Erg Cm-2 Sec-1 Research Articles

TAIGA - a hybrid array for high energy gamma astronomy and cosmic ray physics

The physics motivations and advantages of the new TAIGA (Tunka Advanced Instrument for cosmic ray physics and Gamma Astronomy) detector are presented. TAIGA aims at gamma-ray astronomy at energies from a few TeV to several PeV, as well as cosmic ray physics from 100 TeV to several EeV. For the energy range 30 – 200 TeV the sensitivity of 10 km2 area TAIGA array for the detection of local sources is expected to be 5 × 10-14 erg cm-2 sec-1 for 300 h of observations. Reconstruction of the given EAS energy, incoming direction and its core position, based on the timing TAIGA-HiSCORE data, allows one to increase a distance between the IACTs up to 600-1000 m. The low investments together with the high sensitivity for energies ≥ 30-50 TeV make this pioneering technique very attractive for exploring the galactic PeVatrons and cosmic rays. At present the TAIGA first stage has been constructed in Tunka valley, 50 km West from the Lake Baikal. The first experimental results of the TAIGA first stage are presented.

Ceres Surface Properties by High-Resolution Imaging from Earth

Direct imaging of Ceres has been performed using an adaptive optics system, developed by Laserdot (France), Paris Observatory (Meudon, France), ONERA (France), and ESO. The diffraction limit of the 3.6-m ESO telescope (La Silla, Chile) was obtained at near infrared wavelengths in the K, L ′, and M bands (0.13, 0.25, and 0.30 arcsec, respectively).Several physical parameters for Ceres are deduced from these observations. The rotation is prograde (consistent with previous observations). The pole orientation is λ = 332 ± 5° and β = 70 ± 15°, implying a low obliquity with respect to Ceres orbital plane. The estimated thermal inertia of the regolith is 3.8 ± 1.4 × 104 erg cm-2 sec-1/2K-1. The measured temperature of the warmest area is 235 ± 4 K. The value of the mean radius, 484 ± 20 km, is consistent with earlier values obtained by stellar occultation and thermal infrared photometry. No albedo variations can be detected in reflected light and the center-to-limb distribution clearly departs from a Lambertian distribution.

An Analysis of the Voyager 2 Ultraviolet Spectrometer Occultation Data at Uranus: Inferring Heat Sources and Model Atmospheres

The Voyager 2 Ultraviolet Spectrometer (UVS) stellar and solar occultation data obtained at Uranus have been analyzed to infer smooth thermospheric temperature profiles and heat source characteristics. Temperatures inferred in the upper thermosphere from these occultations are much higher (850 ± 100 K) than can be explained by solar extreme ultraviolet heating alone. Our analysis yields one heat source peaking at ∼1 × 10-5 μbar (range 8 × 10-7-2 × 10-5 micro;bar) with an integrated heating rate of approximately 0.06 (+0.02, -0.04) erg cm-2 sec-1 as the least-squares best fit to all occultation data. The best inferred temperature for the stellar entrance occultation (63.7° S) is at least 50 K cooler near 50 μbar than for the stellar exit occultation (69.7° N), whereas at about 0.1 μbar this temperature contrast is less than 10 K. A constant temperature on pressure surfaces at low altitudes, however, cannot be excluded by the data.

Lipid and Fatty Acid Composition of Synchronized Synechococcus leopoliensis

Abstract The cyanobacterium Synechococcus leopoliensis (Anacystis nidulans, strain L 1402-1) grown at 39 °C and 2 vol. % CO : could be synchronized by a light/dark regime of 3:5 h (white light intensity 1.5 × 104 erg cm-2 sec-1). Content of pigments (chlorophyll a. phycocyanin and carotenoids), R N A and proteins increased linearly up to 100% at the end of the light period while DNA synthesis was lower. Chlorophyll a synthesis was correlated to the photosystem I activity of the isolated thylakoids and to the formation of MGD G . Galacto lipids were synthesized in the light period, only. A lag phase of 2h was observed in the biosynthesis of SQDG and PG. No significant differences were found between the cell and thylakoid fractions. Palmitic (C16:0), hexadecenoic (C16:1) and octadecenoic (C18:1) acid as major com ponents accounted for more than 90% of total fatty acids in MGD G , DGDG and SQDG . PG contains a small amount of stearic (C18:0) and heptadecenoic (C17:1) acid. No significant variations in the fatty acid distribution of all lipids could be detected in the cell fraction during the division cycle. Changes in the ratio of saturated to unsaturated fatty acids were found in isolated thylakoids. only. In experiments with [14C]bicarbonate main radioactivity was measured in galacto lipids while using [14C]acetate SQDG and PG were markedly [14C]labelled. Results were discussed with reference to the findings of eucaryotic algae and the formation of photosynthetic membranes.

Purple membrane vesicles: morphology and proton translocation.

Purple membrane vesicles prepared by different techniques differ widely in their morphology and ability to establish a proton gradient in the light. The procedures used to prepare active vesicles do not completely dissociate the purple membrane and thus preserve a preferential orientation of the protein, while most of the lipid is exchanged for added lipid. Responses to illumination are largely determined by the size of the vesicles and the degree to which bacteriorhodopsin is preferentially oriented. Any attempt to compare the interaction of different lipids with bacteriorhodopsin by measuring the pH response must take these factors into account. With an improved technique we have obtained vesicles of rather uniform size and bacteriorhodopsin orientation, which accumulate protons with an initial rate of 160 ng H+ sec-1 mg-1 protein at light intensities of 10(6) erg cm-2 sec-1. The kinetics of the process are complex and at present insufficiently understood.

NOTE ON ULTRAVIOLET HYDROXYL OBSERVATIONS OF COMET KOHOUTEK

ABSTRACT Observations of hydroxyl (OH) emission from Comet Kohoutek were made during the evening of 24 January 1974, from an altitude of 41,000 feet. The observing plafform was the NASA Convair 990 Flying Laboratory based at Ames Research Center, Moffett Field, Calfforuia. The comet, of visual magnitude 5.5 at the time of observation, was photographed with an fI 1.3 Maksutov slitless spectrograph of 150-mm aperture. This spectru graph used a double quartz prism as the dispersion element to isolate the OH radiation in the low-resolution spectrum. An inertial image-stabilization mirror system was used to reduce image motion due to aircraft roll. A nearly spherical coma of OH about three arc minutes diameter, as observed from an earth-comet distance of 0.88 a.u., was photographed. The OH emission was the strongest feature in the spectrum and produced an irradiance of 3 X 10- erg cm-2 sec-1 at the earth. The uncertainty of the irradiance measurement is about a factor of two. Key words: Comet Kohoutek - hydroxyl - airborne observations

Observations of Cen XR?2, SCO XR?1, and Terrestrial X-Rays

Two identical X-ray experiments were flown on Skylark rockets from Woomera, Australia, during April 1967. Sco XR-l and Cen XR-2 were observed on both flights. The Cen XR-2 flux was (1-5�0'1) X 10-7 erg cm-2 sec-1 (2-8 keY) when first observed but had decreased to (l�0�0�1) X 10-7 erg cm-2 sec-1 and had become softer by the second flight. An X-ray flux from the Earth was observed and found to be due to solar X-rays reflected in the atmosphere.

Absolute intensities in the solar X-ray spectrum near minimum activity

Rocket measurements of absolute intensities in the solar X-ray spectrum on November 4, 1964 around 16:35 UT yield the following results : 1.8·10-2 erg cm-2 sec-1 (wavelength band 44–60 A); and 1.5·10-3 erg cm-2 sec-1 (wavelength band 8–15A). These values were obtained under nearly quiet minimum conditions of the sun.

Wavelength-independent, direct-reading radiometer

A wavelength-independent, direct-reading radiometer has been developed to facilitate radiant power measurements in the near ultra-violet, visible and infra-red range. The sensor probe of the radiometer is designed to convert all incident radiant energy into heat, thereby providing a wavelength-independent method of light measurement. The amount of heat developed is measured with a specially designed `black-body' thermistor bolometer. The bolometer probe dimensions are less than 1 cm × 1 cm × 4 cm so that radiant power measurements can be made in confined areas. The instrument provides direct read-out of incident radiant power in units such as mw cm-2 or erg cm-2 sec-1. The instrument can be used over the range from less than 10-4 w cm-2 to more than 0.25 w cm-2. Depending on the type of window material used in the probe, the radiometer can provide wavelength-independent measurements from 250 nm to more than 40 μm.

Evidence for an Explosion in the Center of the Galaxy M82.

view Abstract Citations (3) References Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS Evidence for an Explosion in the Center of the Galaxy M82. Lynds, C. R. ; Sandage, A. R. Abstract New observations in optical frequencies of the peculiar optical and radio galaxy M82 reveal a massive system of filaments which extends along the minor axis to a height of 3000 pc above and below the fundamental plane. Emission lines typical of low-excitation gaseous nebulae are present. The filaments on both sides of the plane appear to be expanding from the center along the minor axis with velocities ranging up to about 1000 km/sec. The data suggest that an expulsion of matter took place from the central regions of M82 about 1.5 X 106 yr ago. The Ha emission flux from the filaments is estimated to be 1.7 x 10-11 erg cm-2 sec-1 at the earth's surface, which requires a total emitted power of 2 X 1040 erg sec-1 in Ha if the distance modulus of M82 is m-M=27.5. The ion density in the filaments, estimated from the volume emissivity, is 10 protons cm-3, which then requires thst the visible mass of the expanding material is 5.6X106 Mo as an upper limit. An upper limit to the kinetic energy of the visible filaments is 2.4 X 10~ ergs. The filaments form fragments of loops and appear to outline lines of magnetic force. Parts of the filaments appear to radiate weakly in the continuum as well as in the emission lines, and this suggests that optical synchrotron radiation may be present. Polarization measurements of part of the filamentary structure by Elvius and Hall seem to be consistent with this possibility. The radio flux data are combined with an estimate of the optical synchrotron flux, and a theoretical power spectrum is computed. The rate of synchrotron radiation is 2 X 1042 erg sec-1 which amounts to 9 X 10~~ ergs over the lifetime of 1.5 X 106 yr if the power level has been constant over this time interval. Calculation shows that the source of excitation for the observed low-energy recombination spectrum may be the optical synchrotron radiation field which extends to frequencies above the Lyman limit. Publication: The Astronomical Journal Pub Date: September 1963 DOI: 10.1086/109098 Bibcode: 1963AJ.....68R.284L full text sources ADS |