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Deep observation of the NGC 1275 region with MAGIC: search of diffuse gamma-ray emission from cosmic rays in the Perseus cluster
Clusters of galaxies are expected to be reservoirs of cosmic rays (CRs) that should produce diffuse gamma-ray emission due to their hadronic interactions with the intra-cluster medium. The nearby Perseus cool-core cluster, identified as the most promising target to search for such an emission, has been observed with the MAGIC telescopes at very-high energies (VHE, E>100 GeV) for a total of 253 hr from 2009 to 2014. The active nuclei of NGC 1275, the central dominant galaxy of the cluster, and IC 310, lying at about 0.6∘ from the centre, have been detected as point-like VHE gamma-ray emitters during the first phase of this campaign. We report an updated measurement of the NGC 1275 spectrum, which is well described by a power law with a photon index of 3.6±0.2stat±0.2syst between 90 GeV and 1.2 TeV. We do not detect any diffuse gamma-ray emission from the cluster and set stringent constraints on its CR population. In order to bracket the uncertainties over the CR spatial and spectral distributions, we adopt different spatial templates and power-law spectral indexes α. For α=2.2, the CR-to-thermal pressure within the cluster virial radius is constrained to be below 1-2%, except if CRs can propagate out of the cluster core, generating a flatter radial distribution and releasing the CR-to-thermal pressure constraint to <20%. Assuming that the observed radio mini-halo of Perseus is generated by secondary electrons from CR hadronic interactions, we can derive lower limits on the central magnetic field, B0, that depend on the CR distribution. For α=2.2, B0≳5−8μG, which is below the 25 μG inferred from Faraday rotation measurements, whereas, for α≲2.1, the hadronic interpretation of the diffuse radio emission is in contrast with our gamma-ray flux upper limits independently of the magnetic field strength.

External link:
http://arxiv.org/abs/1602.03099

Limits to dark matter annihilation cross-section from a combined analysis of MAGIC and Fermi-LAT observations of dwarf satellite galaxies
We present the first joint analysis of gamma-ray data from the MAGIC Cherenkov telescopes and the Fermi Large Area Telescope (LAT) to search for gamma-ray signals from dark matter annihilation in dwarf satellite galaxies. We combine 158 hours of Segue 1 observations with MAGIC with 6-year observations of 15 dwarf satellite galaxies by the Fermi-LAT. We obtain limits on the annihilation cross-section for dark matter particle masses between 10 GeV and 100 TeV - the widest mass range ever explored by a single gamma-ray analysis. These limits improve on previously published Fermi-LAT and MAGIC results by up to a factor of two at certain masses. Our new inclusive analysis approach is completely generic and can be used to perform a global, sensitivity-optimized dark matter search by combining data from present and future gamma-ray and neutrino detectors.

External link:
http://arxiv.org/abs/1601.06590

Very-high-energy gamma-rays from the Universe's middle age: detection of the z=0.940 blazar PKS 1441+25 with MAGIC
The flat-spectrum radio quasar PKS 1441+25 at a redshift of z = 0.940 is detected between 40 and 250 GeV with a significance of 25.5 {\sigma} using the MAGIC telescopes. Together with the gravitationally lensed blazar QSO B0218+357 (z = 0.944), PKS 1441+25 is the most distant very high energy (VHE) blazar detected to date. The observations were triggered by an outburst in 2015 April seen at GeV energies with the Large Area Telescope on board Fermi. Multi-wavelength observations suggest a subdivision of the high state into two distinct flux states. In the band covered by MAGIC, the variability time scale is estimated to be 6.4 +/- 1.9 days. Modeling the broadband spectral energy distribution with an external Compton model, the location of the emitting region is understood as originating in the jet outside the broad line region (BLR) during the period of high activity, while being partially within the BLR during the period of low (typical) activity. The observed VHE spectrum during the highest activity is used to probe the extragalactic background light at an unprecedented distance scale for ground-based gamma-ray astronomy.

External link:
http://arxiv.org/abs/1512.04435

Teraelectronvolt pulsed emission from the Crab pulsar detected by MAGIC
Aims: To investigate the extension of the very-high-energy spectral tail of the Crab pulsar at energies above 400 GeV. Methods: We analyzed ∼320 hours of good quality data of Crab with the MAGIC telescope, obtained from February 2007 until April 2014. Results: We report the most energetic pulsed emission ever detected from the Crab pulsar reaching up to 1.5 TeV. The pulse profile shows two narrow peaks synchronized with the ones measured in the GeV energy range. The spectra of the two peaks follow two different power-law functions from 70 GeV up to 1.5 TeV and connect smoothly with the spectra measured above 10 GeV by the Large Area Telescope (LAT) on board of the Fermi satellite. When making a joint fit of the LAT and MAGIC data, above 10 GeV, the photon indices of the spectra differ by 0.5±0.1. Conclusions: We measured with the MAGIC telescopes the most energetic pulsed photons from a pulsar to date. Such TeV pulsed photons require a parent population of electrons with a Lorentz factor of at least 5×106. These results strongly suggest IC scattering off low energy photons as the emission mechanism and a gamma-ray production region in the vicinity of the light cylinder.

External link:
http://arxiv.org/abs/1510.07048

Very-high-energy γ-ray observations of novae and dwarf novae with the MAGIC telescopes
In the last five years the Fermi Large Area Telescope (LAT) instrument detected GeV {\gamma}-ray emission from five novae. The GeV emission can be interpreted in terms of an inverse Compton process of electrons accelerated in a shock. In this case it is expected that protons in the same conditions can be accelerated to much higher energies. Consequently they may produce a second component in the {\gamma}-ray spectrum at TeV energies. Aims. We aim to explore the very-high-energy domain to search for {\gamma}-ray emission above 50 GeV and to shed light on the acceleration process of leptons and hadrons in nova explosions. Methods. We have performed observations with the MAGIC telescopes of the classical nova V339 Del shortly after the 2013 outburst, triggered by optical and subsequent GeV {\gamma}-ray detec- tions. We also briefly report on VHE observations of the symbiotic nova YY Her and the dwarf nova ASASSN-13ax. We complement the TeV MAGIC observations with the analysis of con- temporaneous Fermi-LAT data of the sources. The TeV and GeV observations are compared in order to evaluate the acceleration parameters for leptons and hadrons. Results. No significant TeV emission was found from the studied sources. We computed upper limits on the spectrum and night-by-night flux. The combined GeV and TeV observations of V339 Del limit the ratio of proton to electron luminosities to Lp<~0.15 Le.

External link:
http://arxiv.org/abs/1508.04902