1,662 research outputs found
Evidence of Particle Acceleration in the Superbubble 30 Doradus C with NuSTAR
We present evidence of diffuse, non-thermal X-ray emission from the
superbubble 30 Doradus C (30 Dor C) using hard X-ray images and spectra from
NuSTAR observations. For this analysis, we utilize data from a 200 ks targeted
observation of 30 Dor C as well as 2.8 Ms of serendipitous off-axis
observations from the monitoring of nearby SN 1987A. The complete shell of 30
Dor C is detected up to 20 keV, and the young supernova remnant MCSNR
J0536-6913 in the southeast of 30 Dor C is not detected above 8 keV.
Additionally, six point sources identified in previous Chandra and XMM-Newton
investigations have hard X-ray emission coincident with their locations. Joint
spectral fits to the NuSTAR and XMM-Newton spectra across the 30 Dor C shell
confirm the non-thermal nature of the diffuse emission. Given the best-fit
rolloff frequencies of the X-ray spectra, we find maximum electron energies of
70-110 TeV (assuming a B-field strength of 4G), suggesting 30 Dor C is
accelerating particles. Particles are either accelerated via diffusive shock
acceleration at locations where the shocks have not stalled behind the
H shell, or cosmic-rays are accelerated through repeated acceleration
of low-energy particles via turbulence and magnetohydrodynamic waves in the
bubble's interior.Comment: 14 pages, 8 figures, ApJ, in pres
Variability of Tourist Attraction on an International Boundary: Sonora, Mexico Border Towns
This paper explores how and why tourism and tourist districts in border towns vary along a single international boundary. A perception about Mexican border tourism holds that the boundary itself is the primary stimulus to development. While almost every Mexican border town has some tourist function, the nature and extent of that activity will vary with a host of exogenous factors. We argue that Mexican border city tourism is largely a function of these diverse external factors more than simply a presence on the international boundary. Successful tourism in the Mexican border cities is linked to historic advantage and age of settlement, as well as access, degree of promotional effort, and media exposure: To illustrate this assertion, we compare tourist development and the creation and absence of tourist districts at two separate locations along the Sonora-Arizona border: Nogales and San Luis Rio Colorado
NuSTAR observations of the young, energetic radio pulsar PSR B1509-58
We report on Nuclear Spectroscopic Telescope Array (NuSTAR) hard X-ray
observations of the young rotation-powered radio pulsar PSR B150958 in the
supernova remnant MSH 1552. We confirm the previously reported curvature in
the hard X-ray spectrum, showing that a log parabolic model provides a
statistically superior fit to the spectrum compared with the standard power
law. The log parabolic model describes the NuSTAR data, as well as previously
published gamma-ray data obtained with COMPTEL and AGILE, all together spanning
3 keV through 500 MeV. Our spectral modelling allows us to constrain the peak
of the broadband high energy spectrum to be at 2.60.8 MeV, an improvement
of nearly an order of magnitude in precision over previous measurements. In
addition, we calculate NuSTAR spectra in 26 pulse phase bins and confirm
previously reported variations of photon indices with phase. Finally, we
measure the pulsed fraction of PSR B150958 in the hard X-ray energy band for
the first time. Using the energy resolved pulsed fraction results, we estimate
that the pulsar's off-pulse emission has a photon index value between 1.26 and
1.96. Our results support a model in which the pulsar's lack of GeV emission is
due to viewing geometry, with the X-rays originating from synchrotron emission
from secondary pairs in the magnetosphere.Comment: 10 pages, 8 figures, 6 tables, ApJ accepte
Morphology and ornamentation in male magnificent frigatebirds: variation with age class and mating status
Male magnificent frigatebird (Fregata magnificens) ornamentation includes bright iridescent plumage and a red inflatable gular pouch. These signals are displayed during courtship, along with a drumming sound produced through specialized beak clackings resonating in the gular pouch. The extent of white in the plumage identifies three age classes of nonjuvenile male. Here we investigate how morphological and secondary sexual traits correlate with age class and mating status. Even though several age classârelated differences in morphology and visual appearance can be identified, the only features that significantly predict mating success are acoustic components of courtship display. Specifically, males that mate drum at lower fundamental frequenciesâthat is, they have larger gular pouchesâand have a quicker and more constant drumming cadence than unsuccessful males. The fundamental frequency decreases with age class, reflecting an increase in gular pouch size. This implies that females prefer older or possibly more experienced or viable males. Drumming cadence speed and stability might reflect male stamina. Apart from the acoustic differences with mating status, there is a nonsignificant tendency for backâfeather iridescence to be of shorter reflectance wavelength spectra in mated than in unmated males, which, when combined with acoustic variables, improves prediction of age class and mating status
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