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Post Info TOPIC: Quasar 3C454.3
Blobrana


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FSRQ 3C 454.3
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ATel 9723: Brightening of FSRQ 3C 454.3 with an intense optical micro-variability.



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Blobrana


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RE: Quasar 3C454.3
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"Crazy Diamond" breaks record with AGILE
New record for AGILE as it detects the highest gamma radiation emission per quasar 3C 454.3

The AGILE satellite has detected a new super gamma flare coming from a galaxy billions of light-years away, called "Crazy Diamond" because of the unpredictable variability of its emissions. This time we have an even greater flow of energy than in previous cases.



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Blobrana


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A galaxy located billions of light-years away is commanding the attention of NASA's Fermi Gamma-ray Space Telescope and astronomers around the globe. Thanks to a series of flares that began September 15, the galaxy is now the brightest source in the gamma-ray sky -- more than ten times brighter than it was in the summer.
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Blobrana


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3C 454.3 is a quasar/blazar located off the galactic plane. It lies some 7.1 billion light-years away in Pegasus and is currently undergoing a flaring episode that makes it especially bright, especially in the gamma-ray part of the spectrum.
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Blobrana


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When it comes to watching the skies, two sets of eyes are always better than one, especially if one pair can see, say, radio waves, while the other has X-ray or even gamma-ray vision. The Fermi Gamma-Ray Space Telescope's Large Area Telescope collaboration has recently released a paper giving the gamma-ray perspective on an astronomical object that flared last summer, an active galactic nucleus - or quasar - known as 3C 454.3. The paper, accepted by the Astrophysical Journal and posted yesterday on the ArXiv preprint archive, reveals that the structure of these distant, energetic monsters is more complex than scientists had previously guessed. The paper also hints at a more comprehensive picture to come, next time unfolding in full colour, using data from radio, infrared, optical, X-ray and gamma bands.
A quasar is thought to be fuelled by an enormous swirl of gas, or accretion disk, that has gathered around a massive black hole at the center of a distant galaxy. As gas particles stream into the black hole's maw, protons and electrons near the black hole are propelled outward at close to light speeds in a jet perpendicular to the disk. When this jet outshines the surrounding galaxy, it's often called a blazarperhaps one of nature's most powerful particle accelerators. In a process that's poorly understood, the jets quake and shudder, shaking the high-energy beams and causing them to radiate.

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Blobrana


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Quasar 3C 454.3
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Title: Early Fermi Gamma-ray Space Telescope Observations of the Quasar 3C 454.3
Authors: Fermi/LAT Collaboration: A. A. Abdo, et al

This is the first report of Fermi Gamma-ray Space Telescope observations of the quasar 3C 454.3, which has been undergoing pronounced long-term outbursts since 2000. The data from the Large Area Telescope (LAT), covering 2008 July 7 - October 6, indicate strong, highly variable gamma-ray emission with an average flux of ~3 x 10^{-6} photons cm^{-2} s^{-1}, for energies above 100 MeV. The gamma-ray flux is variable, with strong, distinct, symmetrically-shaped flares for which the flux increases by a factor of several on a time scale of about three days. This variability indicates a compact emission region, and the requirement that the source is optically thin to pair-production implies relativistic beaming with Doppler factor delta > 8, consistent with the values inferred from VLBI observations of superluminal expansion (delta ~ 25). The observed gamma-ray spectrum is not consistent with a simple power-law, but instead steepens strongly above ~2 GeV, and is well described by a broken power-law with photon indices of ~2.3 and ~3.5 below and above the break, respectively. This is the first direct observation of a break in the spectrum of a high luminosity blazar above 100 MeV, and it is likely direct evidence for an intrinsic break in the energy distribution of the radiating particles. Alternatively, the spectral softening above 2 GeV could be due to gamma-ray absorption via photon-photon pair production on the soft X-ray photon field of the host AGN, but such an interpretation would require the dissipation region to be located very close (less than 100 gravitational radii) to the black hole, which would be inconsistent with the X-ray spectrum of the source.

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Blobrana


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RE: Quasar 3C454.3
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Title: 3C454.3 reveals the structure and physics of its 'blazar zone'
Authors: M. Sikora (1), R. Moderski (1), G. M. Madejski (2 and 3) ((1) Nicolaus Copernicus Astronomical Center, (2) Stanford Linear Accelerator Center, (3) Kavli Institute for Particle Astrophysics and Cosmology)

Recent multi-wavelength observations of 3C454.3, in particular during its giant outburst in 2005, put severe constraints on the location of the 'blazar zone', its dissipative nature, and high energy radiation mechanisms. As the optical, X-ray, and millimetre light-curves indicate, significant fraction of the jet energy must be released in the vicinity of the millimetre-photosphere, i.e. at distances where, due to the lateral expansion, the jet becomes transparent at millimetre wavelengths. We conclude that this region is located at ~10 parsecs, the distance coinciding with the location of the hot dust region. This location is consistent with the high amplitude variations observed on ~10 day time scale, provided the Lorentz factor of a jet is ~20. We argue that dissipation is driven by reconfinement shock and demonstrate that X-rays and gamma-rays are likely to be produced via inverse Compton scattering of near/mid IR photons emitted by the hot dust. We also infer that the largest gamma-to-synchrotron luminosity ratio ever recorded in this object - having taken place during its lowest luminosity states - can be simply due to weaker magnetic fields carried by a less powerful jet.

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Blobrana


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Calar Alto participates in a multi-observatory effort to study the most luminous quasar ever observed. The object, radio quasar 3C 454.3 in the constellation Pegasus, experienced during 2005 a strong optical outburst that made it observable even with amateur instrumentation (reaching R = 12 mag). According to the WEBT team, "this ourburst peak likely represents the most luminous quasar state ever observed".

quasar3c454 3
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Credit Calar Alto Observatory

The same team quantified the maximum luminosity of this object as MB = -31.4 mag. This means that, at its maximum and when observed in blue light, 3C 454.3 was as bright as 550 billions of suns put together. This is very bright even for a quasar, considering that this object reached an intrinsic brightness, in blue light, around one hundred times more intense than the well known quasar 3C 273. However, the apparent brightness of 3C 454.3 in visible light remained similar to that of 3C 273, due to its much larger distance: 3C 454.3 is located at 12 billions of light-years, while 3C 273 is five times closer ("only" 2.4 billions of light-years).
At present, scientists do not exactly know what caused such an enormous brightening. This remains a mystery that follow-up observations, already planned by this team of astronomers, will help to solve.

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