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Your search keyword '"Ona Wilhelmi, E"' showing total 3 results
Start Over Author "Ona Wilhelmi, E" Journal astronomy and astrophysics
3 results on '"Ona Wilhelmi, E"'

1. Observations of 14 young open star clusters with the HEGRA system of Cherenkov telescopes

Author

Aharonian, F., Akhperjanian, A., Beilicke, M., Bernlöhr, K., Börst, H.-G., Bojahr, H., Bolz, O., Coarasa, T., Contreras, J. L., Cortina, J., 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., Konopelko, A., Kornmeyer, H., Kranich, D., Lampeitl, H., Lopez, M., Lorenz, E., Lucarelli, F., Mang, O., Meyer, H., Mirzoyan, R., Moralejo, A., Ona-Wilhelmi, E., Panter, M., Plyasheshnikov, A., Pühlhofer, G., de 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., Wittek, W., Aharonian, F., Akhperjanian, A., Beilicke, M., Bernlöhr, K., Börst, H.-G., Bojahr, H., Bolz, O., Coarasa, T., Contreras, J. L., Cortina, J., 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., Konopelko, A., Kornmeyer, H., Kranich, D., Lampeitl, H., Lopez, M., Lorenz, E., Lucarelli, F., Mang, O., Meyer, H., Mirzoyan, R., Moralejo, A., Ona-Wilhelmi, E., Panter, M., Plyasheshnikov, A., Pühlhofer, G., de 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.

Abstract

Context.A sample of 14 young open star clusters has been observed in the TeV energy regime with the stereoscopic system of the HEGRA (High Energy Gamma-Ray Astronomy) Cherenkov telescopes from 1997 to 2002, resulting in more than 300 h of observation time.

Published
2006
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2. Observation of the Monoceros Loop SNRregion with the HEGRA system of IACTs

Author

Aharonian, F. A., Akhperjanian, A. G., Beilicke, M., Bernlöhr, K., Börst, H.-G., Bojahr, H., Bolz, O., Coarasa, T., Contreras, J. L., Cortina, J., 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., Meyer, H., Mirzoyan, R., Moralejo, A., Ona-Wilhelmi, E., Panter, M., Plyasheshnikov, A., Pühlhofer, G., Reyes, R. de los, 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., Wittek, W., Aharonian, F. A., Akhperjanian, A. G., Beilicke, M., Bernlöhr, K., Börst, H.-G., Bojahr, H., Bolz, O., Coarasa, T., Contreras, J. L., Cortina, J., 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., Meyer, H., Mirzoyan, R., Moralejo, A., Ona-Wilhelmi, E., Panter, M., Plyasheshnikov, A., Pühlhofer, G., Reyes, R. de los, 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.

Abstract

The array of 5 imaging atmospheric Čerenkov telescopes (IACTs) deployed at La Palma (Canary Islands), and operated by the HEGRA (High Energy Gamma Ray Astronomy) collaboration, was used for observations of the Monoceros Loop SNRregion for a total of about 120 hrs and 20 hrs in ON-source and OFF-source mode, respectively. The giant molecular cloud Rosette Nebula appears in the sky region, close to the south-east part of the SNRrim. Using the HEGRA system of IACTs of rather large field of view (4.3 degree in diameter), we have mapped the extended sky region of $3^\circ \times 3^\circ$associated with the Monoceros SNR/Rosette Nebula, which is centered towards the hard spectrum X-ray point source SAX J0635+533. The EGRET unidentified source of diffuse γ-ray emission (3EG J0634+0521) observed in the energy range between 100 MeV–10 GeV, was effectively in the field of view of our present observations. Also, the GeV source GeV J0633+0645 was within the available field of view. The performance of the IACTs array reveals an energy threshold of 500 GeV and an angular resolution of $0.1^\circ$for γ-rays. In what follows, we present the result of the data analysis and its physical interpretation.

Published
2004
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3. Detection of TeV gamma-rays from the BL Lac 1ES 1959+650 in its low states and during a major outburst in 2002 *

Author

Aharonian, F., Akhperjanian, A., Beilicke, M., Bernlöhr, K., Börst, H.-G., Bojahr, H., Bolz, O., Coarasa, T., Contreras, J. L., Cortina, J., 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., Meyer, H., Mirzoyan, R., Moralejo, A., Ona-Wilhelmi, E., Panter, M., Plyasheshnikov, A., Pühlhofer, G., Reyes, R. de los, Rhode, W., Ripken, J., Robrade, 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., Wittek, W., Aharonian, F., Akhperjanian, A., Beilicke, M., Bernlöhr, K., Börst, H.-G., Bojahr, H., Bolz, O., Coarasa, T., Contreras, J. L., Cortina, J., 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., Meyer, H., Mirzoyan, R., Moralejo, A., Ona-Wilhelmi, E., Panter, M., Plyasheshnikov, A., Pühlhofer, G., Reyes, R. de los, Rhode, W., Ripken, J., Robrade, 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.

Abstract

TeV γ-rays from the BL Lac object 1ES 1959+650  have been measured during the years 2000 and 2001 with a significance of 5.2 σat a value of 5.3% of the Crab flux and in May 2002 during strong outbursts with >$23\,\sigma$at a flux level of up to 2.2 Crab, making 1ES 1959+650  the TeV Blazar with the third best event statistics. The deep observation of 197.4 h has been performed with the HEGRA stereoscopic system of 5 imaging atmospheric Cherenkov telescopes (IACT system). 1ES 1959+650  is located at a redshift of $z = 0.047$, providing an intermediate distance between the nearby Blazars Mkn 421 and Mkn 501, and the much more distant object H1426+428. This makes 1ES 1959+650  an important member of the class of TeV Blazars in view of the absorption of TeV photons by the diffuse extragalactic background radiation (DEBRA). The differential energy spectrum of 1ES 1959+650  during the flares can be fitted by a power law with a spectral index of $2.83 \pm 0.14_{\mbox{\tiny stat}} \pm 0.08_{\mbox{\tiny sys}}$or by a power law with an exponential cut-off at $(4.2^{+0.8}_{-0.6~{\mbox{\tiny stat}}} \pm 0.9_{\mbox{\tiny sys}})$TeV and a spectral index of $1.83 \pm 0.15_{\mbox{\tiny stat}} \pm 0.08_{\mbox{\tiny sys}}$. The low state differential energy spectrum obtained with lower statistics can be described by a pure power law with a spectral index of $3.18 \pm 0.17_{\mbox{\tiny stat}} \pm 0.08_{\mbox{\tiny sys}}$.

Published
2003
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