The GeV to TeV view of SNR IC443: predictions for Fermi

We present a theoretical model that explains the high energy phenomenology of the neighborhood of SNR IC 443, as observed with the Major Atmospheric Gamma Imaging Cherenkov (MAGIC) telescope and the Energetic Gamma-Ray Experiment Telescope (EGRET). We also discuss how the model can be tested with observations by the Fermi Gamma-ray Large Area Space Telescope. We interpret MAGIC J0616+225 as delayed TeV emission of cosmic-rays diffusing from IC 443 and interacting with a known cloud located at a distance of about 20 pc in the foreground of the remnant. This scenario naturally explains the displacement between EGRET and MAGIC sources, their fluxes, and their spectra. Finally, we predict how this context can be observed by Fermi.Comment: To appear in the Proceedings of the 6th Workshop on Science with the New Generation of High Energy Gamma-Ray Experiments (SciNeGHE '08), held in Padova October 200

Simultaneous multi-frequency observation of the unknown redshift blazar PG1553+113 in March-April 2008

5 páginas, 2 figuras, 3 tablas.-- El Pdf del artículo es la versión pre-print: arXiv: arXiv:0911.1088.-- MAGIC Collaboration: et al.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.Major support from Germany’s Bundesministerium f¨ur Bildung, Wissenschaft, Forschung und Technologie and Max-Planck-Gesellschaft, Italy’s Istituto Nazionale di Fisica Nucleare (INFN) and Istituto Nazionale di Astrofisica (INAF), and Spain’s Ministerio de Ciencia e Innovacion is gratefully acknowledged. The work was also supported by Switzerland’s ETH Research grant TH34/043, Poland’s Ministertwo Nauki i Szkolnictwa Wy˙zszego grant N N203 390834, and Germany’s Young Investigator Program of the Helmholtz Gemeinschaft. This work was also supported by Georgian National Science Foundation grant GNSF/ST07/4-180. EP acknowledges support from the Italian Space Agency through grants ASI-INAF I/023/05/0 and ASI I/088/06/0.Peer reviewe

MAGIC observation of the GRB 080430 afterglow

6 páginas, 1 figura.-- El Pdf del artículo es la versión pre-print: arXiv:1004.3665v2.-- MAGIC Collaboration: et al.[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 × 10-11 erg cm-2 s-1 for 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.The support of the German BMBF and MPG, the Italian INFN and Spanish MICINN is gratefully acknowledged. This work was also supported by ETH Research Grant TH 34/043, by the Polish MNiSzW Grant N N203 390834, and by the YIP of the Helmholtz Gemeinschaft.Peer reviewe

The GeV to TeV connection in the environment of SNR IC 443

We have recently interpreted the source MAGIC J0616+225 as a result of delayed TeV emission of cosmic-rays diffusing from IC 443 and interacting with a cloud in the foreground of the remnant. This model was used to make predictions for future observations, especially those to be made with the Fermi satellite. Just recently, AGILE, Fermi, and VERITAS have released new results of their observations of IC 443. In this work, we compare them with the predictions of our model, exploring the GeV to TeV connection in this region of space. We use Fermi data to consider the possibility of constraining the cosmic-ray diffusion features of the environment. We analyze the cosmic-ray distributions, their interactions, and a possible detection of the SNR environment in the neutrino channel.Comment: Accepted for publication in MNRAS. 20 pages, 10 figures, 1 tabl

Multi-messenger model for the starburst galaxy M82

In this paper, a consistent model of the multifrequency emission of the starburst galaxy M82, from radio to gamma-rays is presented and discussed. Predictions for observations with Fermi, MAGIC II/VERITAS and CTA telescopes are made. The model is also used to self-consistenty compute the (all flavors) emission of neutrinos resulting from this starburst galaxy, what can be used in considerations of the diffuse contributions of such objects.Comment: Accepted for publication in The Astrophysical Journa

MAGIC J0616+225 as delayed TeV emission of cosmic-rays diffusing from SNR IC 443

We present a theoretical model that explains the high energy phenomenology of the neighborhood of SNR IC 443, as observed with the Major Atmospheric Gamma Imaging Cherenkov (MAGIC) telescope and the Energetic Gamma-Ray Experiment Telescope (EGRET). We interpret MAGIC J0616+225 as delayed TeV emission of cosmic-rays diffusing from IC 443 and interacting with a known cloud located at a distance of about 20 pc in the foreground of the remnant. This scenario naturally explains the displacement between EGRET and MAGIC sources, their fluxes, and their spectra. We compare this model with others recently presented, and discuss how it can be tested with observations by the Gamma-ray Large Area Telescope (GLAST).Comment: Accepted for publication in MNRAS Letter

Some observational and theoretical aspects of cosmic-ray diffusion

La Tesis contiene ciertos estudios relacionados con la difusión de rayos cósmicos. Está dividida en dos partes, una describe los modelos sobre la fenomenología de difusión de rayos cósmicos, y otra presenta las observaciones realizadas usando el experimento MAGIC y simulaciones del futuro Array de Telescopios Cherenkov (CTA, por sus siglas en inglés). En la primera parte, se introduce la teoría general más aceptada sobre la difusión de rayos cósmicos. Se cree que los remanentes de supernova (SNR) son uno de los escenarios más probables de aceleración de rayos cósmicos, tanto en procesos leptónicos como hadrónicos. El mecanismo de aceleración de partículas en cada SNR se asume que es aceleración por choque difuso (diffusive shock acceleration). Para obtener confirmación observacional de la aceleración de protones y otros núcleos, y distinguirlos de la emisión leptónica, se deben aislar los efectos de los múltiples mensajeros producidos por partículas secundarias. Partiendo de ahí, se desarrolla un modelo sobre los alrededores del SNR IC443 que explica la fenomenología de alta energía: los rayos cósmicos escapan del remanente, los más energéticos alcanzan antes la nube molecular situada delante de la misma y los menos energéticos aún permanecen confinados a los restos del SNR. Los resultados contrastados con las últimas observaciones obtenidas de la fuente explican su aparente desplazamiento cuando se observa a alta y a muy alta energía. También se presenta un modelo multi-frecuencia y multi-mensajero (fotones de todo el espectro electromagnético y neutrinos) de la emisión difusa de la galaxia con un estallido de formación estelar M82. Las predicciones para rayos gamma se comparan con (y explican satisfactoriamente) las posteriores detecciones en el rango energético comprendido entre los giga- y los tera-electronvoltios de las galaxias M82 y NGC 253, realizadas por el satélite Fermi y los experimentos en tierra H.E.S.S. y VERITAS. En la segunda parte de la Tesis, se describe la técnica de detección de rayos gamma desde tierra a través de la radiación Cherenkov. Esta técnica es explotada, entre otros, por el experimento MAGIC. Algunas de las observaciones realizadas por la estudiante con este telescopio se presentan como parte de esta Tesis. En primer lugar, se muestran los límites superiores (upper limits) al flujo de rayos gamma obtenidos con MAGIC-I sobre dos fuentes detectadas por el experimento Milagro y que se corresponden con dos fuentes brillantes del satélite Fermi en la región del SNR G65.1+0.6. Se cree que puedan tratarse de dos púlsares que inyectan energía y partículas en la nebulosa pulsada que las rodea. También se presentan resultados preliminares de observaciones en estéreo (con los dos telescopios MAGIC) del SNR IC443. El número de horas obtenido resulta insuficiente para completar el estudio morfológico dependiente de la energía para el que se enfocaba la obtención de estos datos, pero nuevas observaciones están previstas para el futuro. Finalmente, se introducen por primera vez algunas simulaciones realizadas con el futuro CTA y ciertos estudios espectrales sobre particulares casos científicos. En concreto, dichos estudios se centraron en los objetos ya discutidos en el resto de la Tesis, como el SNR IC443, las galaxias con estallido de formación estelar M82 y NGC 253, y nubes moleculares iluminadas por rayos cósmicos escapados de SNRs cercanos. El observatorio CTA representa el futuro de las observaciones de rayos gamma desde tierra, y prevé que se unan las colaboraciones de todas las instalaciones de telescopios actuales. El rango de energías se verá ampliado, la sensibilidad aumentará un orden de magnitud y la resolución angular se mejorará respecto a los experimentos existentes hoy en día. Esta Tesis representa, pues, sólo el principio de lo que queda por venir.This Thesis deals with certain aspects on cosmic-ray diffusion. It is divided in two parts, one describes phenomenological models of cosmic-ray diffusion, and the other presents observations taken with the MAGIC experiments and simulations of the future Cherenkov Telescope Array (CTA). In the first part, the generally accepted theory for cosmic-ray diffusion is introduced. Supernova remnants (SNRs) are believed to be the more likely scenarios of cosmic-ray acceleration, considering both hadronic and leptonic processes. The mechanism for particle acceleration in each SNR is assumed to be diffusive shock acceleration (DSA). To obtain the observational confirmation of proton and nuclei acceleration, and distinguish it from leptonic emission, the effects of multiple messengers produced by secondary particles must be isolated. Following this, a model for the neighborhood of the SNR IC443 is developed, explaining the high energy phenomenology: cosmic rays escape from the remnant, the most energetic ones reach first the molecular cloud located in front of it and the least energetic ones still remain confined on the shell of the SNR. The results are confronted with the latest observations that are obtained from this source. The apparent displacement between high and very high energy detected sources is explained thanks to this model. Moreover, a multi-frequency and multi-messenger model (i.e., photons from the whole electromagnetic spectrum and neutrinos) for the diffuse emission coming from the starburst galaxy M82 is presented. The gamma-ray predictions are compared to the posterior detections in the energy range between the giga- and the tera-electronvolts of the starburst galaxies M82 and NGC 253, observed by the satellite Fermi and the ground-based experiments H.E.S.S. and VERITAS. The model explains rather satisfactorily these detections at high and very high energy. In the second part of the Thesis, the technique for the gamma-ray detection at ground level through Cherenkov radiation is described. This Cherenkov technique is used in the MAGIC experiment, among others. Some of the observations taken by the student with this telescope facility are presented as part of this Thesis. First, the upper limits to the gamma-ray flux coming from two sources in the region of the SNR G65.1+0.6 when observed with MAGIC-I are shown. These two sources were previously detected by the Milagro experiment and are associated with two bright sources in the Fermi catalog. One of the possible explanations is that these sources are two pulsars powering the pulsar wind nebula that surrounds them. Furthermore, preliminar results of the stereo observations (using the two MAGIC telescopes) of the SNR IC443 are presented. The goal for these observations is performing an energy-dependent morphological study. So far, the obtained number of hours is not enough, although new observations are planned for the near future. Finally, some simulations for the future CTA are presented for the first time, together with several spectral studies regarding interesting scientific cases. In particular, those studies are focused on objects that have been already mentioned in this Thesis, like the SNR IC443 and the starburst galaxies M82 and NGC 253, and also on molecular clouds that are illuminated by cosmic rays which escaped from nearby SNRs. The CTA observatory represents the future of the ground-based gamma-ray observations, and it is likely to include every collaboration from the existing telescope facilities nowadays. The energy range will be widened, the sensitivity will be one order of magnitude improved and the angular resolution will be enhanced respect to the existing experiments up to now. Thus, the present Thesis is just the tip of the iceberg of what is yet to come

Some observational and theoretical aspects of cosmic-ray diffusion

La Tesis contiene ciertos estudios relacionados con la difusión de rayos cósmicos. Está dividida en dos partes, una describe los modelos sobre la fenomenología de difusión de rayos cósmicos, y otra presenta las observaciones realizadas usando el experimento MAGIC y simulaciones del futuro Array de Telescopios Cherenkov (CTA, por sus siglas en inglés). En la primera parte, se introduce la teoría general más aceptada sobre la difusión de rayos cósmicos. Se cree que los remanentes de supernova (SNR) son uno de los escenarios más probables de aceleración de rayos cósmicos, tanto en procesos leptónicos como hadrónicos. El mecanismo de aceleración de partículas en cada SNR se asume que es aceleración por choque difuso (diffusive shock acceleration). Para obtener confirmación observacional de la aceleración de protones y otros núcleos, y distinguirlos de la emisión leptónica, se deben aislar los efectos de los múltiples mensajeros producidos por partículas secundarias. Partiendo de ahí, se desarrolla un modelo sobre los alrededores del SNR IC443 que explica la fenomenología de alta energía: los rayos cósmicos escapan del remanente, los más energéticos alcanzan antes la nube molecular situada delante de la misma y los menos energéticos aún permanecen confinados a los restos del SNR. Los resultados contrastados con las últimas observaciones obtenidas de la fuente explican su aparente desplazamiento cuando se observa a alta y a muy alta energía. También se presenta un modelo multi-frecuencia y multi-mensajero (fotones de todo el espectro electromagnético y neutrinos) de la emisión difusa de la galaxia con un estallido de formación estelar M82. Las predicciones para rayos gamma se comparan con (y explican satisfactoriamente) las posteriores detecciones en el rango energético comprendido entre los giga- y los tera-electronvoltios de las galaxias M82 y NGC 253, realizadas por el satélite Fermi y los experimentos en tierra H.E.S.S. y VERITAS. En la segunda parte de la Tesis, se describe la técnica de detección de rayos gamma desde tierra a través de la radiación Cherenkov. Esta técnica es explotada, entre otros, por el experimento MAGIC. Algunas de las observaciones realizadas por la estudiante con este telescopio se presentan como parte de esta Tesis. En primer lugar, se muestran los límites superiores (upper limits) al flujo de rayos gamma obtenidos con MAGIC-I sobre dos fuentes detectadas por el experimento Milagro y que se corresponden con dos fuentes brillantes del satélite Fermi en la región del SNR G65.1+0.6. Se cree que puedan tratarse de dos púlsares que inyectan energía y partículas en la nebulosa pulsada que las rodea. También se presentan resultados preliminares de observaciones en estéreo (con los dos telescopios MAGIC) del SNR IC443. El número de horas obtenido resulta insuficiente para completar el estudio morfológico dependiente de la energía para el que se enfocaba la obtención de estos datos, pero nuevas observaciones están previstas para el futuro. Finalmente, se introducen por primera vez algunas simulaciones realizadas con el futuro CTA y ciertos estudios espectrales sobre particulares casos científicos. En concreto, dichos estudios se centraron en los objetos ya discutidos en el resto de la Tesis, como el SNR IC443, las galaxias con estallido de formación estelar M82 y NGC 253, y nubes moleculares iluminadas por rayos cósmicos escapados de SNRs cercanos. El observatorio CTA representa el futuro de las observaciones de rayos gamma desde tierra, y prevé que se unan las colaboraciones de todas las instalaciones de telescopios actuales. El rango de energías se verá ampliado, la sensibilidad aumentará un orden de magnitud y la resolución angular se mejorará respecto a los experimentos existentes hoy en día. Esta Tesis representa, pues, sólo el principio de lo que queda por venir.This Thesis deals with certain aspects on cosmic-ray diffusion. It is divided in two parts, one describes phenomenological models of cosmic-ray diffusion, and the other presents observations taken with the MAGIC experiments and simulations of the future Cherenkov Telescope Array (CTA). In the first part, the generally accepted theory for cosmic-ray diffusion is introduced. Supernova remnants (SNRs) are believed to be the more likely scenarios of cosmic-ray acceleration, considering both hadronic and leptonic processes. The mechanism for particle acceleration in each SNR is assumed to be diffusive shock acceleration (DSA). To obtain the observational confirmation of proton and nuclei acceleration, and distinguish it from leptonic emission, the effects of multiple messengers produced by secondary particles must be isolated. Following this, a model for the neighborhood of the SNR IC443 is developed, explaining the high energy phenomenology: cosmic rays escape from the remnant, the most energetic ones reach first the molecular cloud located in front of it and the least energetic ones still remain confined on the shell of the SNR. The results are confronted with the latest observations that are obtained from this source. The apparent displacement between high and very high energy detected sources is explained thanks to this model. Moreover, a multi-frequency and multi-messenger model (i.e., photons from the whole electromagnetic spectrum and neutrinos) for the diffuse emission coming from the starburst galaxy M82 is presented. The gamma-ray predictions are compared to the posterior detections in the energy range between the giga- and the tera-electronvolts of the starburst galaxies M82 and NGC 253, observed by the satellite Fermi and the ground-based experiments H.E.S.S. and VERITAS. The model explains rather satisfactorily these detections at high and very high energy. In the second part of the Thesis, the technique for the gamma-ray detection at ground level through Cherenkov radiation is described. This Cherenkov technique is used in the MAGIC experiment, among others. Some of the observations taken by the student with this telescope facility are presented as part of this Thesis. First, the upper limits to the gamma-ray flux coming from two sources in the region of the SNR G65.1+0.6 when observed with MAGIC-I are shown. These two sources were previously detected by the Milagro experiment and are associated with two bright sources in the Fermi catalog. One of the possible explanations is that these sources are two pulsars powering the pulsar wind nebula that surrounds them. Furthermore, preliminar results of the stereo observations (using the two MAGIC telescopes) of the SNR IC443 are presented. The goal for these observations is performing an energy-dependent morphological study. So far, the obtained number of hours is not enough, although new observations are planned for the near future. Finally, some simulations for the future CTA are presented for the first time, together with several spectral studies regarding interesting scientific cases. In particular, those studies are focused on objects that have been already mentioned in this Thesis, like the SNR IC443 and the starburst galaxies M82 and NGC 253, and also on molecular clouds that are illuminated by cosmic rays which escaped from nearby SNRs. The CTA observatory represents the future of the ground-based gamma-ray observations, and it is likely to include every collaboration from the existing telescope facilities nowadays. The energy range will be widened, the sensitivity will be one order of magnitude improved and the angular resolution will be enhanced respect to the existing experiments up to now. Thus, the present Thesis is just the tip of the iceberg of what is yet to come

PG 1553+113: five years of observations with MAGIC

11 páginas, 6 figuras, 4 tablas.-- Aceptado para su publicación en ApJ.-- MAGIC Collaboration: et al.We present the results of five years (2005-2009) of MAGIC observations of the BL Lac object PG 1553+113 at very high energies (VHEs, E > 100 GeV). Power law fits of the individual years are compatible with a steady mean photon index \Gamma = 4.27 $\pm$ 0.14. In the last three years of data, the flux level above 150 GeV shows a clear variability (probability of constant flux < 0.001%). The flux variations are modest, lying in the range from 4% to 11% of the Crab Nebula flux. Simultaneous optical data also show only modest variability that seems to be correlated with VHE gamma ray variability. We also performed a temporal analysis of (all available) simultaneous Fermi/LAT data of PG 1553+113 above 1 GeV, which reveals hints of variability in the 2008-2009 sample. Finally, we present a combination of the mean spectrum measured at very high energies with archival data available for other wavelengths. The mean spectral energy distribution can be modeled with a one-zone Synchrotron Self Compton (SSC) model, which gives the main physical parameters governing the VHE emission in the blazar jet.The support of the German BMBF and MPG, the Ital- ian INFN, the Swiss National Fund SNF, and the Span- ish MICINN is gratefully acknowledged. This work was also supported by the Marie Curie program, by the CPAN CSD2007-00042 and MultiDark CSD2009-00064 projects of the Spanish Consolider-Ingenio 2010 pro- gramme, by grant DO02-353 of the Bulgaria n NSF, by grant 127740 of the Academy of Finland, by the YIP of the Helmholtz Gemeinschaft, by the DFG Cluster of Ex- cellence “Origin and Structure of the Universe”, by the DFG Collaborative Research Centers SFB823/C4 and SFB876/C3, and by the Polish MNiSzW grant 745/N- HESS-MAGIC/2010/0. Additional support for science analysis during the op- erations phase is gratefully acknowledged from the Istituto Nazionale di Astrofisica in Italy and the Centre National d’Études Spatiales in France.Peer reviewe