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1. MAGIC upper limits to the VHE gamma-ray flux of 3C 454.3 in high emission state

Author

Anderhub, H., Antonelli, L. A., Antoranz, P., Backes, M., Baixeras, C., Balestra, S., Barrio, J. A., Bartko, H., Bastieri, D., Becerra González, J., Becker, J. K., Bednarek, W., Berger, K., Bernardini, E., Biland, A., Bock, R. K., Bonnoli, G., Bordas, P., Borla Tridon, D., Bosch-Ramon, V., Bretz, T., Britvitch, I., Camara, M., Carmona, E., Commichau, S., Contreras, J. L., Cortina, J., Costado, M. T., Covino, S., Curtef, V., Dazzi, F., De Angelis, A., De Cea del Pozo, E., de los Reyes, R., De Lotto, B., De Maria, M., De Sabata, F., Delgado Mendez, C., Dominguez, A., Dorner, D., Doro, M., Elsaesser, D., Errando, M., Ferenc, D., Fernández, E., Firpo, R., Fonseca, M. V., Font, L., Galante, N., García López, R. J., Garczarczyk, M., Gaug, M., Goebel, F., Hadasch, D., Hayashida, M., Herrero, A., Höhne-Mönch, D., Hose, J., Hsu, C. C., Huber, S., Jogler, T., Kranich, D., La Barbera, A., Laille, A., Leonardo, E., Lindfors, E., Lombardi, S., Longo, F., López, M., Lorenz, E., Majumdar, P., Maneva, G., Mankuzhiyil, N., Mannheim, K., Maraschi, L., Mariotti, M., Martínez, M., Mazin, D., Meucci, M., Meyer, M., Miranda, J. M., Mirzoyan, R., Moldón, J., Moles, M., Moralejo, A., Nieto, D., Nilsson, K., Ninkovic, J., Otte, N., Oya, I., Paoletti, R., Paredes, J. M., Pasanen, M., Pascoli, D., Pauss, F., Pegna, R. G., Perez-Torres, M. A., Persic, M., Peruzzo, L., Prada, F., Prandini, E., Puchades, N., Rhode, W., Ribó, M., Rico, J., Rissi, M., Robert, A., Rügamer, S., Saggion, A., Saito, T. Y., Salvati, M., Sanchez-Conde, M., Sartori, P., Satalecka, K., Scalzotto, V., Scapin, V., Schweizer, T., Shayduk, M., Shinozaki, K., Shore, S. N., Sidro, N., Sierpowska-Bartosik, A., Sillanpää, A., Sitarek, J., Sobczynska, D., Spanier, F., Stamerra, A., Stark, L. S., Takalo, L., Tavecchio, F., Temnikov, P., Tescaro, D., Teshima, M., Tluczykont, M., Torres, D. F., Turini, N., Vankov, H., Venturini, A., Vitale, V., Wagner, R. M., Wittek, W., Zabalza, V., Zandanel, F., Zanin, R., Zapatero, J., Vercellone, S., Donnarumma, I., D'Ammando, F., Tavani, M., Anderhub, H., Antonelli, L. A., Antoranz, P., Backes, M., Baixeras, C., Balestra, S., Barrio, J. A., Bartko, H., Bastieri, D., Becerra González, J., Becker, J. K., Bednarek, W., Berger, K., Bernardini, E., Biland, A., Bock, R. K., Bonnoli, G., Bordas, P., Borla Tridon, D., Bosch-Ramon, V., Bretz, T., Britvitch, I., Camara, M., Carmona, E., Commichau, S., Contreras, J. L., Cortina, J., Costado, M. T., Covino, S., Curtef, V., Dazzi, F., De Angelis, A., De Cea del Pozo, E., de los Reyes, R., De Lotto, B., De Maria, M., De Sabata, F., Delgado Mendez, C., Dominguez, A., Dorner, D., Doro, M., Elsaesser, D., Errando, M., Ferenc, D., Fernández, E., Firpo, R., Fonseca, M. V., Font, L., Galante, N., García López, R. J., Garczarczyk, M., Gaug, M., Goebel, F., Hadasch, D., Hayashida, M., Herrero, A., Höhne-Mönch, D., Hose, J., Hsu, C. C., Huber, S., Jogler, T., Kranich, D., La Barbera, A., Laille, A., Leonardo, E., Lindfors, E., Lombardi, S., Longo, F., López, M., Lorenz, E., Majumdar, P., Maneva, G., Mankuzhiyil, N., Mannheim, K., Maraschi, L., Mariotti, M., Martínez, M., Mazin, D., Meucci, M., Meyer, M., Miranda, J. M., Mirzoyan, R., Moldón, J., Moles, M., Moralejo, A., Nieto, D., Nilsson, K., Ninkovic, J., Otte, N., Oya, I., Paoletti, R., Paredes, J. M., Pasanen, M., Pascoli, D., Pauss, F., Pegna, R. G., Perez-Torres, M. A., Persic, M., Peruzzo, L., Prada, F., Prandini, E., Puchades, N., Rhode, W., Ribó, M., Rico, J., Rissi, M., Robert, A., Rügamer, S., Saggion, A., Saito, T. Y., Salvati, M., Sanchez-Conde, M., Sartori, P., Satalecka, K., Scalzotto, V., Scapin, V., Schweizer, T., Shayduk, M., Shinozaki, K., Shore, S. N., Sidro, N., Sierpowska-Bartosik, A., Sillanpää, A., Sitarek, J., Sobczynska, D., Spanier, F., Stamerra, A., Stark, L. S., Takalo, L., Tavecchio, F., Temnikov, P., Tescaro, D., Teshima, M., Tluczykont, M., Torres, D. F., Turini, N., Vankov, H., Venturini, A., Vitale, V., Wagner, R. M., Wittek, W., Zabalza, V., Zandanel, F., Zanin, R., Zapatero, J., Vercellone, S., Donnarumma, I., D'Ammando, F., and Tavani, M.

Abstract

Aims. We report upper limits to the very high energy flux ($E>100$GeV) of the flat spectrum radio quasar 3C 454.3 ($z=0.859$) derived by the Cherenkov telescope MAGIC during the high states of July/August and November/December 2007. We compare the upper limits derived in both time slots with the available quasi-simultaneous MeV-GeV data from the AGILE γ-ray satellite and interpret the observational results in the context of leptonic emission models.

Published
2009
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2. Are beryllium abundances anomalous in stars with giant planets?*

Author

Santos, N. C., Israelian, G., García López, R. J., Mayor, M., Rebolo, R., Randich, S., Ecuvillon, A., Domínguez Cerdeña, C., Santos, N. C., Israelian, G., García López, R. J., Mayor, M., Rebolo, R., Randich, S., Ecuvillon, A., and Domínguez Cerdeña, C.

Abstract

In this paper we present beryllium (Be) abundances in a large sample of 41 extra-solar planet host stars, and for 29 stars without any known planetary-mass companion, spanning a large range of effective temperatures. The Be abundances were derived through spectral synthesis done in standard Local Thermodynamic Equilibrium, using spectra obtained with various instruments. The results seem to confirm that overall, planet-host stars have “normal” Be abundances, although a small, but not significant, difference might be present. This result is discussed, and we show that this difference is probably not due to any stellar “pollution” events. In other words, our results support the idea that the high-metal content of planet-host stars has, overall, a “primordial” origin. However, we also find a small subset of planet-host late-F and early-G dwarfs that might have higher than average Be abundances. The reason for the offset is not clear, and might be related either to the engulfment of planetary material, to galactic chemical evolution effects, or to stellar-mass differences for stars of similar temperature.

Published
2004
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3. Beryllium anomalies in solar-type field stars*

Author

Santos, N. C., Israelian, G., Randich, S., García López, R. J., Rebolo, R., Santos, N. C., Israelian, G., Randich, S., García López, R. J., and Rebolo, R.

Abstract

We present a study of beryllium (Be) abundances in a large sample of field solar-type dwarfs and sub-giants spanning a large range of effective temperatures. The Be abundances, computed using a very uniform set of stellar parameters and near-UV spectra obtained with 3 different instruments, are used to study the depletion of this light element. The analysis shows that Be is severely depleted for F stars, as expected by the light-element depletion models. However, we also show that beryllium abundances decrease with decreasing temperature for stars cooler than ~6000 K, a result that cannot be explained by current theoretical models including rotational mixing, but that is, at least in part, expected from the models that take into account internal wave physics. In particular, the light element abundances of the coolest and youngest stars in our sample suggest that Be, as well as lithium (Li), has already been burned early during their evolution. Furthermore, we find strong evidence for the existence of a Be-gap for solar-temperature stars. The analysis of Li and Be abundances in the sub-giants of our sample also shows the presence of one case that has still detectable amounts of Li, while Be is severely depleted. Finally, we compare the derived Be abundances with Li abundances derived using the same set of stellar parameters. This gives us the possibility to explore the temperatures for which the onset of Li and Be depletion occurs.

Published
2004
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4. Nitrogen abundances in planet-harbouring stars

Author

Ecuvillon, A., Israelian, G., Santos, N. C., Mayor, M., García López, R. J., Randich, S., Ecuvillon, A., Israelian, G., Santos, N. C., Mayor, M., García López, R. J., and Randich, S.

Abstract

We present a detailed spectroscopic analysis of nitrogen abundances in 91 solar-type stars, 66 with and 25 without known planetary mass companions. All comparison sample stars and 28 planet hosts were analysed by spectral synthesis of the near-UV NH band at 3360 Å observed at high resolution with the VLT/UVES, while the near-IR N i7468 Å was measured in 31 objects. These two abundance indicators are in good agreement. We found that nitrogen abundance scales with that of iron in the metallicity range $-0.6 <$[Fe/H] $<+0.4$with the slope $1.08 \pm 0.05$. Our results show that the bulk of nitrogen production at high metallicities was coupled with iron. We found that the nitrogen abundance distribution in stars with exoplanets is the high [Fe/H] extension of the curve traced by the comparison sample of stars with no known planets. A comparison of our nitrogen abundances with those available in the literature shows a good agreement.

Published
2004
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5. Beryllium abundances in stars hosting giant planets*

Author

Santos, N. C., García López, R. J., Israelian, G., Mayor, M., Rebolo, R., García-Gil, A., Taoro, M. R. Pérez de, Randich, S., Santos, N. C., García López, R. J., Israelian, G., Mayor, M., Rebolo, R., García-Gil, A., Taoro, M. R. Pérez de, and Randich, S.

Abstract

We have derived beryllium abundances in a wide sample of stars hosting planets, with spectral types in the range F7V-K0V, aimed at studying in detail the effects of the presence of planets on the structure and evolution of the associated stars. Predictions from current models are compared with the derived abundances and suggestions are provided to explain the observed inconsistencies. We show that while still not clear, the results suggest that theoretical models may have to be revised for stars with $T_\mathrm{eff}<5500$K. On the other hand, a comparison between planet host and non-planet host stars shows no clear difference between both populations. Although preliminary, this result favors a “primordial” origin for the metallicity “excess” observed for the planetary host stars. Under this assumption, i.e. that there would be no differences between stars with and without giant planets, the light element depletion pattern of our sample of stars may also be used to further investigate and constraint Li and Be depletion mechanisms.

Published
2002
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6. Lithium and Hαin stars and brown dwarfs of σOrionis *

Author

Zapatero Osorio, M. R., Béjar, V. J. S., Pavlenko, Ya., Rebolo, R., Allende Prieto, C., Martín, E. L., García López, R. J., Zapatero Osorio, M. R., Béjar, V. J. S., Pavlenko, Ya., Rebolo, R., Allende Prieto, C., Martín, E. L., and García López, R. J.

Abstract

We present intermediate- and low-resolution optical spectra around Hαand Li iλ6708 Å for a sample of 25 low mass stars and 2 brown dwarfs with confirmed membership in the pre-main sequence stellar σOrionis cluster. Our observations are intended to investigate the age of the cluster. The spectral types derived for our target sample are found to be in the range K6–M8.5, which corresponds to a mass interval of roughly 1.2–0.02 $M_{\odot}$on the basis of state-of-the-art evolutionary models. Radial velocities (except for one object) are found to be consistent with membership in the Orion complex. All cluster members show considerable Hαemission and the Li iresonance doublet in absorption, which is typical of very young ages. We find that our pseudo-equivalent widths of Hαand Li i(measured relative to the observed local pseudo-continuum formed by molecular absorptions) appear rather dispersed (and intense in the case of Hα) for objects cooler than M3.5 spectral class, occurring at the approximate mass where low mass stars are expected to become fully convective. The least massive brown dwarf in our sample, S Ori 45 (M8.5, ~0.02 $M_{\odot}$), displays variable Hαemission and a radial velocity that differs from the cluster mean velocity. Tentative detection of forbidden lines in emission indicates that this brown dwarf may be accreting mass from a surrounding disk. We also present recent computations of Li iλ6708 Å curves of growth for low gravities and for the temperature interval (about 4000–2600 K) of our sample. The comparison of our observations to these computations allows us to infer that no lithium depletion has yet taken place in σOrionis, and that the observed pseudo-equivalent widths are consistent with a cluster initial lithium abundance close to the cosmic value. Hence, the upper limit to the σOrionis cluster age can be set at 8 Myr, with a most likely value around 2–4 Myr.

Published
2002
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7. The effect of stellar activity on the Li I6708, Na I5896 and K I7699 Ålines*

Author

Navascués, D. Barrado y, García López, R. J., Severino, G., Gomez, M. T., Navascués, D. Barrado y, García López, R. J., Severino, G., and Gomez, M. T.

Abstract

An analytical model has been developed to empirically study the effects of stellar spots and faculae on the observed equivalent widths of Li i6708, Na i5896 and K i7699 Ålines (and abundances in the case of lithium) in late-type stars, taking into account the changes in the observed magnitudes and colors. Solar spectra corresponding to different active regions are used as input data and a range of filling factors are applied to simulate the surfaces of stars with different levels of activity. Detailed comparisons between predicted and observed photometric colors and equivalent widths are made for late-type stars of the Pleiades and the field. The observed dispersions in K iand Li iequivalent widths for Pleiades stars can be partially accounted by the simultaneous effects of activity on colors and the line formation, indicating that the lithium-rotation connection suggested for ~$0.7{-}0.9 M_\odot$Pleiades stars could be due in part to the stellar activity. However, under realistic values for the filling factors, only a small portion of the observed spread could be explained by these effects.

Published
2001
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8. Lithium abundances in metal-poor stars*

Author

Gutiérrez, C. M., García López, R. J., Rebolo, R., Martín, E. L., François, P., Gutiérrez, C. M., García López, R. J., Rebolo, R., Martín, E. L., and François, P.

Abstract

We present the lithium measurements of a continuing programme of light element abundances in metal-poor stars. New equivalent widths of the Li i$\lambda 670.8$nm resonance line in 67 metal-poor stars covering the metallicity range -3.5 ≤[Fe/H] ≤-0.4 are reported. For about half of this sample, the observations presented here represent the first measurement of the Li iline. The sample allowed a statistical comparison with previous measurements from other authors and a study of the consistency and reliability of the quoted error bars. This paper shows that for most of the stars these error bars are good estimates of the true uncertainties associated with the determination of the equivalent widths of the Li iline. However, about 20% of the stars with two or more independent measurements show discrepancies in the Li iequivalent widths; in these cases, other sources of uncertainty not properly taken into account (binarity effects, cosmic rays, imperfect flat-field correction, continuum determination, etc.) could also be important. Conclusions on the possible lithium abundance trends versus effective temperature or metallicity and on any intrinsic scatter should be treated cautiously until their robustness vis-à-vis these additional uncertainties is proved.

Published
1999
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9. Fe iline shifts in the optical spectrum of the Sun*

Author

Allende Prieto, C., García López, R. J., Allende Prieto, C., and García López, R. J.

Abstract

New improvements in the measurement of both the optical solar spectrum and laboratory wavelengths for lines of neutral iron are combined to extract central wavelength shifts for 1446 lines observed in the Sun. This provides the largest available database of accurate solar wavelengths useful as a reference for comparison with other solar-type stars. It is shown how the velocity shifts correlate with line strength, approaching a constant value, close to zero, for lines with equivalent widths larger than 200 mÅ.

Published
1998
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11. A catalogue of accurate wavelengths in the optical spectrum of the Sun*

Author

Allende Prieto, C., García López, R. J., Allende Prieto, C., and García López, R. J.

Abstract

We present accurate measurements of the central wavelengths of 4947 atomic absorption lines in the solar optical spectrum. The wavelengths, precise to a level $\sim 50-150$m s-1, are given for both flux and disc-centre spectra, as measured in relatively recent FTS solar atlases. This catalogue modernizes existing sources based on photographic measurements and provides a benchmark to test and perform wavelength calibrations of astronomical spectra. It will also permit observers to improve the absolute wavelength calibration of solar optical spectra when lamps are not available at the telescope.

Published
1998
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12. Chromospheric variability in late-type dwarfs from high-resolution spectra of Caii H

Author

García López, R. J., Rebolo, R., Crivellari, L., and Beckman, J. E.

Abstract

We present an analysis of high-resolution (?/d?˜8×104) high signal-to-noise-ratio spectra of late-type chromospherically active dwarfs in Caii H (?3968.47 Å), obtained with the Coudé Auxiliary Telescope plus the Coudé Echelle Spectrometer at ESO, La Silla. Observational parameters employed are the total emission flux attributable to the chromosphere, the asymmetry of the emission component and its bisector, the ratio of the intensities of the blue and red H2 emission peaks, and the absolute wavelengths of the H3 minimum and the mean emission feature. Given time-spaced sets of spectra for each object, which are as yet relatively sparse, we explore the potential use of these observational parameters to deepen our understanding of the chromospheric activity.

Published
1990
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13. MAGIC Observations and multiwavelength properties of the quasar 3C 279 in 2007 and 2009

Author

Aleksić, J., Antonelli, L. A., Antoranz, P., Backes, M., Barrio, J. A., Bastieri, D., Becerra González, J., Bednarek, W., Berdyugin, A., Berger, K., Bernardini, E., Biland, A., Blanch, O., Bock, R. K., Boller, A., Bonnoli, G., Borla Tridon, D., Braun, I., Bretz, T., Cañellas, A., Carmona, E., Carosi, A., Colin, P., Colombo, E., Contreras, J. L., Cortina, J., Cossio, L., Covino, S., Dazzi, F., De Angelis, A., De Cea del Pozo, E., De Lotto, B., Delgado Mendez, C., Diago Ortega, A., Doert, M., Domínguez, A., Dominis Prester, D., Dorner, D., Doro, M., Elsaesser, D., Ferenc, D., Fonseca, M. V., Font, L., Fruck, C., García López, R. J., Garczarczyk, M., Garrido, D., Giavitto, G., Godinović, N., Hadasch, D., Häfner, D., Herrero, A., Hildebrand, D., Hose, J., Hrupec, D., Huber, B., Jogler, T., Klepser, S., Krähenbühl, T., Krause, J., La Barbera, A., Lelas, D., Leonardo, E., Lindfors, E., Lombardi, S., López, M., Lorenz, E., Majumdar, P., Makariev, M., Maneva, G., Mankuzhiyil, N., Mannheim, K., Maraschi, L., Mariotti, M., Martínez, M., Mazin, D., Meucci, M., Miranda, J. M., Mirzoyan, R., Miyamoto, H., Moldón, J., Moralejo, A., Nieto, D., Nilsson, K., Orito, R., Oya, I., Paoletti, R., Pardo, S., Paredes, J. M., Partini, S., Pasanen, M., Pauss, F., Perez-Torres, M. A., Persic, M., Peruzzo, L., Pilia, M., Pochon, J., Prada, F., Prada Moroni, P. G., Prandini, E., Puljak, I., Reichardt, I., Reinthal, R., Rhode, W., Ribó, M., Rico, J., Rügamer, S., Rüger, M., Saggion, A., Saito, K., Saito, T. Y., Salvati, M., Satalecka, K., Scalzotto, V., Scapin, V., Schultz, C., Schweizer, T., Shayduk, M., Shore, S. N., Sillanpää, A., Sitarek, J., Sobczynska, D., Spanier, F., Spiro, S., Stamerra, A., Steinke, B., Storz, J., Strah, N., Surić, T., Takalo, L., Tavecchio, F., Temnikov, P., Terzić, T., Tescaro, D., Teshima, M., Thom, M., Tibolla, O., Torres, D. F., Treves, A., Vankov, H., Vogler, P., Wagner, R. M., Weitzel, Q., Zabalza, V., Zandanel, F., and Zanin, R.

Abstract

Context.3C 279, the first quasar discovered to emit VHE γ-rays by the MAGIC telescope in 2006, was reobserved by MAGIC in January 2007 during a major optical flare and from December 2008 to April 2009 following an alert from the Fermi space telescope on an exceptionally high γ-ray state.Aims.The January 2007 observations resulted in a detection on January 16 with significance 5.4σ, corresponding to a F(>150 GeV) (3.8 ± 0.8) × 10-11ph cm-2s-1while the overall data sample does not show significant signal. The December 2008–April 2009 observations did not detect the source. We study the multiwavelength behaviour of the source at the epochs of MAGIC observations, collecting quasi-simultaneous data at optical and X-ray frequencies and for 2009 also γ-ray data from Fermi.Methods.We study the light curves and spectral energy distribution of the source. The spectral energy distributions of three observing epochs (including the February 2006, which has been previously published) are modelled with one-zone inverse Compton models and the emission on January 16, 2007 also with two zone model and with a lepto-hadronic model.Results.We find that the VHE γ-ray emission detected in 2006 and 2007 challenges standard one-zone model, based on relativistic electrons in a jet scattering broad line region photons, while the other studied models fit the observed spectral energy distribution more satisfactorily.

Published
2011
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14. Search for an extended VHE γ-ray emission from Mrk 421 and Mrk 501 with the MAGIC Telescope

Author

Aleksić, J., Antonelli, L. A., Antoranz, P., Backes, M., Baixeras, C., Barrio, J. A., Bastieri, D., Becerra González, J., Bednarek, W., Berdyugin, A., Berger, K., Bernardini, E., Biland, A., Blanch, O., Bock, R. K., Bonnoli, G., Bordas, P., Borla Tridon, D., Bosch-Ramon, V., Bose, D., Braun, I., Bretz, T., Britzger, D., Camara, M., Carmona, E., Carosi, A., Colin, P., Commichau, S., Contreras, J. L., Cortina, J., Costado, M. T., Covino, S., Dazzi, F., De Angelis, A., De Cea del Pozo, E., De los Reyes, R., De Lotto, B., De Maria, M., De Sabata, F., Delgado Mendez, C., Doert, M., Domínguez, A., Dominis Prester, D., Dorner, D., Doro, M., Elsaesser, D., Errando, M., Ferenc, D., Fonseca, M. V., Font, L., García López, R. J., Garczarczyk, M., Gaug, M., Godinovic, N., Hadasch, D., Herrero, A., Hildebrand, D., Höhne-Mönch, D., Hose, J., Hrupec, D., Hsu, C. C., Jogler, T., Klepser, S., Krähenbühl, T., Kranich, D., La Barbera, A., Laille, A., Leonardo, E., Lindfors, E., Lombardi, S., Longo, F., López, M., Lorenz, E., Majumdar, P., Maneva, G., Mankuzhiyil, N., Mannheim, K., Maraschi, L., Mariotti, M., Martínez, M., Mazin, D., Meucci, M., Miranda, J. M., Mirzoyan, R., Miyamoto, H., Moldón, J., Moles, M., Moralejo, A., Nieto, D., Nilsson, K., Ninkovic, J., Orito, R., Oya, I., Paiano, S., Paoletti, R., Paredes, J. M., Partini, S., Pasanen, M., Pascoli, D., Pauss, F., Pegna, R. G., Perez-Torres, M. A., Persic, M., Peruzzo, L., Prada, F., Prandini, E., Puchades, N., Puljak, I., Reichardt, I., Rhode, W., Ribó, M., Rico, J., Rissi, M., Rügamer, S., Saggion, A., Saito, T. Y., Salvati, M., Sánchez-Conde, M., Satalecka, K., Scalzotto, V., Scapin, V., Schultz, C., Schweizer, T., Shayduk, M., Shore, S. N., Sierpowska-Bartosik, A., Sillanpää, A., Sitarek, J., Sobczynska, D., Spanier, F., Spiro, S., Stamerra, A., Steinke, B., Struebig, J. C., Suric, T., Takalo, L., Tavecchio, F., Temnikov, P., Terzic, T., Tescaro, D., Teshima, M., Torres, D. F., Vankov, H., Wagner, R. M., Weitzel, Q., Zabalza, V., Zandanel, F., Zanin, R., Neronov, A., and Semikoz, D. V.

Abstract

Context.Part of the very high energy γ-ray radiation coming from extragalactic sources is absorbed through the pair production process on the extragalactic background light photons. Extragalactic magnetic fields alter the trajectories of these cascade pairs and, in turn, convert cosmic background photons to γ-ray energies by inverse Compton scattering. These secondary photons can form an extended halo around bright VHE sources.

Published
2010
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15. MAGIC TeV gamma-ray observations of Markarian 421 during multiwavelength campaigns in 2006

Author

Aleksić, J., Anderhub, H., Antonelli, L. A., Antoranz, P., Backes, M., Baixeras, C., Balestra, S., Barrio, J. A., Bastieri, D., Becerra González, J., Becker, J. K., Bednarek, W., Berdyugin, A., Berger, K., Bernardini, E., Biland, A., Bock, R. K., Bonnoli, G., Bordas, P., Borla Tridon, D., Bosch-Ramon, V., Bose, D., Braun, I., Bretz, T., Britzger, D., Camara, M., Carmona, E., Carosi, A., Colin, P., Commichau, S., Contreras, J. L., Cortina, J., Costado, M. T., Covino, S., Dazzi, F., De Angelis, A., de Cea del Pozo, E., De los Reyes, R., De Lotto, B., De Maria, M., De Sabata, F., Delgado Mendez, C., Doert, M., Domínguez, A., Dominis Prester, D., Dorner, D., Doro, M., Elsaesser, D., Errando, M., Ferenc, D., Fonseca, M. V., Font, L., García López, R. J., Garczarczyk, M., Gaug, M., Godinovic, N., Hadasch, D., Herrero, A., Hildebrand, D., Höhne-Mönch, D., Hose, J., Hrupec, D., Hsu, C. C., Jogler, T., Klepser, S., Krähenbühl, T., Kranich, D., La Barbera, A., Laille, A., Leonardo, E., Lindfors, E., Lombardi, S., Longo, F., López, M., Lorenz, E., Majumdar, P., Maneva, G., Mankuzhiyil, N., Mannheim, K., Maraschi, L., Mariotti, M., Martínez, M., Mazin, D., Meucci, M., Miranda, J. M., Mirzoyan, R., Miyamoto, H., Moldón, J., Moles, M., Moralejo, A., Nieto, D., Nilsson, K., Ninkovic, J., Orito, R., Oya, I., Paoletti, R., Paredes, J. M., Partini, S., Pasanen, M., Pascoli, D., Pauss, F., Pegna, R. G., Perez-Torres, M. A., Persic, M., Peruzzo, L., Prada, F., Prandini, E., Puchades, N., Puljak, I., Reichardt, I., Rhode, W., Ribó, M., Rico, J., Rissi, M., Rügamer, S., Saggion, A., Saito, T. Y., Salvati, M., Sánchez-Conde, M., Satalecka, K., Scalzotto, V., Scapin, V., Schweizer, T., Shayduk, M., Shore, S. N., Sierpowska-Bartosik, A., Sillanpää, A., Sitarek, J., Sobczynska, D., Spanier, F., Spiro, S., Stamerra, A., Steinke, B., Strah, N., Struebig, J. C., Suric, T., Takalo, L., Tavecchio, F., Temnikov, P., Tescaro, D., Teshima, M., Torres, D. F., Vankov, H., Wagner, R. M., Zabalza, V., Zandanel, F., and Zanin, R.

Abstract

Context. Wide-range spectral coverage of blazar-type active galactic nuclei is of paramount importance for understanding the particle acceleration mechanisms assumed to take place in their jets. The Major Atmospheric Gamma Imaging Cerenkov (MAGIC) telescope participated in three multiwavelength (MWL) campaigns, observing the blazar Markarian (Mkn) 421 during the nights of April 28 and 29, 2006, and June 14, 2006.Aims. We analyzed the corresponding MAGIC very-high energy observations during 9 nights from April 22 to 30, 2006 and on June 14, 2006. We inferred light curves with sub-day resolution and night-by-night energy spectra.Methods. MAGIC detects γ-rays by observing extended air showers in the atmosphere. The obtained air-shower images were analyzed using the standard MAGIC analysis chain.Results. A strong γ-ray signal was detected from Mkn 421 on all observation nights. The flux (E>250 GeV) varied on night-by-night basis between (0.92±0.11) × 10-10cm-2s-1(0.57 Crab units) and (3.21±0.15) × 10-10cm-2s-1(2.0 Crab units) in April 2006. There is a clear indication for intra-night variability with a doubling time of 36±$10_{\rm stat}$min on the night of April 29, 2006, establishing once more rapid flux variability for this object. For all individual nights γ-ray spectra could be inferred, with power-law indices ranging from 1.66 to 2.47. We did not find statistically significant correlations between the spectral index and the flux state for individual nights. During the June 2006 campaign, a flux substantially lower than the one measured by the Whipple 10-m telescope four days later was found. Using a log-parabolic power law fit we deduced for some data sets the location of the spectral peak in the very-high energy regime. Our results confirm the indications of rising peak energy with increasing flux, as expected in leptonic acceleration models.

Published
2010

16. MAGIC TeV gamma-ray observations of Markarian 421 during multiwavelength campaigns in 2006

Author

Aleksić, J., Anderhub, H., Antonelli, L. A., Antoranz, P., Backes, M., Baixeras, C., Balestra, S., Barrio, J. A., Bastieri, D., Becerra González, J., Becker, J. K., Bednarek, W., Berdyugin, A., Berger, K., Bernardini, E., Biland, A., Bock, R. K., Bonnoli, G., Bordas, P., Borla Tridon, D., Bosch-Ramon, V., Bose, D., Braun, I., Bretz, T., Britzger, D., Camara, M., Carmona, E., Carosi, A., Colin, P., Commichau, S., Contreras, J. L., Cortina, J., Costado, M. T., Covino, S., Dazzi, F., De Angelis, A., de Cea del Pozo, E., De los Reyes, R., De Lotto, B., De Maria, M., De Sabata, F., Delgado Mendez, C., Doert, M., Domínguez, A., Dominis Prester, D., Dorner, D., Doro, M., Elsaesser, D., Errando, M., Ferenc, D., Fonseca, M. V., Font, L., García López, R. J., Garczarczyk, M., Gaug, M., Godinovic, N., Hadasch, D., Herrero, A., Hildebrand, D., Höhne-Mönch, D., Hose, J., Hrupec, D., Hsu, C. C., Jogler, T., Klepser, S., Krähenbühl, T., Kranich, D., La Barbera, A., Laille, A., Leonardo, E., Lindfors, E., Lombardi, S., Longo, F., López, M., Lorenz, E., Majumdar, P., Maneva, G., Mankuzhiyil, N., Mannheim, K., Maraschi, L., Mariotti, M., Martínez, M., Mazin, D., Meucci, M., Miranda, J. M., Mirzoyan, R., Miyamoto, H., Moldón, J., Moles, M., Moralejo, A., Nieto, D., Nilsson, K., Ninkovic, J., Orito, R., Oya, I., Paoletti, R., Paredes, J. M., Partini, S., Pasanen, M., Pascoli, D., Pauss, F., Pegna, R. G., Perez-Torres, M. A., Persic, M., Peruzzo, L., Prada, F., Prandini, E., Puchades, N., Puljak, I., Reichardt, I., Rhode, W., Ribó, M., Rico, J., Rissi, M., Rügamer, S., Saggion, A., Saito, T. Y., Salvati, M., Sánchez-Conde, M., Satalecka, K., Scalzotto, V., Scapin, V., Schweizer, T., Shayduk, M., Shore, S. N., Sierpowska-Bartosik, A., Sillanpää, A., Sitarek, J., Sobczynska, D., Spanier, F., Spiro, S., Stamerra, A., Steinke, B., Strah, N., Struebig, J. C., Suric, T., Takalo, L., Tavecchio, F., Temnikov, P., Tescaro, D., Teshima, M., Torres, D. F., Vankov, H., Wagner, R. M., Zabalza, V., Zandanel, F., and Zanin, R.

Abstract

Context. Wide-range spectral coverage of blazar-type active galactic nuclei is of paramount importance for understanding the particle acceleration mechanisms assumed to take place in their jets. The Major Atmospheric Gamma Imaging Cerenkov (MAGIC) telescope participated in three multiwavelength (MWL) campaigns, observing the blazar Markarian (Mkn) 421 during the nights of April 28 and 29, 2006, and June 14, 2006.

Published
2010
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17. MAGIC observation of the GRB 080430 afterglow

Author

Aleksić, J., Anderhub, H., Antonelli, L. A., Antoranz, P., Backes, M., Baixeras, C., Balestra, S., Barrio, J. A., Bastieri, D., Becerra González, J., Becker, J. K., Bednarek, W., Berdyugin, A., Berger, K., Bernardini, E., Biland, A., Bock, R. K., Bonnoli, G., Bordas, P., Borla Tridon, D., Bosch-Ramon, V., Bose, D., Braun, I., Bretz, T., Britzger, D., Camara, M., Carmona, E., Carosi, A., Colin, P., Commichau, S., Contreras, J. L., Cortina, J., Costado, M. T., Covino, S., Dazzi, F., De Angelis, A., de Cea del Pozo, E., De los Reyes, R., De Lotto, B., De Maria, M., De Sabata, F., Delgado Mendez, C., Doert, M., Domínguez, A., Dominis Prester, D., Dorner, D., Doro, M., Elsaesser, D., Errando, M., Ferenc, D., Fernández, E., Firpo, R., Fonseca, M. V., Font, L., Galante, N., García López, R. J., Garczarczyk, M., Gaug, M., Godinovic, N., Goebel, F., Hadasch, D., Herrero, A., Hildebrand, D., Höhne-Mönch, D., Hose, J., Hrupec, D., Hsu, C. C., Jogler, T., Klepser, S., Krähenbühl, T., Kranich, D., La Barbera, A., Laille, A., Leonardo, E., Lindfors, E., Lombardi, S., Longo, F., López, M., Lorenz, E., Majumdar, P., Maneva, G., Mankuzhiyil, N., Mannheim, K., Maraschi, L., Mariotti, M., Martínez, M., Mazin, D., Meucci, M., Miranda, J. M., Mirzoyan, R., Miyamoto, H., Moldón, J., Moles, M., Moralejo, A., Nieto, D., Nilsson, K., Ninkovic, J., Orito, R., Oya, I., Paoletti, R., Paredes, J. M., Pasanen, M., Pascoli, D., Pauss, F., Pegna, R. G., Perez-Torres, M. A., Persic, M., Peruzzo, L., Prada, F., Prandini, E., Puchades, N., Puljak, I., Reichardt, I., Rhode, W., Ribó, M., Rico, J., Rissi, M., Rügamer, S., Saggion, A., Saito, T. Y., Salvati, M., Sánchez-Conde, M., Satalecka, K., Scalzotto, V., Scapin, V., Schweizer, T., Shayduk, M., Shore, S. N., Sierpowska-Bartosik, A., Sillanpää, A., Sitarek, J., Sobczynska, D., Spanier, F., Spiro, S., Stamerra, A., Steinke, B., Strah, N., Struebig, J. C., Suric, T., Takalo, L., Tavecchio, F., Temnikov, P., Tescaro, D., Teshima, M., Torres, D. F., Turini, N., Vankov, H., Wagner, R. M., Zabalza, V., Zandanel, F., Zanin, R., Zapatero, J., and de Ugarte-Postigo, A.

Abstract

Context. Gamma-ray bursts are cosmological sources emitting radiation from the gamma-rays to the radio band. Substantial observational efforts have been devoted to the study of gamma-ray bursts during the prompt phase, i.e. the initial burst of high-energy radiation, and during the long-lasting afterglows. In spite of many successes in interpreting these phenomena, there are still several open key questions about the fundamental emission processes, their energetics and the environment.Aims. Independently of specific gamma-ray burst theoretical recipes, spectra in the GeV/TeV range are predicted to be remarkably simple, being satisfactorily modeled with power-laws, and therefore offer a very valuable tool to probe the extragalactic background light distribution. Furthermore, the simple detection of a component at very-high energies, i.e. at ~100 GeV, would solve the ambiguity about the importance of various possible emission processes, which provide barely distinguishable scenarios at lower energies.Methods. We used the results of the MAGIC telescope observation of the moderate resdhift (z~ 0.76) GRB 080430 at energies above about 80 GeV, to evaluate the perspective for late-afterglow observations with ground based GeV/TeV telescopes.Results. We obtained an upper limit of F95% CL= 5.5 × 10-11erg cm-2s-1for the very-high energy emission of GRB 080430, which cannot set further constraints on the theoretical scenarios proposed for this object also due to the difficulties in modeling the low-energy afterglow. Nonetheless, our observations show that Cherenkov telescopes have already reached the required sensitivity to detect the GeV/TeV emission of GRBs at moderate redshift (z≲ 0.8), provided the observations are carried out at early times, close to the onset of their afterglow phase.

Published
2010

18. MAGIC observation of the GRB 080430 afterglow

Author

Aleksić, J., Anderhub, H., Antonelli, L. A., Antoranz, P., Backes, M., Baixeras, C., Balestra, S., Barrio, J. A., Bastieri, D., Becerra González, J., Becker, J. K., Bednarek, W., Berdyugin, A., Berger, K., Bernardini, E., Biland, A., Bock, R. K., Bonnoli, G., Bordas, P., Borla Tridon, D., Bosch-Ramon, V., Bose, D., Braun, I., Bretz, T., Britzger, D., Camara, M., Carmona, E., Carosi, A., Colin, P., Commichau, S., Contreras, J. L., Cortina, J., Costado, M. T., Covino, S., Dazzi, F., De Angelis, A., de Cea del Pozo, E., De los Reyes, R., De Lotto, B., De Maria, M., De Sabata, F., Delgado Mendez, C., Doert, M., Domínguez, A., Dominis Prester, D., Dorner, D., Doro, M., Elsaesser, D., Errando, M., Ferenc, D., Fernández, E., Firpo, R., Fonseca, M. V., Font, L., Galante, N., García López, R. J., Garczarczyk, M., Gaug, M., Godinovic, N., Goebel, F., Hadasch, D., Herrero, A., Hildebrand, D., Höhne-Mönch, D., Hose, J., Hrupec, D., Hsu, C. C., Jogler, T., Klepser, S., Krähenbühl, T., Kranich, D., La Barbera, A., Laille, A., Leonardo, E., Lindfors, E., Lombardi, S., Longo, F., López, M., Lorenz, E., Majumdar, P., Maneva, G., Mankuzhiyil, N., Mannheim, K., Maraschi, L., Mariotti, M., Martínez, M., Mazin, D., Meucci, M., Miranda, J. M., Mirzoyan, R., Miyamoto, H., Moldón, J., Moles, M., Moralejo, A., Nieto, D., Nilsson, K., Ninkovic, J., Orito, R., Oya, I., Paoletti, R., Paredes, J. M., Pasanen, M., Pascoli, D., Pauss, F., Pegna, R. G., Perez-Torres, M. A., Persic, M., Peruzzo, L., Prada, F., Prandini, E., Puchades, N., Puljak, I., Reichardt, I., Rhode, W., Ribó, M., Rico, J., Rissi, M., Rügamer, S., Saggion, A., Saito, T. Y., Salvati, M., Sánchez-Conde, M., Satalecka, K., Scalzotto, V., Scapin, V., Schweizer, T., Shayduk, M., Shore, S. N., Sierpowska-Bartosik, A., Sillanpää, A., Sitarek, J., Sobczynska, D., Spanier, F., Spiro, S., Stamerra, A., Steinke, B., Strah, N., Struebig, J. C., Suric, T., Takalo, L., Tavecchio, F., Temnikov, P., Tescaro, D., Teshima, M., Torres, D. F., Turini, N., Vankov, H., Wagner, R. M., Zabalza, V., Zandanel, F., Zanin, R., Zapatero, J., and de Ugarte-Postigo, A.

Abstract

Context. Gamma-ray bursts are cosmological sources emitting radiation from the gamma-rays to the radio band. Substantial observational efforts have been devoted to the study of gamma-ray bursts during the prompt phase, i.e. the initial burst of high-energy radiation, and during the long-lasting afterglows. In spite of many successes in interpreting these phenomena, there are still several open key questions about the fundamental emission processes, their energetics and the environment.

Published
2010
Full Text
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19. Simultaneous multi-frequency observation of the unknown redshift blazar PG 1553+113 in March-April 2008

Author

Aleksić, J., Anderhub, H., Antonelli, L. A., Antoranz, P., Backes, M., Baixeras, C., Balestra, S., Barrio, J. A., Bastieri, D., Becerra González, J., Becker, J. K., Bednarek, W., Berdyugin, A., Berger, K., Bernardini, E., Biland, A., Bock, R. K., Bonnoli, G., Bordas, P., Borla Tridon, D., Bosch-Ramon, V., Bose, D., Braun, I., Bretz, T., Britzger, D., Camara, M., Carmona, E., Carosi, A., Colin, P., Commichau, S., Contreras, J. L., Cortina, J., Costado, M. T., Covino, S., Dazzi, F., De Angelis, A., de Cea del Pozo, E., De los Reyes, R., De Lotto, B., De Maria, M., De Sabata, F., Delgado Mendez, C., Domínguez, A., Dominis Prester, D., Dorner, D., Doro, M., Elsaesser, D., Errando, M., Ferenc, D., Fernández, E., Firpo, R., Fonseca, M. V., Font, L., Galante, N., García López, R. J., Garczarczyk, M., Gaug, M., Godinovic, N., Goebel, F., Hadasch, D., Herrero, A., Hildebrand, D., Höhne-Mönch, D., Hose, J., Hrupec, D., Hsu, C. C., Jogler, T., Klepser, S., Krähenbühl, T., Kranich, D., La Barbera, A., Laille, A., Leonardo, E., Lindfors, E., Lombardi, S., Longo, F., López, M., Lorenz, E., Majumdar, P., Maneva, G., Mankuzhiyil, N., Mannheim, K., Maraschi, L., Mariotti, M., Martínez, M., Mazin, D., Meucci, M., Miranda, J. M., Mirzoyan, R., Miyamoto, H., Moldón, J., Moles, M., Moralejo, A., Nieto, D., Nilsson, K., Ninkovic, J., Orito, R., Oya, I., Paoletti, R., Paredes, J. M., Pasanen, M., Pascoli, D., Pauss, F., Pegna, R. G., Perez-Torres, M. A., Persic, M., Peruzzo, L., Prada, F., Prandini, E., Puchades, N., Puljak, I., Reichardt, I., Rhode, W., Ribó, M., Rico, J., Rissi, M., Rügamer, S., Saggion, A., Saito, T. Y., Salvati, M., Sánchez-Conde, M., Satalecka, K., Scalzotto, V., Scapin, V., Schweizer, T., Shayduk, M., Shore, S. N., Sierpowska-Bartosik, A., Sillanpää, A., Sitarek, J., Sobczynska, D., Spanier, F., Spiro, S., Stamerra, A., Steinke, B., Strah, N., Struebig, J. C., Suric, T., Takalo, L., Tavecchio, F., Temnikov, P., Tescaro, D., Teshima, M., Torres, D. F., Turini, N., Vankov, H., Wagner, R. M., Zabalza, V., Zandanel, F., Zanin, R., Zapatero, J., Pian, E., Bianchin, V., D'Ammando, F., Di Cocco, G., Fugazza, D., Ghisellini, G., Kurtanidze, O. M., Raiteri, C. M., Tosti, G., Treves, A., Vercellone, S., and Villata, M.

Abstract

The blazar PG 1553+113 is a well known TeV γ-ray emitter. In this paper we determine its spectral energy distribution through simultaneous multi-frequency data to study its emission processes. An extensive campaign was carried out between March and April 2008, where optical, X-ray, high-energy (HE) γ-ray, and very-high-energy (VHE) γ-ray data were obtained with the KVA, Abastumani, REM, RossiXTE/ASM, AGILE and MAGIC telescopes, respectively. We combine the data to derive the source's spectral energy distribution and interpret its double-peaked shape within the framework of a synchrotron self-Compton model.

Published
2010

20. Simultaneous multi-frequency observation of the unknown redshift blazar PG 1553+113 in March-April 2008

Author

Aleksić, J., Anderhub, H., Antonelli, L. A., Antoranz, P., Backes, M., Baixeras, C., Balestra, S., Barrio, J. A., Bastieri, D., Becerra González, J., Becker, J. K., Bednarek, W., Berdyugin, A., Berger, K., Bernardini, E., Biland, A., Bock, R. K., Bonnoli, G., Bordas, P., Borla Tridon, D., Bosch-Ramon, V., Bose, D., Braun, I., Bretz, T., Britzger, D., Camara, M., Carmona, E., Carosi, A., Colin, P., Commichau, S., Contreras, J. L., Cortina, J., Costado, M. T., Covino, S., Dazzi, F., De Angelis, A., de Cea del Pozo, E., De los Reyes, R., De Lotto, B., De Maria, M., De Sabata, F., Delgado Mendez, C., Domínguez, A., Dominis Prester, D., Dorner, D., Doro, M., Elsaesser, D., Errando, M., Ferenc, D., Fernández, E., Firpo, R., Fonseca, M. V., Font, L., Galante, N., García López, R. J., Garczarczyk, M., Gaug, M., Godinovic, N., Goebel, F., Hadasch, D., Herrero, A., Hildebrand, D., Höhne-Mönch, D., Hose, J., Hrupec, D., Hsu, C. C., Jogler, T., Klepser, S., Krähenbühl, T., Kranich, D., La Barbera, A., Laille, A., Leonardo, E., Lindfors, E., Lombardi, S., Longo, F., López, M., Lorenz, E., Majumdar, P., Maneva, G., Mankuzhiyil, N., Mannheim, K., Maraschi, L., Mariotti, M., Martínez, M., Mazin, D., Meucci, M., Miranda, J. M., Mirzoyan, R., Miyamoto, H., Moldón, J., Moles, M., Moralejo, A., Nieto, D., Nilsson, K., Ninkovic, J., Orito, R., Oya, I., Paoletti, R., Paredes, J. M., Pasanen, M., Pascoli, D., Pauss, F., Pegna, R. G., Perez-Torres, M. A., Persic, M., Peruzzo, L., Prada, F., Prandini, E., Puchades, N., Puljak, I., Reichardt, I., Rhode, W., Ribó, M., Rico, J., Rissi, M., Rügamer, S., Saggion, A., Saito, T. Y., Salvati, M., Sánchez-Conde, M., Satalecka, K., Scalzotto, V., Scapin, V., Schweizer, T., Shayduk, M., Shore, S. N., Sierpowska-Bartosik, A., Sillanpää, A., Sitarek, J., Sobczynska, D., Spanier, F., Spiro, S., Stamerra, A., Steinke, B., Strah, N., Struebig, J. C., Suric, T., Takalo, L., Tavecchio, F., Temnikov, P., Tescaro, D., Teshima, M., Torres, D. F., Turini, N., Vankov, H., Wagner, R. M., Zabalza, V., Zandanel, F., Zanin, R., Zapatero, J., Pian, E., Bianchin, V., D'Ammando, F., Di Cocco, G., Fugazza, D., Ghisellini, G., Kurtanidze, O. M., Raiteri, C. M., Tosti, G., Treves, A., Vercellone, S., and Villata, M.

Abstract

The blazar PG 1553+113 is a well known TeV γ-ray emitter. In this paper we determine its spectral energy distribution through simultaneous multi-frequency data to study its emission processes. An extensive campaign was carried out between March and April 2008, where optical, X-ray, high-energy (HE) γ-ray, and very-high-energy (VHE) γ-ray data were obtained with the KVA, Abastumani, REM, RossiXTE/ASM, AGILE and MAGIC telescopes, respectively. We combine the data to derive the source's spectral energy distribution and interpret its double-peaked shape within the framework of a synchrotron self-Compton model.

Published
2010
Full Text
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