Person: Miranda Pantoja, José Miguel
Universidad Complutense de Madrid
Faculty / Institute
Estructura de la Materia, Física Térmica y Electrónica
Now showing 1 - 10 of 182
PublicationSearch for very high energy gamma-rays from the z=0.896 quasar 4C+55.17 with the MAGIC telescopes(Wiley, 2014-05) Antoranz Canales, Pedro; Barrio Uña, Juan Abel; Contreras González, José Luis; Fonseca González, Mª Victoria; López Moya, Marcos; Miranda Pantoja, José Miguel; Satalecka, Konstanzja; Scapin, ValeriaThe bright gamma-ray quasar 4C +55.17 is a distant source (z = 0.896) with a hard spectrum at GeV energies as observed by the Large Area Telescope (LAT) on board the Fermi satellite. This source is identified as a good source candidate for very high energy (VHE; > 30 GeV) gamma-rays. In general, VHE gamma-rays from distant sources provide a unique opportunity to study the extragalactic background light (EBL) and underlying astrophysics. The flux intensity of this source in the VHE range is investigated. Then, constraints on the EBL are derived from the attenuation of gamma-ray photons coming from the distant blazar. We searched for a gamma-ray signal from this object using the 35 h observations taken by the MAGIC (Major Atmospheric Gamma-ray Imaging Cherenkov) telescopes between 2010 November and 2011 January. No significant VHE gamma-ray signal was detected. We computed the upper limits of the integrated gamma-ray flux at the 95 per cent confidence level of 9.4 x 10(-12) and 2.5 x 10(-12) cm(-2) s(-1) above 100 and 200 GeV, respectively. The differential upper limits in four energy bins in the range from 80 to 500 GeV are also derived. The upper limits are consistent with the attenuation predicted by low-flux EBL models on the assumption of a simple power-law spectrum extrapolated from LAT data. PublicationSearch for VHE gamma-ray emission from the globular cluster M13 with the Magic telescope(IOP Publishing, 2009-09-01) Antoranz Canales, Pedro; Barrio Uña, Juan Abel; Contreras González, José Luis; Fonseca González, Mª Victoria; Miranda Pantoja, José Miguel; Nieto, DanielBased on MAGIC observations from 2007 June to July, we have obtained an integral upper limit to the VHE energy emission of the globular cluster M13 of F (E > 200 GeV) < 5.1 x 10(-12) cm(-2) s(-1), and differential upper limits for E > 140 GeV. Those limits allow us to constrain the population of millisecond pulsars within M13 and to test models for acceleration of leptons inside their magnetospheres and surrounding. We conclude that in M13 either millisecond pulsars are fewer than expected or they accelerate leptons less efficiently than predicted. PublicationModelling the internal field distribution in human erythrocytes exposed to MW radiation(Elsevier Science SA, 2004-08) Sebastián Franco, José Luis; Muñoz San Martín, Sagrario; Sancho Ruíz, Miguel; Miranda Pantoja, José MiguelThis paper studies the internal electric field distribution in human erythrocytes exposed to MW radiation. For this purpose, an erythrocyte cell model is exposed to linearly polarized electromagnetic (EM) plane waves of frequency 900 MHz and the electric field within the cell is calculated by using a finite element (FE) technique with adaptive meshing. The results obtained show the dependence of the induced electric field distribution on the main modelling parameters, i.e., the electrical properties (permittivity and conductivity) of the membrane and cytoplasm and the orientation of the cell with respect to the applied field. It is found that for certain orientations, the field amplification within the membrane of the erythrocyte shape cell can be higher than the one observed in an equivalent simple spheroidal geometry cell, commonly used in bioelectromagnetism. The present work shows that a better insight of the interaction of electromagnetic fields with basic biological structures is obtained when the most possible realistic cell shape is used. (C) 2004 Elsevier B.V. All rights reserved. PublicationVery high energy gamma-ray radiation from the stellar mass black hole binary Cygnus X-1(IOP Publishing, 2007-08-10) Antoranz Canales, Pedro; Barrio Uña, Juan Abel; Contreras González, José Luis; Fonseca González, Mª Victoria; López Moya, Marcos; Miranda Pantoja, José Miguel; Nieto, DanielWe report on the results from the observations in the very high energy band ( VHE; GeV) of the black E = 100 g hole X- ray binary ( BHXB) Cygnus X- 1. The observations were performed with the MAGIC telescope, for a total of 40 hr during 26 nights, spanning the period between 2006 June and November. Searches for steady gamma - ray signals yielded no positive result, and upper limits to the integral flux ranging between 1% and 2% of the Crab Nebula flux, depending on the energy, have been established. We also analyzed each observation night independently, obtaining evidence of gamma- ray signals at the 4.0 j significance level ( 3.2 j after trial correction) for 154 minutes of effective on- time ( EOT) on September 24 between 20: 58 and 23: 41 UTC, coinciding with an X- ray flare seen by RXTE, Swift, and INTEGRAL. A search for faster- varying signals within a night resulted in an excess with a significance of 4.9 j ( 4.1 j after trial correction) for 79 minutes EOT between 22: 17 and 23: 41 UTC. The measured excess is compatible with a pointlike source at the position of Cygnus X- 1 and excludes the nearby radio nebula powered by its relativistic jet. The differential energy spectrum is well fitted by an unbroken power law described as dN/(dA dt dE) = ( 2.3 +/- 0.6)* 10 ( E/1TeV). This is the first experimental evidence of VHE emission from a stellar mass black hole and therefore from a confirmed accreting X- ray binary. PublicationA low noise 2-20 GHz feedback MMIC-amplifier(IEEE, 2000) Zirath, Herbert; Sakalas, Paulius; Miranda Pantoja, José MiguelA low noise feedback MMIC-amplifier based on a 180 GHz f(max) PHEMT-technology is described. The gain input and output reflection coefficient, de-power consumption, and noise parameters are investigated theoretically and experimentally as a function of dc-bias and frequency. The noise figure is typically 2.5 dB with an associate gain of 22 dB across the 2-20 GHz frequency range. The circuit area is less than 1 mum(2) and the de-power consumption is lower than 100 mW. PublicationThe june 2008 flare of Markarian 421 from optical to TeV energies(IOP Publishing, 2009-01-20) Antoranz Canales, Pedro; Barrio Uña, Juan Abel; Contreras González, José Luis; Fonseca González, Mª Victoria; Miranda Pantoja, José Miguel; Nieto, DanielWe present optical, X-ray, high-energy ((sic) 30 GeV) and very high energy ((sic) 100 GeV; VHE) observations of the high-frequency peaked blazar Mrk 421 taken between 2008 May 24 and June 23. A high-energy gamma-ray signal was detected by AGILE with root TS = 4.5 between June 9 and 15, with F(E > 100 MeV) = 42(-12)(+14) x 10(-8) photons cm(-2) s(-1). This flaring state is brighter than the average flux observed by EGRET by a factor of similar to 3, but still consistent with the highest EGRET flux. In hard X-rays (20-60 keV) SuperAGILE resolved a five-day flare (June 9-15) peaking at similar to 55 mCrab. SuperAGILE, RXTE/ASM and Swift/BAT data show a correlated flaring structure between soft and hard X-rays. Hints of the same flaring behavior are also detected in the simultaneous optical data provided by the GASP-WEBT. A Swift/XRT observation near the flaring maximum revealed the highest 2-10 keV flux ever observed from this source, of 2.6 x 10(-9) erg cm(-2) s(-1) (i.e. > 100 mCrab). A peak synchrotron energy of similar to 3 keV was derived, higher than typical values of similar to 0.5-1 keV. VHE observations with MAGIC and VERITAS between June 6 and 8 showed the flux peaking in a bright state, well correlated with the X-rays. This extraordinary set of simultaneous data, covering a 12-decade spectral range, allowed for a deep analysis of the spectral energy distribution as well as of correlated light curves. The gamma-ray flare can be interpreted within the framework of the synchrotron self-Compton model in terms of a rapid acceleration of leptons in the jet. PublicationAn intermittent extreme BL Lac: MWL study of 1ES 2344+514 in an enhanced state(Wiley, 2020-08) Barrio Uña, Juan Abel; Contreras González, José Luis; Fonseca González, Mª Victoria; Hoang, Kim Dinh; López Moya, Marcos; Miener, Tjark; Miranda Pantoja, José Miguel; Morcuende, D.; Peñil del Campo, Pablo; Saha, Lab; otros, ...Extreme high-frequency BL Lacs (EHBL) feature their synchrotron peak of the broad-band spectral energy distribution (SED) at nu(s) >= 10(17) Hz. The BL Lac object 1ES 2344+514 was included in the EHBL family because of its impressive shift of the synchrotron peak in 1996. During the following years, the source appeared to be in a low state without showing any extreme behaviours. In 2016 August, 1ES 2344+514 was detected with the groundbased gamma-ray telescope FACT during a high gamma-ray state, triggering multiwavelength (MWL) observations. We studied the MWL light curves of 1ES 2344+514 during the 2016 flaring state, using data from radio to very-high-energy (VHE) gamma-rays taken with OVRO, KAIT, KVA, NOT, some telescopes of the GASP-WEBT collaboration at the Teide, Crimean, and St. Petersburg observatories, Swift-UVOT, Swift-XRT, Fermi-LAT, FACT, and MAGIC. With simultaneous observations of the flare, we built the broad-band SED and studied it in the framework of a leptonic and a hadronic model. The VHE gamma-ray observations show a flux level of 55 per cent of the Crab Nebula flux above 300 GeV, similar to the historical maximum of 1995. The combination of MAGIC and Fermi-LAT spectra provides an unprecedented characterization of the inverse-Compton peak for this object during a flaring episode. The Gamma index of the intrinsic spectrum in the VHE gamma-ray band is 2.04 +/- 0.12(stat) +/- 0.15(sys). We find the source in an extreme state with a shift of the position of the synchrotron peak to frequencies above or equal to 1018 Hz. PublicationAnalysis of the electric field induced forces in erythrocyte membrane pores using a realistic cell model(IOP Publishing Ltd, 2006-12-07) Sebastián Franco, José Luis; Muñoz San Martín, Sagrario; Sancho Ruíz, Miguel; Miranda Pantoja, José MiguelWe calculate the induced electric stress forces on transient hydrophobic pores in the membrane of an erythrocyte exposed to an electric field. For this purpose, we use a finite element numerical technique and a realistic shape for the biconcave erythrocyte represented by a set of parametric equations in terms of Jacobi elliptic functions. The results clearly show that the electrical forces on the base and sidewalls of the pore favour the opening of the pore. A comparison of the force densities obtained for an unstretched flat membrane and for the realistic erythrocyte model shows that the thinning and curvature of the membrane cannot be neglected. We also show that the pore deformation depends strongly on the orientation of the pore with respect to the external field, and in particular is very small when the field is tangent to the membrane surface. PublicationDesign, modelling and testing of electro-optical transmitters for the central pixel of the MAGIC telescope camera.(SPIE-Int. Soc. Optical Engineering, 2005) Lucarelli, F.; Antoranz Canales, Pedro; Barrio Uña, Juan Abel; Miranda Pantoja, José Miguel; Fonseca González, Mª VictoriaIn this work we have built an electro-optical system for the transmission of low frequency analogue signals through optical fibre. The main goal was to achieve minimum pulse distortion with maximum dynamic range. The system has been used in the framework of the MAGIC telescope experiment for the transmission of the analogue output from a photo-multiplier dedicated to optical observation of astrophysical objects, in particular pulsars. The received signal polarizes an infrared LED (lambda=850 nm), which converts the pulse into an optical analogue pulse. The electro-optical pulse is transmitted by means of a multi-mode optic fibre and finally amplified and filtered by the optical receiver. The whole system has been tested using a pulse generator resembling the type of pulsed signal we expect from pulsars, that is with period of about tens of milli-seconds and few milli-seconds wide. The system was calibrated in order to: a) obtain a fixed relation between the received pulse and the final data and b) enhance the dynamic range and low distortion. In what follows, we show the behaviour of the optical transmitter under different pulse shapes, amplitude and frequencies up to several hundred Hz. The electro-optical system has been mounted on the MAGIC telescope and tested successfully with the observation of the pulsed optical signal from the Crab pulsar. PublicationProbing the very high energy gamma-ray spectral curvature in the blazar PG 1553+113 with the MAGIC telescopes(Oxford University Press, 2015-07-11) Antoranz Canales, Pedro; Barrio Uña, Juan Abel; Bonnefoy, Simon Francois Albert; Contreras González, José Luis; Fonseca González, Mª Victoria; López Moya, Marcos; Miranda Pantoja, José Miguel; Satalecka, Konstanzja; Scapin, ValeriaPG 1553+113 is a very-high-energy (VHE, E > 100 GeV) γ-ray emitter classified as a BL Lac object. Its redshift is constrained by intergalactic absorption lines in the range 0.4 < z < 0.58. The MAGIC telescopes have monitored the source’s activity since 2005. In early 2012, PG 1553+113 was found in a high-state, and later, in April of the same year, the source reached its highest VHE flux state detected so far. Simultaneous observations carried out in X-rays during 2012 April show similar flaring behaviour. In contrast, the γ-ray flux at E < 100 GeV observed by Fermi-LAT is compatible with steady emission. In this paper, a detailed study of the flaring state is presented. The VHE spectrum shows clear curvature, being well fitted either by a power law with an exponential cut-off or by a log-parabola. A simple power-law fit hypothesis for the observed shape of the PG 1553+113 VHE γ-ray spectrum is rejected with a high significance (fit probability P=2.6 ×10−6). The observed curvature is compatible with the extragalactic background light (EBL) imprint predicted by current generation EBL models assuming a redshift z ∼ 0.4. New constraints on the redshift are derived from the VHE spectrum. These constraints are compatible with previous limits and suggest that the source is most likely located around the optical lower limit, z = 0.4, based on the detection of Lyα absorption. Finally, we find that the synchrotron self-Compton (SSC) model gives a satisfactory description of the observed multi-wavelength spectral energy distribution during the flare.