[ITAL]ORFEUS II[/ITAL] Far-Ultraviolet Observations of 3C 273: The Intrinsic Spectrum

Appenzeller, I.; Krautter, J.; Mandel, H.; Bowyer, Stuart; Dixon, W. V.; Hurwitz, M.; Barnstedt, Jürgen; Grewing, M.; Kappelmann, N.; Krämer, G.

doi:10.1086/311392

Cited by 9 publications

(6 citation statements)

References 15 publications

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“…For our extinction correction, we adopt E(B −V ) = 0.032, as established by Lockman & Savage (1995), and use the extinction curve of Cardelli, Clayton & Mathis (1989), with R V = 3.1. This value of the extinction is also consistent with the E(B − V ) = 0.03 adopted by Lichti et al (1995) and Appenzeller et al (1998).…”

Section: Empirical Models For the Spectrasupporting

confidence: 92%

“…A very low resolution observation with the Voyager UV Spectrometer in the 900-1200 Å band suggested the possibility of a spectral break at about 1000 Å (Reichert et al 1988), perhaps associated with the Lyman edge. Recent observations in the 900-1200 Å region with ORFEUS imply a turnover in the spectrum of 3C 273 near the IUE/ORFEUS transition wavelength at about 1200 Å (Appenzeller et al 1998).…”

Section: Introductionmentioning

confidence: 96%

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The Ultraviolet Peak of the Energy Distribution in 3C 273: Evidence for an Accretion Disk and Hot Corona around a Massive Black Hole

Kriss

Davidsen

Zheng

et al. 1999

ApJ

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We present absolutely calibrated far-ultraviolet spectrophotometry of the quasar 3C 273 covering the 900-1800 Å range. Our ∼ 3 Å resolution spectra were obtained with the Hopkins Ultraviolet Telescope during the Astro-1 mission in December 1990 and during the Astro-2 mission in March 1995. Both spectra exhibit a change in slope near the Lyman limit in the quasar rest frame. At longer UV wavelengths, the continuum has a power-law index of 0.5-0.7, while shortward of the Lyman limit it is 1.2-1.7. The energy distribution in ν f ν therefore peaks close to the quasar Lyman limit. The short wavelength UV power law extrapolates well to match the soft X-ray excess seen in simultaneous observations with the Broad-Band X-ray Telescope and nearly simultaneous ROSAT observations.The general shape of the broad-band spectrum of 3C 273 is consistent with that of an optically thick accretion disk whose emergent spectrum has been Comptonized by a hot medium. Our UV spectrum is well described by a Schwarzschild black hole of 7 × 10 8 M ⊙ accreting matter at a rate of 13 M ⊙ yr −1 through a disk inclined at 60 degrees. Superposed on the intrinsic disk spectrum is an empirically determined Lyman edge of optical depth 0.5. The Comptonizing medium has a Compton parameter y ≈ 1, obtained with an optical depth to electron scattering of unity and a temperature of 4 × 10 8 K.This overall shape is the same as that found by Zheng et al. and Laor et al. in their UV and X-ray composite spectra for quasars, giving physical validity to the composite spectrum approach. When combined with those results, we find that the generic ionizing continuum shape for quasars is a power law of energy index 1.7-2.2, extending from the Lyman limit to ∼1 keV. The observational gap in the extreme ultraviolet for these combined data describing the quasar continuum shape is now only half a decade in frequency.

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Section: Empirical Models For the Spectrasupporting

confidence: 92%

Section: Introductionmentioning

confidence: 96%

The Ultraviolet Peak of the Energy Distribution in 3C 273: Evidence for an Accretion Disk and Hot Corona around a Massive Black Hole

Kriss

Davidsen

Zheng

et al. 1999

ApJ

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“…OBSERVATIONS We present the first intermediate-resolution far-ultraviolet spectrum of the bright quasi-stellar object 3C 273 in the 900-1210 Å band, emphasizing absorption features arising along the line of sight. Appenzeller et al (1998) discuss the intrinsic spectrum of 3C 273. These data were collected with the Berkeley spectrograph (Hurwitz et al 1998) during the ORFEUS-Shuttle Pallet Satellite (SPAS) II mission.…”

Section: ϫ2mentioning

confidence: 98%

[ITAL]ORFEUS II[/ITAL] Far-Ultraviolet Observations of 3C 273: Interstellar and Intergalactic Absorption Lines

Hurwitz

Appenzeller

Barnstedt

et al. 1998

The Astrophysical Journal

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We present the first intermediate-resolution (l/Dl ϭ 3000) spectrum of the bright quasi-stellar object 3C 273 at wavelengths between 900 and 1200 Å . Observations were performed with the Berkeley spectrograph aboard the ORFEUS II mission. We detect Lyb counterparts to intergalactic Lya features identified by Morris and coworkers at cz ϭ 19,900, 1600, and 1000 km s ; counterparts to other putative Lya clouds along the sight Ϫ1 line are below our detection limit. The strengths of the two very low redshift Lyb features, which are believed to arise in Virgo intracluster gas, exceed preflight expectations (Weymann and coworkers), suggesting that the previous determination of the cloud parameters may underestimate the true column densities. A curve-of-growth analysis sets a minimum H i column density of 4 # 10 14 cm for the 1600 km s cloud. We find marginally Ϫ2 Ϫ1 significant evidence for Galactic H along the sight line, with a total column density of about 10 15 cm . We Ϫ2 2 detect the stronger interstellar O vi doublet member unambiguously; the weaker member is blended with other features. If the Doppler b-value for O vi is comparable to that determined for N v by Sembach and collaborators, then the O vi column density is (7 ‫ע‬ 2) # 10 14 cm , significantly above the only previous estimate, by Davidsen. Ϫ2The O vi/N v ratio is about 10, consistent with the low end of the range observed in the disk, as shown in the compilation by Hurwitz & Bowyer. Additional interstellar species detected for the first time toward 3C 273 (at modest statistical significance) include P ii, Fe iii, Ar i, and S iii.

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“…Consequently, Compton processes of a thermal plasma in the disk or in the corona can contribute efficiently to the highenergy radiation. The optical-UV spectrum of 3C 273 also shows strong emission lines, i.e., Ly-α, CIV, OVI, CIII, NIII, and SVI (e.g., Appenzeller et al 1998;Paltani & Türler 2003, and references therein). Therefore it might not be surprising to find a contribution of inverse-Compton scattered radiation from both the disk and the BLR.…”

Section: Origin Of Spectral Breaksmentioning

confidence: 99%

Constraining the location of rapid gamma-ray flares in the flat spectrum radio quasar 3C 273

Rani¹,

Lott²,

Krichbaum³

et al. 2013

A&A

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We present a γ-ray photon flux and spectral variability study of the flat-spectrum radio quasar 3C 273 over a rapid flaring activity period between September 2009 to April 2010. Five major flares were observed in the source during this period. The most rapid flare observed in the source has a flux doubling time of 1.1 hr. The rapid γ-ray flares allow us to constrain the location and size of the γ-ray emission region in the source. The γγ-opacity constrains the Doppler factor δ γ ≥ 10 for the highest energy (15 GeV) photon observed by the Fermi-Large Area Telescope (LAT). Causality arguments constrain the size of the emission region to 1.6 × 10 15 cm. The γ-ray spectra measured over this period show clear deviations from a simple power law with a break in the 1−2 GeV energy range. We discuss possible explanations for the origin of the γ-ray spectral breaks. Our study suggests that the γ-ray emission region in 3C 273 is located within the broad line region (<1.6 pc). The spectral behavior and temporal characteristics of the individual flares indicate the presence of multiple shock scenarios at the base of the jet.

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[ITAL]ORFEUS II[/ITAL] Far-Ultraviolet Observations of 3C 273: The Intrinsic Spectrum

Cited by 9 publications

References 15 publications

The Ultraviolet Peak of the Energy Distribution in 3C 273: Evidence for an Accretion Disk and Hot Corona around a Massive Black Hole

The Ultraviolet Peak of the Energy Distribution in 3C 273: Evidence for an Accretion Disk and Hot Corona around a Massive Black Hole

[ITAL]ORFEUS II[/ITAL] Far-Ultraviolet Observations of 3C 273: Interstellar and Intergalactic Absorption Lines

Constraining the location of rapid gamma-ray flares in the flat spectrum radio quasar 3C 273

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