A sharp X-ray absorption feature in the BL Lacertae object PKS 2155-304

Canizares, C. R.; Kruper, John

doi:10.1086/184233

Cited by 66 publications

(42 citation statements)

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“…The deviations were interpreted in the context of a model in which partially ionized gas that is outÑowing at mildly relativistic (v D 0.1c) speeds absorbs the continuum in overlapping, Dopplerbroadened lines of several ionic species. The model reproduced the 600 eV feature Ðrst reported by Canizares & Kruper (1984).…”

Section: Introductionsupporting

confidence: 74%

“…We note, however, that the spectrum is hardly expected to be a simple power law in the soft X-ray band. Canizares & Kruper (1984) reported not only that the Einstein objective grating spectrometer detected a 600 eV feature but also that the 0.4È1.5 keV data were best Ðt with a very steep (a \ 3È5) power-law model. An alternative explanation by et al (1995) is also consistent with Ko nigl the data : that the power law with a \ 1.65 in the X-ray band extends into the 85È110 data but is then absorbed A by overlapping, Doppler-broadened lines due to partially ionized gas that is outÑowing at mildly relativistic speeds, observed along the line of sight to the continuum source.…”

Section: Spectral Modelingmentioning

confidence: 99%

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EUVEObservations of PKS 2155−304: Variability, Spectra, and a Polarization Measurement Attempt

Marshall¹,

Urry²,

Sambruna³

et al. 2001

ApJ

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The bright BL Lacertae object PKS 2155[304 was observed with the Extreme Ultraviolet Explorer (EUV E) in 1994 May with the primary objective of attempting to measure the EUV polarization using a novel technique. The light curves and spectra from the observation proved very useful, even though the method failed to produce useful polarimetric information owing to large, poorly understood, systematic instrumental e †ects. Light curves from this and previous observations showed variations of a factor of 2 over 1 month in 1993 and up to 25% variations on timescales of hours on several occasions (from four separate observations totalling 25 days spanning 3 yr). The soft X-ray spectra of the source were also derived from the EUV E observations and are comparable in shape to previous observations. The spectra do not show signiÐcant spectral features and are Ðtted acceptably with simple power-law spectra with an energy index a \ 3.0 for an assumed neutral hydrogen column density cm~2. A Ñatter N H \ 1.4 ] 1020 index of 2.0 Ðts the data if the is reduced to 1.2 ] 1020 cm~2, within the 2 p uncertainty on as N H N H derived from 21 cm observations. Previous models that involve extensive absorption troughs with a Ñat-index power law (as extended from the X-ray band) are also consistent with the data.

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Section: Introductionsupporting

confidence: 74%

Section: Spectral Modelingmentioning

confidence: 99%

EUVEObservations of PKS 2155−304: Variability, Spectra, and a Polarization Measurement Attempt

Marshall¹,

Urry²,

Sambruna³

et al. 2001

ApJ

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“…These smooth continua are thought to be generated by synchrotron selfcompton emission from jets of material streaming out of the active nucleus towards us. Canizares & Kruper (1984), however, discovered a soft X-ray absorption feature in the Einstein Objective Grating Spectrometer (OGS) spectrum of the BL Lac PKS 2155-304, and since that time, similar features have been detected in several other objects: 1H1219+301, Markarian 501, PKS 0548-322, Markarian 421 (Madejski et al 1991) and H1426+428 (Madejski et al 1992). This absorption, interpreted in each case as being due to ionised gas intrinsic to the BL Lac, is perhaps the only insight we have into the immediate environment of these enigmatic sources.…”

Section: Introductionmentioning

confidence: 94%

“…The earliest detected feature amongst the objects described here, the absorption trough in Markarian 501, was simply described as being due to highly ionised oxygen (Urry et al 1986). Madejski et al (1991), following the lead of Canizares & Kruper (1984), interpreted their notches as being due to O  Lyα resonance absorption. Sambruna et al (1997) found their ∼0.66 keV feature to be consistent with absorption edges of O -O , and marginally consistent with O  Lyα.…”

Section: +001mentioning

confidence: 99%

Intrinsic absorbers in BL Lac objects: The XMM-Newton view

Blustin

Page

Branduardi‐Raymont

2004

A&A

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Abstract. We present XMM-Newton observations of four BL Lac objects (1H1219+301, H1426+428, Markarian 501 and PKS 0548-322), which have been found with past X-ray missions to contain evidence of broad soft X-ray absorption features. Observations with the high resolution Reflection Grating Spectrometers on XMM-Newton provide the best chance yet of investigating these features. No broad absorption features are observed in any of the objects. Neither do we find convincing evidence for narrow emission and absorption lines in the RGS spectra. We discuss the history of observations of broad absorption features in these four objects, finding that if the features exist then they must be transient, and that -given the frequency of reported observations of them -we can rule out the existence of transient broad absorption features in these objects at 93% confidence.

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“…Most BL Lac objects have X-ray spectra that can be fit by power-laws within smaller bandpasses, such as that of ROSAT ( [12], [17]) More recent results from ASCA [7] and BeppoSAX ( [1], [11], [19]) have generally confirmed this spectral morphology, and also added onto it the possibility of intrinisic spectral curvature across a wider bandpass ( [4], [6], [9], [16]). In addition, earlier missions had indicated that some BL Lac objects showed a deficit in soft X-rays below a power-law model, which had been interpreted by invoking X-ray absorption features at 0.5-0.8 keV ( [3], [8], [14], [15]). But not all bright BL Lacs were found to require such features (e.g., [5]).…”

Section: Introductionmentioning

confidence: 99%

Bl Lac X-Ray Spectra: Simpler Than We Thought

Perlman¹,

Daugherty²,

Koratkar³

et al. 2004

Multiwavelength AGN Surveys

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We report results from XMM-Newton observations of thirteen X-ray bright BL Lacertae objects, selected from the Einstein Slew Survey sample. The spectra are generally well fit by power-law models, with four objects having hard (α < 1; Fν ∝ ν −α ) spectra that indicates synchrotron peaks at > 5 keV. None of our spectra show line features, indicating that soft X-ray absorption "notches" must be rare amongst BL Lacs, rather than common or ubiquitous as had previously been asserted. We find significant curvature in most of the spectra. This curvature is almost certainly intrinsic, as it appears nearly constant from 0.5 to 6 keV, an observation which is inconsistent with the small columns seen in these sources.

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A sharp X-ray absorption feature in the BL Lacertae object PKS 2155-304

Cited by 66 publications

References 0 publications

EUVEObservations of PKS 2155−304: Variability, Spectra, and a Polarization Measurement Attempt

EUVEObservations of PKS 2155−304: Variability, Spectra, and a Polarization Measurement Attempt

Intrinsic absorbers in BL Lac objects: The XMM-Newton view

Bl Lac X-Ray Spectra: Simpler Than We Thought

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