Extremely High energy peaked BL Lac nature of the TeV blazar Mrk 501

Singh, K.K.; Meintjes, P. J.; Ramamonjisoa, F.A.; Tolamatti, A.

doi:10.1016/j.newast.2019.101278

Cited by 12 publications

(11 citation statements)

References 79 publications

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“…We note, however, that the observed 'harder-when-brighter' trend is generally more often observed in blazars (e.g. Bhatta, Mohorian & Bilinsky 2018;Singh et al 2019;Zhang et al 2019), particularly during flaring episodes, than in Seyfert-type AGNs. Since IRAS 17020+4544 and IRAS 16318−472 are both jetted sources it is plausible that the jet emission is influencing and/or connected to the X-ray emission.…”

Section: Discussionmentioning

confidence: 53%

Characterizing continuum variability in the radio-loud narrow-line Seyfert 1 galaxy IRAS 17020+4544

Gonzalez

Gallo

Kosec

et al. 2020

Monthly Notices of the Royal Astronomical Society

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ABSTRACT We present results of temporal and spectral analyses on four XMM–Newton EPIC pn observations of IRAS 17020+4544, a narrow-line Seyfert 1 galaxy with evidence of a radio jet. Analysis of the light curves reveals that this radio-loud source does not behave like the bulk population of its radio-quiet counterparts. A trend of spectral hardening with increased flux is found. Variability is found to increase with energy, though it decreases as the spectrum hardens. The first 40 ks of the most recent observation behave uniquely among the epochs, exhibiting a softer spectral state than at any other time. Possible non-stationarity at low energies is found, with no such effect present at higher energies, suggesting at least two distinct spectral components. A reverberation signature is confirmed, with the lag-frequency, lag-energy, and covariance spectra changing significantly during the soft-state epoch. The temporal analysis suggests a variable power law in the presence of a reflection component, thus motivating such a fit for the 0.3−10 keV EPIC pn spectra from all epochs. We find an acceptable spectral fit using the timing-motivated parameters and report the detection of a broad Fe K emission line, requiring an additional model component beyond the reflection spectrum. We discuss links between this source and other narrow-line Seyfert 1 sources that show evidence of jet activity, finding similarities among this currently very limited sample of interesting objects.

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Section: Discussionmentioning

confidence: 53%

Characterizing continuum variability in the radio-loud narrow-line Seyfert 1 galaxy IRAS 17020+4544

Gonzalez

Gallo

Kosec

et al. 2020

Monthly Notices of the Royal Astronomical Society

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“…The large error bars in the values of optical depth obatined from the Model-Independent Approach are attributed to the uncertainties in the observed VHE spectra. Due its relatively hard γ-ray spectra and no evidence of variability [59], RGB J0710+591 is one the most suitable blazars to probe the EBL models.…”

Section: Rgb J0710+591mentioning

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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“…Other observational features of these sources include hard X-ray and TeV γ-ray spectra, large X-ray to radio flux ratio and lack of short term variability (Bonnoli et al 2015). Sources with these peculiar characteristics are termed as Extremely High Synchrotron-Peaked or simply Extreme Blazars (Singh et al 2019). Due to the hard X-ray spectrum (Γ ≤ 2), the synchrotron peak in the low energy component of the SED is located at energies above few keV.…”

Section: Es 1218+304: An Extreme Blazarmentioning

confidence: 99%

Long-term multiwavelength view of the blazar 1ES 1218+304

Singh

Bisschoff

Soelen

et al. 2019

Monthly Notices of the Royal Astronomical Society

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In this work, we present a multi-wavelength study of the blazar 1ES 1218+304 using near simultaneous observations over 10 years during the period September 1, 2008 to August 31, 2018 (MJD 54710-58361). We have analyzed data from Swift -UVOT, Swift -XRT and Fermi-LAT to study the long term behaviour of 1ES 1218+304 in different energy bands over the last decade. We have also used the archival data from OVRO, MAXI and Swift -BAT available during the above period. The near simultaneous data on 1ES 1218+304 suggest that the long term multi-wavelength emission from the source is steady and does not show any significant change in the source activity. The optical/UV fluxes are found to be dominated by the host galaxy emission and can be modelled using the PEGASE code. However, the time averaged X-ray and γray emisions from the source are reproduced using a single zone leptonic model with log-parabolic distribution for the radiating particles. The intrinsic very high energy γ-ray emission during a low activity state of the source is broadly consistent with the predictions of the leptonic model for blazars. We have investigated the physical properties of the jet and the mass of the super massive black hole at the center of the host galaxy using long term X-ray observations from the Swift -XRT which is in agreement with the value derived using blackbody approximation of the host galaxy. We also discuss the extreme nature of the source on the basis of X-ray and γ-ray observations.

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Extremely High energy peaked BL Lac nature of the TeV blazar Mrk 501

Cited by 12 publications

References 79 publications

Characterizing continuum variability in the radio-loud narrow-line Seyfert 1 galaxy IRAS 17020+4544

Characterizing continuum variability in the radio-loud narrow-line Seyfert 1 galaxy IRAS 17020+4544

Extragalactic background light models and GeV-TeV observation of blazars

Long-term multiwavelength view of the blazar 1ES 1218+304

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