Reconfigurable ASIC for a low level trigger system in Cherenkov Telescope Cameras

A versatile and reconfigurable ASIC is presented, which implements two different con-cepts of low level trigger (L0) for Cherenkov telescopes: the Majority trigger (sum of discriminated inputs) and the Sum trigger concept (analogue clipped sum of inputs). Up to 7 input signals can be processed following one or both of the previous trigger concepts. Each differential pair output of the discriminator is also available as a LVDS output. Differential circuitry using local feedback allows the ASIC to achieve high speed (500 MHz) while maintaining good linearity in a 1 Vpp range. Experimental results are presented. A number of prototype camera designs of the Cherenkov Telescope Array (CTA) project will use this ASIC

A Trigger Interface Board to manage trigger and timing signals in CTA Large-Sized Telescope and Medium-Sized Telescope cameras

One of the main goals of the Cherenkov Telescope Array (CTA) observatory is to improve the $\gamma$-ray detection sensitivity by an order of magnitude, compared to the current ground-based observatories. Widening the energy coverage down to 20 GeV and up to 300 TeV is also an important goal. This goal will be possible by using Large-Sized Telescopes (LSTs) for the energy range of 20--200 GeV, Medium-Sized Telescopes (MSTs) for 100 GeV--10 TeV, and Small-Sized Telescopes (SSTs) for energies above 5 TeV. The LSTs, which focus on the lowest energies, are operated in a region dominated by background events originated from the night sky background. To reduce such background events as much as possible, the LST cameras are only read out if at least two of them have been triggered in a short-time coincidence window. Such trigger is implemented for each LST camera in a dedicated module called Trigger Interface Board (TIB). In addition, the TIB is also used in MSTs equipped with the NectarCAM camera system to manage the different trigger and timing signals between LSTs and MSTs, as well as to monitor the different counting rates and dead-time of the cameras. It also assigns a time stamp to each event, which is recorded along with the information provided by the CTA global timing distribution system, based on the White Rabbit protocol. Therefore, the event arrival time can be determined in a redundant way. In this contribution, the main features and the technical performance of the TIB are presented.Comment: All CTA contributions at arXiv:1709.03483. In Proceedings of the 35th International Cosmic Ray Conference (ICRC2017), Busan, Kore

Divisores Wilkinson con elementos concentrados para procesado de pulsos

Some photodetectors like PMTs and SiPMs give pulses of few nanosecond width at their outputs, which need to be properly processed with analog circuits. Power splitters with two and three outputs are required to distribute this kind of fast pulses equally among different outputs. Good matching and low pass response are necessary to avoid shape deformation, which discard low frequency designs with operational amplifiers. To match these requirements two Wilkinson dividers were designed, substituting the lambda quarter lines for lumped elements. These changes provide us with low pass response and much smaller size, using SMD devices. The splitters were manufactured and measured, with good results

The 2010 very high energy gamma-ray flare and 10 years of multi-wavelength observations of M 87

The giant radio galaxy M 87 with its proximity (16 Mpc), famous jet, and very massive black hole ((3-6) x 10(9) M-circle dot) provides a unique opportunity to investigate the origin of very high energy (VHE; E > 100 GeV) gamma-ray emission generated in relativistic outflows and the surroundings of supermassive black holes. M 87 has been established as a VHE gamma-ray emitter since 2006. The VHE gamma-ray emission displays strong variability on timescales as short as a day. In this paper, results from a joint VHE monitoring campaign on M 87 by the MAGIC and VERITAS instruments in 2010 are reported. During the campaign, a flare at VHE was detected triggering further observations at VHE (H.E.S.S.), X-rays (Chandra), and radio (43 GHz Very Long Baseline Array, VLBA). The excellent sampling of the VHE gamma-ray light curve enables one to derive a precise temporal characterization of the flare: the single, isolated flare is well described by a two-sided exponential function with significantly different flux rise and decay times of tau(rise)(d) = (1.69 +/- 0.30) days and tau(decay)(d) = (0.611 +/- 0.080) days, respectively. While the overall variability pattern of the 2010 flare appears somewhat different from that of previous VHE flares in 2005 and 2008, they share very similar timescales (similar to day), peak fluxes (Phi(>0.35 TeV) similar or equal to (1-3) x 10(-11) photons cm(-2) s(-1)), and VHE spectra. VLBA radio observations of 43 GHz of the inner jet regions indicate no enhanced flux in 2010 in contrast to observations in 2008, where an increase of the radio flux of the innermost core regions coincided with a VHE flare. On the other hand, Chandra X-ray observations taken similar to 3 days after the peak of the VHE gamma-ray emission reveal an enhanced flux from the core (flux increased by factor similar to 2; variability timescale <2 days). The long-term (2001-2010) multi-wavelength (MWL) light curve of M 87, spanning from radio to VHE and including data from Hubble Space Telescope, Liverpool Telescope, Very Large Array, and European VLBI Network, is used to further investigate the origin of the VHE gamma-ray emission. No unique, common MWL signature of the three VHE flares has been identified. In the outer kiloparsec jet region, in particular in HST-1, no enhanced MWL activity was detected in 2008 and 2010, disfavoring it as the origin of the VHE flares during these years. Shortly after two of the three flares (2008 and 2010), the X-ray core was observed to be at a higher flux level than its characteristic range (determined from more than 60 monitoring observations: 2002-2009). In 2005, the strong flux dominance of HST-1 could have suppressed the detection of such a feature. Published models for VHE gamma-ray emission from M 87 are reviewed in the light of the new data

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

© ESO 2010. The MAGIC collaboration would like to thank the Instituto de Astrofisica de Canarias for the excellent working condition at the Observatorio del Roque de los Muchachos at La Palma. Major support from Germany's Bundesministerium fur 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 Wyzszego 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. N.M. would like to thank to C.W. Danforth for the private communication regarding the newly estimated redshift of the source.The blazar PG 1553+113 is a well known TeV gamma-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) gamma-ray, and very-high-energy (VHE) gamma-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.Depto. de Estructura de la Materia, Física Térmica y ElectrónicaFac. de Ciencias FísicasTRUESwitzerland's ETHPoland's Ministertwo Nauki i Szkolnictwa WyzszegoHelmholtz GemeinschaftGeorgian National Science FoundationItalian Space Agencypu

Detection of very high energy radiation from the BL lacertae object PG 1553+113 with the MAGIC telescope

In 2005 and 2006, the MAGIC telescope observed very high energy gamma-ray emission from the distant BL Lac object PG 1553 + 113. The overall significance of the signal was 8.8 sigma for 18.8 hr of observation time. The light curve shows no significant flux variations on a daily timescale; the flux level during 2005 was, however, significantly higher compared to 2006. The differential energy spectrum between similar to 90 and 500 GeV is well described by a power law with photon index. Gamma = 4.2 +/- 0.3. The combined 2005 and 2006 energy spectrum provides an upper limit of z = 0.74 on the redshift of the object

Statistics of VHE γ-rays in temporal association with radio giant pulses from the Crab pulsar

Aims. The aim of this study is to search for evidence of a common emission engine between radio giant pulses (GPs) and very-high-energy (VHE, E& x2004;> & x2004;100 GeV) gamma-rays from the Crab pulsar. Methods. We performed 16 h of simultaneous observations of the Crab pulsar at 1.4 GHz with the Effelsberg radio telescope and the Westerbork Synthesis Radio Telescope (WSRT), and at energies above 60 GeV we used the Major Atmospheric Gamma-ray Imaging Cherenkov (MAGIC) telescopes. We searched for a statistical correlation between the radio and VHE gamma-ray emission with search windows of different lengths and different time lags to the arrival times of a radio GP. A dedicated search for an enhancement in the number of VHE gamma-rays correlated with the occurrence of radio GPs was carried out separately for the P1 and P2 phase ranges, respectively. Results. In the radio data sample, 99444 radio GPs were detected. We find no significant correlation between the GPs and VHE photons in any of the search windows. Depending on phase cuts and the chosen search windows, we find upper limits at a 95% confidence level on an increase in VHE gamma-ray events correlated with radio GPs between 7% and 61% of the average Crab pulsar VHE flux for the P1 and P2 phase ranges, respectively. This puts upper limits on the flux increase during a radio GP between 12% and 2900% of the pulsed VHE flux, depending on the search window duration and phase cuts. This is the most stringent upper limit on a correlation between gamma-ray emission and radio GPs reported so far

MAGIC observations of the microquasar V404 Cygni during the 2015 outburst

The microquasar V404 Cygni underwent a series of outbursts in 2015, June 15-31, during which its flux in hard X-rays (20-40 keV) reached about 40 times the Crab nebula flux. Because of the exceptional interest of the flaring activity from this source, observations at several wavelengths were conducted. The MAGIC telescopes, triggered by the INTEGRAL alerts, followed-up the flaring source for several nights during the period June 18-27, for more than 10 h. One hour of observation was simultaneously conducted on a giant 22 GHz radio flare and a hint of signal at GeV energies seen by Fermi-LAT. The MAGIC observations did not show significant emission in any of the analysed time intervals. The derived flux upper limit, in the energy range 200-1250 GeV, is 4.8 x 10(-12) photons cm(-2) s(-1). We estimate the gamma-ray opacity during the flaring period, which along with our non-detection points to an inefficient acceleration in the V404 Cyg jets if a very high energy emitter is located further than 1 x 10(10) cm from the compact object

MAGIC observations of PG 1553+113 during a multiwavelength campaign in July 2006

The active galactic nucleus PG1553+113 was observed by the MAGIC telescope in July 2006 during a multiwavelength campaign, in which telescopes in the optical, X-ray, and very high energies participated. Although the MAGIC data were affected by strong atmospheric absorption (calima), they were analyzed after applying a correction. In 8.5 h, a signal was detected with a significance of 5.0 sigma. The integral flux above 150 GeV was (2.6 +/- 0.9) x 10(-7) ph s(-1) m(-2). By fitting the differential energy spectrum with a power law, a spectral index of -4.1 +/- 0.3 was obtained

Very high energy gamma-ray radiation from the stellar mass black hole binary Cygnus X-1

We 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