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104 results on '"Prahl, J."'

1. Search for gamma-ray bursts above 20 TeV with the HEGRA AIROBICC Cherenkov array

Author

HEGRA collaboration, Padilla, L., Funk, B., Krawczynski, H., Contreras, J. L., Moralejo, A., Aharonian, F., Akhperjanian, A. G., Barrio, J. A., Beteta, J. G., Cortina, J., Deckers, T., Fonseca, V., Gebauer, H. -J., Gonzalez, J. C., Heinzelmann, G., Horns, D., Kornmayer, H., Lindner, A., Lorenz, E., Magnussen, N., Meyer, H., Mirzoyan, R., Petry, D., Plaga, R., Prahl, J., Prosch, C., Rauterberg, G., Rhode, W., Roehring, A., Sahakian, V., Samorski, M., Schmele, D., Stamm, W., Wiebel-Sooth, B., Willmer, M., and Wittek, W.

Subjects
Astrophysics
Abstract

A search for gamma-ray bursts (GRBs) above 20 TeV within the field of view (1 sr) of the HEGRA AIROBICC Cherenkov array (29N, 18W, 2200 m a.s.l.) has been performed using data taken between March 1992 and March 1993. The search is based on an all-sky survey using four time scales, 10 seconds, 1 minute, 4 minutes and 1 hour. No evidence for TeV-emission has been found for the data sample. Flux upper limits are given. A special analysis has been performed for GRBs detected by BATSE and WATCH. Two partially and two fully contained GRBs in our field of view (FOV) were studied. For GRB 920925c which was fully contained in our FOV, the most significant excess has a probability of 7.7 10**-8 (corresponding to 5.4 sigmas) of being caused by a background fluctuation. Correcting this probability with the appropriate trial factor, yields a 99.7% confidence level for this excess to be related to the GRB (corresponding to 2.7 sigmas). This result is discussed within the framework of the WATCH detection., Comment: 8 pages, 8 figures. Accepted for publication in A&A

Published
1998

6. Experimental Study of Load Carrying Capacity of Point Contacts at Zero Entrainment Velocity

Author

Shogin, B. A, Jones, W. R., Jr, Kingsbury, E. P, Jansen, M. J, and Prahl, J. M

Subjects
Fluid Mechanics And Heat Transfer
Abstract

A capacitance technique was used to monitor the film thickness separating two steel balls while subjecting the ball-ball contact to highly stressed, zero entrainment velocity conditions. Tests were performed in a nitrogen atmosphere and utilized 52100 steel balls and a polyalphaolefin lubricant. Capacitance to film thickness accuracy was verified under pure rolling conditions using established EHL theory. Zero entrainment velocity tests were performed at sliding speeds from 6.0 to 10.0 m/s and for sustained amounts of time to 28.8 min. The protective lubricant film separating the specimens at zero entrainment velocity had a film thickness between 0.10 to 0.14 microns (4 to 6 micro in.), which corresponded to a k value of 4. The formation of an immobile surface film formed by lubricant entrapment is discussed as an explanation of the load carrying capacity at zero entrainment velocity conditions, relevant to the ball-ball contacts occurring in retainerless ball bearings.

Published
1998

7. Observations of H1426+428 with HEGRA -- Observations in 2002 and reanalysis of 1999&2000 data

Author

Aharonian, F., Akhperjanian, A., Beilicke, M., Bernlöhr, K., Börst, H. -G, Bojahr, H., Bolz, O., Coarasa, T., Contreras, J. L., Juan Cortina, Costamante, L., Denninghoff, S., Fonseca, M. V., Girma, M., Götting, N., Heinzelmann, G., Hermann, G., Heusler, A., Hofmann, W., Horns, D., Jung, I., Kankanyan, R., Kestel, M., Kohnle, A., Konopelko, A., Kornmeyer, H., Kranich, D., Lampeitl, H., Lopez, M., Lorenz, E., Lucarelli, F., Mang, O., Mazine, D., Meyer, H., Mirzoyan, R., Moralejo, A., Ona-Wilhelmi, E., Panter, M., Plyasheshnikov, A., Prahl, J., Pühlhofer, G., Los Reyes, R., Rhode, W., Ripken, J., Rowell, G., Sahakian, V., Samorski, M., Schilling, M., Siems, M., Sobzynska, D., Stamm, W., Tluczykont, M., Vitale, V., Völk, H. J., Wiedner, C. A., and Wittek, W.

Subjects
Physics, Astrophysics::High Energy Astrophysical Phenomena, Flux, HEGRA, Astronomy and Astrophysics, Astrophysics, Spectral line, Wavelength, Extragalactic background light, Space and Planetary Science, Absorption (electromagnetic radiation), Cherenkov radiation, BL Lac object
Abstract

The HEGRA system of imaging air Cherenkov telescopes has been used to observe the BL Lac object H1426+428 ($z=0.129$) for 217.5 hours in 2002. In this data set alone, the source is detected at a confidence level of $5.3~\sigma$, confirming this object as a TeV source. The overall flux level during the observations in 2002 is found to be a factor of $\approx 2.5$ lower than during the previous observations by HEGRA in 1999&2000. A new spectral analysis has been carried out, improving the signal-to-noise ratio at the expense of a slightly increased systematic uncertainty and reducing the relative energy resolution to $\Delta E/E\le 12 %$ over a wide range of energies. The new method has also been applied to the previously published data set taken in 1999 and 2000, confirming the earlier claim of a flattening of the energy spectrum between 1 and 5 TeV. The data set taken in 2002 shows again a signal at energies above 1 TeV. We combine the energy spectra as determined by the CAT and VERITAS groups with our reanalyzed result of the 1999&2000 data set and apply a correction to account for effects of absorption of high energy photons on extragalactic background light in the optical to mid infrared band. The shape of the inferred source spectrum is mostly sensitive to the characteristics of the extragalactic background light between wavelengths of 1 and 15~$\mu$m, Comment: 12 pages, 4 Figures, submitted to A&A

Published
2003

8. An unidentified TeV source in the vicinity of Cygnus OB2

Author

Aharonian, F., Akhperjanian, A., Beilicke, M., Bernlohr, K., Borst, H., Bojahr, H., Bolz, O., Coarasa, T., Contreras, J., Cortina, J., Denninghoff, S., Fonseca, V., Girma, M., Gotting, N., Heinzelmann, G., Hermann, G., Heusler, A., Hofmann, W., Horns, D., Jung, I., Kankanyan, R., Kestel, M., Kettler, J., Kohnle, A., Konopelko, A., Kornmeyer, H., Kranich, D., Krawczynski, H., Lampeitl, H., Lopez, M., Lorenz, E., Lucarelli, F., Magnussen, N., Mang, O., Meyer, H., Milite, M., Mirzoyan, R., Moralejo, A., Ona, E., Panter, M., Plyasheshnikov, A., Prahl, J., Puhlhofer, G., Rauterberg, G., Reyes, R., Rhode, W., Ripken, J., Rohring, A., Rowell, G. P., Sahakian, V., Samorski, M., Schilling, M., Schroder, F., Siems, M., Sobzynska, D., Stamm, W., Tluczykont, M., Volk, H. J., Wiedner, C. A., Wittek, W. (HEGRA Collaboration), Uchiyama, Yasunobu, and Takahashi, Tadayuki

Subjects
Physics, Astrophysics (astro-ph), Flux, HEGRA, FOS: Physical sciences, Astronomy and Astrophysics, Radius, Astrophysics, Particle acceleration, Stars, Pulsar, Space and Planetary Science, Cygnus OB2, Heliosphere
Abstract

著者人数：62名, Accepted: 2002-08-09, 資料番号: SA1002274000

Published
2002
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9. Measurement of the radial distribution of Cherenkov light generated by TeV gamma-ray air showers

Author

Aharonian, F. A., Akhperjanian, A. G., Barrio, J. A., Bernlöhr, K., Bojahr, H., Contreras, J. L., Juan Cortina, Daum, A., Deckers, T., Fonseca, V., Fraß, A., Gonzalez, J. C., Heinzelmann, G., Hemberger, M., Hermann, G., Heß, M., Heusler, A., Hofmann, W., Hohl, H., Holl, I., Horns, D., Ibarra, I., Kankanyan, R., Kestel, M., Kirstein, O., Köhler, C., Konopelko, A., Kornmayer, H., Kranich, D., Krawczynski, H., Lampeitl, H., Lindner, A., Lorenz, E., Magnussen, N., Meyer, H., Mirzoyan, R., Moralejo, A., Padilla, L., Panter, M., Petry, D., Plaga, R., Prahl, J., Prosch, C., Pühlhofer, G., Rauterberg, G., Rhode, W., Röhring, A., Samorski, M., Schmele, D., Schröder, F., Stamm, W., Ulrich, M., Völk, H. J., Wiebel-Sooth, B., Wiedner, C. A., Willmer, M., and Wirth, H.

Subjects
Physics, Physics::Instrumentation and Detectors, Astrophysics::High Energy Astrophysical Phenomena, Astrophysics (astro-ph), Gamma ray, Astrophysics::Instrumentation and Methods for Astrophysics, HEGRA, FOS: Physical sciences, Astronomy and Astrophysics, IACT, Radial distribution, Astrophysics, Shower, Air shower, High Energy Physics::Experiment, Cherenkov radiation, Zenith
Abstract

Using air showers induced by TeV gamma-rays from Mrk 501, the radial distribution of Cherenkov light is investigated. The shower geometry is reconstructed from the stereoscopic shower images obtained with the telescopes of the HEGRA IACT system. We observe a change in the shape of the light pool with shower energy, and with zenith angle. Data are well reproduced by Monte-Carlo air shower simulations., Comment: 15 Pages, 8 figures, Latex

Published
1998
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10. The time structure of Cherenkov images generated by TeV gamma-rays and by cosmic rays

Author

Heß, M., Bernlöhra, K., Daum, A., Hemberger, M., Hermann, G., Hofmann, W., Lampeitl, H., Aharonian, F. A., Akhperjanian, A. G., Barrio, J. A., Beteta, J. J. G., Contreras, J. L., Juan Cortina, Deckers, T., Fernandez, J., Fonseca, V., Gonzalez, J. C., Heinzelmann, G., Heusler, A., Hohl, H., Holl, I., Horns, D., Kankanyan, R., Kestel, M., Kirstein, O., Köhler, C., Konopelko, A., Kornmayer, H., Kranich, D., Krawczynski, H., Lindner, A., Lorenz, E., Magnussen, N., Meyer, H., Mirzoyan, R., Moralejo, A., Padilla, L., Panter, M., Petry, D., Plaga, R., Prahl, J., Prosch, C., Pühlhofer, G., Rauterberg, G., Rhode, W., Röhring, A., Samorski, M., Sanchez, J. A., Schmele, D., Schröder, F., Stamm, W., Völk, H. J., Wiebel-Sooth, B., Wiedner, C. A., and Willmer, M.

Subjects
Physics, Photon, Physics::Instrumentation and Detectors, Astrophysics::High Energy Astrophysical Phenomena, Astrophysics (astro-ph), Gamma ray, Astrophysics::Instrumentation and Methods for Astrophysics, HEGRA, FOS: Physical sciences, Astronomy and Astrophysics, Cosmic ray, Astrophysics, law.invention, Core (optical fiber), Telescope, Shower, law, Cherenkov radiation
Abstract

The time profiles of Cherenkov images of cosmic-ray showers and of gamma-ray showers are investigated, using data gathered with the HEGRA system of imaging atmospheric Cherenkov telescopes during the 1997 outbursts of Mrk 501. Photon arrival times are shown to vary across the shower images. The dominant feature is a time gradient along the major axis of the images. The gradient varies with the distance between the telescope and the shower core, and is maximal for large distances. The time profiles of cosmic-ray showers and of gamma-ray showers differ in a characteristic fashion. The main features of the time profiles can be understood in terms of simple geometrical models. Use of the timing information towards improved shower reconstruction and cosmic-ray suppression is discussed., Comment: 25 Pages, 16 figures, Latex

Published
1998
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13. Parched elasto hydrodynamic lubrication film thickness measurement in an instrument ball bearing

Author

Kingsbury, E, Schritz, B, and Prahl, J

Subjects
Mechanical Engineering
Abstract

Parched Elasto Hydrodynamic Lubricant (PEHL) film thickness in a large instrument ball bearing is measured by electrical capacitance across its ball set. Correlation is shown between changes in film thickness and changes in Basic Speed Ratio (BSR) measured at the same time. BSR is confirmed as a sensitive, non-intrusive measure of transients in film thickness in a real bearing.

Published
1988

15. Mechanics of a gaseous film barrier to lubricant wetting of elastohydrodynamically lubricated conjunctions

Author

Prahl, J. M and Hamrock, B. J

Subjects
Mechanical Engineering
Abstract

Two analytical models, one based on simple hydrodynamic lubrication and the other on soft elastohydrodynamic lubrication, are presented and compared to delineate the dominant physical parameters that govern the mechanics of a gaseous film between a small droplet of lubricant and the outer race of a ball bearing. Both models are based on the balance of gravity forces, air drag forces, and air film lubrication forces and incorporate a drag coefficient C sub D and a lubrication coefficient C sub L to be determined from experiment. The soft elastohydrodynamic lubrication (EHL) model considers the effects of droplet deformation and solid-surface geometry; the simpler hydrodynamic lubrication (HL) model assumes that the droplet remains essentially spherical. The droplet's angular position depended primarily on the ratio of gas inertia to droplet gravity forces and on the gas Reynolds number and weakly on the ratio of droplet gravity forces to surface tension forces (Bond number) and geometric ratios for the soft EHL. An experimental configuration in which an oil droplet is supported by an air film on the rotating outer race of a ball bearing within a pressure-controlled chamber produced measurements of droplet angular position as a function of outer-race velocity droplet size and type, and chamber pressure.

Published
1985

17. Evidence for involvement of 17bèta-estradiol in intestinal calcium absorption independent of 1,25-dihydroxyvitamin D3 level in the rat

Author

Colin, E. M., Van Den Bemd, G. J.C.M., Van Aken, M., Christakos, S., De Jonge, H. R., Deluca, H. F., Prahl, J. M., Birkenhäger, J. C., Buurman, C. J., Pols, H. A.P., Van Leeuwen, J. P.T.M., Colin, E. M., Van Den Bemd, G. J.C.M., Van Aken, M., Christakos, S., De Jonge, H. R., Deluca, H. F., Prahl, J. M., Birkenhäger, J. C., Buurman, C. J., Pols, H. A.P., and Van Leeuwen, J. P.T.M.

Published
1999

18. Search for point sources of gamma radiation above 15 TeV with the HEGRA AIROBICC array

Author

Aharonian, F., primary, Akhperjanian, A., additional, Barrio, J. A., additional, Bernlöhr, K., additional, Börst, H., additional, Bojahr, H., additional, Bolz, O., additional, Contreras, J. L., additional, Cortina, J., additional, Denninghoff, S., additional, Fonseca, V., additional, Gebauer, H. J., additional, González, J., additional, Götting, N., additional, Heinzelmann, G., additional, Hermann, G., additional, Heusler, A., additional, Hofmann, W., additional, Horns, D., additional, Jung, I., additional, Kankanyan, R., additional, Kestel, M., additional, Kettler, J., additional, Kohnle, A., additional, Konopelko, A., additional, Kornmayer, H., additional, Kranich, D., additional, Krawczynski, H., additional, Lampeitl, H., additional, López, M., additional, Lorenz, E., additional, Lucarelli, F., additional, Magnussen, N., additional, Mang, O., additional, Meyer, H., additional, Mirzoyan, R., additional, Moralejo, A., additional, Oña, E., additional, Padilla, L., additional, Panter, M., additional, Plaga, R., additional, Plyasheshnikov, A., additional, Prahl, J., additional, Pühlhofer, G., additional, Rauterberg, G., additional, Röhring, A., additional, Rhode, W., additional, Rowell, G., additional, Sahakian, V., additional, Samorski, M., additional, Schilling, M., additional, Schmele, D., additional, Schröder, F., additional, Sevilla, I., additional, Siems, M., additional, Stamm, W., additional, Tluczykont, M., additional, Völk, H. J., additional, Wiedner, C. A., additional, and Wittek, W., additional

Published
2002
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19. This title is unavailable for guests, please login to see more information.

Author

Staal, A., Van Wijnen, A. J., Birkenhäger, J. C., Pols, H. A.P., Prahl, J., DeLuca, H., Gaub, Marie Pierre, Lian, J. B., Stein, G. S., Van Leeuwen, J. P.T.M., Stein, J. L., Staal, A., Van Wijnen, A. J., Birkenhäger, J. C., Pols, H. A.P., Prahl, J., DeLuca, H., Gaub, Marie Pierre, Lian, J. B., Stein, G. S., Van Leeuwen, J. P.T.M., and Stein, J. L.

Published
1996

20. A search for gamma-ray emission from the Galactic plane in the longitude range between $\mathsf{37}^\circ$ and $\mathsf{43}^\circ$

Author

Aharonian, F. A., primary, Akhperjanian, A. G., additional, Barrio, J. A., additional, Bernlöhr, K., additional, Bolz, O., additional, Börst, H., additional, Bojahr, H., additional, Contreras, J. L., additional, Cortina, J., additional, Denninghoff, S., additional, Fonseca, V., additional, Gonzalez, J. C., additional, Götting, N., additional, Heinzelmann, G., additional, Hermann, G., additional, Heusler, A., additional, Hofmann, W., additional, Horns, D., additional, Ibarra, A., additional, Iserlohe, C., additional, Jung, I., additional, Kankanyan, R., additional, Kestel, M., additional, Kettler, J., additional, Kohnle, A., additional, Konopelko, A., additional, Kornmeyer, H., additional, Kranich, D., additional, Krawczynski, H., additional, Lampeitl, H., additional, Lorenz, E., additional, Lucarelli, F., additional, Magnussen, N., additional, Mang, O., additional, Meyer, H., additional, Mirzoyan, R., additional, Moralejo, A., additional, Padilla, L., additional, Panter, M., additional, Plaga, R., additional, Plyasheshnikov, A., additional, Prahl, J., additional, Pühlhofer, G., additional, Rhode, W., additional, Röhring, A., additional, Rowell, G. P., additional, Sahakian, V., additional, Samorski, M., additional, Schilling, M., additional, Schröder, F., additional, Siems, M., additional, Stamm, W., additional, Tluczykont, M., additional, Völk, H. J., additional, Wiedner, C. A., additional, and Wittek, W., additional

Published
2001
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21. A study of Tycho's SNR at TeV energies with the HEGRA CT-System

Author

Aharonian, F. A., primary, Akhperjanian, A. G., additional, Barrio, J. A., additional, Bernlöhr, K., additional, Börst, H., additional, Bojahr, H., additional, Bolz, O., additional, Contreras, J. L., additional, Cortina, J., additional, Denninghoff, S., additional, Fonseca, V., additional, Gonzalez, J. C., additional, Götting, N., additional, Heinzelmann, G., additional, Hermann, G., additional, Heusler, A., additional, Hofmann, W., additional, Horns, D., additional, Ibarra, A., additional, Jung, I., additional, Kankanyan, R., additional, Kestel, M., additional, Kettler, J., additional, Kohnle, A., additional, Konopelko, A., additional, Kornmeyer, H., additional, Kranich, D., additional, Krawczynski, H., additional, Lampeitl, H., additional, Lorenz, E., additional, Lucarelli, F., additional, Magnussen, N., additional, Mang, O., additional, Meyer, H., additional, Mirzoyan, R., additional, Moralejo, A., additional, Padilla, L., additional, Panter, M., additional, Plaga, R., additional, Plyasheshnikov, A., additional, Prahl, J., additional, Pühlhofer, G., additional, Rauterberg, G., additional, Röhring, A., additional, Rhode, W., additional, Rowell, G. P., additional, Sahakian, V., additional, Samorski, M., additional, Schilling, M., additional, Schröder, F., additional, Stamm, W., additional, Tluczykont, M., additional, Völk, H. J., additional, Wiedner, C., additional, and Wittek, W., additional

Published
2001
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22. Evidence for TeV gamma ray emission from Cassiopeia A

Author

Aharonian, F., primary, Akhperjanian, A., additional, Barrio, J., additional, Bernlöhr, K., additional, Börst, H., additional, Bojahr, H., additional, Bolz, O., additional, Contreras, J., additional, Cortina, J., additional, Denninghoff, S., additional, Fonseca, V., additional, Gonzalez, J., additional, Götting, N., additional, Heinzelmann, G., additional, Hermann, G., additional, Heusler, A., additional, Hofmann, W., additional, Horns, D., additional, Ibarra, A., additional, Iserlohe, C., additional, Jung, I., additional, Kankanyan, R., additional, Kestel, M., additional, Kettler, J., additional, Kohnle, A., additional, Konopelko, A., additional, Kornmeyer, H., additional, Kranich, D., additional, Krawczynski, H., additional, Lampeitl, H., additional, Lopez, M., additional, Lorenz, E., additional, Lucarelli, F., additional, Magnussen, N., additional, Mang, O., additional, Meyer, H., additional, Mirzoyan, R., additional, Moralejo, A., additional, Ona, E., additional, Padilla, L., additional, Panter, M., additional, Plaga, R., additional, Plyasheshnikov, A., additional, Prahl, J., additional, Pühlhofer, G., additional, Rauterberg, G., additional, Röhring, A., additional, Rhode, W., additional, Rowell, G. P., additional, Sahakian, V., additional, Samorski, M., additional, Schilling, M., additional, Schröder, F., additional, Siems, M., additional, Stamm, W., additional, Tluczykont, M., additional, Völk, H. J., additional, Wiedner, C. A., additional, and Wittek, W., additional

Published
2001
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23. Search for a TeV gamma-ray halo of Mkn 501

Author

Aharonian, F. A., primary, Akhperjanian, A. G., additional, Barrio, J. A., additional, Bernlöhr, K., additional, Bolz, O., additional, Börst, H., additional, Bojahr, H., additional, Contreras, J. L., additional, Cortina, J., additional, Denninghoff, S., additional, Fonseca, V., additional, Gonzalez, J. C., additional, Götting, N., additional, Heinzelmann, G., additional, Hermann, G., additional, Heusler, A., additional, Hofmann, W., additional, Horns, D., additional, Ibarra, A., additional, Iserlohe, C., additional, Jung, I., additional, Kankanyan, R., additional, Kestel, M., additional, Kettler, J., additional, Kohnle, A., additional, Konopelko, A., additional, Kornmeyer, H., additional, Kranich, D., additional, Krawczynski, H., additional, Lampeitl, H., additional, Lorenz, E., additional, Lucarelli, F., additional, Magnussen, N., additional, Mang, O., additional, Meyer, H., additional, Mirzoyan, R., additional, Moralejo, A., additional, Padilla, L., additional, Panter, M., additional, Plaga, R., additional, Plyasheshnikov, A., additional, Prahl, J., additional, Pühlhofer, G., additional, Rhode, W., additional, Röhring, A., additional, Rowell, G. P., additional, Sahakian, V., additional, Samorski, M., additional, Schilling, M., additional, Schröder, F., additional, Siems, M., additional, Stamm, W., additional, Tluczykont, M., additional, Völk, H. J., additional, Wiedner, C., additional, and Wittek, W., additional

Published
2001
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24. The TeV Energy Spectrum of Markarian 501 Measured with the Stereoscopic Telescope System of HEGRA during 1998 and 1999

Author

Aharonian, F., primary, Akhperjanian, A., additional, Barrio, J., additional, Bernlohr, K., additional, Borst, H., additional, Bojahr, H., additional, Bolz, O., additional, Contreras, J., additional, Cortina, J., additional, Denninghoff, S., additional, Fonseca, V., additional, Gonzalez, J., additional, Gotting, N., additional, Heinzelmann, G., additional, Hermann, G., additional, Heusler, A., additional, Hofmann, W., additional, Horns, D., additional, Iserlohe, C., additional, Ibarra, A., additional, Jung, I., additional, Kankanyan, R., additional, Kestel, M., additional, Kettler, J., additional, Kohnle, A., additional, Konopelko, A., additional, Kornmeyer, H., additional, Kranich, D., additional, Krawczynski, H., additional, Lampeitl, H., additional, Lorenz, E., additional, Lucarelli, F., additional, Magnussen, N., additional, Mang, O., additional, Meyer, H., additional, Mirzoyan, R., additional, Moralejo, A., additional, Padilla, L., additional, Panter, M., additional, Plaga, R., additional, Plyasheshnikov, A., additional, Prahl, J., additional, Puhlhofer, G., additional, Rohring, A., additional, Rhode, W., additional, Rowell, G. P., additional, Sahakian, V., additional, Samorski, M., additional, Schilling, M., additional, Schroder, F., additional, Siems, M., additional, Stamm, W., additional, Tluczykont, M., additional, Volk, H., additional, Wiedner, C., additional, and Wittek, W., additional

Published
2001
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25. Reanalysis of the high energy cutoff of the 1997 Mkn 501 TeV energy spectrum

Author

Aharonian, F. A., primary, Akhperjanian, A. G., additional, Barrio, J. A., additional, Bernlöhr, K., additional, Bolz, O., additional, Börst, H., additional, Bojahr, H., additional, Contreras, J. L., additional, Cortina, J., additional, Denninghoff, S., additional, Fonseca, V., additional, Gonzalez, J. C., additional, Götting, N., additional, Heinzelmann, G., additional, Hermann, G., additional, Heusler, A., additional, Hofmann, W., additional, Horns, D., additional, Ibarra, A., additional, Iserlohe, C., additional, Jung, I., additional, Kankanyan, R., additional, Kestel, M., additional, Kettler, J., additional, Kohnle, A., additional, Konopelko, A., additional, Kornmeyer, H., additional, Kranich, D., additional, Krawczynski, H., additional, Lampeitl, H., additional, Lorenz, E., additional, Lucarelli, F., additional, Magnussen, N., additional, Mang, O., additional, Meyer, H., additional, Mirzoyan, R., additional, Moralejo, A., additional, Padilla, L., additional, Panter, M., additional, Plaga, R., additional, Plyasheshnikov, A., additional, Prahl, J., additional, Pühlhofer, G., additional, Rhode, W., additional, Röhring, A., additional, Rowell, G. P., additional, Sahakian, V., additional, Samorski, M., additional, Schilling, M., additional, Schröder, F., additional, Siems, M., additional, Stamm, W., additional, Tluczykont, M., additional, Völk, H. J., additional, Wiedner, C., additional, and Wittek, W., additional

Published
2001
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26. A search for gamma-ray emission from the Galactic plane in the longitude range between $\mathsf{37}^\circ$and $\mathsf{43}^\circ$

Author

Aharonian, F. A., Akhperjanian, A. G., Barrio, J. A., Bernlöhr, K., Bolz, O., Börst, H., Bojahr, H., Contreras, J. L., Cortina, J., Denninghoff, S., Fonseca, V., Gonzalez, J. C., Götting, N., Heinzelmann, G., Hermann, G., Heusler, A., Hofmann, W., Horns, D., Ibarra, A., Iserlohe, C., Jung, I., Kankanyan, R., Kestel, M., Kettler, J., Kohnle, A., Konopelko, A., Kornmeyer, H., Kranich, D., Krawczynski, H., Lampeitl, H., Lorenz, E., Lucarelli, F., Magnussen, N., Mang, O., Meyer, H., Mirzoyan, R., Moralejo, A., Padilla, L., Panter, M., Plaga, R., Plyasheshnikov, A., Prahl, J., Pühlhofer, G., Rhode, W., Röhring, A., Rowell, G. P., Sahakian, V., Samorski, M., Schilling, M., Schröder, F., Siems, M., Stamm, W., Tluczykont, M., Völk, H. J., Wiedner, C. A., Wittek, W., Aharonian, F. A., Akhperjanian, A. G., Barrio, J. A., Bernlöhr, K., Bolz, O., Börst, H., Bojahr, H., Contreras, J. L., Cortina, J., Denninghoff, S., Fonseca, V., Gonzalez, J. C., Götting, N., Heinzelmann, G., Hermann, G., Heusler, A., Hofmann, W., Horns, D., Ibarra, A., Iserlohe, C., Jung, I., Kankanyan, R., Kestel, M., Kettler, J., Kohnle, A., Konopelko, A., Kornmeyer, H., Kranich, D., Krawczynski, H., Lampeitl, H., Lorenz, E., Lucarelli, F., Magnussen, N., Mang, O., Meyer, H., Mirzoyan, R., Moralejo, A., Padilla, L., Panter, M., Plaga, R., Plyasheshnikov, A., Prahl, J., Pühlhofer, G., Rhode, W., Röhring, A., Rowell, G. P., Sahakian, V., Samorski, M., Schilling, M., Schröder, F., Siems, M., Stamm, W., Tluczykont, M., Völk, H. J., Wiedner, C. A., and Wittek, W.

Abstract

Using the HEGRA system of imaging atmospheric Cherenkov telescopes, a region of the Galactic plane ($-10^\circ < b < 5^\circ$, $38^\circ < l < 43^\circ$) was surveyed for TeV gamma-ray emission, both from point sources and of diffuse nature. The region covered includes 15 known pulsars, 6 known supernova remnants (SNR) and one unidentified EGRET source. No evidence for emission from point sources was detected; upper limits are typically below 0.1 Crab units for the flux above 1 TeV. For the diffuse gamma-ray flux from the Galactic plane, an upper limit of $6.1\times10^{-15}$ph cm-2s-1sr-1MeV-1was derived under the assumption that the spatial distribution measured by the EGRET instrument extends to the TeV regime. This upper flux limit is a factor of about 1.5 larger than the flux expected from the ensemble of gamma-ray unresolved Galactic cosmic ray sources.

Published
2001
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27. Rejection of the Hypothesis That Markarian 501 T[CLC]e[/CLC]V Photons Are Pure Bose-Einstein Condensates

Author

Aharonian, F., primary, Akhperjanian, A., additional, Barrio, J., additional, Bernlöhr, K., additional, Börst, H., additional, Bojahr, H., additional, Bolz, O., additional, Contreras, J., additional, Cortina, J., additional, Denninghoff, S., additional, Fonseca, V., additional, Gonzalez, J., additional, Götting, N., additional, Heinzelmann, G., additional, Hermann, G., additional, Heusler, A., additional, Hofmann, W., additional, Horns, D., additional, Ibarra, A., additional, Iserlohe, C., additional, Jung, I., additional, Kankanyan, R., additional, Kestel, M., additional, Kettler, J., additional, Kohnle, A., additional, Konopelko, A., additional, Kornmeyer, H., additional, Kranich, D., additional, Krawczynski, H., additional, Lampeitl, H., additional, Lorenz, E., additional, Lucarelli, F., additional, Magnussen, N., additional, Mang, O., additional, Meyer, H., additional, Mirzoyan, R., additional, Moralejo, A., additional, Padilla, L., additional, Panter, M., additional, Plaga, R., additional, Plyasheshnikov, A., additional, Prahl, J., additional, Pühlhofer, G., additional, Röhring, A., additional, Rhode, W., additional, Rowell, G., additional, Sahakian, V., additional, Samorski, M., additional, Schilling, M., additional, Schröder, F., additional, Siems, M., additional, Stamm, W., additional, Tluczykont, M., additional, Völk, H. J., additional, Wiedner, C. A., additional, and Wittek, W., additional

Published
2000
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28. The Energy Spectrum of TeV Gamma Rays from the Crab Nebula as Measured by the HEGRA System of Imaging Air Cerenkov Telescopes

Author

Aharonian, F. A., primary, Akhperjanian, A. G., additional, Barrio, J. A., additional, Bernlohr, K., additional, Bojahr, H., additional, Calle, I., additional, Contreras, J. L., additional, Cortina, J., additional, Denninghoff, S., additional, Fonseca, V., additional, Gonzalez, J. C., additional, Gotting, N., additional, Heinzelmann, G., additional, Hemberger, M., additional, Hermann, G., additional, Heusler, A., additional, Hofmann, W., additional, Horns, D., additional, Ibarra, A., additional, Kankanyan, R., additional, Kestel, M., additional, Kettler, J., additional, Kohler, C., additional, Kohnle, A., additional, Konopelko, A., additional, Kornmeyer, H., additional, Kranich, D., additional, Krawczynski, H., additional, Lampeitl, H., additional, Lindner, A., additional, Lorenz, E., additional, Lucarelli, F., additional, Magnussen, N., additional, Mang, O., additional, Meyer, H., additional, Mirzoyan, R., additional, Moralejo, A., additional, Padilla, L., additional, Panter, M., additional, Plaga, R., additional, Plyasheshnikov, A., additional, Prahl, J., additional, Puhlhofer, G., additional, Rauterberg, G., additional, Rohring, A., additional, Sahakian, V., additional, Samorski, M., additional, Schilling, M., additional, Schmele, D., additional, Schroder, F., additional, Stamm, W., additional, Tluczykont, M., additional, Volk, H. J., additional, Wiebel‐Sooth, B., additional, Wiedner, C., additional, Willmer, M., additional, and Wittek, W., additional

Published
2000
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29. Evidence for Involvement of 17β‐Estradiol in Intestinal Calcium Absorption Independent of 1,25‐Dihydroxyvitamin D3 Level in the Rat

Author

Colin, E. M., primary, Van Den Bemd, G. J. C. M., additional, Van Aken, M., additional, Christakos, S., additional, De Jonge, H. R., additional, Deluca, H. F., additional, Prahl, J. M., additional, Birkenhäger, J. C., additional, Buurman, C. J., additional, Pols, H. A. P., additional, and van Leeuwen, J. P. T. M., additional

Published
1999
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30. Distinct conformations of vitamin D receptor/retinoid X receptor-alpha heterodimers are specified by dinucleotide differences in the vitamin D-responsive elements of the osteocalcin and osteopontin genes.

Author

Staal, A, primary, van Wijnen, A J, additional, Birkenhäger, J C, additional, Pols, H A, additional, Prahl, J, additional, DeLuca, H, additional, Gaub, M P, additional, Lian, J B, additional, Stein, G S, additional, van Leeuwen, J P, additional, and Stein, J L, additional

Published
1996
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38. Correlated Intense X-Ray and TeV Activity of Markarian 501 in 1998 June

Author

Sambruna, R. M., Aharonian, F. A., Krawczynski, H., Akhperjanian, A. G., Barrio, J. A., Bernlöhr, K., Bojahr, H., Calle, I., Contreras, J. L., Cortina, J., Denninghoff, S., Fonseca, V., Gonzalez, J. C., Götting, N., Heinzelmann, G., Hemberger, M., Hermann, G., Heusler, A., Hofmann, W., Horns, D., Ibarra, A., Kankanyan, R., Kestel, M., Kettler, J., Köhler, C., Kohnle, A., Konopelko, A., Kornmeyer, H., Kranich, D., Lampeitl, H., Lindner, A., Lorenz, E., Magnussen, N., Mang, O., Meyer, H., Mirzoyan, R., Moralejo, A., Padilla, L., Panter, M., Plaga, R., Plyasheshnikov, A., Prahl, J., Pühlhofer, G., Rauterberg, G., Röhring, A., Sahakian, V., Samorski, M., Schilling, M., Schmele, D., Schröder, F., Stamm, W., Tluczykont, M., Völk, H. J., Wiebel-Sooth, B., Wiedner, C., Willmer, M., Wittek, W., Chou, L., Coppi, P. S., Rothschild, R., and Urry, C. M.

Abstract

We present exactly simultaneous X-ray and TeV monitoring with RXTEand HEGRA of the TeV blazar Mrk 501 during 15 days in 1998 June. After an initial period of very low flux at both wavelengths, the source underwent a remarkable flare in the TeV and X-ray energy bands, lasting for about 6 days and with a larger amplitude at TeV energies than in the X-ray band. At the peak of the TeV flare, rapid TeV flux variability on subhour timescales is found. Large spectral variations are observed at X-rays, with the 3-20 keV photon index of a pure power-law continuum flattening from ? = 2.3 to ? = 1.8 on a timescale of 2-3 days. This implies that during the maximum of the TeV activity the synchrotron peak shifted to energies 50 keV, a behavior similar to that observed during the longer lasting, more intense flare in 1997 April. The TeV spectrum during the flare is described by a power law with photon index ? = 1.9 and an exponential cutoff at ~4 TeV; an indication for spectral softening during the flare decay is observed in the TeV hardness ratios. Our results generally support a scenario in which the TeV photons are emitted via inverse Compton scattering of ambient seed photons by the same electron population responsible for the synchrotron X-rays. The simultaneous spectral energy distributions can be fit with a one-zone synchrotron self-Compton model assuming a substantial increase of the magnetic field and the electron energy by factors of 3 and 10, respectively.

Published
2000
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39. Evidence for presence of an internal thiolester bond in third component of human complement.

Author

Tack, B F, Harrison, R A, Janatova, J, Thomas, M L, and Prahl, J W

Abstract

Treatment of the third component of human complement (C3) with methylamine results in a loss of hemolytic function and the appearance of a thiol group. Studies with [14C]methylamine have indicatd a stoichiometric and covalent reaction with the native protein. Hydrazine-inactivated C3 and C3b prepared with bovine trypsin were unreactive with [14C]-methylamine. Alkylation experiments with [1-14C]iodoacetamide have further established a 1:1 correspondence between methylamine incorporation and expression of the reactive thiol. Autoradiographic analyses of [14C]methylamine-treated C3 and methylamine-inactivated [1-14C]carboxyamidomethylated C3 after NaDodSO4/polyacrylamide gel electrophoresis have shown a specific incorporation of each radiolabel into the alpha polypeptide chain. [14C]Methylamine-treated C3 was immobilized on Sepharose 4B by reaction of the protein thiol with a mixed disulfide. Digestion with bovine trypsin in 4 M urea released 96% of the bound absorbance (at 280 nm) units; the radiolabel remained associated with the Sepharose beads. Peptide material labeled with 14C was eluted with dithiothreitol, carboxymethylated with [3H]iodoacetic acid, and chromatographed on Sephadex G-75. On Edman degradation S-[3H]carboxymethylcysteine was released at step 9 and gamma-glutamyl[14C]-methylamide was released at step 12. We interpret these data to indicate the presence of an internal thiolester bond in native C3. In addition, evidence is presented for an identical reactive site in alpha 2-macroglobulin.

Published
1980
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40. Baculovirus-mediated expression of retinoic acid receptor type gamma in cultured insect cells reveals a difference in specific DNA-binding behavior with the 1,25-dihydroxyvitamin D3 receptor.

Author

Ross, T K, Prahl, J M, Herzberg, I M, and DeLuca, H F

Abstract

The baculovirus genetic expression system has been used to produce murine retinoic acid receptor (RAR) type gamma in Spodoptera frugiperda insect cells and Manduca sexta insect larvae. A hydroxyapatite binding assay revealed production levels of 300 pmol of unoccupied receptor per mg of protein in insect cells, whereas levels from infected insect larvae were found to average 100 pmol of RAR gamma per mg of protein. The cytosolic preparation from infected insect cells exhibited an equilibrium dissociation constant of 2.1 nM as determined by a retinoic acid saturation analysis plotted by the method of Scatchard. A polyclonal antibody directed against RAR gamma recognized the recombinant receptor protein as a 54,000-Da species. Electrophoretic mobility shift analyses demonstrated that protein extracts from RAR gamma-producing insect cells or larvae are capable of retinoic acid responsive element binding. This contrasts with the specific DNA-binding behavior of the insect cell-produced vitamin D receptor, which requires the presence of a mammalian-derived nuclear accessory protein. This distinction between RAR gamma and the vitamin D receptor suggests a difference in the molecular requirements by these two receptors for specific binding of their respective DNA response elements.

Published
1992
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41. Evidence for Involvement of 17β‐Estradiol in Intestinal Calcium Absorption Independent of 1,25‐Dihydroxyvitamin D3Level in the Rat

Author

Colin, E. M., Van Den Bemd, G. J. C. M., Van Aken, M., Christakos, S., De Jonge, H. R., Deluca, H. F., Prahl, J. M., Birkenhäger, J. C., Buurman, C. J., Pols, H. A. P., and van Leeuwen, J. P. T. M.

Abstract

The sex steroid 17β‐estradiol (17β‐E2) has a broad range of actions, including effects on calcium and bone metabolism. This study with 3‐month‐old Brown Norway rats was designed to investigate the role of 17β‐E2in the regulation of calcium homeostasis. Rats were divided in four groups, sham‐operated, ovariectomized (OVX), and OVX supplemented with either a 0.025‐mg or 0.05‐mg 17β‐E2pellet implanted subcutaneously. After 4 weeks, in none of the groups was serum calcium, phosphate, or parathyroid hormone altered compared with the sham group, while only in the OVX rats was a significant reduction in urinary calcium found. Bone mineral density and osteocalcin were modified, as can be expected after OVX and 17β‐E2supplementation. OVX resulted in a nonsignificant increase in serum 1,25‐dihydroxyvitamin D3(1,25(OH)2D3). Supplementation with either one of the 17β‐E2dosages resulted in an 80% reduction of 1,25(OH)2D3and only a 20% reduction in 25‐hydroxyvitamin D3levels. OVX, as well as supplementation with 17β‐E2, did not affect serum levels of vitamin D binding protein. As a consequence, the estimated free 1,25(OH)2D3levels were also significantly decreased in the 17β‐E2‐supplemented group compared with the sham and OVX groups. Next, the consequences for intestinal calcium absorption were analyzed by the in situ intestinal loop technique. Although the 1,25(OH)2D3serum level was increased, OVX resulted in a significant decrease in intestinal calcium absorption in the duodenum. Despite the strongly reduced 1,25(OH)2D3levels (18.1 ± 2.1 and 16.4 ± 2.2 pmol/l compared with 143.5 ± 29 pmol/l for the OVX group), the OVX‐induced decrease in calcium absorption could partially be restored by supplementation with either 0.025 mg or 0.05 mg of 17β‐E2. None of the treatments resulted in a significant change in calcium handling in the jejunum, although the trends were similar as those observed in the duodenum. 17β‐E2did not change the VDR levels in both the intestine and the kidney. In conclusion, the present study demonstrates that 17β‐E2is positively involved in intestinal calcium absorption, and the data strengthen the assertion that 17β‐E2exerts this effect independent of 1,25(OH)2D3. In general, 17β‐E2not only affects bone turnover but also calcium homeostasis via an effect on intestinal calcium absorption.

Published
1999
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42. 24- and 26-homo-1,25-dihydroxyvitamin D3: preferential activity in inducing differentiation of human leukemia cells HL-60 in vitro.

Author

Ostrem, V K, Tanaka, Y, Prahl, J, DeLuca, H F, and Ikekawa, N

Abstract

1,25-Dihydroxyvitamin D3, the hormonal form of vitamin D3, promotes the differentiation of HL-60 human promyelocytic leukemia cells into monocytes. Differentiation changes include the induction of phagocytosis, the initiation of nitroblue tetrazolium-reducing activity, and the appearance of nonspecific acid esterase. We have found that the 24-homo- and 26-homo-1,25-dihydroxyvitamin D3 and their delta 22 analogues are 10-fold more potent than 1,25-dihydroxyvitamin D3 in inducing differentiation of HL-60 cells in vitro. In vivo, these analogues show activity similar to 1,25-dihydroxyvitamin D3 in stimulating intestinal calcium transport in vitamin D-deficient rats. The 24-homoanalogues are significantly less active, whereas the 26-homo derivatives are more active than the natural hormone in mobilizing calcium from bone. This unusual activity pattern cannot be explained on the basis of the affinity of these analogues for the 1,25-dihydroxyvitamin D3 intracellular receptor: both 24-homo- and 26-homo-1,25-dihydroxyvitamin D3 have the same effectiveness as 1,25-dihydroxyvitamin D3 in displacing the tritiated hormone from its receptor in rat intestine or HL-60 cells. These analogues of 1,25-dihydroxyvitamin D3 may be of some interest as possible therapeutic substances, or as tools in understanding the action of 1,25-dihydroxyvitamin D3 in inducing differentiation.

Published
1987
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43. Partial amino acid sequence of porcine 1,25-dihydroxyvitamin D3 receptor isolated by immunoaffinity chromatography.

Author

Brown, T A, Prahl, J M, and DeLuca, H F

Abstract

Monoclonal antibodies against the porcine 1,25-dihydroxyvitamin D3 receptor were immobilized on Sepharose CL-4B and used to obtain a highly purified 1,25-dihydroxyvitamin D3 receptor fraction with a 45% recovery of the 1,25-dihydroxyvitamin D3 binding capacity. The porcine receptor was purified to homogeneity by preparative electrophoresis and digested in sodium dodecyl sulfate/polyacrylamide gels with Staphylococcus aureus strain V8 protease. The resulting peptides were separated by sodium dodecyl sulfate/polyacrylamide gel electrophoresis, electrophoretically transferred to polyvinylidene difluoride membranes, and directly sequenced. The generation and isolation of peptides by this method allows sequencing of proteins present in trace amounts as well as those whose amino termini have been modified. The 1,25-dihydroxyvitamin D3 receptor amino acid sequence corresponded to the sequence predicted from a recently cloned receptor cDNA obtained from rat kidney mRNAs.

Published
1988
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44. Induction of monocytic differentiation of HL-60 cells by 1,25-dihydroxyvitamin D analogs.

Author

Ostrem, V K, Lau, W F, Lee, S H, Perlman, K, Prahl, J, Schnoes, H K, and DeLuca, H F

Abstract

1,25-Dihydroxyvitamin D3, the hormonal form of vitamin D, induces differentiation of HL-60 human promyelocytes into monocyte-like cells in vitro. We assessed the relative activity of 30 analogs of 1,25-dihydroxyvitamin D3 in inducing development of monocytic markers in HL-60 cells. The three differentiation markers assayed were nonspecific acid esterase activity, nitro blue tetrazolium reducing activity, and phagocytic capacity. Of the known metabolites of vitamin D, 1,25-dihydroxyvitamin D3 is the most active; 50% of the cells exhibit the mature phenotype following a 4-day treatment with 10(-8) M 1,25-dihydroxyvitamin D3. Removal of either the C-1 or C-25-hydroxyl group reduces activity by 2 orders of magnitude, while epimerization of the 1 alpha- to 1 beta-hydroxyl group virtually abolishes activity. Elongation of the steroidal side chain of 1,25-dihydroxyvitamin D3 by addition of one carbon at C-24 or C-26 improves the potency by an order of magnitude. Truncation of the steroidal side chain leads to a 10-fold reduction in activity for each carbon removed. Elimination of the C-26 and C-27 methyl groups reduces activity 100-fold. Analogs with short aliphatic side chains as 1 alpha-hydroxyhomo- and bishomopregnacholecalciferol have surprisingly high activity, being only 20-fold less potent than the natural hormone. The activity of most analogs in the HL-60 system parallels their known relative affinities for the well characterized 1,25-dihydroxyvitamin D3 receptor in chick intestine, providing further evidence that this function of 1,25-dihydroxyvitamin D3 is receptor mediated.

Published
1987
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45. The C-terminal sequences of the heavy chains of human immunoglobulin G myeloma proteins of differing isotopes and allotypes

Author

Prahl, J. W.

Abstract

The sequences of the C-terminal octadecapeptides obtained by cyanogen bromide cleavage of the γ-chains of myeloma proteins of the four subclasses, and a urinary heavy-chain-disease protein, have been determined. Although the sequences were markedly homologous, unique replacements were identified that distinguished between the γ2b, γ2c and γ2d subclasses. The data are in accord with the postulated existence of four genetic loci or cistrons, these having arisen by the process of gene duplication.

Published
1967
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46. Allotype-related sequence variation of the heavy chain of rabbit immunoglobulin G

Author

Prahl, J. W. and Porter, R R

Abstract

The heavy chain of rabbit immunoglobulin G exists in three major allotypic patterns, Aa1–Aa3. A comparison of the amino acid compositions of the heavy chains isolated from immunoglobulin IgG homozygous for each allotypic determinant revealed the presence of an additional methionine residue per chain in the Aa3 allotype relative to the Aa1 and Aa2 allotypes. The position of the additional methionine residue was determined by cyanogen bromide cleavage and by tryptic digestion of the γ-chains; it coincided with the inter-Fd–Fc area of the chain. Isolation and characterization of the corresponding tryptic peptides of 31 amino acid residues from each of the allotypes showed the presence of a methionine-for-threonine replacement in the Aa3 allotype, but only in about 70–80% of the molecules. No other allotypic variations were seen in this tryptic peptide. Allotypically related variations in composition were also detected in the N-terminal cyanogen bromide-cleavage peptide.

Published
1968
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47. Evidence for TeV gamma ray emission from Cassiopeia A

Author

Aharonian, F., Akhperjanian, A., Barrio, J., Bernlohr, K., Borst, H., Bojahr, H., Bolz, O., Contreras, J., Cortina, J., Denninghoff, S., Fonseca, V., Gonzalez, J., Gotting, N., Heinzelmann, G., Hermann, G., Heusler, A., Hofmann, W., Horns, D., Ibarra, A., Iserlohe, C., Jung, I., Kankanyan, R., Kestel, M., Kettler, J., Kohnle, A., Konopelko, A., Kornmeyer, H., Kranich, D., Krawczynski, H., Lampeitl, H., Marcos López Moya, Lorenz, E., Lucarelli, F., Magnussen, N., Mang, O., Meyer, H., Mirzoyan, R., Moralejo, A., Ona, E., Padilla, L., Panter, M., Plaga, R., Plyasheshnikov, A., Prahl, J., Puhlhofer, G., Rauterberg, G., Rohring, A., Rhode, W., Rowell, G. P., Sahakian, V., Samorski, M., Schilling, M., Schroder, F., Siems, M., Stamm, W., Tluczykont, M., Volk, H. J., Wiedner, C. A., and Wittek, W.

Subjects
Physics, Spectral index, Astrophysics::High Energy Astrophysical Phenomena, Astrophysics (astro-ph), Gamma ray, FOS: Physical sciences, HEGRA, Astronomy and Astrophysics, Cosmic ray, Astrophysics, law.invention, Cassiopeia A, Telescope, Space and Planetary Science, law, High Energy Physics::Experiment, Supernova remnant, Cherenkov radiation, Astrophysics::Galaxy Astrophysics
Abstract

232 hours of data were accumulated from 1997 to 1999, using the HEGRA Stereoscopic Cherenkov Telescope System to observe the supernova remnant Cassiopeia A. TeV gamma ray emission was detected at the 5 sigma level, and a flux of (5.8 +- 1.2(stat) +- 1.2(syst)) 10^(-9) ph m^(-2) s^(-1) above 1 TeV was derived. The spectral distribution is consistent with a power law with a differential spectral index of -2.5 +- 0.4(stat) +- 0.1(syst) between 1 and 10 TeV. As this is the first report of the detection of a TeV gamma ray source on the "centi-Crab" scale, we present the analysis in some detail. Implications for the acceleration of cosmic rays depend on the details of the source modeling. We discuss some important aspects in this paper., 9 pages, 6 figures, accepted for publication in Astronomy & Astrophysics

48. A study of Tycho's SNR at TeV energies with the HEGRA CT-system

Author

Aharonian, F. A., Akhperjanian, A. G., Barrio, J. A., Bernlöhr, K., Börst, H., Bojahr, H., Bolz, O., Contreras, J. L., Cortina, J., Denninghoff, S., Fonseca, V., Gonzalez, J. C., Götting, N., Heinzelmann, G., Hermann, G., Heusler, A., Hofmann, W., Horns, D., Ibarra, A., Jung, I., Kankanyan, R., Kestel, M., Kettler, J., Kohnle, A., Konopelko, A., Kornmeyer, H., Kranich, D., Krawczynski, H., Lampeitl, H., Lorenz, E., Fabrizio Lucarelli, Magnussen, N., Mang, O., Meyer, H., Mirzoyan, R., Moralejo, A., Padilla, L., Panter, M., Plaga, R., Plyasheshnikov, A., Prahl, J., Pühlhofer, G., Rauterberg, G., Röhring, A., Rhode, W., Rowell, G. P., Sahakian, V., Samorski, M., Schilling, M., Schröder, F., Stamm, W., Tluczykont, M., Völk, H. J., Wiedner, C., and Wittek, W.

Subjects
Physics, Photon, Astrophysics::High Energy Astrophysical Phenomena, Astrophysics (astro-ph), Hadron, FOS: Physical sciences, HEGRA, Flux, Astronomy and Astrophysics, Astrophysics, law.invention, Telescope, Space and Planetary Science, law, Limit (mathematics), Supernova remnant, Astrophysics::Galaxy Astrophysics, Cherenkov radiation
Abstract

Tycho's supernova remnant (SNR) was observed during 1997 and 1998 with the HEGRA Cherenkov Telescope System in a search for gamma-ray emission at energies above ~1 TeV. An analysis of these data, ~65 hours in total, resulted in no evidence for TeV gamma-ray emission. The 3sigma upper limit to the gamma-ray flux (>1 TeV) from Tycho is estimated at 5.78x10^{-13} photons cm^{-2} s^{-1}, or 33 milli-Crab. We interpret our upper limit within the framework of the following scenarios: (1) that the observed hard X-ray tail is due to synchrotron emission. A lower limit on the magnetic field within Tycho may be estimated B>=22 microG, assuming that the RXTE-detected X-rays were due to synchrotron emission. However, using results from a detailed model of the ASCA emission, a more conservative lower limit B>=6 microG is derived. (2) the hadronic model of Drury, Aharonian & Voelk, and (3) the more recent time-dependent kinetic theory of Berezhko & Voelk. Our upper limit lies within the range of predicted values of both hadronic models, according to uncertainties in physical parameters of Tycho, and shock acceleration details. In the latter case, the model was scaled to suit the parameters of Tycho and re-normalised to account for a simplification of the original model. We find that we cannot rule out Tycho as a potential contributor at an average level to the Galactic cosmic-ray flux., 9 pages, 6 figures. Accepted for publication in Astronomy and Astrophysics

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