17,080 research outputs found
Upper limits on the luminosity of the progenitor of type Ia supernova SN2014J
We analysed archival data of Chandra pre-explosion observations of the
position of SN2014J in M82. No X-ray source at this position was detected in
the data, and we calculated upper limits on the luminosities of the progenitor.
These upper limits allow us to firmly rule out an unobscured supersoft X-ray
source progenitor with a photospheric radius comparable to the radius of white
dwarf near the Chandrasekhar mass (~1.38 M_sun) and mass accretion rate in the
interval where stable nuclear burning can occur. However, due to a relatively
large hydrogen column density implied by optical observations of the supernova,
we cannot exclude a supersoft source with lower temperatures, kT < 80 eV. We
find that the supernova is located in the centre of a large structure of soft
diffuse emission, about 200 pc across. The mass, ~3x10^4 M_sun and short
cooling time of the gas, tau_cool ~ 8 Myrs, suggest that it is a
supernova-inflated super-bubble, associated with the region of recent star
formation. If SN2014J is indeed located inside the bubble, it likely belongs to
the prompt population of type Ia supernovae, with a delay time as short as ~ 50
Myrs. Finally, we analysed the one existing post-supernova Chandra observation
and placed upper limit of ~ (1-2) 10^37 erg/s on the X-ray luminosity of the
supernova itself.Comment: 8 pages, 6 figure
Do Local Production, Organic Certification, Nutritional Claims, and Product Branding Pay in Consumer Food Choices?
This research furthers the assessment of consumer demand for locally produced foods, while also considering a host of other food attributes that may interact to influence consumer utility. Using stated preference data from a choice-based conjoint analysis survey instrument, we estimate willingness-to-pay for processed food products (blackberry jam) that are differentiated with respect to their branding, the location of their production, certification as organically produced, branding as a product of a small family farming association, and carrying a State Proud certification. Although price is the most important single attribute influencing consumer choice for our sample, consumers also were willing to pay more for food products produced in their state or in a well identified multistate region. Our sample was more willing to purchase organic products, although there was an indication of some confusion as to the meaning of the NOP organic logo. Our results also supported the notion that consumers are willing to support small family farms with purchases if the product is clearly labeled as a product of small farms. These conclusions have important is significant has important policy and merchandising strategy implications.Conjoint analysis, Choice experiment, Locally produced food, Organic foods, Product differentiation, Produce marketing, State Proud programs, Willingness-to-pay, Agribusiness, Agricultural and Food Policy, Consumer/Household Economics, Food Consumption/Nutrition/Food Safety, Marketing, Q11, Q13,
Mechanisms and Observations of Coronal Dimming for the 2010 August 7 Event
Coronal dimming of extreme ultraviolet (EUV) emission has the potential to be
a useful forecaster of coronal mass ejections (CMEs). As emitting material
leaves the corona, a temporary void is left behind which can be observed in
spectral images and irradiance measurements. The velocity and mass of the CMEs
should impact the character of those observations. However, other physical
processes can confuse the observations. We describe these processes and the
expected observational signature, with special emphasis placed on the
differences. We then apply this understanding to a coronal dimming event with
an associated CME that occurred on 2010 August 7. Data from the Solar Dynamics
Observatory's (SDO) Atmospheric Imaging Assembly (AIA) and EUV Variability
Experiment (EVE) are used for observations of the dimming, while the Solar and
Heliospheric Observatory's (SOHO) Large Angle and Spectrometric Coronagraph
(LASCO) and the Solar Terrestrial Relations Observatory's (STEREO) COR1 and
COR2 are used to obtain velocity and mass estimates for the associated CME. We
develop a technique for mitigating temperature effects in coronal dimming from
full-disk irradiance measurements taken by EVE. We find that for this event,
nearly 100% of the dimming is due to mass loss in the corona
Interstellar H^+_3: possible detection of the 1_(10)â1_(11) transition of H_2D^+
An interstellar line has been detected in emission at the expected submillimeter wavelength of the 1_(10)â1_(11) transition of H_(2)D^+, the deuterated version of the primary ion (H^(+)_(3)) in the favored ion-molecule reaction scheme for interstellar gas phase chemistry. The strength of the line is in approximate agreement with the theoretically anticipated H_(2)D^+ abundance
Luminosity, Energy and Polarization Studies for the Linear Collider: Comparing e+e- and e-e- for NLC and TESLA
We present results from luminosity, energy and polarization studies at a
future Linear Collider. We compare e+e- and e-e- modes of operation and
consider both NLC and TESLA beam parameter specifications at a center-of-mass
energy of 500 GeV. Realistic colliding beam distributions are used, which
include dynamic effects of the beam transport from the Damping Rings to the
Interaction Point. Beam-beam deflections scans and their impact for beam-based
feedbacks are considered. A transverse kink instability is studied, including
its impact on determining the luminosity-weighted center-of-mass energy.
Polarimetry in the extraction line from the IP is presented, including results
on beam distributions at the Compton IP and at the Compton detector.Comment: 17 pages, 12 figures. Presented at 5th International Workshop on
Electron-Electron Interactions at TeV Energies, December 12-14, 2003, Santa
Cruz, C
Charge-exchange limits on low-energy α-particle fluxes in solar flares
This paper reports on a search for flare emission via charge-exchange radiation in the wings of the Lyα line of He II at 304 Ă
, as originally suggested for hydrogen by Orrall and Zirker. Via this mechanism a primary α particle that penetrates into the neutral chromosphere can pick up an atomic electron and emit in the He II bound-bound spectrum before it stops. The Extreme-ultraviolet Variability Experiment on board the Solar Dynamics Observatory gives us our first chance to search for this effect systematically. The Orrall-Zirker mechanism has great importance for flare physics because of the essential roles that particle acceleration plays; this mechanism is one of the few proposed that would allow remote sensing of primary accelerated particles below a few MeV nucleon<sup>â1</sup>. We study 10 events in total, including the Îł-ray events SOL2010-06-12 (M2.0) and SOL2011-02-24 (M3.5) (the latter a limb flare), seven X-class flares, and one prominent M-class event that produced solar energetic particles. The absence of charge-exchange line wings may point to a need for more complete theoretical work. Some of the events do have broadband signatures, which could correspond to continua from other origins, but these do not have the spectral signatures expected from the Orrall-Zirker mechanism
WroNG -- Wroclaw Neutrino Generator of events for single pion production
We constructed a new Monte Carlo generator of events for neutrino CC single
pion production on free nucleon targets. The code uses dynamical models of the
DIS with the PDFs modified according to the recent JLab data and of the Delta
excitation. A comparison with experimental data was done in three channels for
the total cross sections and for the distributions of events in invariant
hadronic mass.Comment: 6 pages, 13 figures, Presented by J.T. Sobczyk at the 3rd
International Workshop on Neutrino-Nucleus Interactions in the Few-GeV
Region, 17-21 March, Gran Sasso(Italy),to appear in the Proceeding
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