相关论文: The far-UV break in quasar energy distributions: d…

A prominent continuum steepening is observed in quasar energy distributions near 1100A. We review possible interpretations for the physical origin of this so-called far-UV break.

The ultraviolet energy distribution of quasars shows a sharp steepening of the continuum shortward of 1000 A (rest-frame). We describe how we came to consider the possibility that this continuum break might be the result of absorption by…

The spectral energy distribution of quasars shows a sharp steepening of the continuum shortward of ~ 1100 A. We present a new dust extinction model consisting of crystalline carbon grains. We analyze the unusual extinction properties of…

Using Chandra and HST archival data, we have studied the individual Spectral Energy Distribution (SED) of 11 quasars. All UV spectra show a spectral break around 1100A. 5 X-ray spectra show the presence of a ``soft excess'' and 7 spectra…

Luminous quasars are known to display a sharp steepening of the continuum near 1100A. This spectral feature is not well fitted by current accretion disk models, unless comptonization of the disk emission is invoked. Absorption by carbon…

The ionizing spectral energy distribution of quasars exhibits a steepening of the distribution shortward of ~ 1200 A. The change of the power-law index from approximately -1 (near-UV) to -2 (far-UV) has so far been interpreted as being…

Changing-look quasars exhibit dramatic variability in broad emission-line fluxes on short timescales. This behavior is challenging to many models of the quasar broad line region, due in large part to the short transition times between high…

The spectral energy distribution of quasars shows a sharp steepening of the continuum shortward of ~ 1100 A. The steepening could be a result of dust absorption. We present a dust extinction model which considers crystalline carbon grains…

One of the models recently proposed to explain the origin of the ultra high energy cosmic rays assumes that these particles may be accelerated by the electromotive force around presently inactive quasar remnants. We study predictions for…

The spectral indexes distribution of a quasar sample is derived from a far-UV survey. A red average spectrum is found which comes in support of significant evolution of the QSO spectral energy distribution (SED) since $z\approx2.5$.

The blue-shifted broad emission lines and/or broad absorption lines seen in many luminous quasars are striking evidence for a broad line region in which radiation driving plays an important role. We consider the case for a similar role for…

We explore the possibility that the steepening observed shortward of 1000A in the energy distribution of quasars may result from absorption by dust, being either intrinsic to the quasar environment or intergalactic. We find that a dust…

We investigate the luminosity and redshift dependence of the quasar continuum by means of composite spectrum using a large non-BAL radio-quiet quasar sample drawn from the Sloan Digital Sky Survey. Quasar continuum slopes in the UV-Opt band…

Quasar outflows may play a crucial role in regulating the host galaxy, although the spatial scale of quasar outflows remain a major enigma, with their acceleration mechanism poorly understood. The kinematic information of outflow is the key…

Although dust is widely found in astrophysics, forming dust is surprisingly difficult. The proper combination of low temperature (<2000 K) and high density is mainly found in the winds of late-type giant and supergiant stars which, as a…

The diffuse cosmic background radiation in the GALEX far ultraviolet (FUV, 1300 \AA\ - 1700 \AA) is deduced to originate only partially in the dust-scattered radiation of FUV-emitting stars: the source of a substantial fraction of the FUV…

We combine submm photometric data of z>4 quasars, to obtain a mean far-infrared (FIR) (rest-frame) spectral energy distribution (SED) of thermal emission from dust, parameterised by a single temperature (T) and power-law emissivity index…

Quasars are notable for the luminous power they emit across decades in frequency from the far-infrared through hard X-rays; emission at different frequencies emerges from physical scales ranging from AUs to parsecs. Each wavelength regime…

We report the discovery of the highly peculiar, radio-loud quasar VPMS J1342+2840 (z ~ 1.3) from the variability and proper motion survey. We present spectroscopic, imaging and photometric observations. The unusual spectrum shows a strong…

Extreme Scattering Events are sometimes manifest in the light-curves of compact radio-quasars at frequencies of a few GHz. These events are not understood. The model which appears to offer the best explanation requires a new population of…