The Blazar Emission Environment: Insight From Soft X-Ray Absorption

Furniss, A.; Fumagalli, Michele; Falcone, A.; Williams, D. A.

doi:10.1088/0004-637x/770/2/109

Cited by 16 publications

(15 citation statements)

References 46 publications

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“…Evidence from millimeter (Fumagalli et al 2012) and X-ray observations (Furniss et al 2013) of 1ES 1959+650 support the existence of intervening gas within the blazar and, therefore, the application of a reflected emission scenario to broadband variability of the source. More specifically, 1ES 1959+650 shows evidence for additional gas in the vicinity of the host galaxy from X-ray absorption in excess to that expected by the Galactic column, as well as a positive detection of molecular CO within the blazar.…”

Section: Abstract: Bl Lacertae Objects: Individual (1es 1959+650) -Gmentioning

confidence: 93%

“…Similarly sized regions of nearby source-free sky were used to estimate the background. The exposures were grouped to ensure a minimum of 20 counts per bin and were fitted with an absorbed power-law model of the form F (E) PL = Ke −N H i σ (E) (E/1 keV) −α , with a free neutral hydrogen column density parameter N H i , as in Furniss et al (2013), to allow for additional absorption of soft X-rays by intervening gas in the vicinity of the blazar or along the line of sight. The model also contains a fitted normalization parameter K and the non-Thompson, energy-dependent photoelectric cross section σ (E), as taken from Morrison & McCammon (1983).…”

Section: Swift Xrtmentioning

confidence: 99%

“…We therefore conclude that the most likely mode of reprocessing the accumulated jet synchrotron emission is Compton reflection of free electrons in the highly ionized cloud. It is not necessary that this is the only cloud within the vicinity of the blazar, maintaining the possibility that there is additional neutral absorbing gas surrounding the blazar, as found in Furniss et al (2013). We only assume that a blob moving relativistically down the jet passes sufficiently close to a cloud that radiation from the blob can temporarily ionize the cloud, so that for a short time the blob emission is reprocessed via Compton reflection off free electrons in the cloud.…”

Section: Time-dependent Description (Reflected Emission)mentioning

confidence: 99%

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INVESTIGATING BROADBAND VARIABILITY OF THE TeV BLAZAR 1ES 1959+650

Aliu¹,

Archambault²,

Arlen³

et al. 2014

ApJ

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We summarize broadband observations of the TeV-emitting blazar 1ES 1959+650, including optical R-band observations by the robotic telescopes Super-LOTIS and iTelescope, UV observations by Swift Ultraviolet and Optical Telescope, X-ray observations by the Swift X-ray Telescope, high-energy gamma-ray observations with the Fermi Large Area Telescope, and very-high-energy (VHE) gamma-ray observations by VERITAS above 315 GeV, all taken between 2012 April 17 and 2012 June 1 (MJD 56034 and 56079). The contemporaneous variability of the broadband spectral energy distribution is explored in the context of a simple synchrotron self Compton (SSC) model. In the SSC emission scenario, we find that the parameters required to represent the high state are significantly different than those in the low state. Motivated by possible evidence of gas in the vicinity of the blazar, we also investigate a reflected emission model to describe the observed variability pattern. This model assumes that the non-thermal emission from the jet is reflected by a nearby cloud of gas, allowing the reflected emission to re-enter the blob and produce an elevated gamma-ray state with no simultaneous elevated synchrotron flux. The model applied here, although not required to explain the observed variability pattern, represents one possible scenario which can describe the observations. As applied to an elevated VHE state of 66% of the Crab Nebula flux, observed on a single night during the observation period, the reflected emission scenario does not support a purely leptonic non-thermal emission mechanism. The reflected emission model does, however, predict a reflected photon field with sufficient energy to enable elevated gamma-ray emission via pion production with protons of energies between 10 and 100 TeV.

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Section: Abstract: Bl Lacertae Objects: Individual (1es 1959+650) -Gmentioning

confidence: 93%

Section: Swift Xrtmentioning

confidence: 99%

Section: Time-dependent Description (Reflected Emission)mentioning

confidence: 99%

See 1 more Smart Citation

INVESTIGATING BROADBAND VARIABILITY OF THE TeV BLAZAR 1ES 1959+650

Aliu¹,

Archambault²,

Arlen³

et al. 2014

ApJ

Self Cite

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show abstract

“…A log-parabolic spectrum (LOGPAR in XSPEC) can be produced by a logparabolic distribution of relativistic particles (Paggi et al 2009). This curved continuum shape could also arise from a power-law particle distribution with a cooled high-energy tail (Furniss et al 2013).…”

Section: Continuum Modelmentioning

confidence: 99%

Probing the physical properties of the intergalactic medium using blazars

Dalton

Morris

Fumagalli

et al. 2021

Monthly Notices of the Royal Astronomical Society

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We use Swift blazar spectra to estimate the key intergalactic medium (IGM) properties of hydrogen column density (${N} {\rm \small {HXIGM}}$), metallicity and temperature over a redshift range of 0.03 ≤ z ≤ 4.7, using a collisional ionisation equilibrium (CIE) model for the ionised plasma. We adopted a conservative approach to the blazar continuum model given its intrinsic variability and use a range of power law models. We subjected our results to a number of tests and found that the ${N}{\rm \small {hxigm}}$ parameter was robust with respect to individual exposure data and co-added spectra for each source, and between Swift and XMM-Newton source data. We also found no relation between ${N}{\rm \small {hxigm}}$ and variations in source flux or intrinsic power laws. Though some objects may have a bulk Comptonisation component which could mimic absorption, it did not alter our overall results. The ${N}{\rm \small {hxigm}}$ from the combined blazar sample scales as (1 + z)1.8 ± 0.2. The mean hydrogen density at z = 0 is n0 = (3.2 ± 0.5) × 10−7 cm−3. The mean IGM temperature over the full redshift range is log(T/K) =6.1 ± 0.1, and the mean metallicity is [X/H] = −1.62 ± 0.04(Z ∼ 0.02). When combining with the results with a gamma-ray burst (GRB) sample, we find the results are consistent over an extended redshift range of 0.03 ≤ z ≤ 6.3. Using our model for blazars and GRBs, we conclude that the IGM contributes substantially to the total absorption seen in both blazar and GRB spectra.

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“…The fit is significantly improved (F-test probability equal to 8 × 10 −5 ) if a break is added to the model, considering an absorbed broken-power-law function. The best-fit parameter values are Γ 1 = 2.01 The observed spectral break could be intrinsic or due to an underestimation of the neutral absorption: in particular, additional absorption due to the blazar host galaxy should be studied (for a detailed analysis of this effect see Perlman et al 2005;Furniss et al 2013). This hypothesis is tested by fitting the data with an absorbed power-law function, letting the value of N H to vary.…”

Section: Swift-xrtmentioning

confidence: 99%

VERITAS detection of gamma-ray flaring activity from the BL Lac object 1ES1727+502 during bright moonlight observations

Cerruti¹

2016

Proceedings of the 34th International Cosmic Ray Conference — PoS(ICRC2015)

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During moonlit nights, observations with ground-based Cherenkov telescopes at very high energies (VHE, E > 100 GeV) are constrained since the photomultiplier tubes (PMTs) in the telescope camera are extremely sensitive to the background moonlight. Observations with the VERITAS telescopes in the standard configuration are performed only with a moon illumination less than 35% of full moon. Since 2012, the VERITAS collaboration has implemented a new observing mode under bright moonlight, by either reducing the voltage applied to the PMTs (reduced-high-voltage configuration, RHV), or by utilizing UV-transparent filters. While these operating modes result in lower sensitivity and increased energy thresholds, the extension of the available observing time is useful for monitoring variable sources such as blazars and sources requiring spectral measurements at the highest energies. In this paper we report the detection of γ-ray flaring activity from the BL Lac object 1ES 1727+502 during RHV observations. This detection represents the first evidence of VHE variability from this blazar. The integral flux is (1.1 ± 0.2) × 10 −11 cm −2 s −1 above 250 GeV, which is about five times higher than the low-flux state. The detection triggered additional VERITAS observations during standard dark-time. Multiwavelength observations with the FLWO 48" telescope, and the Swift and Fermi satellites are presented and used to produce the first spectral energy distribution (SED) of this object during γ-ray flaring activity. The SED is then fitted with a standard synchrotron-self-Compton model, placing constraints on the properties of the emitting region and of the acceleration mechanism at the origin of the relativistic particle population in the jet.

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The Blazar Emission Environment: Insight From Soft X-Ray Absorption

Cited by 16 publications

References 46 publications

INVESTIGATING BROADBAND VARIABILITY OF THE TeV BLAZAR 1ES 1959+650

INVESTIGATING BROADBAND VARIABILITY OF THE TeV BLAZAR 1ES 1959+650

Probing the physical properties of the intergalactic medium using blazars

VERITAS detection of gamma-ray flaring activity from the BL Lac object 1ES1727+502 during bright moonlight observations

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