scholarly journals On reverberation mapping lag uncertainties

2019 ◽  
Vol 491 (4) ◽  
pp. 6045-6064 ◽  
Author(s):  
Z Yu ◽  
C S Kochanek ◽  
B M Peterson ◽  
Y Zu ◽  
W N Brandt ◽  
...  
Keyword(s):  
Stochastic Process ◽  
Correlation Function ◽  
Light Curve ◽  
Cross Correlation ◽  
Systematic Errors ◽  
Light Curves ◽  
Reverberation Mapping ◽  
Uncertainty Estimates ◽  
Gaussian Statistics ◽  
The Continuum

ABSTRACT We broadly explore the effects of systematic errors on reverberation mapping lag uncertainty estimates from javelin and the interpolated cross-correlation function (ICCF) method. We focus on simulated light curves from random realizations of the light curves of five intensively monitored AGNs. Both methods generally work well even in the presence of systematic errors, although javelin generally provides better error estimates. Poorly estimated light-curve uncertainties have less effect on the ICCF method because, unlike javelin , it does not explicitly assume Gaussian statistics. Neither method is sensitive to changes in the stochastic process driving the continuum or the transfer function relating the line light curve to the continuum. The only systematic error we considered that causes significant problems is if the line light curve is not a smoothed and shifted version of the continuum light curve but instead contains some additional sources of variability.

scholarly journals Peering at the outflow mechanisms in the transitional pulsar PSR J1023+0038: simultaneous VLT, XMM-Newton, and Swift high-time resolution observations

2019 ◽  
Vol 631 ◽  
pp. A104 ◽  
Author(s):  
M. C. Baglio ◽  
F. Vincentelli ◽  
S. Campana ◽  
F. Coti Zelati ◽  
P. D’Avanzo ◽  
...  
Keyword(s):  
Correlation Function ◽  
Light Curve ◽  
Cross Correlation ◽  
Near Infrared ◽  
Light Curves ◽  
High Mode ◽  
Cross Correlation Function ◽  
X Ray ◽  
The Cross ◽  
Mode Transitions

We report on a simultaneous near-infrared, optical, and X-ray campaign performed in 2017 with the XMM-Newton and Swift satellites and the HAWK-I instrument mounted on the Very Large Telescope (VLT) on the transitional millisecond pulsar PSR J1023+0038. Near-infrared observations were performed in fast-photometric mode (0.5 s exposure time) in order to detect any fast variation of the flux and correlate this with the optical and X-ray light curves. The optical light curve shows the typical sinusoidal modulation at the system orbital period (4.75 h). No significant flaring or flickering is found in the optical, nor any signs of transitions between active and passive states. On the contrary, the near-infrared light curve displays a bimodal behaviour, showing strong flares in the first part of the curve, and an almost flat trend in the rest. The X-ray light curves instead show a few low-high mode transitions, but no flaring activity is detected. Interestingly, one of the low-high mode transitions occurs at the same time as the emission of an infrared flare. This can be interpreted in terms of the emission of an outflow or a jet: the infrared flare could be due to the evolving spectrum of the jet, which possesses a break frequency that moves from higher (near-infrared) to lower (radio) frequencies after the launching, which has to occur at the low-high mode transition. We also present the cross-correlation function between the optical and near-infrared curves. The near.infrared curve is bimodal, therefore we divided it into two parts (flaring and quiet). While the cross-correlation function of the quiet part is found to be flat, the function that refers to the flaring part shows a narrow peak at ∼10 s, which indicates a delay of the near-infrared emission with respect to the optical. This lag can be interpreted as reprocessing of the optical emission at the light cylinder radius with a stream of matter spiraling around the system due to a phase of radio ejection. This strongly supports a different origin of the infrared flares that are observed for PSR J1023+0038 with respect to the optical and X-ray flaring activity that has been reported in other works on the same source.

scholarly journals Spectroscopic Orbit of the Eclipsing Binary BD +52°2009

1999 ◽  
Vol 170 ◽  
pp. 325-330
Author(s):  
B. Khalesseh
Keyword(s):  
Correlation Function ◽  
Light Curve ◽  
Radial Velocity ◽  
Physical Model ◽  
Cross Correlation ◽  
Cross Correlation Function ◽  
Physical Parameters ◽  
Mass Ratio ◽  
Velocity Measurements ◽  
Eclipsing Binary

AbstractNew radial velocity measurements of the Algol-type eclipsing binary BD +52 °2009, based on Reticon observations, are presented. The velocity measures are based on fitting theoretical profiles, generated by a physical model of the binary, to the observed cross-correlation function (ccf). Such profiles match this function very well, much better in fact than Gaussian profiles, which are generally used. Measuring the ccf’s with Gaussian profiles yields the following results: mp sin3i = 2.55 ± 0.05m⊙, ms sin3i = 1.14 ± 0.03m⊙, (ap + as) sin i = 7.34 ± 0.05R⊙, and mp/ms = 2.23 ± 0.05. However, measuring the ccf’s with theoretical profiles yields a mass ratio of 2.33 and following results: mp sin3i = 2.84 ± 0.05m⊙, ms sin3i = 1.22 ± 0.03m⊙, (ap + as) sin i = 7.56 ± 0.05R⊙. The system has a semi-detached configuration. By combining the solution of a previously published light curve with the spectroscopic orbit, one can obtain the following physical parameters: mp = 2.99m⊙, ms3 = 1.28m⊙, < Tp >= 9600K, < Ts >= 5400K, < Rp >= 2.35R⊙, < Rs >= 2.12R⊙. The system consists of an A0 primary and a G2 secondary.

scholarly journals Multi-wave Monitoring of the Gravitational Lensed Quasar Q0957+561

2011 ◽  
Vol 7 (S285) ◽  
pp. 406-407
Author(s):  
Vyacheslav N. Shalyapin ◽  
Luis J. Goicoechea ◽  
Rodrigo Gil-Merino
Keyword(s):  
Correlation Analysis ◽  
Cross Correlation ◽  
Light Curves ◽  
The Other ◽  
Continuum Emission ◽  
X Ray ◽  
Cross Correlation Analysis ◽  
First Time ◽  
The Continuum

AbstractWe present X-ray (Chandra), ultraviolet (Swift/UVOT; U band) and optical-infrared (Liverpool Telescope; griz bands) continuum light curves of Q0957+561 observed in the first half of 2010. A cross-correlation analysis of the light curves shows that the U-band fluctuation leads the other variations at higher and lower energies. The study constrains the geometry of the continuum emission regions in a distant radio-loud AGN for the first time. We note that our work opens a new window in echo-mapping of high-z AGNs with the use of lensed quasars, since the variability of some of the images of a given multiply-imaged quasar can be predicted in advance, provided there is a modest optical follow-up of the system.

scholarly journals Periodicities in the K2 light curve of HP Librae

2020 ◽  
Vol 500 (1) ◽  
pp. 1222-1230
Author(s):  
Siddhant Solanki ◽  
Thomas Kupfer ◽  
Omer Blaes ◽  
Elmé Breedt ◽  
Simone Scaringi
Keyword(s):  
Light Curve ◽  
Power Spectra ◽  
Periodic Oscillation ◽  
Light Curves ◽  
Precession Frequency ◽  
Frequency Range ◽  
Quasi Periodic Oscillation ◽  
Rates Of Change ◽  
Orbital Frequency ◽  
The Continuum

ABSTRACT We analyse Kepler/K2 light-curve data of the AM CVn system HP Librae (HP Lib). We detect with confidence four photometric periodicities in the system: the orbital frequency, both positive and negative superhumps, and the positive apsidal precession frequency of the accretion disc. This is only the second time that the apsidal precession frequency has ever been directly detected in the photometry of a helium accreting system, after SDSS J135154.46-064309.0. We present phase-folded light curves and sliding power spectra of each of the four periodicities. We measure rates of change of the positive superhump period of ∼10−7 d. We also redetect a quasi-periodic oscillation (QPO) at ∼300 cyc d–1, a feature that has been stable over decades, and show that it is harmonically related to two other QPOs, the lowest of which is centred on the superhump/orbital frequency. The continuum power spectrum is consistent with a single power law with no evidence of any breaks within our observed frequency range.

About The Correlation between the Period and Dispersion of the Light Curve of Mira Type Variables

1979 ◽  
Vol 46 ◽  
pp. 214
Author(s):  
Jamie R. Garcia
Keyword(s):  
Light Curve ◽  
Linear Function ◽  
Systematic Errors ◽  
Light Curves ◽  
Reasonable Accuracy ◽  
Visual Data ◽  
Long Period ◽  
Visual Observations

AbstractDuring the last years we have been involved in research on the periods of Long Period Mira type variables. We obtained periods using photoelectric and visual observations.In order to see that these results have a reasonable accuracy we have made an analysis comparing the photoelectric and visual observations.As a result of this analysis we found a relation between the dispersion of the light curves obtained from visual data and the periods: θv= f(P), where f is a linear function due to the systematic errors of observations.

scholarly journals Time Lag in Sgr A* Intra-Day Variability between the light curves at 90 and 102 GHz

2012 ◽  
Vol 8 (S290) ◽  
pp. 277-278
Author(s):  
Atsushi Miyazaki ◽  
Masato Tsuboi ◽  
Takahiro Tsutsumi
Keyword(s):  
Correlation Function ◽  
Light Curve ◽  
Statistical Significance ◽  
Time Lag ◽  
Light Curves ◽  
Plasma Model ◽  
Sgr A ◽  
The One ◽  
Lower Frequencies

AbstractWe performed the observation of the flux densities of Sgr A* at 90 and 102 GHz on 6 April 2005 using the Nobeyama Millimeter Array in order to detect the time lag between these frequencies. We constructed light curves covering a few hour with 1 min bin, and the Intra-Day Variability, which had a rising phase and intensity peak, of Sgr A* is clearly seen at both frequencies. We calculated the z-transformed discrete correlation function between the light curves of Sgr A* at 90 and 102 GHz. The derived time lag of the flares at these frequencies was approximately zero, contrary to our expectations based on the previously reported time lag at lower frequencies. If the radio flares of Sgr A* are explained by the expanding plasma model, the light curve at 90 GHz would be delayed with respect to the one at 102 GHz. However, we could not find such a delay with statistical significance in our data.

scholarly journals An Eight-Month Monitoring Campaign on a Sample of AGN

1994 ◽  
Vol 159 ◽  
pp. 415-415
Author(s):  
Cláudia Winge ◽  
Bradley M. Peterson ◽  
M.G. Pastoriza ◽  
T. Storchi-Bergmann ◽  
J. Baldwin
Keyword(s):  
Cross Correlation ◽  
Stellar Population ◽  
Light Curves ◽  
Strong Line ◽  
Stellar Content ◽  
Line Flux ◽  
Monitoring Campaign ◽  
Standard Procedures ◽  
Show Evidence ◽  
The Continuum

We present the preliminary results of an 8-month monitoring campaign carried out on 6 AGN during the period December 1991 – July 1992. All but one of our targets showed continuum and/or line variability. The data were obtained using the 2D-Prutti + Cassegrain spectrograph at the CTIO 1.0-m telescope, and reduced following standard procedures. The slit width was 5″ and the nuclear spectra were extracted in a 10″ aperture. The wavelength coverage is 3500–7200Å, with 8Å resolution. The data were flux calibrated using standard stars and then normalized using the [O III] λ5007Å line flux for each object. NGC 6814: our spectra reveal that this object is still in a low state of activity and within the S/N ratio of our data, no variability was observed during this campaign. The stellar population is dominant in the nuclear spectrum and a synthesis using the star cluster library of Bica (1988) indicates a mainly old (∼ 86% of the continuum flux at 5870Å due to a population with age ≥ 10 Gyr), [Z/Z⊙] ≥ 0.3 stellar content, with an intrinsic reddening of E(B–V)=0.20. NGC 3227: using an off-nuclear spectrum corresponding to the two 5″×10″ regions 20.4″ E/W of the nucleus, we obtained also a mainly old (77% at 5870Å with age ≥ 10 Gyr), [Z/Z⊙]=0.3) synthetic stellar population, which contributes ∼ 43% of the nuclear light at 5600Å. The cross correlation of the 4245Å continuum and Hβ light curves results in a 18±3 -day lag. IC 4329A: our data show evidence of variability as a slow and constant increase in both continuum and lines fluxes, but no isolated event was detected. ESO141-G55: the light curves show small variations in the continuum, but no noticeable line variability. Akn 120 and Fairall 9: the data consists of two sets of spectra, separated by ∼ 6 months. Within each set little or no variability was detected, but strong line and continuum variations occurred between them.

scholarly journals Redshift-Space Distortions and f(z) from Group-Galaxy Correlations

2014 ◽  
Vol 11 (S308) ◽  
pp. 342-343
Author(s):  
F. G. Mohammad ◽  
S. de la Torre ◽  
L. Guzzo ◽  
D. Bianchi ◽  
J. A. Peacock
Keyword(s):  
Growth Rate ◽  
Correlation Function ◽  
Cross Correlation ◽  
Systematic Errors ◽  
Cross Correlation Function ◽  
Multipole Moments ◽  
Simulation Results ◽  
Group Galaxy

AbstractWe investigate the accuracy achievable on measurements of the the growth rate of structure f(z) using redshift-space distortions (RSD), when (a) these are measured on the group-galaxy cross correlation function; (b) the latter is expanded over a modified version of the conventional spherical armonics, “truncated multipole moments”. Simulation results give first indications that this combination can push systematic errors on f(z) below 3%, using scales r ⩾ 10h−1 Mpc.

scholarly journals The PLATO Solar-like Light-curve Simulator

2019 ◽  
Vol 624 ◽  
pp. A117 ◽  
Author(s):  
R. Samadi ◽  
A. Deru ◽  
D. Reese ◽  
V. Marchiori ◽  
E. Grolleau ◽  
...  
Keyword(s):  
Light Curve ◽  
Random Noise ◽  
Systematic Errors ◽  
Space Mission ◽  
Magnetic Activity ◽  
Light Curves ◽  
Point Spread Functions ◽  
Earth Like Planets ◽  
Indispensable Tool ◽  
Stellar Seismology

Context. ESA’s PLATO space mission, to be launched by the end of 2026, aims to detect and characterise Earth-like planets in their habitable zone using asteroseismology and the analysis of the transit events. The preparation of science objectives will require the implementation of hare-and-hound exercises relying on the massive generation of representative simulated light-curves. Aims. We developed a light-curve simulator named the PLATO Solar-like Light-curve Simulator (PSLS) in order to generate light-curves representative of typical PLATO targets, that is showing simultaneously solar-like oscillations, stellar granulation, and magnetic activity. At the same time, PSLS also aims at mimicking in a realistic way the random noise and the systematic errors representative of the PLATO multi-telescope concept. Methods. To quantify the instrumental systematic errors, we performed a series of simulations at pixel level that include various relevant sources of perturbations expected for PLATO. From the simulated pixels, we extract the photometry as planned on-board and also simulate the quasi-regular updates of the aperture masks during the observations. The simulated light-curves are then corrected for instrumental effects using the instrument point spread functions reconstructed on the basis of a microscanning technique that will be operated during the in-flight calibration phases of the mission. These corrected and simulated light-curves are then fitted by a parametric model, which we incorporated in PSLS. Simulation of the oscillations and granulation signals rely on current state-of-the-art stellar seismology. Results. We show that the instrumental systematic errors dominate the signal only at frequencies below ∼20 μHz. The systematic errors level is found to mainly depend on stellar magnitude and on the detector charge transfer inefficiency. To illustrate how realistic our simulator is, we compared its predictions with observations made by Kepler on three typical targets and found a good qualitative agreement with the observations. Conclusions. PSLS reproduces the main properties of expected PLATO light-curves. Its speed of execution and its inclusion of relevant stellar signals as well as sources of noises representative of the PLATO cameras make it an indispensable tool for the scientific preparation of the PLATO mission.

scholarly journals Dust Reverberation Mapping of Z229−15

2020 ◽  
Author(s):  
Amit Kumar Mandal ◽  
Suvendu Rakshit ◽  
C S Stalin ◽  
Dominika Wylezalek ◽  
Markus Kissler Patig ◽  
...  
Keyword(s):  
Time Delays ◽  
Cross Correlation ◽  
Rest Frame ◽  
Function Analysis ◽  
Large Error ◽  
Light Curves ◽  
Infrared Light ◽  
Reverberation Mapping ◽  
Photometric Observations ◽  
Error Bars

Abstract We report results of the dust reverberation mapping (DRM) on the Seyfert 1 galaxy Z229−15 at z = 0.0273. Quasi-simultaneous photometric observations for a total of 48 epochs were acquired during the period 2017 July to 2018 December in B, V, J, H and Ks bands. The calculated spectral index (α) between B and V bands for each epoch was used to correct for the accretion disk (AD) component present in the infrared light curves. The observed α ranges between −0.99 and 1.03. Using cross-correlation function analysis we found significant time delays between the optical V and the AD corrected J, H and Ks light curves. The lags in the rest frame of the source are $12.52^{+10.00}_{-9.55}$ days (between V and J), $15.63^{+5.05}_{-5.11}$ days (between V and H) and $20.36^{+5.82}_{-5.68}$ days (between V and Ks). Given the large error bars, these lags are consistent with each other. However, considering the lag between V and Ks bands to represent the inner edge of the dust torus, the torus in Z229−15 lies at a distance of 0.017 pc from the central ionizing continuum. This is smaller than that expected from the radius luminosity (R−L) relationship known from DRM. Using a constant α = 0.1 to account for the AD component, as is normally done in DRM, the deduced radius ( 0.025 pc) lies close to the expected R−L relation. However, usage of constant α in DRM is disfavoured as the α of the ionizing continuum changes with the flux of the source.

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