scholarly journals X-ray dips and a complex UV/X-ray cross-correlation function in the black hole candidate MAXI J1820+070

2019 ◽  
Vol 488 (1) ◽  
pp. L18-L23 ◽  
Author(s):  
J J E Kajava ◽  
S E Motta ◽  
A Sanna ◽  
A Veledina ◽  
M Del Santo ◽  
...  
Keyword(s):  
Black Hole ◽  
Correlation Function ◽  
Cross Correlation ◽  
Timing Analysis ◽  
Cross Correlation Function ◽  
X Rays ◽  
X Ray ◽  
Black Hole Candidate ◽  
Uv Emission ◽  
Partial Covering

ABSTRACT MAXI J1820+070, a black hole candidate first detected in early 2018 March, was observed by XMM–Newton during the outburst rise. In this letter we report on the spectral and timing analysis of the XMM–Newton X-ray and UV data, as well as contemporaneous X-ray data from the Swift satellite. The X-ray spectrum is well described by a hard thermal Comptonization continuum. The XMM–Newton X-ray light curve shows a pronounced dipping interval, and spectral analysis indicates that it is caused by a moderately ionized partial covering absorber. The XMM–Newton/OM U-filter data do not reveal any signs of the 17 h orbital modulation that was seen later on during the outburst decay. The UV/X-ray cross-correlation function shows a complex shape, with a peak at positive lags of about 4 s and a precognition dip at negative lags, which is absent during the X-ray dipping episode. Such shape could arise if the UV emission comes partially from synchrotron self-Compton emission near the black hole, as well as from reprocessing of the X-rays in the colder accretion disc further out.

scholarly journals Fast infrared variability from the black hole candidate MAXI J1535−571 and tight constraints on the modelling

2021 ◽  
Vol 503 (1) ◽  
pp. 614-624
Author(s):  
F M Vincentelli ◽  
P Casella ◽  
D M Russell ◽  
M C Baglio ◽  
A Veledina ◽  
...  
Keyword(s):  
Black Hole ◽  
Cross Correlation ◽  
Light Curves ◽  
X Rays ◽  
X Ray ◽  
Black Hole Candidate ◽  
Near Ir ◽  
The Cross ◽  
Short Time ◽  
Ir Light

ABSTRACT We present the results regarding the analysis of the fast X-ray/infrared (IR) variability of the black hole transient MAXI J1535−571. The data studied in this work consist of two strictly simultaneous observations performed with XMM–Newton (X-rays: 0.7–10 keV), VLT/HAWK-I (Ks band, 2.2 μm) and VLT/VISIR (M and PAH2_2 bands, 4.85 and 11.88 μm, respectively). The cross-correlation function between the X-ray and near-IR light curves shows a strong asymmetric anticorrelation dip at positive lags. We detect a near-IR QPO (2.5σ) at 2.07 ± 0.09 Hz simultaneously with an X-ray QPO at approximately the same frequency (f0 = 2.25 ± 0.05). From the cross-spectral analysis, a lag consistent with zero was measured between the two oscillations. We also measure a significant correlation between the average near-IR and mid-IR fluxes during the second night, but find no correlation on short time-scales. We discuss these results in terms of the two main scenarios for fast IR variability (hot inflow and jet powered by internal shocks). In both cases, our preliminary modelling suggests the presence of a misalignment between the disc and jet.

scholarly journals The soft X-ray cluster-AGN spatial cross-correlation function in theROSAT-NEP survey

2007 ◽  
Vol 465 (1) ◽  
pp. 35-40 ◽  
Author(s):  
N. Cappelluti ◽  
H. Böhringer ◽  
P. Schuecker ◽  
E. Pierpaoli ◽  
C. R. Mullis ◽  
...  
Keyword(s):  
Correlation Function ◽  
Cross Correlation ◽  
Cross Correlation Function ◽  
X Ray

scholarly journals X-ray Observations of Blazars with Ginga and ASCA

1994 ◽  
Vol 159 ◽  
pp. 383-383 ◽  
Author(s):  
M. Tashiro ◽  
K. Makishima ◽  
Y. Kohmura ◽  
T. Ohashi ◽  
C. Otani ◽  
...  
Keyword(s):  
Correlation Function ◽  
Cross Correlation ◽  
Cross Correlation Function ◽  
Function Technique ◽  
X Ray ◽  
Data Points ◽  
Bl Lacs ◽  
Clockwise Hysteresis

Among 13 BL Lacs observed with Ginga, 1H 0323+022, Mkn 421 and PKS 2155-304 exhibited significant variablity during each (typically one day) observation. On the flux-hardness plane, the data points obtained from each source draw a sort of clockwise hysteresis motion. It means that the spectrum hardens before the source gets brighter, while the spectrum softens before the source becomes fainter. Such a soft-lag behavior, first pointed out for PKS2155-304 by Sembay et al. These properties were also confirmed with the discrete cross correlation function technique.

scholarly journals Accretion-outflow connection in the outliers of the “universal” radio/X-ray correlation

2010 ◽  
Vol 6 (S275) ◽  
pp. 255-259
Author(s):  
M. Coriat ◽  
S. Corbel ◽  
L. Prat ◽  
J. C. A. Miller-Jones ◽  
D. Cseh ◽  
...  
Keyword(s):  
Black Hole ◽  
Compact Objects ◽  
X Rays ◽  
X Ray ◽  
Black Hole Candidate ◽  
Long Term Study ◽  
Hard State ◽  
Universal Correlation ◽  
X Ray Binaries

AbstractIn recent years, numerous efforts have been devoted to unravel the connection between accretion flow and jets in accreting compact objects. Here we report new constraints on these issues, through the long term study of the radio and X-ray behaviour of the black hole candidate H 1743–322. This source is known to be one of the “outliers” of the universal radio/X-ray correlation, i.e. a group of stellar mass accreting black holes displaying fainter radio emission for a given X-ray luminosity, than expected from the correlation. In this work we find, at high X-ray luminosity in the hard state, a tight radio/X-ray correlation with an unusual steep slope of b = 1.38 ± 0.03. This correlation then breaks below ~5 × 10−3LEdd (M/10M⊙)−1 in X-rays and becomes shallower. When compared with radio/X-ray data from other black hole X-ray binaries, we see that the deviant points of H 1743–322 join the universal correlation and seem to follow it at low luminosity. Based on these results, we investigate several hypotheses that could explain both the b ~ 1.4 slope and the transition toward the universal correlation.

scholarly journals SWIFT J1753.5-0127: A Surprising Optical/X-Ray Cross-Correlation Function

2008 ◽  
Vol 682 (1) ◽  
pp. L45-L48 ◽  
Author(s):  
Martin Durant ◽  
Poshak Gandhi ◽  
Tariq Shahbaz ◽  
Andy P. Fabian ◽  
Jon Miller ◽  
...  
Keyword(s):  
Correlation Function ◽  
Cross Correlation ◽  
Cross Correlation Function ◽  
X Ray

scholarly journals A NICER look at the state transitions of the black hole candidate MAXI J1535−571 during its reflares

2020 ◽  
Vol 496 (2) ◽  
pp. 1001-1012 ◽  
Author(s):  
V A Cúneo ◽  
K Alabarta ◽  
L Zhang ◽  
D Altamirano ◽  
M Méndez ◽  
...  
Keyword(s):  
Black Hole ◽  
Neutron Star ◽  
Timing Analysis ◽  
The State ◽  
State Transitions ◽  
X Ray ◽  
Black Hole Binaries ◽  
Black Hole Candidate ◽  
Hard State ◽  
Higher Sensitivity

ABSTRACT The black hole candidate and X-ray binary MAXI J1535−571 was discovered in 2017 September. During the decay of its discovery outburst, and before returning to quiescence, the source underwent at least four reflaring events, with peak luminosities of ∼1035–36 erg s−1 (d/4.1 kpc)2. To investigate the nature of these flares, we analysed a sample of NICER (Neutron star Interior Composition Explorer) observations taken with almost daily cadence. In this work, we present the detailed spectral and timing analysis of the evolution of the four reflares. The higher sensitivity of NICER at lower energies, in comparison with other X-ray detectors, allowed us to constrain the disc component of the spectrum at ∼0.5 keV. We found that during each reflare the source appears to trace out a q-shaped track in the hardness–intensity diagram similar to those observed in black hole binaries during full outbursts. MAXI J1535−571 transits between the hard state (valleys) and softer states (peaks) during these flares. Moreover, the Comptonized component is undetected at the peak of the first reflare, while the disc component is undetected during the valleys. Assuming the most likely distance of 4.1 kpc, we find that the hard-to-soft transitions take place at the lowest luminosities ever observed in a black hole transient, while the soft-to-hard transitions occur at some of the lowest luminosities ever reported for such systems.

scholarly journals X-ray cross-correlation analysis of the low-mass X-ray binary 4U 1636-53

2014 ◽  
Vol 10 (S306) ◽  
pp. 397-399
Author(s):  
Ya-Juan Lei
Keyword(s):  
Correlation Function ◽  
Correlation Analysis ◽  
Cross Correlation ◽  
X Rays ◽  
X Ray ◽  
Cross Correlation Analysis ◽  
Low Mass ◽  
Cross Correlations ◽  
The Cross ◽  
Positive Correlations

AbstractWe analyze the cross-correlation function of the soft and hard X-rays of the atoll source 4U 1636-53 with RXTE data. The results show that the cross-correlations evolve along the different branches of the color-color diagram. At the lower left banana states, we have both positive and ambiguous correlations, and positive correlations are dominant for the lower banana and the upper banana states. The anti-correlation is detected at the top of the upper banana states. The cross-correlations of two atoll sources 4U 1735-44 and 4U 1608-52 have been studied in previous work, and the anti-correlations are detected at the lower left banana or the top of the upper banana states. Our results show that, in the 4U 1636-53, the distribution of the cross-correlations in the color-color diagram is similar to those of 4U 1735-44 and 4U 1608-52, and confirm further that the distribution of cross-correlations in color-color diagram could be correlated with the luminosity of the source.

scholarly journals Swift UVOT observations of the 2015 outburst of V404 Cygni

2019 ◽  
Vol 488 (4) ◽  
pp. 4843-4857 ◽  
Author(s):  
S R Oates ◽  
S Motta ◽  
A P Beardmore ◽  
D M Russell ◽  
P Gandhi ◽  
...  
Keyword(s):  
Black Hole ◽  
Time Lag ◽  
Neutral Hydrogen ◽  
Ultra Violet ◽  
Temporal Variations ◽  
X Rays ◽  
Optical Telescope ◽  
X Ray ◽  
Uv Emission ◽  
Optical Time

ABSTRACT The black hole binary, V404 Cygni, went into outburst in 2015 June, after 26 years of X-ray quiescence. We observed the outburst with the Neil Gehrels Swift observatory. We present optical/UV observations taken with the Swift Ultra-violet Optical Telescope, and compare them with the X-ray observations obtained with the Swift X-ray Telescope. We find that dust extinction affecting the optical/UV does not correlate with absorption due to neutral hydrogen that affects the X-ray emission. We suggest there is a small inhomogeneous high-density absorber containing a negligible amount of dust, close to the black hole. Overall, temporal variations in the optical/UV appear to trace those in the X-rays. During some epochs we observe an optical time-lag of (15–35) s. For both the optical/UV and X-rays, the amplitude of the variations correlates with flux, but this correlation is less significant in the optical/UV. The variability in the light curves may be produced by a complex combination of processes. Some of the X-ray variability may be due to the presence of a local, inhomogeneous and dust-free absorber, while variability visible in both the X-ray and optical/UV may instead be driven by the accretion flow: the X-rays are produced in the inner accretion disc, some of which are reprocessed to the optical/UV; and/or the X-ray and optical/UV emission is produced within the jet.

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