ASCA Observations of NLS1s: BH Mass Estimation from X-ray Variability and X-ray Spectra

ASCA observations of Narrow-Line Seyfert 1 galaxies (NLS1s) are presented. We focus on the black hole size of the NLS1 sources by employing two independent methods for the mass estimation; one is using X-ray variability, the other is using a blackbody fit to the soft component. Although the coincidence is not good for some sources, the mass estimated by these methods ranges from 1e5 to 1e7 solar masses, systematically smaller than those for typical (broad line) Seyfert 1. We consider the small mass black hole to be the principal cause of the several extreme characteristics of the NLS1s.Comment: Contributed talk presented at the Joint MPE,AIP,ESO workshop on NLS1s, Bad Honnef, Dec. 1999, to appear in New Astronomy Reviews; also available at http://wave.xray.mpe.mpg.de/conferences/nls1-worksho

Self-phase-locked frequency-by-two divider OPO with a residual fractional frequency instability of 8.1O(-18)

We directly measure the phase difference between the subharmonic waves of a self-phase-locked frequency by-2-divider OPO using a phase-sensitive detector scheme. The relative frequency instability of frequency division by 2 is measured to be 8.10(-18

Laser gain measurements at 193 nm in a small discharge cell containing ArF excimer laser gas mixtures

Spatial and temporal gain profiles as well as the peak net gain at 193 nm have been measured in X-ray preionized discharges excited by a single pulse electrical system working in the charge transfer mode. Ar- and F2-containing laser gas mixtures with He or Ne as a buffer gas have been used. With a pumping pulse duration of ~ 100 ns (FWHM) and a specific peak power deposition of ~ 1 MW cm-3 bar-1 in a gas mixture containing F2 : Ar : He (0.1%:5%:94.9%), at 2 bar total pressure, a very high peak net gain coefficient of ~30% cm-1 was measured in the gas discharge. The FWHM of the gain waveform was ~ 60 n

Coherent and incoherent radiation from a channel-guided laser wakefield accelerator

Coherent and incoherent electromagnetic radiation emitted from a\ud channel-guided laser wakefield accelerator (LWFA) is calculated based on the\ud Lienard–Wiechert potentials. It is found that at wavelengths longer than the\ud bunch length, the radiation is coherent. The coherent radiation, which typically\ud lies in the infrared range, shows features that reveal details of the acceleration process and properties of the electron bunch, such as its duration, charge, energy, and offset with respect to the wakefield axis. It is found that the LWFA emits energy predominantly in the coherent range of frequencies. The incoherent range of the spectrum, which extends to the x-ray frequency range, consists of rather broad peaks caused by the acceleration. The radiated energy, power and the pulse duration are estimated

Charged particle interaction with a chirped electromagnetic pulse

It is found that a charged particle can get a net energy gain from the interaction with an electromagnetic chirped pulse. Theoretically, the energy gain increases with the pulse amplitude and with the relative frequency variation in the pulse

Generation of ultra-short relativistic-electron-bunch by a laser wakefield

The possibility of the generation of an ultra-short (about one micron long) relativistic (up to a few GeVs) electron-bunch in a moderately nonlinear laser wakefield excited in an underdense plasma by an intense laser pulse is investigated. The ultra-short bunch is formed by trapping, effective compression (both in longitudinal and in transverse directions) and acceleration of an initially nonrelativistic (with kinetic energy of a few hundreds keVs) e-bunch that is injected in front of the laser pulse. The initial bunch may be of poor quality, may have a duration in the order of the laser pulse length or longer and can be generated by a laser-driven photo-cathode RF gun. Our 1D and 3D calculations predict that the accelerated ultra-short bunch will show a low energy spread of less than one percent and a low transverse emittance in the order of a nanometer. An energy gain in the GeV-range is feasible at an accelerating distance of a few centimetres. The total number of accelerated electrons is restricted by the beam loading effect only and can reach a value of 10/sup 8/-10/sup 9/

A 10-day ASCA Observation of the Narrow-line Seyfert~1 galaxy IRAS 13224-3809

(Abridged) We present an analysis of a 10-day continuous ASCA observation of the narrow-line Seyfert 1 galaxy IRAS 13224-3809. The soft (0.7-1.3 keV) and hard (1.3-10 keV) X-ray band light curves binned to 5000s reveal trough-to-peak variations by a factor >25 and 20, respectively. The light curves in the soft and hard bands are strongly correlated without any significant delay. However, this correlation is not entirely due to changes in the power-law flux alone but also due to changes in the soft X-ray hump emission above the power law. The presence of a soft X-ray hump below 2 keV, previously detected in ROSAT and ASCA data, is confirmed. Time resolved spectroscopy using daily sampling reveals changes in the power-law slope, with Gamma in the range 1.74-2.47, however, day-to-day variations in Gamma are not significant. The Soft hump emission is found to dominate the observed variability on a timescale of a week, but on shorter timescales (20000s) the power-law component appears to dominate the observed variability. Flux resolved spectroscopy reveals that at high flux levels the power law becomes steeper and the soft hump more pronounced. The steepening of the photon index with the fluxes in the soft and hard bands can be understood in the framework of disk/corona models in which accretion disk is heated by viscous dissipation as well as by reprocessing of hard X-rays following an X-ray flare resulting from coronal dissipation through magnetic reconnection events.Comment: 29 pages, 16 figures, To apear in A&

Temporal extension of stable glow discharges in fluorine-based excimer laser gas mixtures by the addition of xenon

The effect of addition of xenon on the long term homogeneity of discharges in F2and ArF excimer laser gas mixtures was investigated in a small-volume discharge chamber. The gas mixture in the discharge chamber was preionized by X-rays. A special electrical excitation circuit containing a pulse forming line provided a long, square-shaped current pumping pulse of a predetermined duration to the discharge electrodes. The initiation and the development of the discharge was monitored via its fluorescence signal with an intensified CCD camera. We found that adding Xe up to partial pressures of 0.53 mbar extended the homogeneous phase of the discharge from 80 ns to approximately 200 ns in He/F2as well as in He/Ar/F2and Ne/Ar/F2excimer laser gas mixtures. Monitoring of the ArF and XeF spontaneous emission signals showed that the formation of ArF excimers remained unaffected by the addition of xenon (up to 1.3 mbar) to the laser gas mixture

Femtosecond electron-bunch dynamics in laser wakefields and vacuum

Recent advances in laser wakefield acceleration demonstrated the generation of extremely short (with a duration of a few femtoseconds) relativistic electron bunches with relatively low (of the order of couple of percent) energy spread. In this article we study the dynamics of such bunches in drift space (vacuum) and in channel-guided laser wakefields. Analytical solutions were found for the transverse coordinate of an electron and for the bunch envelope in the wakefield in the case of arbitrary change in the energy. Our results show strong bunch dynamics already on a millimeter scale propagation distance both in plasma and in vacuum. When the bunch propagates in vacuum, its transverse sizes grow considerably; the same is observed for the normalized bunch emittance that worsens the focusability of the bunch. A scheme of two-stage laser wakefield accelerator with small drift space between the stages is proposed. It is found that fast longitudinal betatron phase mixing occurs in a femtosecond bunch when it propagates along the wakefield axis. When bunch propagates off axis, strong bunch decoherence and fast emittance degradation due to the finite bunch length was observed