Jenni Adams

Stockholm University, Tukholma, Stockholm, Sweden

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Publications (5)17.08 Total impact

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    ABSTRACT: We analyse the sensitivity of IceCube-DeepCore to annihilation of neutralino dark matter in the solar core, generated within a 25 parameter version of the minimally supersymmetric standard model (MSSM-25). We explore the 25-dimensional parameter space using scanning methods based on importance sampling and using DarkSUSY 5.0.6 to calculate observables. Our scans produced a database of 6.02 million parameter space points with neutralino dark matter consistent with the relic density implied by WMAP 7-year data, as well as with accelerator searches. We performed a model exclusion analysis upon these points using the expected capabilities of the IceCube-DeepCore Neutrino Telescope. We show that IceCube-DeepCore will be sensitive to a number of models that are not accessible to direct detection experiments such as SIMPLE, COUPP and XENON100, indirect detection using Fermi-LAT observations of dwarf spheroidal galaxies, nor to current LHC searches.
    Journal of Cosmology and Astroparticle Physics 10/2012; 2013(03). · 6.04 Impact Factor
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    ABSTRACT: Based on three years of Fermi Large Area Telescope (LAT) gamma-ray data of the Virgo cluster, evidence for an extended emission associated with dark matter pair annihilation in the b b-bar channel has been reported by Han et al. [1]. After an in depth spatial and temporal analysis, we argue that the tentative evidence for a gamma-ray excess from the Virgo cluster is mainly due to the appearance of a population of previously unresolved gamma-ray point sources in the region of interest. These point sources are not part of the LAT second source catalogue (2FGL), but are found to be above the standard detection significance threshold when three or more years of LAT data is included.
    Physical review D: Particles and fields 07/2012;
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    Anthony M. Brown, Jenni Adams
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    ABSTRACT: We report the discovery of high-energy \gamma-ray emission from the Broad Line Radio Galaxy (BLRG) Pictor A with a significance of ~5.8\sigma (TS=33.4), based on three years of observations with the Fermi Large Area Telescope (LAT) detector. The three-year averaged E>0.2 GeV \gamma-ray spectrum is adequately described by a power-law, with a photon index, \Gamma, of $2.93 \pm 0.03$ and a resultant integrated flux of $F_{\gamma}=(5.8\pm0.7) \times 10^{-9}$ ph cm$^{-2}$s$^{-1}$. A temporal investigation of the observed \gamma-ray flux, which binned the flux into year long intervals, reveals that the flux in the third year was 50% higher than the three-year average flux. This observation, coupled with the fact that this source was not detected in the first two years of {Fermi-LAT observations, suggests variability on timescales of a year or less. Synchrotron Self-Compton modelling of the spectral energy distribution of a prominent hot-spot in Pictor A's western radio lobe is performed. It is found that the models in which the \gamma-ray emission originates within the lobes, predicts an X-ray flux larger than that observed. Given that the X-ray emission in the radio lobe hot-spots has been resolved with the current suite of X-ray detectors, we suggest that the \gamma-ray emission from Pictor A originates from within its jet, which is in agreement with other \gamma-ray loud BLRGs. This suggestion is consistent with the evidence that the \gamma-ray flux is variable on timescales of a year or less.
    Monthly Notices of the Royal Astronomical Society 12/2011; 421(3). · 5.52 Impact Factor
  • Anthony M. Brown, Jenni Adams
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    ABSTRACT: We report on our study of the high-energy γ-ray emission from the Fanaroff–Riley type I (FR I) radio galaxy NGC 1275, based on 2 yr of observations with the Fermi Large Area Telescope (LAT) detector. Previous Fermi studies of NGC 1275 had found evidence for spectral and flux variability on monthly time-scales during the first year of Fermi-LAT observations. This variability is also seen in the larger 2-yr data set, during which we observe a large γ-ray flare (2010 June–August). The increased photon statistics from this large flare have allowed the discovery of flux variability from NGC 1275 on the time-scales of days. The largest flux variation observed during this flare being a factor of ∼3 from 1 day to the next and a resultant e-folding rise time of 1.51 ± 0.2 d. The 2-yr-averaged E > 100 MeV γ-ray spectrum is adequately described by a power-law spectrum, with a photon index, Γ, of 2.09 ± 0.02, and a resultant integrated flux of Fγ= (2.2 ± 0.1) × 10−7 photon cm−2 s−1. While no hysteresis was observed in the photon index–flux (Γγ versus Fγ) parameter space, there was obvious ‘harder-when-brighter’ behaviour observed during the large γ-ray flare. Furthermore, during this large flare, NGC 1275 appeared to migrate from the FR I radio galaxy to the BL Lac object region of the photon index–luminosity (Γγ versus Lγ) paramater space. In this paper, we present details of our Fermi-LAT analysis of NGC 1275, including a brief discussion on its implications for γ-ray blazar sources.
    Monthly Notices of the Royal Astronomical Society 03/2011; 413(4):2785 - 2790. · 5.52 Impact Factor
  • Source
    Anthony M. Brown, Jenni Adams
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    ABSTRACT: We report on our study of the high-energy $\gamma-$ray emission from the FR I radio galaxy NGC 1275, based on two years of observations with the Fermi-LAT detector. Previous Fermi studies of NGC 1275 had found evidence for spectral and flux variability on monthly timescales during the first year of Fermi-LAT observations. This variability is also seen in the larger two year data set, during which we observe a large $\gamma-$ray flare (June-August 2010). The increased photon statistics from this large flare have allowed the discovery of flux variability from NGC 1275 on the timescales of days. The largest flux variation observed during this flare being a factor of $\sim 3$ from one day to the next and a resultant $e$-folding risetime of $1.51\pm0.2$ days. The two year averaged $E>$100 MeV $\gamma-$ray spectrum is adequately described by a power-law spectrum, with a photon index, $\Gamma$, of $2.09 \pm 0.02$, and a resultant integrated flux of $F_{\gamma}=(2.2\pm0.1) \times 10^{-7}$ ph cm$^{-2}$s$^{-1}$. While no hysteresis was observed in the photon index$-$flux ($\Gamma_{\gamma}$ vs F$_{\gamma}$) parameter space, there was obvious `harder-when-brighter' behaviour observed during the large $\gamma-$ray flare. Furthermore, during this large flare, NGC 1275 appeared to migrate from the FR I radio galaxy to the BL Lac object region of the photon index$-$luminosity ($\Gamma_{\gamma}$ vs L$_{\gamma}$) paramater space. In this paper we present details of our Fermi-LAT analysis of NGC 1275, including a brief discussion on its implications for $\gamma-$ray blazar sources.
    01/2011;