Optical flux behaviour of a sample of<i>Fermi</i>blazars

Marchesini, E. J.; Andruchow, I.; Cellone, S. A.; Combi, J. A.; Zibecchi, L.; Martı́, Josep; Romero, Gustavo E.; Muñoz‐Arjonilla, A. J.; Luque-Escamilla, Pedro L.; Sánchez‐Sutil, J. R.

doi:10.1051/0004-6361/201527632

Cited by 12 publications

(11 citation statements)

References 92 publications

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“…Since blazars are extremely variable sources in all energy ranges (e.g. Abdo et al 2010b;Stroh & Falcone 2013;Marchesini et al 2016;Paliya et al 2017b), to accurately constrain the sources' SED and to reliably measure the X-ray spectral parameters, we also obtain quasi-simultaneous observations from a variety of facilities. The soft X-ray and UV-optical bands are covered by the Neil Gehrels Swift Observatory X-ray Telescope (Swift-XRT; Burrows et al 2005) and Ultraviolet and Optical Telescope (Swift-UVOT; Roming et al 2005).…”

Section: Introductionmentioning

confidence: 99%

NuSTAR Perspective on High-redshift MeV Blazars

Marcotulli

Paliya

Ajello

et al. 2020

ApJ

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With bolometric luminosities exceeding 10 48 erg s −1 , powerful jets and supermassive black holes at their center, MeV blazars are some of the most extreme sources in the Universe. Recently, the Fermi-Large Area Telescope detected five new γ-ray emitting MeV blazars beyond redshift z = 3.1. With the goal of precisely characterizing the jet properties of these extreme sources, we started a multiwavelength campaign to follow them up with joint NuSTAR, Swift and SARA observations. We observe six high-redshift quasars, four of them belonging to the new γ-ray emitting MeV blazars. Thorough X-ray analysis reveals spectral flattening at soft X-ray for three of these objects. The source NVSS J151002+570243 also shows a peculiar re-hardening of the X-ray spectrum at energies E > 6 keV. Adopting a one-zone leptonic emission model, this combination of hard X-rays and γ-rays enables us to determine the location of the Inverse Compton peak and to accurately constrain the jet characteristics. In the context of the jet-accretion disk connection, we find that all six sources have jet powers exceeding accretion disk luminosity, seemingly validating this positive correlation even beyond z > 3. Our six sources are found to have 10 9 M ⊙ black holes, further raising the space density of supermassive black holes in the redshift bin z = [3, 4].

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Section: Introductionmentioning

confidence: 99%

NuSTAR Perspective on High-redshift MeV Blazars

Marcotulli

Paliya

Ajello

et al. 2020

ApJ

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“…Due to the peculiar orientation of the jet that enhances the radiation because of the relativistic boosting , blazars are known to emit over entire electromagnetic spectrum, from low energy radio waves to very high energy γ-rays. In addition to that, another defining characteristic feature displayed by blazars is the rapid and high amplitude flux variations observed at all the accessible wavelengths (see, e.g., Stalin et al 2002;Sagar et al 2004;Jorstad et al 2010;Aleksić et al 2011;Bachev et al 2012;Paliya et al 2015a;Marchesini et al 2016). Based on the equivalent width (EW) of the optical emission lines, blazars are classified as flat spectrum radio quasars (FSRQs) and BL Lac objects with FSRQs exhibit broad emission lines (EW>5Å).…”

Section: Introductionmentioning

confidence: 99%

Intra-night Optical Variability Monitoring of Fermi Blazars: First Results from 1.3 m J. C. Bhattacharya Telescope

Paliya

Stalin

Ajello

et al. 2017

ApJ

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We report the first results obtained from our campaign to characterize the intranight-optical variability (INOV) properties of Fermi detected blazars, using the observations from the recently commissioned 1.3 m J C Bhattacharya telescope (JCBT). During the first run, we were able to observe 17 blazars in the Bessel R filter for ∼137 hrs. Using C and scaled F -statistics, we quantify the extent of INOV and derive the duty cycle (DC) which is the fraction of time during which a source exhibits a substantial flux variability. We find a high DC of 40% for BL Lac objects and the flat spectrum radio quasars are relatively less variable (DC ∼ 15%). However, when estimated for blazars sub-classes, a high DC of ∼59% is found in low synchrotron peaked (LSP) blazars, whereas, intermediate and high synchrotron peaked objects have a low DC of ∼11% and 13%, respectively. We find evidences about the association of the high amplitude INOV with the γ-ray flaring state. We also notice a high polarization during the elevated INOV states (for the sources that have polarimetric data available), thus supporting the jet based origin of the observed variability. We plan to enlarge the sample and utilize the time availability from the small telescopes, such as 1.3 m JCBT, to strengthen/verify the results obtained in this work and those existed in the literature.

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“…Optical observations of blazars both in photometry (e.g., Marchesini et al 2016a;Raiteri et al 2019;Abeysekara et al 2020) and spectroscopy (e.g., Landoni et al 2015;Ricci et al 2015;Álvarez Crespo et al 2016;Peña-Herazo et al 2019; de Menezes et al 2020) provide an excellent tool to characterize their broad band emission and a to pinpoint their classification through the detection (or lack of it) of strong emission lines. In this section, we collect the photometric and spectroscopic data available in public catalogs with the goal of obtaining a better characterization of the ABC sources.…”

Section: Optical Datamentioning

confidence: 99%

A new multiwavelength census of blazars

Paggi

Bonato

Raiteri

et al. 2020

A&A

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Context. Blazars are the rarest and most powerful active galactic nuclei. They play a crucial and expanding role in the multifrequency and multimessenger astrophysics of today. Dominating the high-energy extragalactic sky, they have been recently associated with high-energy astrophysical neutrinos and they may be among the accelerators of the ultra-high energy cosmic rays. Current blazar catalogs, however, are incomplete and they are depleted, in particular, at low Galactic latitudes. Aims. Our study is aimed at augmenting the current blazar census, starting from a sample of ALMA calibrators that provides more homogeneous sky coverage, especially at low Galactic latitudes, to build a catalog of blazar candidates that can provide candidate counterparts to unassociated γ-ray sources and sources of high-energy neutrino emission or ultra-high energy cosmic rays. Methods. Based on the ALMA Calibrator Catalog, we compiled a selection of 1580 ALMA Blazar Candidates (ABCs) for which we collected multiwavelength information, including Gaia photometric, parallax, and proper motion data, as well as SDSS and LAMOST photometric and spectral data, WISE photometric data, X-ray (Swift-XRT, Chandra-ACIS and XMM-Newton-EPIC) count-rates and spectra, and Fermi-LAT fluxes and spectral slopes. We also compared our ALMA Blazar Candidates with existing blazar catalogs, such as 4FGL, 3HSP, WIBRaLS2, and the KDEBLLACS. Results. The ABC catalog fills in the gaps with regard to low Galactic latitude sources in current blazar catalogs. By cross-matching this catalog with Gaia DR2, SDSS DR12, LAMOST DR5, AllWISE, and 4FGL catalogs, we obtained 805, 295, 31, 1311, and 259 matches, respectively. ALMA Blazar Candidates are significantly dimmer than known blazars in the Gaia g band, while the difference in the Gaia b − r color between the two populations is less pronounced. Also, ABC sources appear bluer in SDSS than known blazars, although with low statistical significance. Most ABCs classified as QSO and BL Lac fall into the SDSS color regions of low redshift quasars, with some QSOs entering the regions of higher redshift quasars. We collected 110 optical spectra in SDSS DR12 and LAMOST DR5, which mostly classify the corresponding sources as QSO (98), while 12 sources turned out to be galactic objects. Regarding the WISE colors, we found that ABC sources are significantly bluer than known blazars in the w2 − w3 and w3 − w4 colors. In X-ray, we detected 173 ABCs and we were able to extract X-ray spectra for 92 of them. Our sources are, on average, similar in the X-ray band to known blazars in terms of count rates and spectral slopes, implying that our sample covers the same region of the blazar parameter space in this band. A comparison of γ-ray properties shows that the ABCs are, on average, dimmer and that their γ-ray spectra are softer than known blazars, indicating a significant contribution on the part of FSRQ sources. Making use of WISE colors, we classified 715 ABCs as candidate γ-ray blazar of different classes. Conclusions. We built a new catalog of 1580 candidate blazars with a rich multiwavelength data-set, filling in the gaps for low Galactic latitude sources in current blazar catalogs. This will be particularly important for the identification of the source population of high-energy neutrinos or ultra-high energy cosmic rays, or to verify the Gaia optical reference frame. In addition, ALMA Blazar Candidates can be investigated both through optical spectroscopic observation campaigns or through repeated photometric observations for variability studies. In this context, the data collected by the upcoming LSST surveys will provide a key tool for investigating the possible blazar nature of these sources.

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Optical flux behaviour of a sample ofFermiblazars

Cited by 12 publications

References 92 publications

NuSTAR Perspective on High-redshift MeV Blazars

NuSTAR Perspective on High-redshift MeV Blazars

Intra-night Optical Variability Monitoring of Fermi Blazars: First Results from 1.3 m J. C. Bhattacharya Telescope

A new multiwavelength census of blazars

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