arXiv subjects

Javier Rico

Publications and source records attributed to Javier Rico.

31 records · Page 2Linked to original sources

arXiv2011

Search for VHE signals from microquarsars with MAGIC

Microquasars are accreting binary systems displaying relativistic radio jets where very high energy gamma rays might be produced via Inverse Compton scattering. The detection of the microquasar Cygnus X-3 above 100 MeV by both Fermi/LAT and AGILE satellites, together with the short flares from Cygnus X-1 reported by AGILE, confirmed that this class of astrophysical objects are interesting candidates for very high energy gamma-ray observations. The stand-alone imaging atmospheric Cherenkov MAGIC telescope, and later on the recently inaugurated stereoscopic system, made a significant effort to search for signals from microquasars. This paper reviews all MAGIC results of Cygnus X-3, Cygnus X-1, Scorpius X-1, and SS 433 observations. The stand-alone MAGIC telescope observed Cygnus X-3 for almost 60 hrs from March 2006 until August 2009 in many different X-ray spectral states where a very high energy emission is predicted and also simultaneously with a flux enhancement at high energies detected by Fermi/LAT. No significant signal was found in any of the observed conditions. The MAGIC stereoscopic system pointed at the Z-type low-mass X-ray binary Scorpius X-1 in May 2010 for ~8 hrs. Simultaneous soft X-ray measurements allowed to define the X-ray spectral state of the source which could emit very-high-energy photons in the horizontal branch. MAGIC did not detect the source and put some constraints on the maximum TeV luminosity to jet power ratio. Further observations of Cygnus X-1 were also carried out with the new and twice as sensitive stereoscopic system in Autumn 2009 for a total amount of 30 hrs. Finally, we also report on SS 433 observations obtained during two periods of minimum absorption processes from the accretion disk.

astro-ph.HE↗

arXiv2009

The MAGIC Data Center

The MAGIC I telescope produces currently around 100TByte of raw data per year that is calibrated and reduced on-site at the Observatorio del Roque de los Muchachos (La Palma). Since February 2007 most of the data have been stored and further processed in the Port d'Informacio Cientifica (PIC), Barcelona. This facility, which supports the GRID Tier 1 center for LHC in Spain, provides resources to give the entire MAGIC Collaboration access to the reduced telescope data. It is expected that the data volume will increase by a factor 3 after the start-up of the second telescope, MAGIC II. The project to improve the MAGIC Data Center to meet these requirements is presented. In addition, we discuss the production of high level data products that will allow a more flexible analysis and will contribute to the international network of astronomical data (European Virtual Observatory). For this purpose, we will have to develop a new software able to adapt the analysis process to different data taking conditions, such as different trigger configurations or mono/stereo telescope observations.

astro-ph.IM↗

arXiv2009

Studies of the Influence of Moonlight on Observations with the MAGIC Telescope

The ground-based imaging atmospheric Cherenkov technique is currently the most powerful observation method for very high energy gamma rays. With its specially designed camera and readout system, the MAGIC Telescope is capable of observing also during nights with a comparatively high level of night-sky background light. This allows to extend the MAGIC duty cycle by 30% compared to dark-night observations without moon. Here we investigate the impact of increased background light on single-pixel level and show the performance of observations in the presence of moonlight conditions to be consistent with dark night observations.

astro-ph.IM↗

arXiv2009

First bounds on the VHE gamma-ray emission from isolated Wolf-Rayet binary systems

Different theoretical models predict VHE gamma-ray emission to arise in tight binary star systems (high mass-loss and high wind speeds), which has not been confirmed experimentally so far. Here we present the first bounds on the VHE emission from two isolated Wolf-Rayet star binaries, WR147 and WR146, obtained with the MAGIC telescope.

astro-ph.HE↗

arXiv2009

Status and recent results of MAGIC

MAGIC is a single-dish Cherenkov telescope located on La Palma (Spain), hence with an optimal view on the Northern sky. Sensitive in the 30 GeV-30 TeV energy band, it is nowadays the only ground-based instrument being able to measure high-energy gamma-rays below 100 GeV. We review the most recent experimental results obtained using MAGIC.

astro-ph.HE↗

arXiv2008

Results of MAGIC on Galactic sources

astro-ph↗

arXiv2008

The variable super-orbital modulation of Cygnus X-1

We study the super-orbital modulation present in the Cygnus X-1 X-ray data, usually attributed to the precession of the accretion disk and relativistic jets. We find a new, strong, 326+-2 d period modulation starting in 2005, in Swift/BAT and RXTE/ASM light curves (LCs). We also investigate Vela5B/ASM and ArielV/ASM archival data and confirm the previously reported ~290 d periodic modulation, and therefore confirming that the super-orbital period is not constant. Finally, we study RXTE/ASM LC before 2005 and find that the previously reported ~150 d period is most likely an artifact due to the use of a Fourier-power based analysis under the assumption that the modulation has a constant period along the whole data sample. Instead, we find strong indications of several discrete changes of the precession period, happening in coincidence with soft and failed state-transition episodes. We also find a hint of correlation between the period and the amplitude of the modulation. The detection of gamma-rays above 100 GeV with MAGIC in September 2006 happened in coincidence with a maximum of the super-orbital modulation. The next maximum will happen between 2 and 14 of July 2008, when the observational conditions of Cygnus X-1 with ground-based Cherenkov telescopes, such as MAGIC and VERITAS, are optimal.

astro-ph↗

arXiv2006

Results from MAGIC's first observation cycle on galactic sources

During its Cycle I, the MAGIC telescope targeted about 250 hours several galactic sources sought to be, or detected previously by other experiments in the same energy domain, gamma-ray emitters. This paper reviews some results of such MAGIC observations covering, among others, supernova remnants, the Galactic Center and microquasars. We will concentrate on the recent discovery at very high energy gamma-rays of the microquasar LS I +61 303.

astro-ph↗

arXiv2003

Results from the ICARUS T600 module - A measurement of the muon decay spectrum

We have studied the muon decay energy spectrum from a sample of stopping muon events acquired during the test run of the ICARUS T600 prototype. This detector allows the spatial reconstruction of the events with fine granularity, hence the precise measurement of the muon range and dE/dx with high sampling rate. This information is used to compute the correction factors needed for the calorimetric reconstruction. The Michel rho parameter is then measured by comparison of the experimental and Monte Carlo simulated muon decay spectra, obtaining rho = 0.72 +/- 0.06 (stat) +/- 0.08 (syst).

hep-ex↗

arXiv2002

Status of ICARUS

The ICARUS detector is a liquid argon time projection chamber. It provides three dimensional imaging and calorimetry of ionizing particles over a large volume, with high granularity. Its Physics program includes the study of atmospheric, solar, supernovae and beam neutrinos as well as proton decay searches. The ICARUS technology has reached maturity with the construction and test (during summer 2001) of a 600 ton detector, demonstrating the feasibility of building large mass devices relevant for non-accelerator physics. During this test run, more than 27000 cosmic ray events have been acquired. These data allow to assess the detector performance, i.e. the spatial reconstruction, calorimetry and particle identification.

hep-ex↗

arXiv1999

Four Fermion Contact Terms in Charged Current Processes and Large Extra Dimensions

We study the bounds that can be obtained on four-fermion contact terms from the experimental data for (e+ p -> \bar{nu} X) obtained at HERA and (p \bar{p} -> e ν), measured at TEVATRON. We compare these bounds with the ones available in the literature. Finally, we apply these results to study the compactification radius in theories with large extra dimensions and we obtain the bound M_c >= 3.3 TeV.

hep-ph↗

arXiv1997

Physics Beyond the Standard Model at HERA

This talk is divided in two parts. In the first one we discuss the signals of the Minimal Supersymmetric Standard Model through the production of \tilde{e} \tilde{q}. The second part is devoted to contact terms. The bounds on the mass scale Lambda obtained from atomic parity violation experiments and from LEP are reviewed. Afterwards, we show that the excess of events at high Q^2 observed at HERA could be explained in terms of these contact terms.

hep-ph↗

arXiv1997

Contact terms in charged current processes at HERA

We obtain bounds on the mass scales characterizing four-fermion contact interactions in charged current processes. The bounds arise from the Q^2 and x distributions in the processes e p -> νX measured by the two HERA experiments, H1 and ZEUS.

hep-ph↗