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Register a new userRXTE Observations of 3C273 between 1996 and 2000:Variability Timescale and Jet Power
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We present the results of a long-look monitoring of 3C273 with RXTE between 1996 and 2000. A total of 230 observations amounts to a net exposure of 845ksec, with this spectral and variability analysis of 3C273 covering the longest observation period available at hard X-ray energies. Flux variations by a factor of 4 have been detected over 4years, whereas less than 30% flux variations have been observed for individual flares on time-scales of 3 days. Two temporal methods, the power spectrum density (PSD) and the structure function (SF), have been used to study the variability characteristics of 3C273. The hard X-ray photon spectra generally show a power-law shape with a differential photon index of G = 1.6+-0.1. In 10 of 261 data segments, exceptions to power-law behaviour have been found: (i) an additional soft excess below 4keV, and (ii) a broad Fe fluorescent line feature with EW = 100-200 eV. Our new observations of these previously reported X-ray features may imply that 3C273 is a unique object whose hard X-ray emission occasionally contains a component which is not related to a beamed emission (Seyfert like), but most hard X-rays are likely to originate in inverse Compton radiation from the relativistic jet (blazar like). Multi-frequency spectra from radio to gamma-ray are presented in addition to our RXTE results. The X-ray time variability and spectral evolution are discussed in the framework of beamed, synchrotron self-Compton picture. We consider the ``power balance (both radiative and kinetic) between the accretion disk, sub-pc-scale jet, and the 10kpc-scale jet.
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The gamma-ray emission above 250 GeV from the BL Lac object Markarian 421 was observed by the CAT Cherenkov imaging telescope between December, 1996, and June, 2000. In 1998, the source produced a series of small flares, making it the second extragalactic source detected by CAT. The time-averaged differential spectrum has been measured from 0.3 to 5 TeV, which is well fitted with a power law with an index of -2.88+-0.12(stat)+-0.06(syst). In 2000, the source showed an unprecedented activity, with variability time-scales as short as one hour, as for instance observed during the night between 4 and 5 February. The 2000 time-averaged spectrum measured is compatible with that of 1998, but some indication of a spectral curvature is found between 0.3 and 5 TeV. The possibility of TeV spectral hardening during flares is also discussed, and the results are compared to those obtained on the other TeV BL Lac, Markarian 501.
We present a comprehensive examination of the X-ray variability of the narrow line Seyfert 1 (NLS1) galaxy NGC4051. We combine over 6.5 years of frequent monitoring observations by RXTE with a >100ks continuous observation by XMM-Newton and so present a powerspectral density (PSD) covering an unprecedented frequency range of over 6.5 decades from <1e-8 to >1e-2 Hz. The combined RXTE and XMM-Newton PSD is a very good match to the PSD of the galactic black hole binary system (GBH) Cyg X-1 when in a `high, rather than `low, state providing the first definite confirmation of an AGN in a `high state. We find a break in the PSD at a frequency u_{B}=8e-4 Hz. If u_{B} scales linearly with mass then, assuming a black hole (BH) mass of 10 M_solar for Cyg X-1, we imply a BH mass of 3e-5 M_solar in NGC4051, which is consistent with the recently reported reverberation mapped value. Hence NGC4051 is emitting at sim30% L_{Edd}. We note that the higher energy photons lag the lower energy ones and that the lag is greater for variations of longer Fourier period and increases with the energy separation of the bands. Variations in different wavebands are very coherent at long Fourier periods but the coherence decreases at shorter periods and as the energy separation between bands increases. This behaviour is similar to that of GBHs and suggests a radial distribution of frequencies and photon energies with higher energies and higher frequencies being associated with smaller radii [ABRIDGED].
We report results from Chandra observations of the X-ray jet of 3C~273 during the calibration phase in 2000 January. The zeroeth-order images and spectra from two 40-ks exposures with the HETG and LETG+ACIS-S show a complex X-ray structure. The brightest optical knots are detected and resolved in the 0.2-8 keV energy band. The X-ray morphology tracks well the optical. However, while the X-ray brightness decreases along the jet, the outer parts of the jet tend to be increasingly bright with increasing wavelength. The spectral energy distributions of four selected regions can best be explained by inverse Compton scattering of (beamed) cosmic microwave background photons. The model parameters are compatible with equipartition and a moderate Doppler factor, which is consistent with the one-sidedness of the jet. Alternative models either imply implausible physical conditions and energetics (the synchrotron self-Compton model) or are sufficiently ad hoc to be unconstrained by the present data (synchrotron radiation from a spatially or temporally distinct particle population).
We present timing and spectral analysis of the data collected by the Extreme Ultraviolet Explorer Satellite (EUVE) for the Seyfert 1 galaxy NGC 4051 during 1996. NGC 4051 was observed twice in May 1996 and again in December 1996 for a total of more than 200 ks. The observations were always simultaneous with hard X-ray observations conducted with the Rossi X-Ray Timing Explorer (RXTE). The EUVE light curves are extremely variable during each observation, with the maximum variability of more than a factor of 15 from peak to minimum. We detected signal in the EUVE spectrograph in the 75-100 A range which is well fitted by absorbed power law models. We illustrate the results of our spectral and detailed power spectrum analysis performed on EUVE data and the comparison with RXTE lightcurves and discuss the constraint we can place on the mass of the central object and on the size of the emitting region.
Using Chandra X-ray and VLA radio data, we investigate the scaling relationship between jet power, P_jet, and synchrotron luminosity, P_rad. We expand the sample presented in Birzan et al. (2008) to lower radio power by incorporating measurements for 21 gEs to determine if the Birzan et al. (2008) P_jet-P_rad scaling relations are continuous in form and scatter from giant elliptical galaxies (gEs) up to brightest cluster galaxies (BCGs). We find a mean scaling relation of P_jet approximately 5.8x10^43 (P_rad/10^40)^(0.70) erg/s which is continuous over ~6-8 decades in P_jet and P_rad with a scatter of approximately 0.7 dex. Our mean scaling relationship is consistent with the model presented in Willott et al. (1999) if the typical fraction of lobe energy in non-radiating particles to that in relativistic electrons is > 100. We identify several gEs whose radio luminosities are unusually large for their jet powers and have radio sources which extend well beyond the densest parts of their X-ray halos. We suggest that these radio sources are unusually luminous because they were unable to entrain appreciable amounts of gas.
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