7,118 research outputs found
TeV gamma rays and cosmic rays from the nucleus of M87, a mis-aligned BL Lac object
The unresolved nuclear region of M87 emits strong non-thermal emission from
radio to X-rays. Assuming this emission to originate in the pc scale jet
aligned at to the line of sight, we interpret this
emission in the context of the Synchrotron Proton Blazar (SPB) model. We find
the observed nuclear jet emission to be consistent with M87 being a mis-aligned
BL Lac Object and predict gamma-ray emission extending up to at least 100 GeV
at a level easily detectable by GLAST and MAGIC, and possibly by VERITAS
depending on whether it is high-frequency or low-frequency peaked. Predicted
neutrino emission is below the sensitivity of existing and planned neutrino
telescopes. Ultra-high energy neutrons produced in pion photoproduction
interactions decay into protons after escaping from the host galaxy. Because
energetic protons are deflected by the intergalactic magnetic field, the
protons from the decay of neutrons emitted in all directions, including along
the jet axis where the Doppler factor and hence emitted neutron energies are
higher, can contribute to the observed ultra-high energy cosmic rays. We
consider the propagation of these cosmic ray protons to Earth and conclude that
M87 could account for the observed flux if the extragalactic magnetic field
topology were favourable.Comment: 17 pages, 6 figures. 3 additional references plus minor changes,
acctepted for publication in Astroparticle Physic
ÂĄAmericano! Roger Clyne and the Peacemakers Rock the Borderlands of Transnational America
Cataloged from PDF version of article.In the mid 1990s, Roger Clyne was frontman for The Refreshments,
well-known in the Tempe, AZ college scene and briefly famous for their
radio pop single, âBanditos.â Since The Refreshmentsâ first indie release
album in 1994, Roger Clyne and his new band, Roger Clyne & the
Peacemakers,2 have become a staple on the independent music scene in
Arizona and the US Southwest. While Clyneâs music lapses into happy
stereotypes and romanticized depictions of the US-Mexico borderlands,
his musical utopia represents an alternative cultural politics that explores
(albeit clumsily) border crossings, difference, and transnationalism. Using
a personal interviews with Clyne and a critical reading of his lyrics,
this article explores how Clyne invokes the US-Mexico borderlands as
a region with specific landscapes, musical traditions, and mythologies,
and also as a metaphor for social change (by breaking down barriers).
He revises traditional US-Mexico borderlands musical traditions, such
as the border ballad (corrido), and asserts a transnational borderlands
identityâthe ÂĄAmericano!âthat exists comfortably uncomfortable between
the seams (and sounds) of cultures. Clyneâs music is significant for the
way it asks listeners and critics to reimagine the musical-cultural spaces
of nation and identity, while advocating for compassionate alternatives to
violence from a region characterized by power imbalances, inequality, and
violence.
Critic Josh Kun tells us that popular music gives us space to encounter
ourselvesâwe hear ourselves in our favorite songs and come to know and
build our identities through our relationships with music. The convergence
of sound, space, and identity creates âaudiotopias,â Kun argues, where
listeners confront âthe spaces that the music itself contains, the spaces
that music fills up, the spaces that music helps us to imagineâ (21).3 An
analysis of Roger Clyneâs music and lyrics is enriched by Kunâs theory of
audiotopias. As audiotopias, Clyneâs musical borderlands are a chronotope
defined by border crossings that offer new ways of charting contemporar
All the Pretty Mexican Girls: Whiteness and Racial Desire in Cormac McCarthy's All the Pretty Horses and Cities of the Plain
Cataloged from PDF version of article.âAll the Pretty Mexican Girls: Whiteness and Racial Desire in Cormac McCarthyâs All the Pretty Horses and Cities of the Plainâ uses a critical analysis of race and gender to argue that John Grady Coleâs relationship with Alejandra and Magdalena invokes a larger and longer history of the commodification and sexualization of womenâs bodies in the contact zone of the US-Mexico borderlands. The critical concerns this article addresses seek to re-situate McCarthyâs influential borderlands writing within a more nuanced series of border encounters that expose how transactions between regional, national, and international material realities on the US-Mexico border make available certain identities and modes of representation. Exposing the links between McCarthyâs representations and real-world material realities are crucial to this analysis because they reveal how McCarthy both accounts for and disavows the operations of power and history on the US-Mexico border. McCarthyâs border novels represent an in-between space where western history and the Western genre can be self-consciously invoked and revised, but only to a certain extent. John Grady Cole may be a more compassionate and âpolitically correctâ John Wayne, yet the violence, sexual and otherwise, perpetrated on the bodies of brown women in the Border Trilogy reminds us how much McCarthyâs white masculinities rely on such abject bodies in order to fashion their own ambivalent agency in the brutal world of McCarthyâs borderlands
The Monoceros very-high-energy gamma-ray source
The H.E.S.S. telescope array has observed the complex Monoceros Loop
SNR/Rosette Nebula region which contains unidentified high energy EGRET sources
and potential very-high-energy (VHE) gamma-ray source. We announce the
discovery of a new point-like VHE gamma-ray sources, HESS J0632+057. It is
located close to the rim of the Monoceros SNR and has no clear counterpart at
other wavelengths. Data from the NANTEN telescope have been used to investigate
hadronic interactions with nearby molecular clouds. We found no evidence for a
clear association. The VHE gamma-ray emission is possibly associated with the
lower energy gamma-ray source 3EG J0634+0521, a weak X-ray source 1RXS
J063258.3+054857 and the Be-star MWC 148.Comment: 4 pages, 4 figures, Contribution to the 30th ICRC, Merida Mexico,
July 200
The GeV-TeV Connection in Galactic gamma-ray sources
Recent observations with atmospheric Cherenkov telescope systems such as
H.E.S.S. and MAGIC have revealed a large number of new sources of
very-high-energy (VHE) gamma-rays from 100 GeV - 100 TeV, mostly concentrated
along the Galactic plane. At lower energies (100 MeV - 10 GeV) the
satellite-based instrument EGRET revealed a population of sources clustering
along the Galactic Plane. Given their adjacent energy bands a systematic
correlation study between the two source catalogues seems appropriate. Here,
the populations of Galactic sources in both energy domains are characterised on
observational as well as on phenomenological grounds. Surprisingly few common
sources are found in terms of positional coincidence and spectral consistency.
These common sources and their potential counterparts and emission mechanisms
will be discussed in detail. In cases of detection only in one energy band, for
the first time consistent upper limits in the other energy band have been
derived. The EGRET upper limits are rather unconstraining due to the
sensitivity mismatch to current VHE instruments. The VHE upper limits put
strong constraints on simple power-law extrapolation of several of the EGRET
spectra and thus strongly suggest cutoffs in the unexplored energy range from
10 GeV - 100 GeV. Physical reasons for the existence of cutoffs and for
differences in the source population at GeV and TeV energies will be discussed.
Finally, predictions will be derived for common GeV - TeV sources for the
upcoming GLAST mission bridging for the first time the energy gap between
current GeV and TeV instruments.Comment: (1) Kavli Institute for Particle Astrophysics and Cosmology (KIPAC),
Stanford, USA (2) Stanford University, W.W. Hansen Experimental Physics Lab
(HEPL) and KIPAC, Stanford, USA (3) ICREA & Institut de Ciencies de l'Espai
(IEEC-CSIC) Campus UAB, Fac. de Ciencies, Barcelona, Spain. (4) School of
Physics and Astronomy, University of Leeds, UK. Paper Submitted to Ap
Discussion: Reporting and calibration of post-bomb 14C data
The definitive paper by Stuiver and Polach (1977) established the conventions for reporting of radiocarbon data for chronological and geophysical studies based on the radiocactive decay of 14C in the sample since the year of sample death or formation. Several ways of reporting 14C activity levels relative to a standard were also established, but no specific instructions were given for reporting nuclear weapons-testing (post-bomb) 14C levels in samples. Because the use of post-bomb 14C is becoming more prevalent in forensice, biology, and geosciences, a convention needs to be adopted. We advocate the use of fraction modern with a new symbol F14C to prevent confusion with the previously used Fm, which may or may not have been fractionation-corrected. We also discuss the calibration of post-bomb 14c samples and the available data sets and compilations, but do not give a recommendation for a particular data set
Marine reservoir corrections : St. Helena, South Atlantic Ocean
We present the first marine reservoir age and âR determination for the island of St. Helena using marine mollusk radiocarbon dates obtained from an historical context of known age. This represents the first marine reservoir age and âR determination in the southern Atlantic Ocean within thousands of kilometers of the island. The depletion of 14C in the shells indicates a rather larger reservoir age for that portion of the surface Atlantic than models indicate. The implication is that upwelling old water along the Namibian coast is transported for a considerable distance, although it is likely to be variable on a decadal timescale. An artillerymanâs button, together with other artifacts found in a midden, demonstrate association of the mollusk shells with a narrow historic period of AD 1815â1835
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