The <i>γ</i>-ray sky seen at X-ray energies

Marchesini, E. J.; Paggi, A.; Massaro, F.; Masetti, N.; D’Abrusco, R.; Andruchow, I.; Menezes, Raniere de

doi:10.1051/0004-6361/201936285

Cited by 12 publications

(9 citation statements)

References 132 publications

(120 reference statements)

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“…A relatively broad distribution of spectral shapes for lowpeaked sources was also reported in a recent study by Marchesini et al (2019). The authors analyzed a large sample of high-and low-peaked BL Lac type objects in the soft X-ray band and found an especially broad distribution of hardness ratios for the log-peaked sub-set, which has been attributed to the intersecting region of synchrotron and HE bump in the SED.…”

Section: Individual Sources With Peculiar Hard X-ray Propertiessupporting

confidence: 66%

Hard X-ray properties of radio-selected blazars

Langejahn

Kadler

Wilms

et al. 2020

A&A

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Context. Hard X-ray properties of beamed AGN have been published in the 105-month Swift/BAT catalog, but there have not been any studies carried out so far on a well-defined, radio-selected sample of low-peaked blazars in the hard X-ray band. Aims. Using the statistically complete MOJAVE-1 sample, we aim to determine the hard X-ray properties of radio-selected blazars, including the enigmatic group of gamma-ray-faint blazars. Additionally, we aim to determine the contribution of radio-selected lowpeaked blazars to the diffuse CXB. Methods. We determined photon indices, fluxes, and luminosities in the range of 20 keV -100 keV of the X-ray spectra of blazars and other extragalactic jets from the MOJAVE-1 sample, derived from the 105-month Swift/BAT survey. We calculated log N-log S distributions and determined the luminosity functions.Results. The majority of the MOJAVE-1 blazars are found to be hard X-ray emitters albeit many at low count rates. The log Nlog S distribution for the hard X-ray emission of radio-selected blazars is clearly non-Euclidean, in contrast to the radio flux density distribution. Approximately 0.2% of the CXB in the 20 keV -100 keV band can be resolved into MOJAVE-1 blazars. Conclusions. The peculiar log N-log S distribution disparity might be attributed to different evolutionary paths in the X-ray and radio bands, as tested by luminosity-function modeling. X-ray variability can be ruled out as the dominant contributor. Low-peaked blazars constitute an intrinsically different source population in terms of CXB contribution compared to similar studies of X-ray-selected blazars. The hard X-ray flux and spectral index can serve as a good proxy for the gamma-ray detection probability of individual sources. Future observations combining deep X-ray survey, for example, with eROSITA, and targeted gamma-ray observations with CTA can benefit strongly from the tight connection between these high-energy bands for the different blazar sub-classes. 1 arXiv:2004.00477v1 [astro-ph.HE] 1 Apr 2020 M. Langejahn et al.: Hard X-ray properties of radio-selected blazars quasars (FSRQ), out of 1632 sources, including 114 unclassified AGN and an additional 129 unidentified sources. The recent 4FGL catalog of the gamma-ray all-sky survey from Fermi/LAT (The Fermi-LAT collaboration 2019) alone contains 1102 BL Lac type and 681 FSRQ type blazars out of a total of 2940 associated blazars and blazar candidates.In this work, we perform a detailed analysis of X-ray data from the most recent Swift/BAT survey maps for the radioselected MOJAVE-1 (Monitoring Of Jets in Active galactic nuclei with VLBA Experiments) beamed AGN sample. We report the hard X-ray characteristics in the 20 keV -100 keV band of this statistically complete extragalactic jet sample, which is mostly composed of blazars.This paper is structured as follows: Sect. 2 gives a short introduction to the MOJAVE program as well as the Swift mission and describes the object samples and data basis we used. The analysis, including the applied methods and assumptions...

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Section: Individual Sources With Peculiar Hard X-ray Propertiessupporting

confidence: 66%

Hard X-ray properties of radio-selected blazars

Langejahn

Kadler

Wilms

et al. 2020

A&A

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“…Data collected by Swift X-Ray Telescope (XRT) were downloaded from the HEASARC 8 data archive and processed using the xrtdas software (Capalbi et al 2005) developed at the ASI Science Data Center and included in the HEAsoft package (v. 6.26.1) distributed by HEASARC, using a procedure similar to the one illustrated in Paggi et al (2013) and Marchesini et al (2019). Swift-XRT photon counting (PC) data were available for 325 ABC sources.…”

Section: Swift-xrtmentioning

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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“…Since the release of the First Fermi LAT Point Source Catalog (1FGL; Abdo et al 2010c) and until the latest, the Fourth Fermi LAT Point Source Catalog (4FGL; Abdollahi et al 2020), it was quite clear that an almost constant fraction, about one-third, of all detected objects were and still are UGSs , lacking an assigned low-energy counterpart (Peña-Herazo et al 2020), or being simply unclassified mainly due to the lack of an optical spectrum, recently labeled as blazar candidates of uncertain type (BCUs; see also Acero et al 2015;Ackermann et al 2015). Hundreds of blazars were discovered thanks to new follow-up observations of UGSs and BCUs available at radio (Kovalev 2009;Massaro et al 2013;Petrov et al 2013;Nori et al 2014;Schinzel et al 2015;Giroletti et al 2016), optical (Paiano et al 2017a), and X-ray (Cheung et al 2012;Acero et al 2013;Paggi et al 2013;Takeuchi et al 2013;Landi et al 2015;Kaur et al 2018Kaur et al , 2019Marchesini et al 2019aMarchesini et al , 2020 frequencies, as well as the application of statistical methods (Ackermann et al 2012a;Doert & Errando 2014;Salvetti et al 2017), but hundreds of them are probably still unknown (Massaro et al 2012c;D'Abrusco et al 2013).…”

Section: Introductionmentioning

confidence: 99%

An Optical Overview of Blazars with LAMOST. I. Hunting Changing-look Blazars and New Redshift Estimates

Peña-Herazo

Massaro

et al. 2021

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The extragalactic γ-rays sky observed by the Fermi Large Area Telescope (LAT) is dominated by blazars. In the fourth release of the Fermi LAT Point Source Catalog (4FGL) are sources showing a multifrequency behavior similar to that of blazars but lacking an optical spectroscopic confirmation of their nature, known as blazar candidates of uncertain type (BCUs). We aim at confirming the blazar nature of BCUs and test if new optical spectroscopic observations can reveal spectral features, allowing us to get a redshift estimate for known BL Lac objects. We also aim to search for and discover changing-look blazars (i.e., blazars that show a different classification at different epochs). We carry out an extensive search for optical spectra available in the Large Sky Area Multi-object Fibre Spectroscopic Telescope (LAMOST) Data Release 5 (DR5) archive. We select sources out of the 4FGL catalog, the list of targets from our follow-up spectroscopic campaign of unidentified or unassociated γ-ray sources, and the multifrequency catalog of blazars: the Roma-BZCAT. We select a total of 392 spectra. We also compare some of the LAMOST spectra with those available in the literature. We classify 20 BCUs confirming their blazar-like nature. Then we obtain 15 new redshift estimates for known blazars. We discover 26 transitional (i.e., changing-look) blazars that changed their classification. Finally, we are able to confirm the blazar-like nature of six BL Lac candidates. All remaining sources analyzed agree with previous classifications. BL Lac objects are certainly the most elusive type of blazars in the γ-ray extragalactic sky.

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The γ-ray sky seen at X-ray energies

Cited by 12 publications

References 132 publications

Hard X-ray properties of radio-selected blazars

Hard X-ray properties of radio-selected blazars

A new multiwavelength census of blazars

An Optical Overview of Blazars with LAMOST. I. Hunting Changing-look Blazars and New Redshift Estimates

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