Detection of VHE gamma-ray emission from the distant blazar 1ES 1101-232 with HESS
and broadband characterisation

Aharonian, F.; Akhperjanian, A. G.; Bazer‐Bachi, A. R.; Beilicke, M.; Benbow, W.; Berge, D.; Bernlöhr, K.; Boisson, C.; Bolz, O.; Borrel, V.; Braun, I.; Brion, E.; Brown, A. M.; Bühler, R.; Büsching, I.; Boutelier, T.; Carrigan, S.; Chadwick, P. M.; Chounet, L.‐M.; Coignet, G.; Cornils, R.; Costamante, L.; Degrange, B.; Dickinson, H. J.; Djannati‐Ataï, A.; Drury, L. O’c.; Dubus, G.; Egberts, K.; Emmanoulopoulos, D.; Espigat, P.; Farnier, C.; Feinstein, F.; Ferrero, E.; Fiaßon, A.; Fontaine, G.; Funk, S.; Füling, M.; Gallant, Y. A.; Giebels, B.; Glicenstein, J. F.; Glück, B.; Goret, P.; Hadjichristidis, C.; Hauser, D.; Hauser, M.; Heinzelmann, G.; Henri, G.; Hermann, G.; Hinton, J. A.; Hoffmann, A.; Hofmann, W.; Holleran, M.; Hoppe, S.; Horns, D.; Jachołkowska, A.; Jager, O. C. de; Kendziorra, E.; Kerschhaggl, M.; Khélifi, B.; Komin, Nu.; Kosack, K.; Lamanna, G.; Latham, I. J.; Gallou, R. Le; Lemière, A.; Lemoine‐Goumard, M.; Löhse, T.; Martin, Jean‐Michel; Martineau‐Huynh, O.; Marcowith, A.; Masterson, C.; Maurin, G.; McComb, T. J. L.; Moulin, Emmanuel; Naurois, M. de; Nedbal, D.; Nolan, S. J.; Noutsos, A.; Olive, J.-P.; Orford, K. J.; Osborne, J. L.; Panter, M.; Pelletier, G.; Petrucci, P.-O.; Pita, S.; Pühlhofer, G.; Punch, M.; Ranchon, S.; Raubenheimer, Britt; Raue, M.; Rayner, S. M.; Reimer, A.; Ripken, J.; Rob, L.; Rolland, L.; Rosier‐Lees, S.; Rowell, G.; Sahakian, V.; Santangelo, A.; Saugé, L.; Schlenker, S.; Schlickeiser, R.; Schröder, R.; Schwanke, U.; Schwarzburg, S.; Schwemmer, S.; Shalchi, A.; Sol, H.; Spangler, D.; Spanier, F.; Steenkamp, R.; Stegmann, C.; Superina, G.; Tam, P. H. T.; Tavernet, J.‐P.; Terrier, R.; Tluczykont, M.; Eldik, C. van; Vasileiadis, G.; Venter, C.; Vialle, J. P.; Vincent, P.; Völk, H. J.; Wagner, S. J.; Ward, M. J.

doi:10.1051/0004-6361:20077057

Cited by 120 publications

(74 citation statements)

References 68 publications

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“…The combined data indicate that a single, hard power law fits the intrinsic spectrum over the combined HE-VHE γ-ray ranges, constraining the peak of the IC emission to lie at energies greater than ∼1-2 TeV. Thus, 1ES 0414+009 seems to belong to the subclass of HBLs characterized by Compton peak energies in the multi-TeV range, like 1ES 1101-232 (Aharonian et al 2007b), 1ES 0347-121 (Aharonian et al 2007a), 1ES 0229+200 (Aharonian et al 2007c;Tavecchio et al 2009), or 1ES 1218+304 (Acciari et al 2009). …”

Section: Discussionmentioning

confidence: 80%

Discovery of hard-spectrumγ-ray emission from the BL Lacertae object 1ES 0414+009

Abramowski¹,

Acero²,

Aharonian³

et al. 2012

A&A

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Context. 1ES 0414+009 (z = 0.287) is a distant high-frequency-peaked BL Lac object, and has long been considered a likely emitter of very-highenergy (VHE, E > 100 GeV) γ-rays due to its high X-ray and radio flux. Aims. Observations in the VHE γ-ray band and across the electromagnetic spectrum can provide insights into the origin of highly energetic particles present in the source and the radiation processes at work. Because of the distance of the source, the γ-ray spectrum might provide further limits on the level of the extragalactic background light (EBL). Methods. We report observations made between October 2005 and December 2009 with H.E.S.S., an array of four imaging atmospheric Cherenkov telescopes. Observations at high energies (HE, 100 MeV-100 GeV) with the Fermi-LAT instrument in the first 20 months of its operation are also reported. To complete the multi-wavelength picture, archival UV and X-ray observations with the Swift satellite and optical observations with the ATOM telescope are also used. Results. Based on the observations with H.E.S.S., 1ES 0414+009 is detected for the first time in the VHE band. An excess of 224 events is measured, corresponding to a significance of 7.8σ. The photon spectrum of the source is well described by a power law, with photon index of Γ VHE = 3.45 ± 0.25 stat ± 0.20 syst . The integral flux above 200 GeV is (1.88 ± 0.20 stat ± 0.38 syst ) ×10 −12 cm −2 s −1 . Observations with the Fermi-LAT in the first 20 months of operation show a flux between 200 MeV and 100 GeV of (2.3 ± 0.2 stat ) × 10 −9 erg cm −2 s −1 , and a spectrum well described by a power-law function with a photon index Γ HE = 1.85 ± 0.18. Swift/XRT observations show an X-ray flux between 2 and 10 keV of (0.8−1) × 10 −11 erg cm −2 s −1 , and a steep spectrum Γ X = (2.2−2.3). Combining X-ray with optical-UV data, a fit with a log-parabolic function locates the synchrotron peak around 0.1 keV. Conclusions. Although the GeV-TeV observations do not provide better constraints on the EBL than previously obtained, they confirm a low density of the EBL, close to the lower limits from galaxy counts. The absorption-corrected HE and VHE γ-ray spectra are both hard and have similar spectral indices (≈1.86), indicating no significant change of slope between the HE and VHE γ-ray bands, and locating the γ-ray peak in the SED above 1-2 TeV. As for other TeV BL Lac objects with the γ-ray peak at such high energies and a large separation between the two SED humps, this average broad-band SED represents a challenge for simple one-zone synchrotron self-Compton models, requiring a high Doppler factor and very low B-field.

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Section: Discussionmentioning

confidence: 80%

Discovery of hard-spectrumγ-ray emission from the BL Lacertae object 1ES 0414+009

Abramowski¹,

Acero²,

Aharonian³

et al. 2012

A&A

Self Cite

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show abstract

“…X-ray measurements of the relative positions of the forward and reverse shocks and contact discontinuity in Tycho's SNR also indicate modification of the remnant dynamics by the acceleration of cosmic-ray ions (Warren et al 2005). γ -ray emission in the TeV range from some SNRs, observed with ground-based telescopes, seems to confirm that particles are indeed being accelerated to energies approaching the knee of the cosmic-ray spectrum (Enomoto et al 2002;Aharonian et al 2007aAharonian et al , 2007bKatagiri et al 2005). However, there is growing debate as to whether the origin of this high-energy emission is hadronic or leptonic in nature, as reviewed in Reynolds (2008).…”

Section: Introductionmentioning

confidence: 91%

FERMILARGE AREA TELESCOPE OBSERVATIONS OF SUPERNOVA REMNANTS INTERACTING WITH MOLECULAR CLOUDS

Castro

Slane

2010

ApJ

121

115

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We report the detection of γ -ray emission coincident with four supernova remnants (SNRs) using data from the Large Area Telescope on board the Fermi Gamma-ray Space Telescope. G349.7+0.2, CTB 37A, 3C 391, and G8.7−0.1 are SNRs known to be interacting with molecular clouds, as evidenced by observations of hydroxyl (OH) maser emission at 1720 MHz in their directions. SNR shocks are expected to be sites of cosmic-ray acceleration, and clouds of dense material can provide effective targets for production of γ -rays from π 0 decay. The observations reveal unresolved sources in the direction of G349.7+0.2, CTB 37A, and 3C 391, and a possibly extended source coincident with G8.7−0.1, all with significance levels greater than 10σ .

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“…In this category, all sources are assembled that show a variability index <41.64 in the 2FGL which corresponds to a likelihood fit probability of more than 1% that the source is steady (Fermi-LAT Collaboration 2012). For these sources simultaneous measurements are not required regardless if they are steady (like 1ES 1101-232, Aharonian et al 2007b) or variable (like H 1426+428, see below) at VHE. This does not affect the upper limits derived here because the Fermi index remains valid as a lower limit independent of the VHE index.…”

Section: Sample Tested Against Concavity Criteriamentioning

confidence: 99%

Limits on the extragalactic background light in theFermiera

Meyer

Raue

Mazin

et al. 2012

A&A

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Very high energy (VHE, energy E < ∼ 100 GeV) γ-rays from cosmological sources are attenuated due to the interaction with photons of the extragalactic background light (EBL) in the ultraviolet to infrared wavelength band. The EBL, thus, leaves an imprint on the observed energy spectra of these objects. In the last four years, the number of extragalactic VHE sources discovered with imaging atmospheric Cherenkov telescopes (IACTs), such as MAGIC, H.E.S.S., and VERITAS, has doubled. Furthermore, the measurements of the Fermi satellite brought new insights into the intrinsic spectra of the sources at GeV energies. In this paper, upper limits on the EBL intensity are derived by considering the most extensive VHE source sample ever used in this context. This is accomplished by constructing a large number of generic EBL shapes and combining spectral informations from Fermi and IACTs together with minimal assumptions about the source physics at high and very high γ-ray energies. The evolution of the EBL with redshift is accounted for and the possibility of the formation of an electromagnetic cascade and the implications on the upper limits are explored. The EBL density at z = 0 is constrained over a broad wavelength range between 0.4 and 100 μm. At optical wavelengths, the EBL density is constrained below 24 nW m −2 sr −1 and below 5 nW m −2 sr −1 between 8 μm and 31 μm.

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Detection of VHE gamma-ray emission from the distant blazar 1ES 1101-232 with HESS and broadband characterisation

Cited by 120 publications

References 68 publications

Discovery of hard-spectrumγ-ray emission from the BL Lacertae object 1ES 0414+009

Discovery of hard-spectrumγ-ray emission from the BL Lacertae object 1ES 0414+009

FERMILARGE AREA TELESCOPE OBSERVATIONS OF SUPERNOVA REMNANTS INTERACTING WITH MOLECULAR CLOUDS

Limits on the extragalactic background light in theFermiera

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