Hunting extreme BL Lacertae blazars with Fermi-Large Area Telescope

Rosillo, Mireia Nievas; Domínguez, A.; Chiaro, G.; Mura, G. La; Brill, A.; Paliya, Vaidehi S.

doi:10.1093/mnras/stac491

Cited by 9 publications

(4 citation statements)

References 108 publications

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“…Here, we found that, except for the model of the 2020 (E4) flare, the parameters suggest the existence of equipartition within a factor of a few. This is in line with the results presented by Nievas Rosillo et al (2022), where one-component models are used to reproduce the broadband emission of a sample of HBLs and EHBLs. Tavecchio & Ghisellini (2016) also note that by using two-component models it is possible to reproduce the observed SEDs of BL Lacs assuming equipartition between both energy densities.…”

Section: Equipartition and Jet Powersupporting

confidence: 90%

Long-term multi-wavelength study of 1ES 0647+250

Acciari

Aniello

Ansoldi

et al. 2023

A&A

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Context. The BL Lac object 1ES 0647+250 is one of the few distant γ-ray emitting blazars detected at very high energies (VHEs; 100 GeV) during a non-flaring state. It was detected with the MAGIC telescopes during a period of low activity in the years 2009-2011 as well as during three flaring activities in the years 2014, 2019, and 2020, with the highest VHE flux in the last epoch. An extensive multi-instrument data set was collected as part of several coordinated observing campaigns over these years. Aims. We aim to characterise the long-term multi-band flux variability of 1ES 0647+250, as well as its broadband spectral energy distribution (SED) during four distinct activity states selected in four different epochs, in order to constrain the physical parameters of the blazar emission region under certain assumptions. Methods. We evaluated the variability and correlation of the emission in the different energy bands with the fractional variability and the Ztransformed discrete correlation function, as well as its spectral evolution in X-rays and γ rays. Owing to the controversy in the redshift measurements of 1ES 0647+250 reported in the literature, we also estimated its distance in an indirect manner through a comparison of the GeV and TeV spectra from simultaneous observations with Fermi-LAT and MAGIC during the strongest flaring activity detected to date. Moreover, we interpret the SEDs from the four distinct activity states within the framework of one-component and two-component leptonic models, proposing specific scenarios that are able to reproduce the available multi-instrument data. Results. We find significant long-term variability, especially in X-rays and VHE γ rays. Furthermore, significant (3-4σ) correlations were found between the radio, optical, and high-energy (HE) γ-ray fluxes, with the radio emission delayed by about ∼400 days with respect to the optical and γ-ray bands. The spectral analysis reveals a harder-when-brighter trend during the non-flaring state in the X-ray domain. However, no clear patterns were observed for either the enhanced states or the HE (30 MeV

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Section: Equipartition and Jet Powersupporting

confidence: 90%

Long-term multi-wavelength study of 1ES 0647+250

Acciari

Aniello

Ansoldi

et al. 2023

A&A

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“…A third plausible scenario to explain the excess emission at the lowest frequencies is that we could be seeing the emission from the host galaxy (e.g., Ghisellini et al 2017;Archer et al 2018;Nievas Rosillo et al 2022). Fitting the IR to UV data with a single temperature blackbody, we obtain a T eff,host ∼ 10 4 K and a luminosity of L host ∼ 10 45 erg cm −2 s 1 .…”

Section: Modeling Resultsmentioning

confidence: 92%

Identifying the 3FHL Catalog. VI. Results of the 2019 Gemini Optical Spectroscopy

Rajagopal

Marcotulli

Labrie

et al. 2023

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Active galactic nuclei with their relativistic jets pointed toward the observer are a class of luminous gamma-ray sources commonly known as blazars. The study of this source class is essential to unveil the physical processes powering these extreme jets, to understand their cosmic evolution, as well as to indirectly probe the extragalactic background light. To do so, however, one needs to correctly classify and measure a redshift for a large sample of these sources. The Third Fermi–LAT Catalog of High-Energy Sources (3FHL) contains 1212 blazars detected at energies greater than 10 GeV. However, ∼25% of these sources are unclassified and ∼56% lack redshift information. To increase the optical completeness of blazars in the 3FHL catalog, we devised an optical spectroscopic follow-up campaign using 4 m and 8 m telescopes. In this paper, we present the results of the last part of this campaign, where we observed 5 blazars using the 8 m Gemini-S telescope in Chile. We report all the 5 sources to be classified as BL Lacs, a redshift lower limit for 2 sources, and featureless spectra for the remaining 3 sources. We also performed a one-zone leptonic fit to the two sources with the redshift lower limits.

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“…Additionally, HSPs have a higher n log p s , making their synchrotron bump more easily scattered into the TeV band by the relativistic electrons. However, it is not obvious that extreme n log p s values lead to the emission of TeV gamma rays by itself, as it also depends on many other properties of the emission region, such as electron distribution, magnetic field strength, internal absorption, and the redshift of the source (Nievas Rosillo et al 2022). Lin & Fan (2016) gathered 662 Fermi BL Lacs, including 47 TeV sources, and compared the multiwavelength observation properties of the TeVs with those of the non-TeVs.…”

Section: Introductionmentioning

confidence: 99%

Exploring TeV Candidates of Fermi Blazars through Machine Learning

Zhu

Lin

Xiao

et al. 2023

ApJ

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In this work, we make use of a supervised machine-learning algorithm based on Logistic Regression (LR) to select TeV blazar candidates from the 4FGL-DR2/4LAC-DR2, 3FHL, 3HSP, and 2BIGB catalogs. LR constructs a hyperplane based on a selection of optimal parameters, named features, and hyperparameters whose values control the learning process and determine the values of features that a learning algorithm ends up learning, to discriminate TeV blazars from non-TeV blazars. In addition, it gives the probability (or logistic) that a source may be considered a TeV blazar candidate. Non-TeV blazars with logistics greater than 80% are considered high-confidence TeV candidates. Using this technique, we identify 40 high-confidence TeV candidates from the 4FGL-DR2/4LAC-DR2 blazars and we build the feature hyperplane to distinguish TeV and non-TeV blazars. We also calculate the hyperplanes for the 3FHL, 3HSP, and 2BIGB. Finally, we construct the broadband spectral energy distributions for the 40 candidates, testing for their detectability with various instruments. We find that seven of them are likely to be detected by existing or upcoming IACT observatories, while one could be observed with extensive air shower particle detector arrays.

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Hunting extreme BL Lacertae blazars with Fermi-Large Area Telescope

Cited by 9 publications

References 108 publications

Long-term multi-wavelength study of 1ES 0647+250

Long-term multi-wavelength study of 1ES 0647+250

Identifying the 3FHL Catalog. VI. Results of the 2019 Gemini Optical Spectroscopy

Exploring TeV Candidates of Fermi Blazars through Machine Learning

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