The effect of photomeson production by the universal radiation field on high-energy cosmic rays
Photomeson production by universal radiation field and effects on high energy cosmic rays
Stecker, F. W.↗
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Multi-functional layered structure having structural and radiation shielding attributes
A cosmic and solar radiation shielding structure that also has structural attributes is comprised of three layers. The first layer is 30-42 percent by volume of ultra-high molecular weight (UHMW) polyethylene fibers, 18-30 percent by volume of graphite fibers, and a remaining percent by volume of an epoxy resin matrix. The second layer is approximately 68 percent by volume of UHMW polyethylene fibers and a remaining percent by volume of a polyethylene matrix. The third layer is a ceramic material.
Kaul, Raj K.↗
THE FIRST LIMITS ON THE ULTRA-HIGH ENERGY NEUTRINO FLUENCE FROM GAMMA-RAY BURSTS
We set the first limits on the ultra-high energy (UHE) neutrino fluence at energies greater than 10{sup 9} GeV from gamma-ray bursts (GRBs) based on data from the second flight of the Antarctic Impulsive Transient Antenna (ANITA). During the 31 day flight of ANITA-II, 26 GRBs were recorded by Swift or Fermi. Of these, we analyzed the 12 GRBs which occurred during quiet periods when the payload was away from anthropogenic activity. In a blind analysis, we observe 0 events on a total background of 0.0044 events in the combined prompt window for all 12 low-background bursts. We also observe 0 events from the remaining 14 bursts. We place a 90% confidence level limit on the E{sup -4} prompt neutrino fluence between 10{sup 8} GeV < E < 10{sup 12} GeV of E{sup 4}{Phi} = 2.5 x 10{sup 17} GeV{sup 3} cm{sup -2} from GRB090107A. This is the first reported limit on the UHE neutrino fluence from GRBs above 10{sup 9} GeV, and the strongest limit above 10{sup 8} GeV.
79 ASTRONOMY AND ASTROPHYSICS↗
OBSERVATIONAL SEARCH FOR PeV-EeV TAU NEUTRINO FROM GRB081203A
We report the first observational search for tau neutrinos ({nu}{sub {tau}}) from gamma-ray bursts (GRBs) using one of the Ashra light collectors. The Earth-skimming {nu}{sub {tau}} technique of imaging Cherenkov {tau} showers was applied as a detection method. We set stringent upper limits on the {nu}{sub {tau}} fluence in PeV-EeV region for 3780 s (between 2.83 and 1.78 hr before) and another 3780 s (between 21.2 and 22.2 hr after) surrounding GRB081203A triggered by the Swift satellite. This first search for PeV-EeV {nu}{sub {tau}} complements other experiments in energy range and methodology, and suggests the prologue of 'multi-particle astronomy' with a precise determination of time and location.
79 ASTRONOMY AND ASTROPHYSICS↗
ARE LOW-LUMINOSITY GAMMA-RAY BURSTS GENERATED BY RELATIVISTIC JETS?
Low-luminosity gamma-ray bursts (ll-GRBs) constitute a subclass of GRBs that play a central role in the GRB-supernova connection. While ll-GRBs differ from typical long GRBs (LGRBs) in many aspects, they also share some common features. Therefore, the question whether the gamma-ray emission of ll-GRBs and LGRBs has a common origin is of great interest. Here we address this question by testing whether ll-GRBs, like LGRBs according to the Collapsar model, can be generated by relativistic jets that punch holes in the envelopes of their progenitor stars. The Collapsar model predicts that the durations of most observed bursts will be comparable to, or longer than, the time it takes the jets to break out of the star. We calculate the jet breakout times of ll-GRBs and compare them to the observed durations. We find that there is a significant excess of ll-GRBs with durations that are much shorter than the jet breakout time and that these are inconsistent with the Collapsar model. We conclude that the processes that dominate the gamma-ray emission of ll-GRBs and of LGRBs are most likely fundamentally different.
79 ASTRONOMY AND ASTROPHYSICS↗
EXPLORING THE GALAXY MASS-METALLICITY RELATION AT z {approx} 3-5
Long-duration gamma-ray bursts (GRBs) provide a premier tool for studying high-redshift star-forming galaxies thanks to their extreme brightness and association with massive stars. Here we use GRBs to study the galaxy stellar mass-metallicity (M{sub *}-Z) relation at z {approx} 3-5, where conventional direct metallicity measurements are extremely challenging. We use the interstellar medium metallicities of long GRB hosts derived from afterglow absorption spectroscopy, in conjunction with host galaxy stellar masses determined from deep Spitzer 3.6 {mu}m observations of 20 GRB hosts. We detect about 1/4 of the hosts with M{sub AB}(I) {approx} -21.5 to -22.5 mag and place a limit of M{sub AB}(I) {approx}> -19 mag on the remaining hosts from a stacking analysis. Using these observations, we present the first rest-frame optical luminosity distribution of long GRB hosts at z {approx}> 3 and find that it is similar to the distribution of long GRB hosts at z {approx} 1. In comparison to Lyman-break galaxies at the same redshift, GRB hosts are generally fainter, but the sample is too small to rule out an overall similar luminosity function. On the other hand, the GRB hosts appear to be more luminous than the population of Ly{alpha} emitters at z {approx} 3-4. Using a conservative range of mass-to-light ratios for simple stellar populations (with ages of 70 Myr to {approx}2 Gyr), we infer the host stellar masses and present mass-metallicity measurements at z {approx} 3-5 ((z) {approx} 3.5). We find that the detected GRB hosts, with M{sub *} {approx} 2 x 10{sup 10} M{sub sun}, display a wide range of metallicities, but that the mean metallicity at this mass scale, Z {approx} 0.3 Z{sub sun}, is lower than measurements at z {approx}< 3. Combined with stacking of the non-detected hosts with M{sub *} {approx}< 3 x 10{sup 9} M{sub sun} and Z {approx}< 0.1 Z{sub sun}, we find tentative evidence for the existence of an M{sub *}-Z relation at z {approx} 3.5 and continued evolution of this relation to systematically lower metallicities from z {approx} 2.
79 ASTRONOMY AND ASTROPHYSICS↗
PTF 10bzf (SN 2010ah): A BROAD-LINE Ic SUPERNOVA DISCOVERED BY THE PALOMAR TRANSIENT FACTORY
We present the discovery and follow-up observations of a broad-line Type Ic supernova (SN), PTF 10bzf (SN 2010ah), detected by the Palomar Transient Factory (PTF) on 2010 February 23. The SN distance is {approx_equal}218 Mpc, greater than GRB 980425/SN 1998bw and GRB 060218/SN 2006aj, but smaller than the other SNe firmly associated with gamma-ray bursts (GRBs). We conducted a multi-wavelength follow-up campaign with Palomar 48 inch, Palomar 60 inch, Gemini-N, Keck, Wise, Swift, the Allen Telescope Array, Combined Array for Research in Millimeter-wave Astronomy, Westerbork Synthesis Radio Telescope, and Expanded Very Large Array. Here we compare the properties of PTF 10bzf with those of SN 1998bw and other broad-line SNe. The optical luminosity and spectral properties of PTF 10bzf suggest that this SN is intermediate, in kinetic energy and amount of {sup 56}Ni, between non-GRB-associated SNe like 2002ap or 1997ef, and GRB-associated SNe like 1998bw. No X-ray or radio counterpart to PTF 10bzf was detected. X-ray upper limits allow us to exclude the presence of an underlying X-ray afterglow as luminous as that of other SN-associated GRBs such as GRB 030329 or GRB 031203. Early-time radio upper limits do not show evidence for mildly relativistic ejecta. Late-time radio upper limits rule out the presence of an underlying off-axis GRB, with energy and wind density similar to the SN-associated GRB 030329 and GRB 031203. Finally, by performing a search for a GRB in the time window and at the position of PTF 10bzf, we find that no GRB in the interplanetary network catalog could be associated with this SN.
79 ASTRONOMY AND ASTROPHYSICS↗
The radiation-induced rotation of cosmic dust particles: A feasibility study
A crossed beam, horizontal optical trap, used to achieve laser levitation of particles in an effort to determine how solar radiation produces high spin rate in interplanetary dust particles, is described. It is suggested that random variations in albedo and geometry give rise to a nonzero effective torque when the influence of a unidrectional source of radiaton (due to the Sun) over the surface of a interplanetary dust particle is averaged. This resultant nonzero torque is characterized by an asymmetry factor which is the ratio of the effective moment arm to the maximum linear dimension of the body and is estimated to be 5 X 10 to the minus four power. It is hoped that this symmetry factor, which stabilizes the nonstatistical response of the particle, can be measured in a future Spacelab experiment.
Misconi, N. Y.↗
Means of measuring the earth's velocity through the 3 deg radiation field.
Earth velocity relative to 3 K cosmic background radiation field measured by determining anisotropy with wideband detector sensitive at mm IR wavelengths
Condon, J. J.↗
CO OBSERVATIONS OF THE HOST GALAXY OF GRB 000418 AT z = 1.1
We performed CO (J = 2-1) observations of the host galaxy of GRB 000418 at z = 1.1181 with the Plateau de Bure Interferometer. Previous studies show that the host galaxy has properties similar to those of an ultraluminous infrared galaxy (ULIRG). The star formation rate (SFR) of the host galaxy as derived from submillimeter and radio continuum emission is a few 100 M{sub sun} yr{sup -1}, which is an order of magnitude greater than the SFR derived from optical line emission. The large discrepancy between the SFRs derived from different observing wavelengths indicates the presence of a bulk of dust-obscured star formation and molecular gas that is enough to sustain the intense star formation. We failed to detect CO emission and derived 2{sigma} upper limits on the velocity-integrated CO (2-1) luminosity of L'{sub CO} < 6.9 x 10{sup 9} K km s{sup -1} pc{sup 2} and the molecular gas mass of M{sub H{sub 2}}< 5.5x10{sup 9} M{sub sun} by adopting a velocity width of 300 km s{sup -1} and a CO-to-H{sub 2} conversion factor of {alpha}{sub CO} = 0.8 M{sub sun} (K km s{sup -1} pc{sup 2}){sup -1}, which are standard values for ULIRGs. The lower limit on the ratio of far-infrared luminosity to CO luminosity, a measure of the star formation efficiency, is higher compared to that of other gamma-ray burst hosts and other galaxy populations, which is consistent with active star formation taking place in this galaxy.
79 ASTRONOMY AND ASTROPHYSICS↗
COMPOSITION OF SOLAR COSMIC RAYS
Composition of solar cosmic rays - radiation hazard
SOLAR COSMIC RAY↗
Critical issues in connection with human missions to Mars: protection of and from the Martian environment
Human missions to Mars are planned to happen within this century. Activities associated therewith will interact with the environment of Mars in two reciprocal ways: (i) the mission needs to be protected from the natural environmental elements that can be harmful to human health, the equipment or to their operations; (ii) the specific natural environment of Mars should be protected so that it retains its value for scientific and other purposes. The following environmental elements need to be considered in order to protect humans and the equipment on the planetary surface: (i) cosmic ionizing radiation, (ii) solar particle events; (iii) solar ultraviolet radiation; (iv) reduced gravity; (v) thin atmosphere; (vi) extremes in temperatures and their fluctuations; and (vii) surface dust. In order to protect the planetary environment, the requirements for planetary protection as adopted by COSPAR for lander missions need to be revised in view of human presence on the planet. Landers carrying equipment for exobiological investigations require special consideration to reduce contamination by terrestrial microorganisms and organic matter to the greatest feasible extent. Records of human activities on the planet's surface should be maintained in sufficient detail that future scientific experimenters can determine whether environmental modifications have resulted from explorations. c2002 COSPAR. Published by Elsevier Science Ltd. All rights reserved.
Extraterrestrial Environment↗
Comparison of RESRAD-Derived External Dose to TLD Dose - 18522
At the Nevada National Security Site, external dose at corrective action sites is generally estimated using environmental thermoluminescent dosimeters (TLDs). These devices integrate the penetrating radiation dose at the location being evaluated. Because these devices will also integrate the external dose from natural sources of penetrating radiation (e.g., cosmic rays and naturally occurring radionuclides in soil), the natural background external dose level as measured by TLDs placed in similar but unaffected areas is subtracted from the gross TLD reading. The use of TLDs to estimate the external dose component of the total effective dose was determined to be the most effective method because the TLDs are exposed for an extended time period and TLDs are compliant with Title 10 Code of Federal Regulations Part 835.402, 'Individual Monitoring,' to monitor individual exposures. At sample locations where no TLD results are available (such as subsurface locations), estimated external dose is calculated from a RESRAD-derived external dose using radionuclide activities measured from soil samples. A comparison of estimated external doses from locations where both TLD data and soil sample data are available is presented herein. This comparison demonstrates that estimated external dose using RESRAD and soil sample radionuclide activities generally results in a significantly lower external dose than by using TLD results. (author)
12 MANAGEMENT OF RADIOACTIVE AND NON-RADIOACTIVE W↗
Noble gas abundances in lunar material - Cosmic ray spallation products and radiation ages from the Sea of Tranquility and the Ocean of Storms
Cosmic ray spallation products and radiation age determination from spectral analysis of noble gas components in lunar rocks
Bogard, D. D.↗
PHOTON-INDUCED EVOLUTIONARY RATES OF LiHe{sup +} ({sup 1}{Sigma}{sup +}) IN EARLY UNIVERSE FROM ACCURATE QUANTUM COMPUTATIONS
The radiative association rates for the formation of LiHe{sup +} molecules in their ground electronic state have been calculated employing an accurate ab initio potential energy curve and the dipole moment function. The enhancement of this rate, which may arise from stabilizing emissions stimulated by the cosmic background radiation field, has also been calculated and analyzed in the context of early universe conditions. Direct photodissociation processes have also been studied using local thermal equilibrium cross sections and rates are reported for temperatures between 600 and 9000 K. These photochemical processes are in turn analyzed and discussed as a function of the redshift z that is expected to operate in the early universe chemical kinetics. All data suggest very low residual abundances of this molecule and therefore its marginal role within early universe chemistry.
74 ATOMIC AND MOLECULAR PHYSICS↗
Modeling surface backgrounds from radon progeny plate-out
The next generation low-background detectors operating deep underground aim for unprecedented low levels of radioactive backgrounds. The surface deposition and subsequent implantation of radon progeny in detector materials will be a source of energetic background events. We investigate Monte Carlo and model-based simulations to understand the surface implantation profile of radon progeny. Depending on the material and region of interest of a rare event search, these partial energy depositions can be problematic. Motivated by the use of Ge crystals for the detection of neutrinoless double-beta decay, we wish to understand the detector response of surface backgrounds from radon progeny. We look at the simulation of surface decays using a validated implantation distribution based on nuclear recoils and a realistic surface texture. Results of the simulations and measured α spectra are presented.
46 INSTRUMENTATION RELATED TO NUCLEAR SCIENCE AND ↗
FORMATION OF BLACK HOLE AND ACCRETION DISK IN A MASSIVE HIGH-ENTROPY STELLAR CORE COLLAPSE
We present the first numerical result of fully general relativistic axisymmetric simulations for the collapse of a rotating high-entropy stellar core to a black hole and an accretion disk. The simulations are performed taking into account the relevant microphysics. We adopt as initial conditions a spherical core with constant electron fraction (Y{sub e} = 0.5) and entropy per baryon s = 8 k{sub B} , and angular velocity is superimposed. In the early phase, the core collapses in a homologous manner. Then it experiences a weak bounce due to the gas pressure of free nucleons. Because the bounce is weak, the core eventually collapses to a black hole. Subsequent evolution depends on initial angular velocity. When the rotation is not fast, a geometrically thin (but optically thick) accretion disk is formed, and shock waves are formed in the inner part of the disk. For the moderately rotating case, the thin accretion disk eventually expands to become a geometrically thick torus after sufficient accumulation of the thermal energy is generated at the shocks. Furthermore, convection occurs inside the torus. Neutrino luminosities vary violently with time because of the convective motion. For the rapidly rotating case, by contrast, a geometrically thick torus is formed soon after the black hole formation, and the convective activity is weak due to the presence of an epicyclic mode.
79 ASTRONOMY AND ASTROPHYSICS↗
THE ATACAMA COSMOLOGY TELESCOPE: CALIBRATION WITH THE WILKINSON MICROWAVE ANISOTROPY PROBE USING CROSS-CORRELATIONS
We present a new calibration method based on cross-correlations with the Wilkinson Microwave Anisotropy Probe (WMAP) and apply it to data from the Atacama Cosmology Telescope (ACT). ACT's observing strategy and map-making procedure allows an unbiased reconstruction of the modes in the maps over a wide range of multipoles. By directly matching the ACT maps to WMAP observations in the multipole range of 400 < l < 1000, we determine the absolute calibration with an uncertainty of 2% in temperature. The precise measurement of the calibration error directly impacts the uncertainties in the cosmological parameters estimated from the ACT power spectra. We also present a combined map based on ACT and WMAP data that has a high signal-to-noise ratio over a wide range of multipoles.
79 ASTRONOMY AND ASTROPHYSICS↗