Mrk501 is a very high-energy (VHE) gamma-ray blazar located at z=0.034. During a period of two weeks in July 2014, the highest X-ray activity of Mrk501 was observed in ~14 years of operation of the ...Neil Gehrels Swift Gamma-ray Burst Observatory. We characterize the broadband variability of Mrk501 from radio to VHE gamma rays, and evaluate whether it can be interpreted within theoretical scenarios widely used to explain the broadband emission from blazars. The temporal evolution of the most prominent and variable segments of the SED is described with a one-zone synchrotron self-Compton model with variations in the break energy of the electron energy distribution (EED), and with some adjustments in the magnetic field strength and spectral shape of the EED. A narrow feature at ~3 TeV was observed in the VHE spectrum measured on 2014 July 19 (MJD 56857.98), which is the day with the highest X-ray flux (\(>0.3\) keV) measured during the entire Swift mission. This feature is inconsistent with the classical analytic functions to describe the measured VHE spectra (power law, log-parabola, and log-parabola with exponential cutoff) at more than 3\(\sigma\). A fit with a log-parabola plus a narrow component is preferred over the fit with a single log-parabola at more than 4\(\sigma\), and a dedicated Monte Carlo simulation estimated the significance of this extra component to be larger than 3\(\sigma\). Under the assumption that this VHE spectral feature is real, we show that it can be reproduced with three distinct theoretical scenarios: a) a pileup in the EED due to stochastic acceleration; b) a structured jet with two-SSC emitting regions, with one region dominated by an extremely narrow EED; and c) an emission from an IC pair cascade.
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>100 GeV) gamma-rays from the Crab pulsar. 16 hours 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 with the Major Atmospheric Gamma-ray Imaging Cherenkov (MAGIC) telescopes were performed. 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. 99444 radio GPs have been detected in the radio data sample. 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 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 of 12% to 2900% (depending on search window duration and phase cuts) of the pulsed VHE flux. This is the most stringent upper limit on a correlation between gamma-ray emission and radio GPs reported so far.}
Monthly Notices of the Royal Astronomical Society, Volume 483,
Issue 4, March 2019, Pages 4578-4585 SNR G24.7+0.6 is a 9.5 kyrs radio and $\gamma$-ray supernova remnant evolving
in a dense medium. In ...the GeV regime, SNR G24.7+0.6
(3FHL\,J1834.1--0706e/FGES\,J1834.1--0706) shows a hard spectral index
($\Gamma$$\sim$2) up to $200$\,GeV, which makes it a good candidate to be
observed with Cherenkov telescopes such as MAGIC. We observed the field of view
of \snr\ with the MAGIC telescopes for a total of 31 hours. We detect very high
energy $\gamma$-ray emission from an extended source located 0.34\degr\ away
from the center of the radio SNR. The new source, named \mgc\ is detected up to
5\,TeV, and its spectrum is well-represented by a power-law function with
spectral index of $2.74 \pm 0.08$. The complexity of the region makes the
identification of the origin of the very-high energy emission difficult,
however the spectral agreement with the LAT source and overlapping position at
less than 1.5$\sigma$ point to a common origin. We analysed 8 years of
\fermi-LAT data to extend the spectrum of the source down to 60\,MeV.
\fermi-LAT and MAGIC spectra overlap within errors and the global broad band
spectrum is described by a power-law with exponential cutoff at
$1.9\pm0.5$\,TeV. The detected $\gamma$-ray emission can be interpreted as the
results of proton-proton interaction between the supernova and the CO-rich
surrounding.
A&A 623, A175 (2019) The mechanisms producing fast variability of the $\gamma$-ray emission in
active galactic nuclei are under debate. The MAGIC telescopes detected a fast
very high energy (VHE, ...E$>100$ GeV) $\gamma$-ray flare from BL Lacertae on 2015
June 15. The flare had a maximum flux of $(1.5\pm 0.3)\times 10^{-10}$ photons
cm$^{-2}$ s$^{-1}$ and halving time of $26\pm8$ minutes. The MAGIC observations
were triggered by a high state in the optical and high energy (HE, E$>100$ MeV)
$\gamma$-ray bands. In this paper we present the MAGIC VHE $\gamma$-ray data
together with multiwavelength data from radio, optical, X-rays, and HE $\gamma$
rays from 2015 May 1 to July 31. Well-sampled multiwavelength data allow us to
study the variability in detail and compare it to the other epochs when fast
VHE $\gamma$-ray flares have been detected from this source. Interestingly, we
find that the behaviour in radio, optical, X-rays and HE $\gamma$-rays is very
similar to two other observed VHE $\gamma$-ray flares. In particular, also
during this flare there was an indication of rotation of the optical
polarization angle and of activity at the 43\,GHz core. These repeating
patterns indicate a connection between the three events. We also test modelling
of the spectral energy distribution, based on constraints from the light curves
and VLBA observations, with two different geometrical setups of two-zone
inverse Compton models. In addition we model the $\gamma$-ray data with the
star-jet interaction model. We find that all of the tested emission models are
compatible with the fast VHE $\gamma$-ray flare, but all have some tension with
the multiwavelength observations.
A population of globular clusters (GCs) has been recently established by the Fermi-LAT telescope as a new class of GeV \(\gamma\)-ray sources. Leptons accelerated to TeV energies, in the inner ...magnetospheres of MSPs or in their wind regions, should produce \(\gamma\)-rays through the inverse Compton scattering in the dense radiation field from the huge population of stars. We have conducted deep observations of the globular cluster M15 with the MAGIC telescopes and used 165 hrs in order to search for \(\gamma\)-ray emission. A strong upper limit on the TeV \(\gamma\)-ray flux \(<3.2\times 10^{-13}\mathrm{cm^{-2}s^{-1}}\) above 300 GeV (\(<0.26\%\) of the Crab nebula flux) has been obtained. We interpret this limit as a constraint on the efficiency of the acceleration of leptons in the magnetospheres of the MSPs. We constrain the injection rate of relativistic leptons, \(\eta_{\rm e}\), from the MSPs magnetospheres and their surrounding. We conclude that \(\eta_{\rm e}\) must be lower than expected from the modelling of high energy processes in MSP inner magnetospheres. For leptons accelerated with the power law spectrum in the MSP wind regions, \(\eta_{\rm e}\) is constrained to be much lower than derived for the wind regions around classical pulsars. These constraints are valid for the expected range of magnetic field strengths within the GC and for the range of likely energies of leptons injected from the inner magnetospheres, provided that the leptons are not removed from the globular cluster very efficiently due to advection process. We discuss consequences of these constraints for the models of radiation processes around millisecond pulsars.
The HAWC Collaboration released the 2HWC catalog of TeV sources, in which 19 show no association with any known high-energy (HE; E > 10 GeV) or very-high-energy (VHE; E > 300 GeV) sources. This ...catalog motivated follow-up studies by both the MAGIC and Fermi-LAT observatories with the aim of investigating gamma-ray emission over a broad energy band. In this paper, we report the results from the first joint work between HAWC, MAGIC and Fermi-LAT on three unassociated HAWC sources: 2HWC J2006+341, 2HWC J1907+084* and 2HWC J1852+013*. Although no significant detection was found in the HE and VHE regimes, this investigation shows that a minimum 1 degree extension (at 95% confidence level) and harder spectrum in the GeV than the one extrapolated from HAWC results are required in the case of 2HWC J1852+013*, while a simply minimum extension of 0.16 degrees (at 95% confidence level) can already explain the scenario proposed by HAWC for the remaining sources. Moreover, the hypothesis that these sources are pulsar wind nebulae is also investigated in detail.
We report on observations of the pulsar / Be star binary system PSR J2032+4127 / MT91 213 in the energy range between 100 GeV and 20 TeV with the VERITAS and MAGIC imaging atmospheric Cherenkov ...telescope arrays. The binary orbit has a period of approximately 50 years, with the most recent periastron occurring on 2017 November 13. Our observations span from 18 months prior to periastron to one month after. A new, point-like, gamma-ray source is detected, coincident with the location of PSR J2032+4127 / MT91 213. The gamma-ray light curve and spectrum are well-characterized over the periastron passage. The flux is variable over at least an order of magnitude, peaking at periastron, thus providing a firm association of the TeV source with the pulsar / Be star system. Observations prior to periastron show a cutoff in the spectrum at an energy around 0.5 TeV. This result adds a new member to the small population of known TeV binaries, and it identifies only the second source of this class in which the nature and properties of the compact object are firmly established. We compare the gamma-ray results with the light curve measured with the X-ray Telescope (XRT) on board the Neil Gehrels \textit{Swift} Observatory and with the predictions of recent theoretical models of the system. We conclude that significant revision of the models is required to explain the details of the emission we have observed, and we discuss the relationship between the binary system and the overlapping steady extended source, TeV J2032+4130.
The BL Lac object S5~0716+714, a highly variable blazar, underwent an impressive outburst in January 2015 (Phase A), followed by minor activity in February (Phase B). The MAGIC observations were ...triggered by the optical flux observed in Phase A, corresponding to the brightest ever reported state of the source in the R-band. The comprehensive dataset collected is investigated in order to shed light on the mechanism of the broadband emission. Multi-wavelength light curves have been studied together with the broadband Spectral Energy Distributions (SEDs). The data set collected spans from radio, optical photometry and polarimetry, X-ray, high-energy (HE, 0.1 GeV < E < 100 GeV) with \textit{Fermi}-LAT to the very-high-energy (VHE, E>100 GeV) with MAGIC. The flaring state of Phase A was detected in all the energy bands, providing for the first time a multi-wavelength sample of simultaneous data from the radio band to the VHE. In the constructed SED the \textit{Swift}-XRT+\textit{NuSTAR} data constrain the transition between the synchrotron and inverse Compton components very accurately, while the second peak is constrained from 0.1~GeV to 600~GeV by \textit{Fermi}+MAGIC data. The broadband SED cannot be described with a one-zone synchrotron self-Compton model as it severely underestimates the optical flux in order to reproduce the X-ray to \(\gamma\)-ray data. Instead we use a two-zone model. The EVPA shows an unprecedented fast rotation. An estimation of the redshift of the source by combined HE and VHE data provides a value of \(z = 0.31 \pm 0.02_{stats} \pm 0.05_{sys}\), confirming the literature value. The data show the VHE emission originating in the entrance and exit of a superluminal knot in and out a recollimation shock in the inner jet. A shock-shock interaction in the jet seems responsible for the observed flares and EVPA swing. This scenario is also consistent with the SED modelling.
Fast radio bursts (FRBs) are bright flashes observed typically at GHz frequencies with millisecond duration, whose origin is likely extragalactic. Their nature remains mysterious, motivating searches ...for counterparts at other wavelengths. FRB 121102 is so far the only source known to repeatedly emit FRBs and is associated with a host galaxy at redshift \(z \simeq 0.193\). We conducted simultaneous observations of FRB 121102 with the Arecibo and MAGIC telescopes during several epochs in 2016--2017. This allowed searches for millisecond-timescale burst emission in very-high-energy (VHE) gamma rays as well as the optical band. While a total of five FRBs were detected during these observations, no VHE emission was detected, neither of a persistent nature nor burst-like associated with the FRBs. The average integral flux upper limits above 100 GeV at 95% confidence level are \(6.6 \times 10^{-12}~\mathrm{photons\ cm^{-2}\ s^{-1}}\) (corresponding to luminosity \(L_{\rm VHE} \lesssim 10^{45}~\mathrm{erg\ s^{-1}}\)) over the entire observation period, and \(1.2 \times 10^{-7}~ \mathrm{photons\ cm^{-2}\ s^{-1}}\) (\(L_{\rm VHE} \lesssim 10^{49}~\mathrm{erg\ s^{-1}}\)) over the total duration of the five FRBs. We constrain the optical U-band flux to be below 8.6 mJy at 5-\(\sigma\) level for 1-ms intervals around the FRB arrival times. A bright burst with U-band flux \(29~\mathrm{mJy}\) and duration \(\sim 12\) ms was detected 4.3 s before the arrival of one FRB. However, the probability of spuriously detecting such a signal within the sampled time space is 1.5% (2.2 \(\sigma\), post-trial), i.e. consistent with the expected background. We discuss the implications of the obtained upper limits for constraining FRB models.
Clusters of galaxies are the largest known gravitationally bound structures in the Universe, with masses around \(10^{15}\ M_\odot\), most of it in the form of dark matter. The ground-based Imaging ...Atmospheric Cherenkov Telescope MAGIC made a deep survey of the Perseus cluster of galaxies using almost 400 h of data recorded between 2009 and 2017. This is the deepest observational campaign so far on a cluster of galaxies in the very high energy range. We search for gamma-ray signals from dark matter particles in the mass range between 200 GeV and 200 TeV decaying into standard model pairs. We apply an analysis optimized for the spectral and morphological features expected from dark matter decays and find no evidence of decaying dark matter. From this, we conclude that dark matter particles have a decay lifetime longer than \(\sim10^{26}\)~s in all considered channels. Our results improve previous lower limits found by MAGIC and represent the strongest limits on decaying dark matter particles from ground-based gamma-ray instruments.
