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.

scholarly journals Possible ~1 hour quasi-periodic oscillation in narrow-line Seyfert 1 galaxy MCG–06–30–15

2018 ◽  
Vol 616 ◽  
pp. L6 ◽  
Author(s):  
Alok C. Gupta ◽  
Ashutosh Tripathi ◽  
Paul J. Wiita ◽  
Minfeng Gu ◽  
Cosimo Bambi ◽  
...  
Keyword(s):  
Light Curve ◽  
Energy Range ◽  
Periodic Oscillation ◽  
Light Curves ◽  
Narrow Line ◽  
Quasi Periodic Oscillation ◽  
X Ray ◽  
S Period

We found a possible ~1 h quasi-periodic oscillation (QPO) in a ~55 ks X-ray observation of the narrow-line Seyfert 1 galaxy MCG–06–30–15 made with the XMM-Newton EPIC/pn detector in the energy range 0.3–10 keV. We identify a total modulation of ~16% in the light curve and find a ≃3670 s quasi-period using Lomb-Scargle periodogram (LSP) and weighted wavelet Z-transform (WWZ) techniques. Our analyses of eight light curves of MCG–06–30–15, indicated the possible presence of an oscillation during one of them. The LSP indicates a statistically significant (≃3σ) QPO detection. A WWZ analysis shows that the signal at this possible roughly 3670 s period is present, and rather persistent, throughout the observation; however, a signal around 8735 s is more persistent. We briefly discuss models that can produce X-ray QPOs with such periods in narrow line Seyfert 1 galaxies, as both other claimed QPO detections in this class of AGN had very similar periods.

scholarly journals Complex variability of Kepler AGN revealed by recurrence analysis

2020 ◽  
Vol 497 (3) ◽  
pp. 3418-3439 ◽  
Author(s):  
R A Phillipson ◽  
P T Boyd ◽  
A P Smale ◽  
M S Vogeley
Keyword(s):  
Time Series ◽  
Light Curve ◽  
Time Scales ◽  
Power Spectra ◽  
Periodic Oscillation ◽  
Light Curves ◽  
Recurrence Analysis ◽  
Spectra Analysis ◽  
Modes Of Variability ◽  
Underlying Processes

ABSTRACT The advent of new time domain surveys and the imminent increase in astronomical data expose the shortcomings of traditional time series analysis (such as power spectra analysis) in characterizing the abundantly varied, complex, and stochastic light curves of Active Galactic Nuclei (AGNs). Recent applications of novel methods from non-linear dynamics have shown promise in characterizing higher modes of variability and time-scales in AGN. Recurrence analysis in particular can provide complementary information about characteristic time-scales revealed by other methods, as well as probe the nature of the underlying physics in these objects. Recurrence analysis was developed to study dynamical trajectories in phase space, which can be constructed from 1D time series such as light curves. We apply the methods of recurrence analysis to two optical light curves of Kepler-monitored AGN. We confirm the detection and period of an optical quasi-periodic oscillation in one AGN, and confirm multiple other time-scales recovered from other methods ranging from 5 to 60 d in both objects. We detect regions in the light curves that deviate from regularity, provide evidence of determinism and non-linearity in the mechanisms underlying one light curve (KIC 9650712), and determine realizations of a linear stochastic process describe the dominant variability in the other light curve (Zwicky 229–015). We discuss possible underlying processes driving the dynamics of the light curves and their diverse classes of variability.

scholarly journals A minimal timescale for the continuum in 4U 1608-52 and Aql X-1

2021 ◽  
Vol 502 (1) ◽  
pp. L72-L78
Author(s):  
K Mohamed ◽  
E Sonbas ◽  
K S Dhuga ◽  
E Göğüş ◽  
A Tuncer ◽  
...  
Keyword(s):  
Black Hole ◽  
Neutron Star ◽  
Power Spectra ◽  
Light Curves ◽  
State Transitions ◽  
Strong Positive Correlation ◽  
Present Evidence ◽  
X Ray ◽  
X Ray Binaries ◽  
The Continuum

ABSTRACT Similar to black hole X-ray binary transients, hysteresis-like state transitions are also seen in some neutron-star X-ray binaries. Using a method based on wavelets and light curves constructed from archival Rossi X-ray Timing Explorer observations, we extract a minimal timescale over the complete range of transitions for 4U 1608-52 during the 2002 and 2007 outbursts and the 1999 and 2000 outbursts for Aql X-1. We present evidence for a strong positive correlation between this minimal timescale and a similar timescale extracted from the corresponding power spectra of these sources.

scholarly journals Stochastic modeling of kHz quasi-periodic oscillation light curves

2006 ◽  
Vol 452 (2) ◽  
pp. 383-386 ◽  
Author(s):  
R. Vio ◽  
P. Rebusco ◽  
P. Andreani ◽  
H. Madsen ◽  
R. V. Overgaard
Keyword(s):  
Stochastic Modeling ◽  
Periodic Oscillation ◽  
Light Curves ◽  
Quasi Periodic Oscillation

scholarly journals Distribution of twin kHz QPOs in LMXBs

2012 ◽  
Vol 8 (S290) ◽  
pp. 327-328
Author(s):  
D. H. Wang ◽  
L. Chen
Keyword(s):  
Common Property ◽  
Periodic Oscillation ◽  
Quasi Periodic Oscillation ◽  
Mean Values ◽  
Orbital Frequency ◽  
Low Mass ◽  
The Common ◽  
The Mean ◽  
X Ray Binaries ◽  
Z Sources

AbstractWith kilohertz quasi-periodic oscillation (kHz QPO) sources in neutron star low mass X-ray binaries (NS-LMXBs) published up to now, we analyze the centroid frequency (ν) distribution of twin kHz QPOs. We find that Atoll and Z sources show the similar distributions of ν1 and ν2, which indicate that twin kHz QPOs may be the common property of NS-LXMBs and have the similar physical origins. The mean values of ν1 and ν2 in Atoll sources are higher than those in Z sources, and we consider that this may because the QPO signals are sheltered by the thicken accretion disk or corona in Z sources. The maximums of ν2 in both Atoll and Z sources are the same order as the Keplerian orbital frequency of the NS surface, so kHz QPOs could occur near the NS surface.

scholarly journals A possible γ-ray quasi-periodic oscillation of ∼314 days in the blazar OJ 287

2020 ◽  
Vol 499 (1) ◽  
pp. 653-658
Author(s):  
Pankaj Kushwaha ◽  
Arkadipta Sarkar ◽  
Alok C Gupta ◽  
Ashutosh Tripathi ◽  
Paul J Wiita
Keyword(s):  
Light Curve ◽  
Active Galactic Nuclei ◽  
Galactic Nuclei ◽  
Periodic Oscillation ◽  
Large Area ◽  
Quasi Periodic Oscillation ◽  
Bl Lacertae ◽  
Emission Models ◽  
Γ Ray ◽  
Blazar Oj 287

ABSTRACT We report the detection of a probable γ-ray quasi-periodic oscillation (QPO) of around 314 d in the monthly binned 0.1–300 GeV γ-ray Fermi-Large Area Telescope light curve of the well-known BL Lacertae blazar OJ 287. To identify and quantify the QPO nature of the γ-ray light curve of OJ 287, we used the Lomb–Scargle periodogram (LSP), REDFIT, and weighted wavelet Z-transform (WWZ) analyses. We briefly discuss possible emission models for radio-loud active galactic nuclei that can explain a γ-ray QPO of such a period in a blazar.

Detection of Sectoral Modes in the Eclipsing Binary KIC 4851217

2017 ◽  
Vol 14 (S339) ◽  
pp. 295-298
Author(s):  
M. Fedurco ◽  
Š. Parimucha ◽  
P. Gajdoš
Keyword(s):  
Light Curve ◽  
Frequency Analysis ◽  
Secondary Component ◽  
Frequency Range ◽  
Eclipsing Binary ◽  
Quadrupole Mode ◽  
Linear Coupling ◽  
Orbital Frequency ◽  
Short Period ◽  
Low Amplitude

AbstractKIC 4851217 is a short period eclipsing binary (P = 2.47 days) in the field of the Kepler K1 mission. As well as variability caused by the eclipses, low-amplitude pulsations are also present in the data. A frequency analysis of the residual light-curve revealed δ Sct pulsations in the frequency range from 15–21 d−1 with amplitudes up to 3.5 mmag. Strong linear coupling (fi = fp + kforb) to orbital frequency was found, indicating tidally locked modes. From an analysis of 5 selected groups of frequencies we identified a radial mode on the secondary component, 3 dipole modes (l = |m| = 1), one of them present on the secondary component, and a quadrupole mode (l = |m| = 2), also located on the secondary component.

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 Probing the X-ray Variability of X-ray Binaries

2003 ◽  
Vol 214 ◽  
pp. 236-239
Author(s):  
Wenfei Yu
Keyword(s):  
Neutron Star ◽  
Light Curve ◽  
Time Scale ◽  
Accretion Rate ◽  
Power Spectra ◽  
The Other ◽  
Periodic Oscillations ◽  
X Ray ◽  
Orbital Frequency ◽  
X Ray Binaries

Kilohertz quasi-periodic oscillations (kHz QPOs) has been regarded as representing the Keplerian frequency at the inner disk edge in the neutron star X-ray binaries. The so-called “parallel tracks” on the plot of the kHz QPO frequency vs. X-ray flux in neutron star X-ray binaries, on the other hand, show the correlation between the kHz QPO frequency and the X-ray flux on time scales from hours to days. This is suspected as caused by the variations of the mass accretion rate through the accretion disk surrounding the neutron star. We show here that by comparing the correlation between the kHz QPO frequency and the X-ray count rate on a certain QPO time scale observed approximately simultaneous in the Fourier power spectra of the X-ray light curve, we have found evidences that the X-ray flux of millihertz QPOs in neutron star X-ray binaries is generated inside the inner disk edge if adopting that the kilohertz QPO frequency is an orbital frequency at the inner disk edge.

ON THE HBO MECHANISM OF X-RAY NEUTRON STAR

2001 ◽  
Vol 10 (05) ◽  
pp. 625-632 ◽  
Author(s):  
C. M. ZHANG
Keyword(s):  
Neutron Star ◽  
Empirical Formula ◽  
Accretion Rate ◽  
Periodic Oscillation ◽  
Precession Frequency ◽  
Relativistic Motion ◽  
Quasi Periodic Oscillation ◽  
Motion Mechanism ◽  
X Ray ◽  
Proposed Model

We ascribe the 15–60 Hz Quasi Periodic Oscillation (QPO) to the periastron precession frequency of the orbiting accreted matter at the boundary of magnetosphere-disk of X-ray neutron star (NS). Considering the relativistic motion mechanism for the kHz QPO, that the radii of the inner disk and magnetosphere-disk of NS are correlated with each other by a factor is assumed. The obtained conclusions include: all QPO frequencies increase with increasing the accretion rate. The theoretical relations between 15–60 Hz QPO (HBO) frequency and the twin kHz QPOs are similar to the measured empirical formula. Further, the better fitted NS mass by the proposed model is about 1.9 solar masses for the detected LMXBs.

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