Gamma-Rays From the Quasar PKS 1441+25: Story of an Escape

Abeysekara, A. U.; Archambault, S.; Archer, A.; Aune, T.; Barnacka, A.; Benbow, W.; Bird, R.; Biteau, J.; Buckley, J. H.; Bugaev, V.; Cardenzana, J. V.; Cerruti, M.; Chen, X.; Christiansen, J. L.; Ciupik, L.; Connolly, Michael; Coppi, P.; Cui, Wei; Dickinson, H. J.; Dumm, J.; Eisch, J.; Errando, M.; Falcone, A.; Feng, Q.; Finley, J. P.; Fleischhack, Henrike; Flinders, A.; Fortin, P.; Fortson, L.; Furniss, A.; Gillanders, G. H.; Griffin, S.; Grube, J.; Gyuk, G.; Hütten, Moritz; Håkansson, N.; Hanna, D.; Holder, J.; Humensky, T. B.; Johnson, C. A.; Kaaret, Philip; Kar, P.; Kelley-Hoskins, N.; Khassen, Y.; Kieda, D.; Krause, M.; Krennrich, F.; Kumar, S.; Lang, M. J.; Maier, G.; McArthur, S.; McCann, A.; Meagher, K.; Moriarty, P.; Mukherjee, R.; Nieto, D.; Bhróithe, A. O Faoláin De; Ong, R. A.; Otte, A. N.; Park, N.; Perkins, J. S.; Petrashyk, A.; Pohl, M.; Popkow, A.; Pueschel, E.; Quinn, J.; Ragan, K.; Ratliff, G.; Reynolds, P. T.; Richards, G.; Roache, E.; Rousselle, J.; Santander, M.; Sembroski, G. H.; Shahinyan, K.; Smith, A. W.; Staszak, D.; Telezhinsky, I.; Todd, N.; Tucci, J. V.; Tyler, J.; Vassiliev, V. V.; Vincent, S.; Wakely, S. P.; Weiner, O. M.; Weinstein, A. J.R.; Wilhelm, A.; Williams, D. A.; Zitzer, B.; Smith, Paul S.; Holoien, T. W. S.; Prieto, J. L.; Kochanek, C. S.; Stanek, K. Z.; Shappee, B. J.; Hovatta, T.; Max-Moerbeck, W.; Pearson, T. J.; Reeves, R.; Richards, J. L.; Readhead, A. C. S.; Madejski, G. M.; Djorgovski, S. G.; Drake, A. J.; Graham, M. J.; Mahabal, A.

doi:10.1088/2041-8205/815/2/l22

Cited by 90 publications

(67 citation statements)

References 43 publications

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“…We aim to probe whether the excess radiation of CIBER is a new EBL component, in the background that the recent EBL models are repeatedly tested in many literatures and are generally agreed with the γ-ray observations, see e.g., Refs. [19,25,31,[35][36][37][38][39]. Hence, we build four absorption models, i.e., GCA (Gilmore EBL+CIBER+ALP), GA (Gilmore EBL+ALP), GC (Gilmore EBL+CIBER) and GEBL (Gilmore EBL).…”

Section: Discussionmentioning

confidence: 99%

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Testing the CIBER cosmic infrared background measurements and axionlike particles with observations of TeV blazars

et al. 2020

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The first measurements from the CIBER experiment of extragalactic background light (EBL) in near-infrared (NIR) band exhibit a higher intensity than those inferred through γ-ray observations. Recent theoretical-EBL intensities are typically consistent with the very high energy (VHE) γ-ray observations. Yet, it is possible that the excess NIR radiation is a new component of EBL and not in tension with the TeV spectra of distant blazars, since the hypothetical axion-like particle (ALP) may lead to a reduced opacity of the Universe for VHE γ-rays. In order to probe whether the excess component arises mainly from EBL, thirteen observed spectra in high energy and VHE ranges from ten distant TeV BL Lac objects are fitted by four theoretical spectra which involve theoretical EBL (Gilmore ), Gilmore's EBL model including photon/ALP coupling, Gilmore's EBL with CIBER excess and the latter including photon/ALP coupling respectively. We find the goodness of fit for the model with CIBER excess can be improved with a significance of 7.6 σ after including the photon/ALP coupling; Thus, the ALP/photon mixing mechanism can effectively alleviate the tension; However, the Gilmore EBL model, on the whole, is more compatible with the observed spectra compared to those with ALP, although individual blazars such as PKS 1424+240 and 1ES 1101-232 prefer the ALP-model. Our results suggest that the recent EBL models can solely explain the VHE γ-ray observations, and assuming the existence of the ALP to alleviate the tension is not required in a statistical sense, thus the excess over the EBL models is less likely to be a new EBL component. * EBL intensities (for reviews see e.g. Refs. [1,16,17]) and test the empirical EBL models, e.g. Refs. [8][9][10][11][12][13], by comparing the difference between the assumed-intrinsic spectra and the observed one. Thanks to the discovery of more and more distant Tev blazars, several groups have detected this imprint, e.g. Refs. [15,18,19], and found the intensities were near the galaxy-count lower limits.The spectra of a few individual blazars such as PKS1424+240 appear to be unexpectedly hard [34]. Furthermore, hints for a reduced gamma-ray opacity in the form of a pair-production anomaly [20] (i.e., VHE γ-ray observations require an EBL level below the lower limits from galaxy counts), or unusual redshift-dependent intrinsic (after correction for EBL absorption) spectral hardening found in large samples, have been claimed by several authors [21][22][23][24]. However, no significant and systematic anomalies on the entire sample were revealed by recent systematic studies of spectra fitted with recent theoretical EBL absorption on large samples of VHE blazars, see e.g., 33,34]. The intensities of these recent EBL models (e.g. Franceschini 2008 [8], Dominguez 2011 [9], Kneiske 2010 [10], Finke 2010 [11], Gilmore 2012 [12], Stecker 2016 [13]) are close to that from the galaxy counts. At present, many EBL measurements inferred by γ-ray observations reveal that its intensities are generally consistent with ...

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Section: Discussionmentioning

confidence: 99%

“…At present, many EBL measurements inferred by γ-ray observations reveal that its intensities are generally consistent with those given by the recent EBL models, see e.g., Refs. [19,25,31,32,[35][36][37][38][39].However, most of the direct local measurements of EBL from several different groups (e.g. Refs.…”

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confidence: 99%

Testing the CIBER cosmic infrared background measurements and axionlike particles with observations of TeV blazars

et al. 2020

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“…The similarity of the non-thermal (likely jet-dominated) components of the SEDs of γ-NLS1s and FSRQs seems to suggest that similar processes (i.e., external-Compton dominated γ-ray emission) may be at work in both classes of sources (e.g., Abdo et al 2009a;Berton et al 2016;Arrieta-Lobo et al 2017). Currently, seven FSRQs have been detected by IACTs (Mirzoyan 2017;Mukherjee & VERITAS Collaboration 2017;Cerruti et al 2017;Ahnen et al 2015;Abeysekara et al 2015;Sitarek et al 2015;Aleksić et al 2011;H.E.S.S. Collaboration et al 2013;MAGIC Collaboration et al 2008; also see TeVCat 5 for further references).…”

Section: Discussionmentioning

confidence: 99%

Prospects for gamma-ray observations of narrow-line Seyfert 1 galaxies with the Cherenkov Telescope Array

Romano

Vercellone

Foschini

et al. 2018

Monthly Notices of the Royal Astronomical Society

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Gamma-ray emitting narrow-line Seyfert 1 (γ-NLS1) galaxies possibly harbour relatively low-mass black holes (10 6 -10 8 M ⊙ ) accreting close to the Eddington limit, and share many characteristics with their sibling sources, flat-spectrum radio quasars. Although they have been detected in the MeV-GeV band with Fermi-LAT, they have never been seen in the very high energy band with current imaging atmospheric Cherenkov telescopes (IACTs). Thus, they are key targets for the next-generation IACT, the Cherenkov Telescope Array (CTA). In a previous work we selected, by means of extensive simulations, the best candidates for a prospective CTA detection (SBS 0846+513, PMN J0948+0022, and PKS 1502+036) taking into account the effects of both the intrinsic absorption (approximated with a cut-off at 30 GeV), and the extra-galactic background light on the propagation of γ-rays. In this work we simulate the spectra of these three sources by adopting more realistic broad-line region (BLR) absorption models. In particular, we consider the detailed treatment of γ-γ absorption in the radiation fields of the BLR as a function of the location of the γ-ray emission region with parameters inferred from observational constraints. We find that, due to the energy range extent and its sensitivity, CTA is particularly well suited to locate the γ-ray emitting region in γ-NLS1. In particular CTA will be able not only to distinguish whether the γ-ray emitting region is located inside or outside the BLR, but also where inside the BLR it may be.

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“…Observation of the blazars by the large area telescope (LAT) onboard the Fermi satellite in energy range from 30 MeV to more than 500 GeV provides a very strong observational evidence regarding the intrinsic MeV-GeV emission from them [29]. Combined MeV-GeV and TeV observations have provided a new tool to constrain the EBL intensity [30,31,32,33,34,35,36,37]. Recently, the Fermi-LAT observations have been used to indirectly measure the EBL from the absorption features seen in the γ-ray spectra of blazars beyond the redshift z > 1 [38,39].…”

Section: Introductionmentioning

confidence: 99%

Extragalactic background light models and GeV-TeV observation of blazars

Singh

Meintjes

2020

NRIAG Journal of Astronomy and Geophysics

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The extragalactic background light (EBL) in the ultraviolet to far-infrared wavelength range is dominated by the emissions from stars in galaxies and reflects the time-integrated history of the light production and reprocessing in the Universe. Direct measurements of the EBL are affected by the interplanetary dust and galactic emission. Hence, the absolute level of EBL is subject to considerable uncertainties. Observations of very high energy (VHE) blazars located at cosmological distances by the Fermi-Large Area Telescope (LAT) and ground-based gamma-ray telescopes (e.g. H.E.S.S., MAGIC, VERITAS, TACTIC) provide a measurement of the EBL that is independent of the direct observations. The interaction of VHE or TeV photons originated from the distant blazars with the low energy EBL photons via e − e + pair-production can be used as a powerful tool to probe the different EBL models in the wavelength range 0.1-1000µm. In this paper, we use two different methods to determine the opacity of the VHE γ-ray photons caused by the low energy EBL photons and study the consequences of six different EBL models. The first method-Model-Dependent Approach, uses various EBL models for estimating the opacity as a function of the source redshift and energy. The second method-Model-Independent Approach, relies on using the simultaneous observations of blazars in the MeV-GeV energy range from the Fermi-LAT and in TeV band from the ground-based Cherenkov telescopes. We make underline assumption that the extrapolation of the LAT spectrum of blazars to TeV energies is either a good estimate or an upper limit for the intrinsic VHE spectrum of the source. We apply this method on the simultaneous observations of a few blazars PKS 2155-304, RGB J0710+591, 1ES 1218+304 and RBS 0413 at different redshifts to demonstrate a comparative study of six prominent EBL models. Opacities of the VHE γ-ray photons predicted by the Model-Independent Approach are systematically larger than the ones estimated from the Model-Dependent Approach using the six EBL models. Therefore, the γ-ray observations of blazars can be used to set a strict upper limit on the opacity of the Universe to the VHE γ-rays at a given redshift.

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Gamma-Rays From the Quasar PKS 1441+25: Story of an Escape

Cited by 90 publications

References 43 publications

Testing the CIBER cosmic infrared background measurements and axionlike particles with observations of TeV blazars

Testing the CIBER cosmic infrared background measurements and axionlike particles with observations of TeV blazars

Prospects for gamma-ray observations of narrow-line Seyfert 1 galaxies with the Cherenkov Telescope Array

Extragalactic background light models and GeV-TeV observation of blazars

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