع في المدى(31.57 to 87.06nGyh-1)، (59.91 to 162.75nGyh-1) بمعدل يساوي 43.66nGyh-1 ,83.13nGyh-1 على التوالي. حسبت الجرعة السنوية المؤثرة الخارجية (AEDout) والداخلية (AEDin) ووجدت انها تقع في المدى (0.294 to 0.798mSvh-1), (0.039 to 0.107mSvh-1) بمعدل يساوي 0.053mSvh-1 &nbsp;و0.407mSvh-1 على التوالي. حسبت قيم الجرعة المكافئة السنوية للغدة التناسلية AGDE ووجدت انها تقع في المدى (226.13 to 605.55μSvh-1) بمعدل يساوي.312.52 μSvh-1-بينما حسبت قيمة كل من ( excess life-time cancer risk (ELCRout الخارجي وكذلك (excess life-time cancer risk (ELCRin الداخلي ووجدت انها تقع في المدى (0.135×10-3 to 0.374×10-3)، (1.029×10-3 to 2.79 ×10-3) بمعدل يساوي (3-10×0.187)، (3-10×1.427) على التوالي. جميع النتائج التي حصلنا عليها للعينات قيد الدراسة اقل من القيمة العليا المسموح بها والموصى بها منThe World Health Organization and EU Council وان الاشعاعات الناتجة عن النويدات الطبيعية لاتشكل خطورة على الحياة البشرية.Twenty three marine sediment samples taken from the side beach from the Abyan beach, Aden Gulf, Yemen to measuring the activity concentration of terrestrial radionuclides radium-226, thorium-232 and potassium-40 and its associated hazard indices using gamma spectrometer with High-Purity Germanium HPGe detector. The average activity concentration of natural radionuclides 226Ra, 232Th and 40k in marine sediments samples under investigation were 16.25± 0.63Bqkg-1, for Ra-226, 23.80± 1.46Bqkg-1 for Th-232 and 518.54±44.61Bqkg-1 for K-40 respectively. The radiation hazard indices which resulting from the presence of natural radionuclides in marine sediment samples were calculated and the obtained results indicate that the average value of radium equivalent activity was 90.21Bqkg-1. The average value of External hazard index Hex was 0.243 and the average values of internal hazard index Hin was 0.287. The average value of outdoor absorbed dose rate Dout was 43.66nGyh−1 and indoor absorbed dose rate Din was 83.13nGyh−1. The average values of annual outdoor effective dose AEDout was 0.053mSvy-1and the annual indoor effective dose AEDin was 0.407mSvy-1. The average values of the annual gonadal dose equivalent AGDE were 312.52μSvy-1. While the average values of outdoor excess life-time cancer risk ELCRout was 0.187×10−3 and the indoor excess life-time cancer risk ELCRin was 1.427×10−3. They are less than worldwide limits

Fermi Gamma-ray Imaging of a Radio Galaxy

The Fermi Gamma-ray Space Telescope has detected the gamma-ray glow emanating from the giant radio lobes of the radio galaxy Centaurus A. The resolved gamma-ray image shows the lobes clearly separated from the central active source. In contrast to all other active galaxies detected so far in high-energy gamma-rays, the lobe flux constitutes a considerable portion (>1/2) of the total source emission. The gamma-ray emission from the lobes is interpreted as inverse Compton scattered relic radiation from the cosmic microwave background (CMB), with additional contribution at higher energies from the infrared-to-optical extragalactic background light (EBL). These measurements provide gamma-ray constraints on the magnetic field and particle energy content in radio galaxy lobes, and a promising method to probe the cosmic relic photon fields.Comment: 27 pages, includes Supplementary Online Material; corresponding authors: C.C. Cheung, Y. Fukazawa, J. Knodlseder, L. Stawar

Detection of Gamma-Ray Emission from the Starburst Galaxies M82 and NGC 253 with the Large Area Telescope on Fermi

We report the detection of high-energy gamma-ray emission from two starburst galaxies using data obtained with the Large Area Telescope on board the Fermi Gamma-ray Space Telescope. Steady point-like emission above 200 MeV has been detected at significance levels of 6.8 sigma and 4.8 sigma respectively, from sources positionally coincident with locations of the starburst galaxies M82 and NGC 253. The total fluxes of the sources are consistent with gamma-ray emission originating from the interaction of cosmic rays with local interstellar gas and radiation fields and constitute evidence for a link between massive star formation and gamma-ray emission in star-forming galaxies.Comment: Submitted to ApJ Letter

MHD models of Pulsar Wind Nebulae

Pulsar Wind Nebulae (PWNe) are bubbles or relativistic plasma that form when the pulsar wind is confined by the SNR or the ISM. Recent observations have shown a richness of emission features that has driven a renewed interest in the theoretical modeling of these objects. In recent years a MHD paradigm has been developed, capable of reproducing almost all of the observed properties of PWNe, shedding new light on many old issues. Given that PWNe are perhaps the nearest systems where processes related to relativistic dynamics can be investigated with high accuracy, a reliable model of their behavior is paramount for a correct understanding of high energy astrophysics in general. I will review the present status of MHD models: what are the key ingredients, their successes, and open questions that still need further investigation.Comment: 18 pages, 5 figures, Invited Review, Proceedings of the "ICREA Workshop on The High-Energy Emission from Pulsars and their Systems", Sant Cugat, Spain, April 12-16, 201

MEASUREMENT OF NATURAL RADIOACTIVITY IN TAP WATER SAMPLES FOR SELECTED REGIONS IN ADEN GOVERNORATE, YEMEN

تمَّ قياس النشاط الاشعاعي الطبيعي لاحدى عشر عينة من مياه الشرب من الحنفية من مناطق مختلفة في منازل مديريات محافظة عدن باستخدام كاشف الجرمانيوم عالي النقاوة (.(HPGe اظهرت النتائج ان اعلى تركيز للراديوم-226 لعينات مياه الشرب من الحنفية وجدت في العينة T7 في مديرية دار سعد والتي تساوي (0.525±0.29)Bq/L بينما اقل قيمة وجدت في العينة T11 في مديرية عدن الصغرى والتي تساوي (0.017±0.0060)Bq/L بمعدل تركيز للراديوم-226 يساوي (0.228±0.13)Bq/L. فيما اطهرت النتائج ان اعلى تركيز للثوريوم -232 لعينات مياه الشرب من الحنفية هي في العينة T5 في مديرية خورمكسر والتي تساوي &nbsp;(0.319±0.18)Bq/L بينما اقل قيمة وجدت في العينة T11 &nbsp;في مديرية عدن الصغرى والتي تساوي (0.009±0.0010)Bq/L بمعدل تركيز للثوريوم -232 يساوي (0.129±0.089)Bq/L. كما اظهرت النتائج ان اعلى تركيز للبوتاسيوم-40 لعينات مياه الشرب من الحنفية وجدت في العينة T2 في مديرية المعلا والتي تساوي (0.40±0.26)Bq/L بينما اقل قيمة وجدت في العينة T11 &nbsp;في مديرية عدن الصغرى والتي تساوي (0.027±0.0040)Bq/L بمعدل تركيز للبوتاسيوم-40 يساوي (0.141±0.021)Bq/L. حسبت الجرعة السنوية المؤثرة الممتصة الناتجة عن استهلاك مياه الشرب من الحنفية للفئات العمرية الثلاث الرضع، الاطفال والبالغين، وجد انها تقع في المدى (5.67to178.16μSv/y), (3.05 to 98.77μSv/y), (3.41to119.08μSv/y) بمعدل يساوي,42.65μSv/y ,87.62μSv/y, 48.62μSv/y للفئات العمرية الثلاث الرضع, الاطفال والبالغين على التوالي. هذه القيم للجرعة السنوية المؤثرة الناتجة عن استهلاك المياه تعد قليلة مقارنة مع الحد الموصى به عالميا" من جانب منظمة الصحة العالمية وكذلك منظمة &nbsp;EU Council والتي تساوي(260μSv year-1and 200μSv year-1) &nbsp;لكل من الراديوم -226 والثوريوم-232&nbsp; لمياه الشرب من الحنفية. فيما حسب معامل خطورة السرطان ELCR وجد انه يقع في المدى ( (1.19×10-5 to 38.56×10-5بمعدل يساوي (.(16.39 ×10-5 من الواضح ان معامل خطورة السرطان في عينات مياه الشرب من الحنفية اقل من القيمة الموصى بها عالميا" والتي تساوي (145×10−5)&nbsp; بشكل عام اظهرت النتائج ان تركيز الراديوم-226، الثوريوم -232 وكذلك البوتاسيوم-40 في عينات مياه الشرب من الحنفية قيد الدراسة اقل من القيمة العليا المسموح بها والموصى بها من قبل الوكالة الامريكية لحماية البئية (USEPA, 2012) والتي تساوي (11.1Bq/L) &nbsp;ولاتشكل المياة من الحنفية اي خطورة على الحياة البشرية ولايوجد اي ضرر على المياة المستخدمة للشرب من الحنفية.In the present work, we have measured specific activity concentrations of in eleven tap water samples for selected regions in Aden governorate by using high purity germanium detector (HPGe). The (HPGe) detector (CANBERA-model 7229N, USA) with an efficiency of 35% and energy resolution (2.6keV) at energy (1332.6keV) for 60Co, the high purity N-type semiconductor detector with physical characteristics of (geometry closed-end coaxial, (3×3 inch). The results have shown that, The highest value of specific activity concentration of 226Ra was found in in T7 Daar-Saad region which was equal to (0.525±0.29)Bq/L, while the lowest value of specific activity concentration of 226Ra was found in T11 Aden Assughra region which was equal to (0.017±0.006)Bq/L with an average value of (0.228±0.13)Bq/L. The highest value of specific activity concentration of 232Th was found in in T5 Khor-makser region which was equal to (0.319±0.18)Bq/L,&nbsp; while the lowest value of specific activity concentration of 232Th was found in T11 Aden Assughra region which was equal to (0.009±0.001)Bq/L with an average values of (0.129±0.089)Bq/L. The highest value of specific activity concentration of (40K) was found in in T2 (Al-Ma,allah) region which was equal to (0.4±0.26)Bq/L, while the lowest value of specific activity concentration of (40K) was found in T11 Aden Assughra region which was equal to (0.027±0.004)Bq/L with an average values of&nbsp; (0.141±0.021)Bq/L respectively. The annual ingestion effective dose (AED) ranged from (3.05 to 98.77μSv/y), (5.67 to 178.16μSv/y), and (3.41 to 119.08μSv/y), with average values of 42.65μSv/y, 78.62μSv/y and 48.62μSv/y, for infants, children and adults respectively. The excess lifetime cancer risk (ELCR) have been calculated, its values were lower than the world’s average value of (0.29×10−3) as reported by EPA. The overall annual effective dose and cancer risks corresponding to radionuclide intake in tap water were below the recommended maximum values. It was inferred from the findings of this study that the water used as the sample does not have any significant radiological impacts to human body and is safe to be used as drinking water

Search for gamma-ray emission from magnetars with the Fermi Large Area Telescope

We report on the search for 0.1-10 GeV emission from magnetars in 17 months of Fermi Large Area Telescope (LAT) observations. No significant evidence for gamma-ray emission from any of the currently-known magnetars is found. The most stringent upper limits to date on their persistent emission in the Fermi-LAT energy range are estimated between ~10^{-12}-10^{-10} erg/s/cm2, depending on the source. We also searched for gamma-ray pulsations and possible outbursts, also with no significant detection. The upper limits derived support the presence of a cut-off at an energy below a few MeV in the persistent emission of magnetars. They also show the likely need for a revision of current models of outer gap emission from strongly magnetized pulsars, which, in some realizations, predict detectable GeV emission from magnetars at flux levels exceeding the upper limits identified here using the Fermi-LAT observations.Comment: ApJ Letters in press; Corresponding authors: Caliandro G. A., Hadasch D., Rea N., Burnett