Science Data Center for Astrophysics

Versoix, Switzerland

Science Data Center for Astrophysics

Versoix, Switzerland
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Ahnen M.L.,ETH Zurich | Ansoldi S.,University of Udine | Ansoldi S.,Kyoto University | Antonelli L.A.,National institute for astrophysics | And 175 more authors.
Monthly Notices of the Royal Astronomical Society | Year: 2017

We present the first detection of the nearby (z = 0.084) low-luminosity BL Lac object 1ES 1741+196 in the very high energy (E > 100 GeV) band. This object lies in a triplet of interacting galaxies. Early predictions had suggested 1ES 1741+196 to be, along with several other high-frequency BL Lac sources, within the reach of MAGIC detectability. Its detection by MAGIC, later confirmed by VERITAS, helps to expand the small population of known TeV BL Lacs. The source was observed with the MAGIC telescopes between 2010 April and 2011 May, collecting 46 h of good quality data. These observations led to the detection of the source at 6.0 σ confidence level, with a steady flux F(>100 GeV) = (6.4 ± 1.7stat ± 2.6syst ) × 10−12 ph cm−2 s−1 and a differential spectral photon index Ɣ = 2.4 ± 0.2stat ± 0.2syst in the range of ∼80 GeV–3 TeV. To study the broad-band spectral energy distribution (SED) simultaneous with MAGIC observations, we use KVA, Swift/UVOT and XRT and Fermi/LAT data. One-zone synchrotron-self-Compton (SSC) modelling of the SED of 1ES 1741+196 suggests values for the SSC parameters that are quite common among known TeV BL Lacs except for a relatively low Doppler factor and slope of electron energy distribution. A thermal feature seen in the SED is well matched by a giant elliptical's template. This appears to be the signature of thermal emission from the host galaxy, which is clearly resolved in optical observations. © 2017 The Authors


Ahnen M.L.,ETH Zurich | Ansoldi S.,University of Udine | Ansoldi S.,Kyoto University | Antonelli L.A.,National institute for astrophysics | And 168 more authors.
Astronomy and Astrophysics | Year: 2017

Context. In this work we present data from observations with the MAGIC telescopes of SN 2014J detected on January 21 2014, the closest Type Ia supernova since Imaging Air Cherenkov Telescopes started to operate. Aims. We aim to probe the possibility of very-high-energy (VHE; E ≥ 100 GeV) gamma rays produced in the early stages of Type Ia supernova explosions. Methods. We performed follow-up observations after this supernova (SN) explosion for five days, between January 27 and February 2 2014. We searched for gamma-ray signals in the energy range between 100 GeV and several TeV from the location of SN 2014J using data from a total of ∼5.5 h of observations. Prospects for observing gamma rays of hadronic origin from SN 2014J in the near future are also being addressed. Results. No significant excess was detected from the direction of SN 2014J. Upper limits at 95% confidence level on the integral flux, assuming a power-law spectrum, dF/dE ∝ E-r, with a spectral index of ⌈ = 2.6, for energies higher than 300 GeV and 700 GeV, are established at 1.3×10-12 and 4.1×10-13 photons cm-2 s-1, respectively. Conclusions. For the first time, upper limits on the VHE emission of a Type Ia supernova are established. The energy fraction isotropically emitted into TeV gamma rays during the first ∼10 days after the supernova explosion for energies greater than 300 GeV is limited to 10-6 of the total available energy budget (∼1051 erg). Within the assumed theoretical scenario, the MAGIC upper limits on the VHE emission suggest that SN 2014J will not be detectable in the future by any current or planned generation of Imaging Atmospheric Cherenkov Telescopes. © 2017 ESO.

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