Confirmation of the 62 Day X-Ray Periodicity from M82

Using 400 days of new X-ray monitoring of M82, we confirm the 62 day periodicity previously reported. In the full data set spanning 1124 days, we find a period of 62.0 +/- 0.3 days and a coherence, Q = 22.3, that is consistent with a strictly periodic signal. We estimate that the probability of chance occurrence of our observed signal is 6E-7. The light curve folded at this period is roughly sinusoidal and has a peak to peak amplitude of (0.99 +/- 0.10) x 10^-11 erg cm^-2 s^-1. Confirmation of the periodicity strengthens our previous suggestion that the 62 day modulation is due to orbital motion within an X-ray binary.Comment: 4 pages, to appear in Ap

X-ray Variability Characteristics of the Seyfert 1 Galaxy NGC 3783

We have characterized the energy-dependent X-ray variability properties of the Seyfert~1 galaxy NGC 3783 using archival XMM-Newton and Rossi X-ray Timing Explorer data. The high-frequency fluctuation power spectral density function (PSD) slope is consistent with flattening towards higher energies. Light curve cross correlation functions yield no significant lags, but peak coefficients generally decrease as energy separation of the bands increases on both short and long timescales. We have measured the coherence between various X-ray bands over the temporal frequency range of 6e-8 to 1e-4 Hz; this range includes the temporal frequency of the low-frequency power spectral density function (PSD) break tentatively detected by Markowitz et al. and includes the lowest temporal frequency over which coherence has been measured in any AGN to date. Coherence is generally near unity at these temporal frequencies, though it decreases slightly as energy separation of the bands increases. Temporal frequency-dependent phase lags are detected on short time scales; phase lags are consistent with increasing as energy separation increases or as temporal frequency decreases. All of these results are similar to those obtained previously for several Seyfert galaxies and stellar-mass black hole systems. Qualitatively, these results are consistent with the variability models of Kotov et al. and Lyubarskii, wherein the X-ray variability is due to inwardly propagating variations in the local mass accretion rate.Comment: Accepted for publication in The Astrophysical Journal, 2005, vol. 635, p. 180; version 2 has minor grammatical changes; 23 pages; uses emulateapj

Clinical Appraisals of Individual Differences in Treatment Responsivity Among Patients With Psychopathy: A Consensual Qualitative Research Study

This study addressed which factors expert clinicians consider crucial in successful completion versus dropout in the mandatory forensic psychiatric treatment of psychopathic patients in the Netherlands. Eleven clinicians were interviewed about patient characteristics, treatment (provider) characteristics, and other factors they deemed associated with failure (transfer to another facility) or completion. The interviews were coded using the guidelines of Consensual Qualitative Research (CQR). Overall, extremely high scores on Psychopathy Checklist–Revised (PCL-R) Facets 1 (Deceitful Interpersonal Style) and 2 (Defective Affective Experience) were thought to impede treatment retention, particularly by its negative impact on motivation and therapeutic relationship. Older patients, those with a prosocial network, and/or patients with comorbid borderline traits appeared to fare better. Treatment success was deemed more likely when treatment goals and expectations are stipulated in a concrete fashion, when an extended and gradual resocialization trajectory is offered, and the treatment team is expert, cohesive, and stable.</p

Phase synchronization from noisy univariate signals

We present methods for detecting phase synchronization of two unidirectionally coupled, self-sustained noisy oscillators from a signal of the driven oscillator alone. One method detects soft, another hard phase locking. Both are applied to the problem of detecting phase synchronization in von Karman vortex flow meters.Comment: 4 pages, 4 figure

Mass Measurements of AGN from Multi-Lorentzian Models of X-ray Variability. I. Sampling Effects in Theoretical Models of the rms^2-M_BH Correlation

Recent X-ray variability studies suggest that the log of the square of the fractional rms variability amplitude, rms^2, seems to correlate with the log of the AGN black-hole mass, M_BH, with larger black holes being less variable for a fixed time interval. This has motivated the theoretical modeling of the rms^2-M_BH correlation with the aim of constraining AGN masses based on X-ray variability. A viable approach to addressing this problem is to assume an underlying power spectral density with a suitable mass dependence, derive the functional form of the rms^2-M_BH correlation for a given sampling pattern, and investigate whether the result is consistent with the observations. For simplicity, previous studies, inspired by the similarities shared by the timing properties of AGN and X-ray binaries, have explored model power spectral densities characterized by broken power laws. and ignored, in general, the distorting effects that the particular sampling pattern imprints in the observed power spectral density. Motivated by the latest timing results from X-ray binaries, obtained with RXTE, we propose that AGN broad-band noise spectra consist of a small number of Lorentzian components. This assumption allows, for the first time, to fully account for sampling effects in theoretical models of X-ray variability in an analytic manner. We show that, neglecting sampling effects when deriving the fractional rms from the model power spectral density can lead to underestimating it by a factor of up to 80% with respect to its true value for the typical sampling patterns used to monitor AGN. We discuss the implications of our results for the derivation of AGN masses using theoretical models of the rms^2-M_BH correlation. (Abridged)Comment: The Astrophysical Journal, in press, 11 pages, 6 figure

Design of a Secure and Decentralized Location Service for Agent Platforms

Abstract. Agent platforms designed for Internet-scale, open networks need scalable and secure location services for agents and services. The location service based on the Fonkey public key distribution infrastructure presented in this paper has been designed and implemented for this purpose. It is scalable in the total number of published identifier–contact address pairs, the number of updates/changes, and the number of agent platforms publishing and requesting contact addresses. This system also supports a signing mechanism to authenticate the publisher of an identifier–contact address pair. Experimental results show that the current implementation based on the Bunshin/Free Pastry overlay network exhibits good scaling behavior.

A variability study of the Seyfert 2 galaxy NGC 6300 with XMM-Newton

We present the results of timing analysis of the XMM-Newton observation of the Seyfert 2 galaxy NGC 6300. The hard X-ray spectrum above 2 keV consists of a Compton-thin-absorbed power law, as is often seen in Seyfert 2 galaxies. We clearly detected rapid time variability on a time scale of about 1000 s from the light curve above 2 keV. The excess variance of the time variability (sigma2_RMS) is calculated to be ~0.12, and the periodogram of the light curve is well represented by a power law function with a slope of 1.75. In contrast with previous results from Seyfert 2 nuclei, these variability characteristics are consistent with those of Seyfert 1 galaxies. This consistency suggests that NGC 6300 has a similar black hole mass and accretion properties as Seyfert 1 galaxies. Using the relation between time variability and central black hole mass by Hayashida et al. (1998), the black hole mass of NGC 6300 is estimated to be ~2.8x10^5 Mo. Taking uncertainty of this method into account, the black hole mass is less than 10^7 Mo. Taking the bolometric luminosity of 3.3x10^43 erg/s into consideration, this yields an accretion rate of > 0.03 of the Eddington value, and comparable with estimates from Seyfert 1 galaxies using this method. The time variability analysis suggests that NGC 6300 actually has a Seyfert 1 nucleus obscured by a thick matter, and more generally provides a new pillar of support for the unified model of Seyfert galaxies based on obscuration.Comment: 11 pages, 6 figures, accepted for publication in Ap

The nature of the intranight variability of radio-quiet quasars

We select a sample of 10 radio-quiet quasars with confirmed intranight optical variability and with available X-ray data. We compare the variability properties and the broad band spectral constraints to the predictions of intranight variability by three models: (i) irradiation of an accretion disk by a variable X-ray flux (ii) an accretion disk instability (iii) the presence of a weak blazar component. We concluded that the third model, e.g. the blazar component model, is the most promising if we adopt a cannonball model for the jet variable emission. In this case, the probability of detecting the intranight variability is within 20-80%, depending on the ratio of the disk to the jet optical luminosity. Variable X-ray irradiation mechanism is also possible but only under additional requirement: either the source should have a very narrow Hbeta line or occasional extremely strong flares should appear at very large disk radii.Comment: MNRAS (in press