Article

# MAGIC observations of the giant radio galaxy M87 in a low-emission state between 2005 and 2007

[more]
07/2012; DOI: 10.1051/0004-6361/201117827
Source: arXiv

ABSTRACT We present the results of a long M87 monitoring campaign in very high energy
$\gamma$-rays with the MAGIC-I Cherenkov telescope. We aim to model the
persistent non-thermal jet emission by monitoring and characterizing the very
high energy $\gamma$-ray emission of M87 during a low state. A total of 150\,h
of data were taken between 2005 and 2007 with the single MAGIC-I telescope, out
of which 128.6\,h survived the data quality selection. We also collected data
in the X-ray and \textit{Fermi}--LAT bands from the literature (partially
contemporaneous). No flaring activity was found during the campaign. The source
was found to be in a persistent low-emission state, which was at a confidence
level of $7\sigma$. We present the spectrum between 100\,GeV and 2\,TeV, which
is consistent with a simple power law with a photon index $\Gamma=2.21\pm0.21$
and a flux normalization at 300\,GeV of $(7.7\pm1.3) \times 10^{-8}$ TeV$^{-1}$
s$^{-1}$ m$^{-2}$. The extrapolation of the MAGIC spectrum into the GeV energy
range matches the previously published \textit{Fermi}--LAT spectrum well,
covering a combined energy range of four orders of magnitude with the same
spectral index. We model the broad band energy spectrum with a spine layer
model, which can satisfactorily describe our data.

### Full-text

Available from: Mosè Mariotti, Jul 02, 2015
1 Follower
·
212 Views
• Source
##### Article: Pinpointing Extragalactic Neutrino Sources in Light of Recent IceCube Observations
[Hide abstract]
ABSTRACT: The IceCube Collaboration has recently reported the observation of a flux of high-energy astrophysical neutrinos. The angular distribution of events is consistent with an isotropic arrival direction of neutrinos which is expected for an extragalactic origin. We estimate the prospects of detecting individual neutrino sources from a quasi-diffuse superposition of many extragalactic sources at the level of the IceCube observation. Our analysis takes into account ensemble variations of the source distribution as well as the event statistics of individual sources. We show that IceCube in its present configuration is sensitive to rare < 10^-8 Mpc^-3 yr^-1 transient source classes within 5 years of operation via the observation of multiplets. Identification of time-independent sources is more challenging due to larger backgrounds. We estimate that during the same period IceCube is sensitive to sparse sources with densities of < 10^-6 Mpc^-3 via association of events with the closest 100 sources of an ensemble. We show that a next-generation neutrino observatory with 5 times the effective area of IceCube and otherwise similar detector performance would increase the sensitivity to source densities and rates by about two orders of magnitude.
Physical Review D 06/2014; 90(4). DOI:10.1103/PhysRevD.90.043005 · 4.86 Impact Factor