X-ray flux variability of active galactic nuclei observed using NuSTAR

Rani, Priyanka; Stalin, C. S.; Rakshit, Suvendu

doi:10.1093/mnras/stw3228

Cited by 39 publications

(27 citation statements)

References 89 publications

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“…X-rays in AGN originate from the AGN accretion disk itself as well as from the jet. The general properties have been reviewed by Brandt & Alexander (2015), and a detailed discussion of the X-ray variability in 81 AGN observed with NuSTAR is given by Rani et al (2017). 65% of their sources show significant variability on hourly timescales.…”

Section: Oir Uv and X-ray Observationsmentioning

confidence: 99%

Relativistic Jets from Active Galactic Nuclei

Blandford

Meier

Readhead

2019

Annu. Rev. Astron. Astrophys.

689

466

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The nuclei of most normal galaxies contain supermassive black holes, which can accrete gas through a disk and become active. These active galactic nuclei (AGNs) can form jets that are observed on scales from astronomical units to megaparsecs and from meter wavelengths to TeV energies. High-resolution radio imaging and multiwavelength/messenger campaigns are elucidating the conditions under which this happens. Evidence is presented that: ▪ Relativistic AGN jets are formed when the black hole spins and the the accretion disk is strongly magnetized, perhaps on account of gas accreting at high latitude beyond the black hole sphere of influence. ▪ AGN jets are collimated close to the black hole by magnetic stress associated with a disk wind. ▪ Higher-power jets can emerge from their galactic nuclei in a relativistic, supersonic, and proton-dominated state, and they terminate in strong, hot spot shocks; lower-power jets are degraded to buoyant plumes and bubbles. ▪ Jets may accelerate protons to EeV energies, which contribute to the cosmic ray spectrum and may initiate pair cascades that can efficiently radiate synchrotron γ-rays. ▪ Jets were far more common when the Universe was a few billion years old and black holes and massive galaxies were growing rapidly. ▪ Jets can have a major influence on their environments, stimulating and limiting the growth of galaxies. The observational prospects for securing our understanding of AGN jets are bright.

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Section: Oir Uv and X-ray Observationsmentioning

confidence: 99%

Relativistic Jets from Active Galactic Nuclei

Blandford

Meier

Readhead

2019

Annu. Rev. Astron. Astrophys.

689

466

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“…As the source is radio-quiet, not much contamination to the observed flux variations is expected from the jet of the source. The variability nature of the source was characterized using the normalized excess variance (Edelson et al 2002;Vaughan et al 2003;Rani et al 2017)…”

Section: Light Curvesmentioning

confidence: 99%

Determination of the size of the dust torus in H0507+164 through optical and infrared monitoring

Mandal

Rakshit

Kurian

et al. 2018

Monthly Notices of the Royal Astronomical Society

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The time delay between flux variations in different wavelength bands can be used to probe the inner regions of active galactic nuclei (AGN). Here, we present the first measurements of the time delay between optical and near-infrared (NIR) flux variations in H0507+164, a nearby Seyfert 1.5 galaxy at z = 0.018. The observations in the optical V-band and NIR J, H and K s bands carried over 35 epochs during the period October 2016 to April 2017 were used to estimate the inner radius of the dusty torus. From a careful reduction and analysis of the data using crosscorrelation techniques, we found delayed responses of the J, H and K s light curves to the V-band light curve. In the rest frame of the source, the lags between optical and NIR bands are found to be 27.1 +13.5 −12.0 days (V vs. J), 30.4 +13.9 −12.0 days (V vs. H) and 34.6 +12.1 −9.6 days (V vs. K s). The lags between the optical and different NIR bands are thus consistent with each other. The measured lags indicate that the inner edge of dust torus is located at a distance of 0.029 pc from the central UV/optical AGN continuum. This is larger than the radius of the broad line region of this object determined from spectroscopic monitoring observations thereby supporting the unification model of AGN. The location of H0507+164 in the τ-M V plane indicates that our results are in excellent agreement with the now known lag-luminosity scaling relationship for dust in AGN.

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“…wide variety of variability patterns with timescales ranging from intraday to years and amplitudes going from few percents to orders of magnitude (e.g. Rani et al 2017;Kapanadze et al 2018a,b). So IGR J20569+4940 moderate variability on long timescale and the absence of strong variations in the NuSTAR light curve are both consistent with its classification as a BL Lac.…”

Section: Nustar Resultsmentioning

confidence: 99%

NuSTAR Observations of the Unidentified INTEGRAL Sources: Constraints on the Galactic Population of HMXBs

Clavel

Tomsick

Hare

et al. 2019

ApJ

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The NuSTAR Legacy program 'Unidentified INTEGRAL sources' targeted faint hard X-ray sources revealed by INTEGRAL in the Galactic plane in order to provide conclusive identification of their nature and insights on the population of faint hard X-ray sources. The NuSTAR and Swift/XRT observations obtained in 2015-2017 contributed to the successful identification of five persistent sources. Here, we report on the spectral and variability analyses which helped to consolidate the classifications of IGR J10447-6027, IGR J16181-5407 and IGR J20569+4940 as active galactic nuclei, and IGR J17402-3656 as an intermediate polar. An optical spectrum of the blazar IGR J20569+4940 is also presented. Combining these results with successful identifications of other such faint and persistent INTEGRAL sources reported in the literature, we investigate possible implications for the population of persistent high mass X-ray binaries (HMXBs) below the identification completion limit of the INTEGRAL survey. The current trend hints at a deficit of persistent HMXBs below F 17−60keV = 10 −11 erg cm −2 s −1 , but additional efforts dedicated to classifying faint hard X-ray sources are needed before we can draw solid conclusions.

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X-ray flux variability of active galactic nuclei observed using NuSTAR

Cited by 39 publications

References 89 publications

Relativistic Jets from Active Galactic Nuclei

Relativistic Jets from Active Galactic Nuclei

Determination of the size of the dust torus in H0507+164 through optical and infrared monitoring

NuSTAR Observations of the Unidentified INTEGRAL Sources: Constraints on the Galactic Population of HMXBs

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