Página 1 dos resultados de 4530 itens digitais encontrados em 0.041 segundos

Functional timing analysis of VLSI circuits containing complex gates; Análise de timing funcional de circuitos VLSI contendo portas complexas

Guntzel, Jose Luis Almada
Fonte: Universidade Federal do Rio Grande do Sul Publicador: Universidade Federal do Rio Grande do Sul
Tipo: Tese de Doutorado Formato: application/pdf
ENG
Relevância na Pesquisa
66.19%
The recent advances in CMOS technology have allowed for the fabrication of transistors with submicronic dimensions, making possible the integration of tens of millions devices in a single chip that can be used to build very complex electronic systems. Such increase in complexity of designs has originated a need for more efficient verification tools that could incorporate more appropriate physical and computational models. Timing verification targets at determining whether the timing constraints imposed to the design may be satisfied or not. It can be performed by using circuit simulation or by timing analysis. Although simulation tends to furnish the most accurate estimates, it presents the drawback of being stimuli dependent. Hence, in order to ensure that the critical situation is taken into account, one must exercise all possible input patterns. Obviously, this is not possible to accomplish due to the high complexity of current designs. To circumvent this problem, designers must rely on timing analysis. Timing analysis is an input-independent verification approach that models each combinational block of a circuit as a direct acyclic graph, which is used to estimate the critical delay. First timing analysis tools used only the circuit topology information to estimate circuit delay...

Verificação e otimização de atraso durante a síntese física de circuitos integrados CMOS; Timing verification and optimization in physical synthesis of cmos integrated circuits

Santos, Cristiano Lopes dos
Fonte: Universidade Federal do Rio Grande do Sul Publicador: Universidade Federal do Rio Grande do Sul
Tipo: Dissertação Formato: application/pdf
POR
Relevância na Pesquisa
55.97%
Este trabalho propõe um método de otimização de atraso, através de dimensionamento de transistores, o qual faz parte de um fluxo automático de síntese física de circuitos combinacionais em tecnologia CMOS estática. Este fluxo de síntese física é independente de biblioteca de células, sendo capaz de realizar, sob demanda, a geração do leiaute a partir de um netlist de transistores. O método de otimização proposto faz com que este fluxo de síntese física seja capaz de realizar a geração do leiaute orientado pelas restrições de atraso, garantindo a operação do circuito na freqüência especificada pelo projetista. Este trabalho inclui também uma pesquisa sobre os principais métodos de verificação e otimização de atraso, principalmente aqueles que podem ser aplicados quando a etapa de síntese física chega ao nível de transistores. Um método de análise de timing funcional é utilizado para identificar o atraso e o caminho críticos e, com isso, guiar o método de otimização proposto. Desta forma, não existe desperdício de esforço e desempenho para reduzir o atraso de caminhos que não contribuem efetivamente para determinar a freqüência do circuito. O método proposto neste trabalho explora as possibilidades oferecidas por ser independente de biblioteca de células...

Switching noise and timing characteristics in nanoscale integrated circuits

Salman, Emre (1981 - ); Friedman, Eby G.
Fonte: University of Rochester Publicador: University of Rochester
Tipo: Tese de Doutorado Formato: Number of Pages:xxxvii, 348 leaves.; Illustrations:ill.
ENG
Relevância na Pesquisa
45.86%
Thesis (Ph. D.)--University of Rochester. Dept. of Electrical and Computer Engineering, 2009.; Continuous progress in the design and manufacturing of integrated circuits (ICs) has enabled the integration of more than two billion transistors on the same die with clock frequencies well above several gigahertz. These improvements have triggered the era of system-on-chip (SoC) and system-in-package (SiP), drastically changing the classical understanding of noise in complex ICs. Traditionally, device noise has been the primary concern for analog ICs while digital ICs have typically been considered to be relatively immune to noise. This situation has changed significantly due to denser integration and faster signal transition times. Specifically, switching noise has become a primary design criterion for both mixed-signal and high performance synchronous digital ICs. Voltage fluctuations on the power/ground nodes of a circuit, i.e., power/ground noise, is a type of switching noise affecting both mixed-signal and digital ICs. A methodology is proposed to accurately estimate the worst case power/ground noise in an inductive power/ground distribution network with a decoupling capacitor. In mixed-signal ICs, power/ground noise affects the highly sensitive analog/RF blocks through the monolithic substrate...

Applying non-constant volatility analysis methods to software timeliness.

Brennan, Shane; Cahill, Vinny; Clarke, Siobhán
Fonte: University of Limerick Publicador: University of Limerick
Tipo: Conference item; all_ul_research; ul_published_reviewed; none
ENG
Relevância na Pesquisa
56.08%
peer-reviewed; Timing analysis is the application of one or more well-established predictive methods to derive the likely timing behaviour of a specific software task executing on a particular hardware platform. Current approaches towards timing analysis are predicated on the presumption that the software under test is always fixed, i.e., it remains unchanged once deployed to the target hardware. A dynamically adaptable system modifies its behaviour in unanticipated ways, and at unpredictable intervals, to exploit the prevailing operational environment. However, when the software is capable of runtime adaptation, statically derived timing estimates are incapable of accurately capturing the changes in the software timeliness caused by functional adaptations. Traditional timing analysis methods cannot be applied to a dynamically adaptive system, due to the inconstant nature of the software, the unpredictable scheduling of functional adaptations, and the need to produce timing estimates at runtime. This paper describes a work in progress with the aim of statistically forecasting software timeliness using non-constant volatility methods. We outline how timing bounds may be derived for an adaptable software system, with changeable underlying functionality...

Inferring the presence of reverse proxies through timing analysis

Alexander, Daniel R.
Fonte: Monterey, California: Naval Postgraduate School Publicador: Monterey, California: Naval Postgraduate School
Tipo: Tese de Doutorado
Relevância na Pesquisa
65.89%
Approved for public release; distribution is unlimited; Approved for public release; distribution is unlimited; This thesis presents a method for inferring the presence of a reverse proxy server using packet timing analysis from the vantage point of a client system. This method can determine whether Internet users are receiving web content from the actual source or from some potentially spoofed proxy device; leading to better risk assessment and understanding of the cyber terrain. By using only the measurement and comparison of three-way handshake and content request/delivery packet round trip times, we identify an accurate classifier that detects the presence of a reverse proxy server with over 98% accuracy. This is an improvement over other inference methods because all measurements can be done from an external client machine. A secondary yet significant contribution is the robust data set that was produced as a result of this research. We have collected a set of over 6 million data points from a known set of 30 globally dispersed machines, which was instrumental in our research efforts and will be used for further studies and exploration.; Outstanding Thesis; Outstanding Thesis; Major, United States Army

Timing analysis of an inter-cell mobility procedure for a wired/wireless PROFIBUS network

Ferreira, Luis; Tovar, Eduardo
Fonte: IPP-Hurray Group Publicador: IPP-Hurray Group
Tipo: Relatório
Publicado em //2004 ENG
Relevância na Pesquisa
45.89%
Recently, there have been a few research efforts towards extending the capabilities of fieldbus networks to encompass wireless support. In previous works we have proposed a hybrid wired/wireless PROFIBUS network solution where the interconnection between the heterogeneous communication media was accomplished through bridge-like interconnecting devices. The resulting networking architecture embraced a Multiple Logical Ring (MLR) approach, thus with multiple independent tokens, where the communication between different domains was supported by the Inter-Domain Protocol (IDP). The proposed architecture also supports mobility of stations between different wireless cells. To that hybrid wired/wireless networking architecture we have proposed a worst-case response timing analysis of the IDP, without considering inter-cell mobility (or handoff) of stations. In this paper, we advance that previous work by proposing a worst-case timing analysis of the mobility procedure.

Timing Analysis of Fixed Priority SelfSuspending Sporadic Tasks

Nelissen, Geoffrey; Fonseca, José; Raravi, Gurulingesh; Nélis, Vincent
Fonte: Instituto Politécnico do Porto Publicador: Instituto Politécnico do Porto
Tipo: Conferência ou Objeto de Conferência
Publicado em //2015 ENG
Relevância na Pesquisa
45.93%
27th Euromicro Conference on Real-Time Systems (ECRTS 2015), Lund, Sweden.; Many real-time systems include tasks that need to suspend their execution in order to externalize some of their operations or to wait for data, events or shared resources. Although commonly encountered in real-world systems, study of their timing analysis is still limited due to the problem complexity. In this paper, we invalidate a claim made in one of the earlier works [1], that led to the common belief that the timing analysis of one self-suspending task interacting with non-self-suspending sporadic tasks is much easier than in the periodic case. This work highlights the complexity of the problem and presents a method to compute the exact worst-case response time (WCRT) of a self-suspending task with one suspension region. However, as the complexity of the analysis might rapidly grow with the number of tasks, we also define an optimization formulation to compute an upper-bound on the WCRT for tasks with multiple suspendion regions. In the experiments, our optimization framework outperforms all previous analysis techniques and often finds the exact WCRT.

Timing analysis: from predictions to certificates

Gaspar, Nuno Miguel Pires
Fonte: Universidade da Beira Interior Publicador: Universidade da Beira Interior
Tipo: Dissertação de Mestrado
Publicado em //2010 ENG
Relevância na Pesquisa
55.93%
In real-time systems timing properties must be satisfied in order to guarantee that deadlines will be met. In this context, the calculation of theworst-case execution time(WCET) is of paramount importance for schedulability analysis. However, this problem can be difficult if the underlying architecture possesses features like caches and pipelines. This thesis presents all the necessary steps for the safe and preciseWCET calculation. We focus ourselves in the use of static analysis-based methods, and in the ARMarchitecture as target platform. Moreover, in order to ensure the correctness of our calculation to a program consumer, we produce a certificate (or proof ) whose validity entails compliance with the calculated WCET. This evidence permits to locally validate the calculated WCET, avoiding the need of a blind confidence on the producer.

WASP-14 b: Transit Timing analysis of 19 light curves

Raetz, St.; Maciejewski, G.; Seeliger, M.; Marka, C.; Fernandez, M.; Güver, T.; Gögüs, E.; Nowak, G.; Vanko, M.; Berndt, A.; Eisenbeiss, T.; Mugrauer, M.; Trepl, L.; Gelszinnis, J.
Fonte: Universidade Cornell Publicador: Universidade Cornell
Tipo: Artigo de Revista Científica
Publicado em 06/07/2015
Relevância na Pesquisa
45.91%
Although WASP-14 b is one of the most massive and densest exoplanets on a tight and eccentric orbit, it has never been a target of photometric follow-up monitoring or dedicated observing campaigns. We report on new photometric transit observations of WASP-14 b obtained within the framework of "Transit Timing Variations @ Young Exoplanet Transit Initiative" (TTV@YETI). We collected 19 light-curves of 13 individual transit events using six telescopes located in five observatories distributed in Europe and Asia. From light curve modelling, we determined the planetary, stellar, and geometrical properties of the system and found them in agreement with the values from the discovery paper. A test of the robustness of the transit times revealed that in case of a non-reproducible transit shape the uncertainties may be underestimated even with a wavelet-based error estimation methods. For the timing analysis we included two publicly available transit times from 2007 and 2009. The long observation period of seven years (2007-2013) allowed us to refine the transit ephemeris. We derived an orbital period 1.2 s longer and 10 times more precise than the one given in the discovery paper. We found no significant periodic signal in the timing-residuals and...

\emph{RXTE} Timing Analysis of the AXP 1E 2259+586

Icdem, Burcin; Baykal, Altan; Inam, S. Cagdas
Fonte: Universidade Cornell Publicador: Universidade Cornell
Tipo: Artigo de Revista Científica
Relevância na Pesquisa
45.94%
We report the pulse timing analysis of \emph{Rossi X-ray Timing Explorer} (\emph{RXTE}) observations of the anomalous X-ray pulsar 1E 2259+586 from its 2002 outburst to October, 2010. Our objectives are to extend the work on the recovery stage after the 2002 glitch, investigate the variations caused by the second glitch which occurred in 2007 and look for other unusual events, if any, that arise in the regular spin-down trend of the source. The recovery of the 2002 glitch gives good fit when the two-exponential glitch model of the Crab pulsar is used, rather than the standard glitch model, in the 1360-day interval after the first glitch. The sampling of the following 260-day is not frequent enough to be phase-connected. After that interval, our timing analysis yields that there is a fractional frequency change of $\frac{\Delta\nu}{\nu}\sim8.20(2)\times10^{-7}$. Moreover, we report two frequency shifts of fractional changes, $\frac{\Delta\nu}{\nu}\sim3\times10^{-8},-1\times10^{-8}$: The first one at MJD $\sim53750$ had a positive fractional frequency change in contrast to the second one at MJD $\sim54880$ for which the pulse frequency decreased. These frequency shifts both resemble the microglitches observed in radio pulsars.; Comment: 13 pages...

No Time for Dead Time: Timing analysis of bright black hole binaries with NuSTAR

Bachetti, Matteo; Harrison, Fiona A.; Cook, Rick; Tomsick, John; Schmid, Christian; Grefenstette, Brian W.; Barret, Didier; Boggs, Steven E.; Christensen, Finn E.; Craig, William W.; Fabian, Andrew C.; Fürst, Felix; Gandhi, Poshak; Hailey, Charles J.; Ka
Fonte: Universidade Cornell Publicador: Universidade Cornell
Tipo: Artigo de Revista Científica
Publicado em 10/09/2014
Relevância na Pesquisa
45.96%
Timing of high-count rate sources with the NuSTAR Small Explorer Mission requires specialized analysis techniques. NuSTAR was primarily designed for spectroscopic observations of sources with relatively low count-rates rather than for timing analysis of bright objects. The instrumental dead time per event is relatively long (~2.5 msec), and varies by a few percent event-to-event. The most obvious effect is a distortion of the white noise level in the power density spectrum (PDS) that cannot be modeled easily with the standard techniques due to the variable nature of the dead time. In this paper, we show that it is possible to exploit the presence of two completely independent focal planes and use the cross power density spectrum to obtain a good proxy of the white noise-subtracted PDS. Thereafter, one can use a Monte Carlo approach to estimate the remaining effects of dead time, namely a frequency-dependent modulation of the variance and a frequency-independent drop of the sensitivity to variability. In this way, most of the standard timing analysis can be performed, albeit with a sacrifice in signal to noise relative to what would be achieved using more standard techniques. We apply this technique to NuSTAR observations of the black hole binaries GX 339-4...

Timing Analysis of Light Curves in the Tartarus Active Galactic Nuclei Database

O'Neill, Paul M.; Nandra, Kirpal; Papadakis, Iossif E.; Turner, T. Jane
Fonte: Universidade Cornell Publicador: Universidade Cornell
Tipo: Artigo de Revista Científica
Publicado em 24/03/2004
Relevância na Pesquisa
45.89%
The Tartarus database contains products for 529 ASCA observations of active galactic nuclei. We have been updating Tartarus to include observing sequences conducted after 1999 January. The revised database will contain products for 375 objects, with a total of 614 observing sequences. We have begun a systematic timing analysis of the Tartarus light curves. We present here some preliminary results of an investigation into the relation between excess variance and black-hole mass. Having optimised our analysis to minimize the scatter in the variance measurements, we find that the narrow-line active galactic nuclei follow roughly the same relation as the broad-line objects.; Comment: 4 pages,1 figure, to appear in proceedings "X-Ray Timing 2003: Rossi and Beyond", ed. P. Kaaret, F. K. Lamb, & J. H. Swank (Melville, NY: American Institute of Physics)

New Methods for Timing Analysis of Transient Events, Applied to Fermi/GBM Magnetar Bursts

Huppenkothen, Daniela; Watts, Anna L.; Uttley, Phil; van der Horst, Alexander J.; van der Klis, Michiel; Kouveliotou, Chryssa; Gogus, Ersin; Granot, Jonathan; Vaughan, Simon; Finger, Mark H.
Fonte: Universidade Cornell Publicador: Universidade Cornell
Tipo: Artigo de Revista Científica
Publicado em 06/03/2013
Relevância na Pesquisa
45.91%
In order to discern the physical nature of many gamma-ray sources in the sky, we must look not only in spectral and spatial dimensions, but also understand their temporal variability. However, timing analysis of sources with a highly transient nature, such as magnetar bursts, is difficult: standard Fourier techniques developed for long-term variability generally observed, for example, from AGN often do not apply. Here, we present newly developed timing methods applicable to transient events of all kinds, and show their successful application to magnetar bursts observed with Fermi/GBM. Magnetars are a prime subject for timing studies, thanks to the detection of quasi-periodicities in magnetar Giant Flares and their potential to help shed light on the structure of neutron stars. Using state-of-the art statistical techniques, we search for quasi-periodicities (QPOs) in a sample of bursts from Soft Gamma Repeater SGR J0501+4516 observed with Fermi/GBM and provide upper limits for potential QPO detections. Additionally, for the first time, we characterise the broadband variability behaviour of magnetar bursts and highlight how this new information could provide us with another way to probe these mysterious objects.; Comment: 2012 Fermi Symposium proceedings - eConf C121028

Transit timing analysis of CoRoT-1b

Csizmadia, Sz.; Renner, S.; Barge, P.; Agol, E.; Aigrain, S.; Alonso, R.; Almenara, J. M.; Bonomo, A. S.; Borde, P.; Bouchy, F.; Cabrera, J.; Deeg, H. J.; De la Reza, R.; Deleuil, M.; Dvorak, R.; Erikson, A.; Guenther, E. W.; Fridlund, M.; Gondoin, P.; Gu
Fonte: Universidade Cornell Publicador: Universidade Cornell
Tipo: Artigo de Revista Científica
Publicado em 18/11/2009
Relevância na Pesquisa
45.91%
CoRoT, the pioneer space-based transit search, steadily provides thousands of high-precision light curves with continuous time sampling over periods of up to 5 months. The transits of a planet perturbed by an additional object are not strictly periodic. By studying the transit timing variations (TTVs), additional objects can be detected in the system. A transit timing analysis of CoRoT-1b is carried out to constrain the existence of additional planets in the system. We used data obtained by an improved version of the CoRoT data pipeline (version 2.0). Individual transits were fitted to determine the mid-transit times, and we analyzed the derived $O-C$ diagram. N-body integrations were used to place limits on secondary planets. No periodic timing variations with a period shorter than the observational window (55 days) are found. The presence of an Earth-mass Trojan is not likely. A planet of mass greater than $\sim 1$ Earth mass can be ruled out by the present data if the object is in a 2:1 (exterior) mean motion resonance with CoRoT-1b. Considering initially circular orbits: (i) super-Earths (less than 10 Earth-masses) are excluded for periods less than about 3.5 days, (ii) Saturn-like planets can be ruled out for periods less than about 5 days...

Pulsar timing analysis in the presence of correlated noise

Coles, W.; Hobbs, G.; Champion, D. J.; Manchester, R. N.; Verbiest, J. P. W.
Fonte: Universidade Cornell Publicador: Universidade Cornell
Tipo: Artigo de Revista Científica
Publicado em 26/07/2011
Relevância na Pesquisa
45.97%
Pulsar timing observations are usually analysed with least-square-fitting procedures under the assumption that the timing residuals are uncorrelated (statistically "white"). Pulsar observers are well aware that this assumption often breaks down and causes severe errors in estimating the parameters of the timing model and their uncertainties. Ad hoc methods for minimizing these errors have been developed, but we show that they are far from optimal. Compensation for temporal correlation can be done optimally if the covariance matrix of the residuals is known using a linear transformation that whitens both the residuals and the timing model. We adopt a transformation based on the Cholesky decomposition of the covariance matrix, but the transformation is not unique. We show how to estimate the covariance matrix with sufficient accuracy to optimize the pulsar timing analysis. We also show how to apply this procedure to estimate the spectrum of any time series with a steep red power-law spectrum, including those with irregular sampling and variable error bars, which are otherwise very difficult to analyse.; Comment: Accepted by MNRAS

X-ray Timing Analysis of Six Pulsars Using ESA's XMM-Newton Observatory

Martin-Carrillo, A.; Kirsch, M.; Kendziorra, E.; Staubert, R.
Fonte: Universidade Cornell Publicador: Universidade Cornell
Tipo: Artigo de Revista Científica
Publicado em 10/12/2007
Relevância na Pesquisa
45.98%
We present results of a timing analysis of various isolated pulsars using ESA's \emph{XMM-Newton} observatory. Isolated pulsars are useful for calibration purposes because of their stable emission. We have analyzed six pulsars with different pulse profiles in a range of periods between 15 and 200 ms. All observations were made using the \emph{EPIC-pn camera} in its faster modes (Small window, Timing and Burst modes). We investigate the relative timing accuracy of the camera by comparing the pulse periods determined from the \emph{EPIC-pn camera} observations with those from radio observations. As a result of our analysis we conclude that the relative timing accuracy of the \emph{EPIC-pn camera} is of the order of $1\times 10^{-8}$.; Comment: Published in Proceedings of the 14th Young Scientists Conference on Astronomy and Space Physics, Kyiv, Ukraine, April 23-28, 2007

Generative pulsar timing analysis

Lentati, L; Alexander, P.; Hobson, M. P.
Fonte: Universidade Cornell Publicador: Universidade Cornell
Tipo: Artigo de Revista Científica
Relevância na Pesquisa
46.04%
A new Bayesian method for the analysis of folded pulsar timing data is presented that allows for the simultaneous evaluation of evolution in the pulse profile in either frequency or time, along with the timing model and additional stochastic processes such as red spin noise, or dispersion measure variations. We model the pulse profiles using `shapelets' - a complete ortho-normal set of basis functions that allow us to recreate any physical profile shape. Any evolution in the profiles can then be described as either an arbitrary number of independent profiles, or using some functional form. We perform simulations to compare this approach with established methods for pulsar timing analysis, and to demonstrate model selection between different evolutionary scenarios using the Bayesian evidence. %s The simplicity of our method allows for many possible extensions, such as including models for correlated noise in the pulse profile, or broadening of the pulse profiles due to scattering. As such, while it is a marked departure from standard pulsar timing analysis methods, it has clear applications for both new and current datasets, such as those from the European Pulsar Timing Array (EPTA) and International Pulsar Timing Array (IPTA).; Comment: 11 pages...

Phase-Resolved Timing Analysis of GRS 1915+105 in Its {\rho} State

Yan, Shu-Ping; Wang, Na; Ding, Guo-Qiang; Qu, Jin-Lu
Fonte: Universidade Cornell Publicador: Universidade Cornell
Tipo: Artigo de Revista Científica
Relevância na Pesquisa
45.89%
We made a phase-resolved timing analysis of GRS 1915+105 in its {\rho} state and obtained detailed {\rho} cycle evolutions of the frequency, the amplitude and the coherence of low-frequency quasi-periodic oscillation (LFQPO). We combined our timing results with the spectral study by Neilsen et al. to perform an elaborate comparison analysis. Our analyses show that the LFQPO frequency does not scale with the inner disk radius, but it is related to the spectral index, indicating a possible correlation between the LFQPOs and the corona. The LFQPO amplitude spectrum and other results are naturally explained by tying the LFQPO to the corona. The similarities of the spectra of variability parameters between the LFQPO from {\rho} state and those from more steady states indicate that the LFQPOs of GRS 1915+105 in very different states seem to share the same origin.; Comment: 21 pages, 4 figures, accepted for publication in ApJ

RXTE Observation of Cygnus X-1: II. Timing Analysis

Nowak, Michael A.; Vaughan, Brian A.; Wilms, Joern; Dove, James B.; Begelman, Mitchell C.
Fonte: Universidade Cornell Publicador: Universidade Cornell
Tipo: Artigo de Revista Científica
Publicado em 27/07/1998
Relevância na Pesquisa
45.94%
We present timing analysis for a Rossi X-ray Timing Explorer observation of Cygnus X-1 in its hard/low state. This was the first RXTE observation of Cyg X-1 taken after it transited back to this state from its soft/high state. RXTE's large effective area, superior timing capabilities, and ability to obtain long, uninterrupted observations have allowed us to obtain measurements of the power spectral density (PSD), coherence function, and Fourier time lags to a decade lower in frequency and half a decade higher in frequency than typically was achieved with previous instruments. Notable aspects of our observations include a weak 0.005 Hz feature in the PSD coincident with a coherence recovery; a `hardening' of the high-frequency PSD with increasing energy; a broad frequency range measurement of the coherence function, revealing rollovers from unity coherence at both low and high frequency; and an accurate determination of the Fourier time lags over two and a half decades in frequency. As has been noted in previous similar observations, the time delay is approximately proportional to f^(-0.7), and at a fixed Fourier frequency the time delay of the hard X-rays compared to the softest energy channel tends to increase logarithmically with energy. Curiously...

No Time for Dead Time: Timing analysis of bright black hole binaries with NuSTAR

Bachetti, Matteo; Harrison, Fiona A.; Cook, Rick; Tomsick, John; Schmid, Christian; Grefenstette, Brian W.; Barret, Didier; Boggs, Steven E.; Christensen, Finn E.; Craig, William W.; Fabian, Andrew C.; Fürst, Felix; Gandhi, Poshak; Hailey, Charles J.; Ka
Fonte: American Astronomical Society Publicador: American Astronomical Society
Tipo: Article; PeerReviewed Formato: application/pdf; application/pdf
Publicado em 20/02/2015
Relevância na Pesquisa
45.96%
Timing of high-count rate sources with the NuSTAR Small Explorer Mission requires specialized analysis techniques. NuSTAR was primarily designed for spectroscopic observations of sources with relatively low count-rates rather than for timing analysis of bright objects. The instrumental dead time per event is relatively long (∼2.5 msec), and varies by a few percent event-to-event. The most obvious effect is a distortion of the white noise level in the power density spectrum (PDS) that cannot be modeled easily with the standard techniques due to the variable nature of the dead time. In this paper, we show that it is possible to exploit the presence of two completely independent focal planes and use the cross power density spectrum to obtain a good proxy of the white noise-subtracted PDS. Thereafter, one can use a Monte Carlo approach to estimate the remaining effects of dead time, namely a frequency-dependent modulation of the variance and a frequency-independent drop of the sensitivity to variability. In this way, most of the standard timing analysis can be performed, albeit with a sacrifice in signal to noise relative to what would be achieved using more standard techniques. We apply this technique to NuSTAR observations of the black hole binaries GX339−4...