X-ray Spectral Variability and Rapid Variability of the Soft X-ray Spectrum Seyfert 1 Galaxies Ark 564 and Ton S180

The bright, soft X-ray spectrum Seyfert 1 galaxies Ark 564 and Ton S180 were monitored for 35 days and 12 days with ASCA and RXTE (and EUVE for Ton S180). The short time scale (hours-days) variability patterns were very similar across energy bands, with no evidence of lags between any of the energy bands studied. The fractional variability amplitude was almost independent of energy band. It is difficult to simultaneously explain soft Seyferts stronger variability, softer spectra, and weaker energy-dependence of the variability relative to hard Seyferts. The soft and hard band light curves diverged on the longest time scales probed, consistent with the fluctuation power density spectra that showed relatively greater power on long time scales in the softest bands. The simplest explanation is that a relatively hard, rapidly-variable component dominates the total X-ray spectrum and a slowly-variable soft excess is present in the lowest energy channels of ASCA. Although it would be natural to identify the latter with an accretion disk and the former with a corona surrounding it, a standard thin disk could not get hot enough to radiate significantly in the ASCA band, and the observed variability time scales are much too short. The hard component may have a more complex shape than a pure power-law. The most rapid factor of 2 flares and dips occurred within ~1000 sec in Ark 564 and a bit more slowly in Ton S180. The speed of the luminosity changes rules out viscous or thermal processes and limits the size of the individual emission regions to <~15 Schwarzschild radii (and probably much less), that is, to either the inner disk or small regions in a corona

ROSAT PSPC detection of soft X-ray absorption in GB 1428+4217: The most distant matter yet probed with X-ray spectroscopy

We report on a ROSAT PSPC observation of the highly-luminous z = 4.72 radio-loud quasar GB 1428+4217 obtained between 1998 December 11 and 17, the final days of the ROSAT satellite. The low-energy sensitivity of the PSPC detector was employed to constrain the intrinsic X-ray absorption of the currently most distant X-ray detected object. Here we present the detection of significant soft X-ray absorption towards GB 1428+4217, making the absorbing material the most distant matter yet probed with X-ray spectroscopy. X-ray variability by 25+-8 per cent is detected on a timescale of 6500 s in the rest frame. The X-ray variation requires an unusually high radiative efficiency of at least 4.2, further supporting the blazar nature of the source.Comment: 6 pages incl. 6 figures, accepted for publication in Monthly Notice

A gain-coefficient switched Alexandrite laser

We report on a gain-coefficient switched Alexandrite laser. An electro-optic modulator is used to switch between high and low gain states by making use of the polarization dependent gain of Alexandrite. In gain-coefficient switched mode, the laser produces 85 ns pulses with a pulse energy of 240 mJ at a repetition rate of 5 Hz.Comment: 8 pages, 5 figure

Spectropolarimetry of the Luminous Narrow-Line Seyfert Galaxies IRAS 20181-2244 and IRAS 13224-3809

We observed the narrow-line Seyfert 1 galaxies IRAS 20181-2244 and IRAS 13324-3809 with a new spectropolarimeter on the RC spectrograph at the CTIO 4m telescope. Previously it had been suggested that IRAS 20181-2244 was a Type 2 QSO and thus might contain an obscured broad-line region which could be detected by the presence of broad Balmer lines in the polarized flux. We found the object to be polarized at about 2%, and constant with wavelength, (unlike most narrow-line Seyfert 1s), but with no evidence of broad Balmer lines in polarized flux. The spectropolarimetry indicates that the scattering material is inside the BLR. IRAS 13224-3809, notable for its high variability in X-ray and UV wavelengths, has a low polarization consistent with a Galactic interstellar origin.Comment: 19 pages using (AASTEX) aaspp4.sty and 5 postscript figures To be published in the Astrophysical Journa

Mapping individual electromagnetic field components inside a photonic crystal

We present a method to map the absolute electromagnetic field strength inside photonic crystals. We apply the method to map the electric field component Ez of a two-dimensional photonic crystal slab at microwave frequencies. The slab is placed between two mirrors to select Bloch standing waves and a subwavelength spherical scatterer is scanned inside the resulting resonator. The resonant Bloch frequencies shift depending on the electric field at the position of the scatterer. To map the electric field component Ez we measure the frequency shift in the reflection and transmission spectrum of the slab versus the scatterer position. Very good agreement is found between measurements and calculations without any adjustable parameters.Comment: 12 pages, 7 figure

HST STIS Ultraviolet Spectral Evidence for Outflow in Extreme Narrow-line Seyfert 1 Galaxies: I. Data and Analysis

We present HST STIS observations of two extreme NLS1s, IRAS 13224-3809 and 1H 0707-495. The spectra are characterized by very blue continua, broad, strongly blueshifted high-ionization lines (including \ion{C}{4} and \ion{N}{5}), and narrow, symmetric intermediate- (including \ion{C}{3}], \ion{Si}{3}], \ion{Al}{3}) and low-ionization (e.g., \ion{Mg}{2}) lines centered at their rest wavelengths. The emission-line profiles suggest that the high-ionization lines are produced in a wind, and the intermediate- and low-ionization lines are produced in low-velocity gas associated with the accretion disk or base of the wind. In this paper, we present the analysis of the spectra from these two objects; in a companion paper we present photoionization analysis and a toy dynamical model for the wind. The highly asymmetric profile of \ion{C}{4} suggests that it is dominated by emission from the wind, so we develop a template for the wind from the \ion{C}{4} line. We model the bright emission lines in the spectra using a combination of this template, and a narrow, symmetric line centered at the rest wavelength. We also analyzed a comparison sample of HST spectra from 14 additional NLS1s, and construct a correlation matrix of emission line and continuum properties. A number of strong correlations were observed, including several involving the asymmetry of the \ion{C}{4} line.Comment: 26 pages, 10 figures, accepted for publication in ApJ with no change

Black hole mass and accretion rate of active galactic nuclei with double-peaked broad emission lines

(Abridged) Using an empirical relation between the broad line region size and optical continuum luminosity, we estimated the black hole mass and accretion rate for 135 AGNs with double-peaked broad emission lines in two samples. With black hole masses from $3\times 10^7M_\odot$ to $5\times 10^9M_\odot$, these AGNs have the dimensionless accretion rates (Eddington ratios) between 0.001 and 0.1, and the bolometric luminosity between $10^{43}erg/s$ and $10^{46}erg/s$, both being significantly larger than those of several previously known low-luminosity double-peaked AGNs. The optical-X-ray spectra indices, $\alpha_{OX}$, of these high-luminosity double-peaked AGNs is between 1 and 1.9. Modest correlations of the $\alpha_{OX}$ value with the Eddington ratio and bolometric luminosity indicate that double-peaked AGNs with higher Eddington ratio or higher luminosity tend to have larger $\alpha_{OX}$ value. Therefore we suggested that the accretion process in some high-luminosity double-peaked AGNs is probably different from that of low-luminosity objects where an ADAF-like accretion flow was thought to exist. This is also supported by the presence of possible big blue bumps in the spectra of some double-peaked AGNs with higher Eddington ratios. We noticed that the prototype double-peaked emission line AGN, Arp 102B, may be an ``intermediate'' object between the high and low luminosity double-peaked AGNs. In addition, we found an apparent strong anti-correlation between the peak separation of double-peaked profile and Eddington ratio. If it is real, it may provide us a clue to understand why double-peaked broad emission lines were hardly found in luminous AGNs with Eddington ratio larger than 0.1.Comment: 24 pages, 6 figures, accepted by Ap

XMM-Newton Spectroscopy of the Starburst Dominated Ultra Luminous Infrared Galaxy NGC 6240

We present new XMM-Newton observation of the Ultra Luminous Infrared Galaxy (ULIRG) NGC 6240. We analyze the reflecting grating spectrometer (RGS) data, and data from the other instruments, and find a starburst dominated 0.5-3 keV spectrum with global properties resembling those observed in M82 but with a much higher luminosity. We show that the starburst region can be divided into an outer zone, beyond a radius of about 2.1 kpc, with a gas temperature of about 10^7 K and a central region with temperatures in the range (2-6) x 10^7 K. The gas in the outer region emits most of the observed Oviii Lyman-alpha line and the gas in the inner region the emission lines of higher ionization ions, including a strong Fexxv line. We also identify a small inner part, very close to the active nuclei, with typical Seyfert 2 properties including a large amount of photoionized gas producing a strong Fe K-alpha 6.4 keV line. The combined abundance, temperature and emission measure analysis indicates super solar Ne/O, Mg/O, Si/O, S/O and possibly also Fe/O. The analysis suggests densities in the range of (0.07-0.28) x epsilon^(-1/2) cm^(-3) and a total thermal gas mass of about 4 x 10^8 x epsilon^(1/2) solar masses, where epsilon is the volume filling factor. We used a simple model to argue that a massive starburst with an age of about 2 x 10^7 years can explain most of the observed properties of the source. NGC 6240 is perhaps the clearest case of an X-ray bright luminous AGN, in a merger, whose soft X-ray spectrum is dominated by a powerful starburst.Comment: 10 pages, 6 diagrams, accepted by ApJ, added a few minor change

XMM-Newton monitoring of X-ray variability in the quasar PKS 0558-504

We present the temporal analysis of X-ray observations of the radio-loud Narrow-Line Seyfert 1 galaxy (NLS1) PKS 0558-504 obtained during the XMM-Newton Calibration and Performance Verification (Cal/PV) phase. The long term light curve is characterized by persistent variability with a clear tendency for the X-ray continuum to harden when the count rate increases. Another strong correlation on long time scales has been found between the variability in the hard band and the total flux. On shorter time scales the most relevant result is the presence of smooth modulations, with characteristic time of ~ 2 hours observed in each individual observation. The short term spectral variability turns out to be rather complex but can be described by a well defined pattern in the hardness ratio-count rate plane.Comment: 6 pages, 7 figures, accepted for publication in A&A special issue on first results from XM

Differences Between The Optical/Uv Spectra Of X-Ray Bright And X-Ray Faint QSOs

We contrast measurements of composite optical and ultraviolet (UV) spectra constructed from samples of QSOs defined by their soft X-ray brightness. X-ray bright (XB) composites show stronger emission lines in general, but particularly from the narrow line region. The difference in the [OIII]/Hbeta ratio is particularly striking, and even more so when blended FeII emission is properly subtracted. The correlation of this ratio with X-ray brightness were principal components of QSO spectral diversity found by Boroson & Green (1992). We find here that other, much weaker narrow optical forbidden lines ([OII] and NeV) are enhanced by factors of 2 to 3 in our XB composites, and that narrow line emission is also strongly enhanced in the XB UV composite. Broad permitted line fluxes are slightly larger for all XB spectra, but the narrow/broad line ratio stays similar or increases strongly with X-ray brightness for all strong permitted lines except Hbeta. Spectral differences between samples divided by their relative X-ray brightness (as measured by alpha_{ox}) exceed those seen between complementary samples divided by luminosity or radio loudness. We propose that the Baldwin effect may be a secondary correlation to the primary relationship between alpha_{ox} and emission line equivalent width. We conclude that either 1) equivalent width depends strongly on the SHAPE of the ionizing continuum, as crudely characterized here by alpha_{ox} or 2) both equivalent width and alpha_{ox} are related to some third parameter characterizing the QSO physics. One such possibility is intrinsic warm absorption; a soft X-ray absorber situated between the broad and narrow line regions can successfully account for many of the properties observed.Comment: 16 pages including 3 figures, AAS latex, plus 4 tables totaling 5 pages, to appear in ApJ Vol. 498, May 1, 199