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  • 1
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    Very High Energy Outburst of Markarian 501 in May 2009 (2016)
    In:  Other Sources
    Details
    Publication Date: 2019-07-13
    Description: The very high energy (VHE; E great than 100 GeV) blazar Markarian 501 was observed between April 17 and May 5 (MJD 5493854956), 2009, as part of an extensive multi-wavelength campaign from radio to VHE. Strong VHE -ray activity was detected on May 1st with Whipple and VERITAS, when the flux (E greater than 400 GeV) increased to 10 times the pre-flare baseline flux (3.9 x 10(exp -11 ph cm(exp -2 S(exp -1), reaching five times the flux of the Crab Nebula. This coincided with a decrease in the optical polarization and a rotation of the polarization angle by 15deg. This VHE flare showed a fast flux variation with an increase of a factor approximately 4 in 25 min, and a falling time of approximately 50 min. We present the observations of the quiescent state previous to the flare and of the high state after the flare, focusing on the flux and spectral variability from Whipple, VERITAS, Fermi-LAT, RXTE, and Swift combined with optical and radio data.
    Keywords: Astrophysics
    Type: GSFC-E-DAA-TN44061 , Astronomy & Astrophysics (ISSN 0004-6361) (e-ISSN 1432-0746); 594; A76
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  • 2
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    A global paleoclimate observing system (2001)
    American Association for the Advancement of Science (AAAS)
    Details
    Publication Date: 2001-07-11
    Description: 〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Alverson, K -- Bradley, R -- Briffa, K -- Cole, J -- Hughes, M -- Larocque, I -- Pedersen, T -- Thompson, L -- Tudhope, S -- New York, N.Y. -- Science. 2001 Jul 6;293(5527):47-8.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/11444288" target="_blank"〉PubMed〈/a〉
    Keywords: Animals ; Carbon Dioxide/metabolism ; *Climate ; Cnidaria/physiology ; Conservation of Natural Resources ; Greenhouse Effect ; Humans ; Ice ; Oceans and Seas ; Rain ; Seawater/analysis/chemistry ; Specimen Handling/*methods ; Temperature ; Time Factors ; Trees/growth & development/physiology
    Print ISSN: 0036-8075
    Electronic ISSN: 1095-9203
    Topics: Biology , Chemistry and Pharmacology , Computer Science , Medicine , Natural Sciences in General , Physics
    Published by American Association for the Advancement of Science (AAAS)
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  • 3
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    Historical overfishing and the recent collapse of coastal ecosystems (2001)
    American Association for the Advancement of Science (AAAS)
    Details
    Publication Date: 2001-07-28
    Description: Ecological extinction caused by overfishing precedes all other pervasive human disturbance to coastal ecosystems, including pollution, degradation of water quality, and anthropogenic climate change. Historical abundances of large consumer species were fantastically large in comparison with recent observations. Paleoecological, archaeological, and historical data show that time lags of decades to centuries occurred between the onset of overfishing and consequent changes in ecological communities, because unfished species of similar trophic level assumed the ecological roles of overfished species until they too were overfished or died of epidemic diseases related to overcrowding. Retrospective data not only help to clarify underlying causes and rates of ecological change, but they also demonstrate achievable goals for restoration and management of coastal ecosystems that could not even be contemplated based on the limited perspective of recent observations alone.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Jackson, J B -- Kirby, M X -- Berger, W H -- Bjorndal, K A -- Botsford, L W -- Bourque, B J -- Bradbury, R H -- Cooke, R -- Erlandson, J -- Estes, J A -- Hughes, T P -- Kidwell, S -- Lange, C B -- Lenihan, H S -- Pandolfi, J M -- Peterson, C H -- Steneck, R S -- Tegner, M J -- Warner, R R -- New York, N.Y. -- Science. 2001 Jul 27;293(5530):629-37.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉Scripps Institution of Oceanography, University of California, San Diego, La Jolla, CA 92093-0244, USA. jbcj@ucsd.edu〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/11474098" target="_blank"〉PubMed〈/a〉
    Keywords: Animals ; Archaeology ; Bacteria ; Cnidaria ; Conservation of Natural Resources ; *Ecosystem ; Eutrophication ; *Fishes ; Geologic Sediments ; Humans ; *Marine Biology ; Seaweed ; Shellfish ; Time Factors
    Print ISSN: 0036-8075
    Electronic ISSN: 1095-9203
    Topics: Biology , Chemistry and Pharmacology , Computer Science , Medicine , Natural Sciences in General , Physics
    Published by American Association for the Advancement of Science (AAAS)
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  • 4
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    Regional-scale assembly rules and biodiversity of coral reefs (2001)
    American Association for the Advancement of Science (AAAS)
    Details
    Publication Date: 2001-05-26
    Description: Tropical reef fishes and corals exhibit highly predictable patterns of taxonomic composition across the Indian and Pacific Oceans. Despite steep longitudinal and latitudinal gradients in total species richness, the composition of these key taxa is constrained within a remarkably narrow range of values. Regional-scale variation in reef biodiversity is best explained by large-scale patterns in the availability of shallow-water habitat. Once habitat area is accounted for, there is surprisingly little residual effect of latitude or longitude. Low-diversity regions are most vulnerable to human impacts such as global warming, underscoring the urgent need for integrated management at multinational scales.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Bellwood, D R -- Hughes, T P -- New York, N.Y. -- Science. 2001 May 25;292(5521):1532-5.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉Centre for Coral Reef Biodiversity, Department of Marine Biology, James Cook University, Townsville, Qld 4811, Australia. david.bellwood@jcu.edu.au〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/11375488" target="_blank"〉PubMed〈/a〉
    Keywords: Animals ; *Cnidaria/classification/physiology ; Conservation of Natural Resources ; *Ecosystem ; *Fishes/classification/physiology ; Geography ; Greenhouse Effect ; Indian Ocean ; Pacific Ocean ; Temperature
    Print ISSN: 0036-8075
    Electronic ISSN: 1095-9203
    Topics: Biology , Chemistry and Pharmacology , Computer Science , Medicine , Natural Sciences in General , Physics
    Published by American Association for the Advancement of Science (AAAS)
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  • 5
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    Global trajectories of the long-term decline of coral reef ecosystems (2003)
    American Association for the Advancement of Science (AAAS)
    Details
    Publication Date: 2003-08-16
    Description: Degradation of coral reef ecosystems began centuries ago, but there is no global summary of the magnitude of change. We compiled records, extending back thousands of years, of the status and trends of seven major guilds of carnivores, herbivores, and architectural species from 14 regions. Large animals declined before small animals and architectural species, and Atlantic reefs declined before reefs in the Red Sea and Australia, but the trajectories of decline were markedly similar worldwide. All reefs were substantially degraded long before outbreaks of coral disease and bleaching. Regardless of these new threats, reefs will not survive without immediate protection from human exploitation over large spatial scales.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Pandolfi, John M -- Bradbury, Roger H -- Sala, Enric -- Hughes, Terence P -- Bjorndal, Karen A -- Cooke, Richard G -- McArdle, Deborah -- McClenachan, Loren -- Newman, Marah J H -- Paredes, Gustavo -- Warner, Robert R -- Jackson, Jeremy B C -- New York, N.Y. -- Science. 2003 Aug 15;301(5635):955-8.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉Department of Paleobiology, MRC-121, National Museum of Natural History, Post Office Box 37012, Smithsonian Institution, Washington, DC 20013-7012, USA. pandolfi.john@nmnh.si.edu〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/12920296" target="_blank"〉PubMed〈/a〉
    Keywords: Animals ; Anthozoa/*growth & development ; Conservation of Natural Resources ; Culture ; *Ecosystem ; Humans ; Population Dynamics ; Principal Component Analysis ; Time Factors
    Print ISSN: 0036-8075
    Electronic ISSN: 1095-9203
    Topics: Biology , Chemistry and Pharmacology , Computer Science , Medicine , Natural Sciences in General , Physics
    Published by American Association for the Advancement of Science (AAAS)
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  • 6
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    A Giant Radio Halo in a Low-Mass SZ-Selected Galaxy Cluster: ACT-CL J0256.5+0006 (2016)
    In:  Other Sources
    Details
    Publication Date: 2019-07-13
    Description: We present the detection of a giant radio halo (GRH) in the Sunyaev-Zel'dovich (SZ)-selected merging galaxy cluster ACT-CL J0256.5+0006 (zeta = 0.363), observed with the Giant Metrewave Radio Telescope at 325 MHz and 610 MHz. We find this cluster to host a faint (S(sub 610) = 5.6 +/- 1.4 mJy) radio halo with an angular extent of 2.6 arcmin, corresponding to 0.8 Mpc at the cluster redshift, qualifying it as a GRH. J0256 is one of the lowest-mass systems, M(sub 500,SZ) = (5.0 +/- 1.2) x 10(sup14) solar mass foud to host a GRH. We measure the GRH at lower significance at 325 MHz (S(sub 325) = 10.3 +/- 5.3 mJy), obtaining a spectral index measurement of alpha sup 610 sub 325 = 1.0(sup +0.7)(sub 0.9). This result is consistent with the mean spectral index of the population of typical radio halos, alpha = 1.2 +/- 0.2. Adopting the latter value, we determine a 1.4 GHz radio power of P(sub 1.4GHz) = (1.0 +/- 03) x 10(sup 24) W Hz(sup -1), placing this cluster within the scatter of known scaling relations. Various lines of evidence, including the ICM morphology, suggest that ACT-CL J0256.5+0006 is composed of two subclusters. We determine a merger mass ratio of 7:4, and a line-of-sight velocity difference of perpendicular = 1880 +/- 210 km s(sup -1). We construct a simple merger model of infer relevant time-scales in the merger. From its location on the P1.4GHz-L(sub x) scaling relation, we infer that we observe ACT-CL J0256.5+0006 just before first core crossing.
    Keywords: Astrophysics
    Type: GSFC-E-DAA-TN32419 , Monthly Notices Letters of the Royal Astronomical Observatory (e-ISSN 1745-3933); 459; 4; 4240-4258
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  • 7
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    Tests of General Relativity and Fundamental Physics with Space-based Gravitational Wave Detectors (2019)
    In:  CASI
    Details
    Publication Date: 2019-07-20
    Description: Low-frequency gravitational-wave astronomy can perform precision tests of general relativity and probe fundamental physics in a regime previously inaccessible. A space-based detector will be a formidable tool to explore gravity's role in the cosmos, potentially telling us if and where Einstein's theory fails and providing clues about some of the greatest mysteries in physics and astronomy, such as dark matter and the origin of the Universe.
    Keywords: Astrophysics
    Type: GSFC-E-DAA-TN67178 , GSFC-E-DAA-TN66949
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  • 8
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    The Origin of the Iron-Rich Knot in Tycho's Supernova Remnant (2017)
    In:  Other Sources
    Details
    Publication Date: 2019-07-13
    Description: X-ray observations of supernova remnants (SNRs) allow us to investigate the chemical inhomogeneity of ejecta, offering unique insight into the nucleosynthesis in supernova explosions. Here we present detailed imaging and spectroscopic studies of the Fe knot located along the eastern rim of the Type Ia SNR Tycho ( SN 1572) using Suzaku and Chandra long-exposure data. Surprisingly, the Suzaku spectrum of this knot shows no emission from Cr, Mn, or Ni, which is unusual for the Fe-rich regions in this SNR. Within the framework of the canonical delayed-detonation models for SN Ia, the observed mass ratios M(sub Cr)/M(sub Fe) is less than 0.023, M(sub Mn)/M(sub Fe) is less than 0.012, and M(sub Ni)/M(sub Fe) is less than 0.029 (at 90% confidence) can only be achieved for a peak temperature of (5.3 - 5.7) x 10(exp. 9) K and a neutron excess of approximately less than 2.0 x 10(exp. -3). These constraints rule out the deep, dense core of a Chandrasekhar-mass white dwarf as the origin of the Fe knot and favor either incomplete Si burning or an Alpha-rich freeze-out regime, probably close to the boundary. An explosive He burning regime is a possible alternative, although this hypothesis is in conflict with the main properties of this SNR.
    Keywords: Astrophysics
    Type: GSFC-E-DAA-TN45948 , The Astrophysical Journal (ISSN 0004-637X) (e-ISSN 1538-4357); 834; 2; 124
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  • 9
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    Temperature Structure in the Perseus Cluster Core Observed with Hitomi (2018)
    In:  Other Sources
    Details
    Publication Date: 2019-07-13
    Description: The present paper investigates the temperature structure of the X-ray emitting plasma in the core of the Perseus cluster using the 1.8-20.0 keV data obtained with the Soft X-ray Spectrometer (SXS) onboard the Hitomi Observatory. A series of four observations were carried out, with a total effective exposure time of 338 ks and covering a central region _ 7 in diameter. The SXS was operated with an energy resolution of _5 eV (full width at half maximum) at 5.9 keV. Not only fine structures of K-shell lines in He-like ions but also transitions from higher principal quantum numbers are clearly resolved from Si through Fe. This enables us to perform temperature diagnostics using the line ratios of Si, S, Ar, Ca, and Fe, and to provide the first direct measurement of the excitation temperature and ionization temperature in the Perseus cluster. The observed spectrum is roughly reproduced by a single temperature thermal plasma model in collisional ionization equilibrium, but detailed line ratio diagnostics reveal slight deviations from this approximation. In particular, the data exhibit an apparent trend of increasing ionization temperature with increasing atomic mass, as well as small differences between the ionization and excitation temperatures for Fe, the only element for which both temperatures can be measured. The best-fit two-temperature models suggest a combination of 3 and 5 keV gas, which is consistent with the idea that the observed small deviations from a single temperature approximation are due to the effects of projection of the known radial temperature gradient in the cluster core along the line of sight. Comparison with the Chandra/ACIS and the XMM-Newton/RGS results on the other hand suggests that additional lower-temperature components
    Keywords: Astrophysics
    Type: GSFC-E-DAA-TN54095 , Publications of the Astronomical Society of Japan (ISSN 0004-6264) (e-ISSN 2053-051X); 70; 2
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  • 10
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    Multiwavelength Characterization of an ACT-Selected, Lensed Dusty Star-Forming Galaxy at zeta 2.64 (2017)
    In:  Other Sources
    Details
    Publication Date: 2019-07-13
    Description: We present C I(21) and multi-transition C-12 O observations of a dusty star-forming galaxy, ACT J2029+0120,which we spectroscopically confirm to lie at zeta = 2.64. We detect CO(3-2), CO(5-4), CO(7-6), CO(8-7), and C I(2-1) at high significance, tentatively detect HCO+(4-3), and place strong upper limits on the integrated strength of dense gas tracers (HCN(4-3) and CS(7-6)). Multi-transition CO observations and dense gas tracers can provide valuable constraints on the molecular gas content and excitation conditions in high-redshift galaxies. We therefore use this unique data set to construct a CO spectral line energy distribution (SLED) of the source, which is most consistent with that of a ULIRG Seyfert or QSO host object in the taxonomy of the Herschel Comprehensive ULIRG Emission Survey. We employ RADEX models to fit the peak of the CO SLED, inferring a temperature of T approximately 117 K and n(sub H2) approximately 10(exp5) cm(exp -3), most consistent with a ULIRGQSO object and the presence of high-density tracers. We also find that the velocity width of the C I line is potentially larger than seen in all CO transitions forth is object, and that the L'(sub Ci(2-1))/L'(sub CO(3-2))ratio is also larger than seen in other lensed and unlensed submillimeter galaxies and QSO hosts; if confirmed, this anomaly could be an effect of differential lensing of a shocked molecular outflow.
    Keywords: Astrophysics
    Type: GSFC-E-DAA-TN46867 , The Astrophysical Journal (ISSN 0004-637X) (e-ISSN 1538-4357); 844; 2; 110
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