scholarly journals Spikey: self-lensing flares from eccentric SMBH binaries

2020 ◽  
Vol 495 (4) ◽  
pp. 4061-4070 ◽  
Author(s):  
Betty X Hu ◽  
Daniel J D’Orazio ◽  
Zoltán Haiman ◽  
Krista Lynne Smith ◽  
Bradford Snios ◽  
...  
Keyword(s):  
Rest Frame ◽  
Relativistic Effects ◽  
Light Curves ◽  
Optical Data ◽  
Spectral Slope ◽  
X Ray ◽  
Periodic Behaviour ◽  
Black Hole Binary ◽  
High Cadence ◽  
Rule Out

ABSTRACT We examine the light curves of two quasars, motivated by recent suggestions that a supermassive black hole binary (SMBHB) can exhibit sharp lensing spikes. We model the variability of each light curve as due to a combination of two relativistic effects: the orbital relativistic Doppler boost and gravitational binary self-lensing. In order to model each system, we extend previous Doppler plus self-lensing models to include eccentricity. The first quasar is identified in optical data as a binary candidate with a 20-yr period (Ark 120), and shows a prominent spike. For this source, we rule out the lensing hypothesis and disfavour the Doppler-boost hypothesis due to discrepancies in the measured versus recovered values of the binary mass and optical spectral slope. The second source, which we nickname Spikey, is the rare case of an active galactic nucleus identified in Kepler’s high-quality, high-cadence photometric data. For this source, we find a model, consisting of a combination of Doppler modulation and a narrow symmetric lensing spike, consistent with an eccentric SMBHB with a mass of $M_{\text{tot}} = 3\times 10^{7} {\, \mathrm{M}_{\odot }}$, rest-frame orbital period T = 418 d, eccentricity e = 0.5, and seen at an inclination of 8○ from edge-on. This interpretation can be tested by monitoring Spikey for periodic behaviour and recurring flares in the next few years. In preparation for such monitoring, we present the first X-ray observations of this object taken by the Neil Gehrels Swift Observatory.

scholarly journals Optical Photometry of LMXBs: UW CrB (=MS 1603+260) and V1408 Aql (=4U 1957+115)

2015 ◽  
Vol 2 (1) ◽  
pp. 50-54
Author(s):  
P. A. Mason ◽  
E. L. Robinson ◽  
S. Gomez ◽  
J. V. Segura
Keyword(s):  
Black Hole ◽  
Orbital Period ◽  
Light Curves ◽  
Optical Data ◽  
Published Data ◽  
Type I ◽  
Optical Photometry ◽  
Mean Intensity ◽  
X Ray ◽  
Low Mass

We present new optical observations of V1408 Aql (= 4U 1957+115), the only low mass X-ray binary, black hole candidate known to be in a persistently soft state. We combine new broadband optical photometry with previously published data and derive a precise orbital ephemeris. The optical light curves display sinusoidal variations modulated on the orbital period as well as large night to night changes in mean intensity. The amplitude of the variations increases with mean intensity while maintaining sinusoidal shape. Considering the set of constraints placed by the X-ray and optical data we argue that V1408 Aql may harbor a very low mass black hole. Optical light curves of UW CrB display partial eclipses of the accretion disk by the donor star that vary both in depth and orbital phase. The new eclipses of UW CrB in conjunction with published eclipse timings are well fitted with a linear ephemeris. We derive an upper limit to the rate of change of the orbital period. By including the newly observed type I bursts with published bursts in our analysis, we find that optical bursts are not observed between orbital phases 0.93 and 0.07, i.e. they are not observable during partial eclipses of the disk.

scholarly journals The Magnetic Corona: Magnetic Reconnection in Solar Flares

2004 ◽  
Vol 219 ◽  
pp. 91-102
Author(s):  
Harry P. Warren
Keyword(s):  
Spatial Resolution ◽  
Solar Flares ◽  
Light Curves ◽  
Small Scale ◽  
Flare Loop ◽  
X Ray ◽  
Stellar Flares ◽  
Emission Models ◽  
Reconnection Model ◽  
High Cadence

The ability of the Transition Region and Coronal Explorer (TRACE) to image the Sun at high spatial resolution and high cadence over a very broad range of temperatures makes it a unique instrument for observing solar flare plasma. TRACE observations have confirmed the reconnection model for solar flares, at least qualitatively. TRACE flare observations show impulsive footpoint brightenings that are followed by the formation of high-temperature loops in the corona. These loops then cool to lower temperatures, forming post-flare loop arcades. Comparisons between TRACE and lower spatial resolution Yohkoh Soft X-Ray Telescope (SXT) observations have revealed that solar flares are composed of a multitude of fine coronal loops. Detailed hydrodynamic modeling of flare light curves shows that this fine scale structuring is crucial to understanding the evolution of the observed emission. Models based on single, isothermal loops are not consistent with the TRACE observations. Models based on the sequential heating of small-scale loops, in contrast, are able to reproduce many of the salient features of the observed light curves. We will discuss the implication of these results for more energetic stellar flares as well as smaller-scale events that may be responsible for the heating of solar active region loops.

scholarly journals A detailed X-ray investigation of ζ Puppis

2018 ◽  
Vol 609 ◽  
pp. A81 ◽  
Author(s):  
Yaël Nazé ◽  
Tahina Ramiaramanantsoa ◽  
Ian R. Stevens ◽  
Ian D. Howarth ◽  
Anthony F. J. Moffat
Keyword(s):  
Large Scale ◽  
Light Curves ◽  
Optical Data ◽  
X Rays ◽  
X Ray ◽  
Large Scale Structures ◽  
Line Shapes ◽  
Cyclic Behaviour ◽  
Flux Change ◽  
Before And After

Context. One of the optically brightest and closest massive stars, ζ Pup, is also a bright X-ray source. Previously, its X-ray emission was found to be variable with light curves harbouring “trends” with a typical timescale longer than the exposure length, i.e. >1 d. The origin of these changes was proposed to be linked to large-scale structures in the wind of ζ Pup, but further characterization of the variability at high energies was needed to investigate this scenario. Aims. Since the previous papers of this series, a number of new X-ray observations have become available. Furthermore, a cyclic behaviour with a 1.78 d period was identified in long optical photometric runs, which is thought to be associated with the launching mechanism of large-scale wind structures. Methods. We analysed these new X-ray data, revisited the old data, and compared the X-ray light curves with the optical data, notably those taken simultaneously. Results. The behaviour of ζ Pup in X-rays cannot be explained in terms of a perfect clock because the amplitude and shape of its variations change with time. For example, ζ Pup was much more strongly variable between 2007 and 2011 than before and after this interval. Comparing the X-ray spectra of the star at maximum and minimum brightness yields no compelling difference beyond the overall flux change: the temperatures, absorptions, and line shapes seem to remain constant, well within errors. The only common feature between X-ray datasets is that the variation amplitudes appear maximum in the medium (0.6–1.2 keV) energy band. Finally, no clear and coherent correlation can be found between simultaneous X-ray and optical data. Only a subgroup of observations may be combined coherently with the optical period of 1.78 d, although the simultaneous optical behaviour is unknown. Conclusions. The currently available data do not reveal any obvious, permanent, and direct correlation between X-ray and optical variations. The origin of the X-ray variability therefore still needs to be ascertained, highlighting the need for long-term monitoring in multiwavelengths, i.e. X-ray, UV, and optical.

scholarly journals Optical and X-ray rest-frame light curves of the BAT6 sample

2014 ◽  
Vol 565 ◽  
pp. A72 ◽  
Author(s):  
A. Melandri ◽  
S. Covino ◽  
D. Rogantini ◽  
R. Salvaterra ◽  
B. Sbarufatti ◽  
...  
Keyword(s):  
Rest Frame ◽  
Light Curves ◽  
X Ray

scholarly journals Rapid spectral transition of the black hole binary V404 Cygni

2020 ◽  
Vol 634 ◽  
pp. A94
Author(s):  
J. J. E. Kajava ◽  
C. Sánchez-Fernández ◽  
J. Alfonso-Garzón ◽  
S. E. Motta ◽  
A. Veledina
Keyword(s):  
Black Hole ◽  
Optical Data ◽  
X Ray ◽  
Rapid Changes ◽  
Photon Index ◽  
Order Of Magnitude ◽  
Best Fitting ◽  
Black Hole Binary ◽  
Flux Increase ◽  
Magnitude Increase

During the June 2015 outburst of the black hole binary V404 Cyg, rapid changes in the X-ray brightness and spectra were common. The INTEGRAL monitoring campaign detected spectacular Eddington-limited X-ray flares, but also rapid variations at much lower flux levels. On 2015 June 21 at 20 h 50 min, the 3–10 keV JEM-X data as well as simultaneous optical data started to display a gradual brightening from one of these low-flux states. This was followed 15 min later by an order-of-magnitude increase of flux in the 20–40 keV IBIS/ISGRI light curve in just 15 s. The best-fitting model for both the pre- and post-transition spectra required a Compton-thick partially covering absorber. The absorber parameters remained constant, but the spectral slope varied significantly during the event, with the photon index decreasing from Γ ≈ 3.7 to Γ ≈ 2.3. We propose that the rapid 20–40 keV flux increase was either caused by a spectral state transition that was hidden from our direct view, or that there was a sudden reduction in the amount of Compton down-scattering of the primary X-ray emission in the disk outflow.

scholarly journals The black hole X-ray transient Swift J1357.2–0933 as seen with Swift and NuSTAR during its 2017 outburst

2019 ◽  
Vol 485 (3) ◽  
pp. 3064-3075 ◽  
Author(s):  
Aru Beri ◽  
B E Tetarenko ◽  
A Bahramian ◽  
Diego Altamirano ◽  
Poshak Gandhi ◽  
...  
Keyword(s):  
Black Hole ◽  
Coming Out ◽  
Broad Band ◽  
Light Curves ◽  
Optical Data ◽  
Optical Telescope ◽  
X Ray ◽  
Optical Light Curve ◽  
Band Spectra ◽  
Inner Region

ABSTRACT We report on observations of black hole Swift J1357.2–0933, a member of the modest population of very faint X-ray transients. This source has previously shown intense dips in the optical light curve, a phenomena that has been linked to the existence of a ‘unique toroidal structure’ in the inner region of the disc, seen at a high inclination. Our observations, carried out by the Neil Gehrels Swift and NuSTAR X-ray observatories, do not show the presence of intense dips in the optical light curves. We find that the X-ray light curves do not show any features that would straightforwardly support an edge-on configuration or high inclination configuration of the orbit. This is similar to what was seen in the X-ray observations of the source during its 2011 outburst. Moreover, the broad-band spectra were well described with an absorbed power-law model without any signatures of cut-off at energies above 10 keV, or any reflection from the disc or the putative torus. Thus, the X-ray data do not support the unique ‘obscuring torus’ scenario proposed for J1357. We also performed a multiwavelength study using the data of X-ray telescope and Ultraviolet/Optical Telescope aboard Swift, taken during the ∼4.5 months duration of the 2017 outburst. This is consistent with what was previously inferred for this source. We found a correlation between the simultaneous X-ray and ultraviolet/optical data and our study suggests that most of the reprocessed flux must be coming out in the ultraviolet.

scholarly journals X-ray properties of dust-obscured galaxies with broad optical/UV emission lines

2020 ◽  
Vol 499 (2) ◽  
pp. 1823-1840
Author(s):  
Fan Zou (邹凡) ◽  
William N Brandt ◽  
Fabio Vito ◽  
Chien-Ting Chen (陳建廷) ◽  
Gordon P Garmire ◽  
...  
Keyword(s):  
Rest Frame ◽  
Emission Lines ◽  
Host Galaxy ◽  
Broad Line ◽  
X Ray ◽  
Bolometric Luminosity ◽  
Uv Emission ◽  
Black Hole Growth ◽  
Hole Growth ◽  
Rule Out

ABSTRACT Dust-obscured galaxies (DOGs) with extreme infrared luminosities may represent a key phase in the co-evolution of galaxies and supermassive black holes. We select 12 DOGs at 0.3 ≲ z ≲ 1.0 with broad Mg ii or H β emission lines and investigate their X-ray properties utilizing snapshot observations (∼3 ks per source) with Chandra. By assuming that the broad lines are broadened due to virial motions of broad-line regions, we find that our sources generally have high Eddington ratios (λEdd). Our sources generally have moderate intrinsic X-ray luminosities (LX ≲ 1045 erg s−1), which are similar to those of other DOGs, but are more obscured. They also present moderate outflows and intense starbursts. Based on these findings, we conclude that high-λEdd DOGs are closer to the peaks of both host-galaxy and black hole growth compared to other DOGs, and that (active galactic nucleus) AGN feedback has not swept away their reservoirs of gas. However, we cannot fully rule out the possibility that the broad lines are broadened by outflows, at least for some sources. We investigate the relations among LX, AGN rest-frame 6 μm monochromatic luminosity, and AGN bolometric luminosity, and find the relations are consistent with the expected ones.

scholarly journals Exploratory X-Ray Monitoring of Luminous Radio-quiet Quasars at High Redshift: Extended Time-series Analyses and Stacked Imaging Spectroscopy

2021 ◽  
Vol 923 (1) ◽  
pp. 111
Author(s):  
Marcus O. Thomas ◽  
Ohad Shemmer ◽  
W. N. Brandt ◽  
Maurizio Paolillo ◽  
Shai Kaspi ◽  
...  
Keyword(s):  
Time Series ◽  
Rest Frame ◽  
High Redshift ◽  
Imaging Spectroscopy ◽  
Optical Monitoring ◽  
Spectral Slope ◽  
Mean Power ◽  
X Ray ◽  
Time Series Analyses ◽  
The Mean

Abstract We present three new Chandra X-ray epochs along with new ground-based optical–UV observations as the third installment in a time-series analysis of four high-redshift (z ≈ 4.1–4.4) radio-quiet quasars. In total, we present nine epochs for these sources with rest-frame temporal baselines of ∼1300–2000 days. We utilize the X-ray data to determine basic variability properties, as well as produce mean spectra and stacked images based on effective exposure times of ∼40–70 ks per source. We perform time-series analyses in the soft and hard bands, separately, and compare variability properties to those of sources at lower redshifts and luminosities. The magnitude of X-ray variability of our sources remains consistent with or lower than that of similar sources at lower redshifts, in agreement with the variability–luminosity anticorrelation. The mean power-law photon indices in the stacked Chandra spectra of our sources are consistent with the values measured from their archival XMM-Newton spectra separated by about 3 yr in the rest frame. Along with the X-ray observations, we provide near-simultaneous optical monitoring of the sources in the optical–UV regime. The overall variability in the optical-to-X-ray spectral slope is consistent with sources at lower redshifts, and the optical–UV observations display mild variability on monthly timescales.

scholarly journals IGR J17329-2731: The birth of a symbiotic X-ray binary

2018 ◽  
Vol 613 ◽  
pp. A22 ◽  
Author(s):  
E. Bozzo ◽  
A. Bahramian ◽  
C. Ferrigno ◽  
A. Sanna ◽  
J. Strader ◽  
...  
Keyword(s):  
Neutron Star ◽  
Compact Object ◽  
Light Curves ◽  
Strong Absorption ◽  
Emission Lines ◽  
Optical Data ◽  
X Rays ◽  
X Ray ◽  
The Past ◽  
X Ray Binaries

We report on the results of the multiwavelength campaign carried out after the discovery of the INTEGRAL transient IGR J17329-2731. The optical data collected with the SOAR telescope allowed us to identify the donor star in this system as a late M giant at a distance of 2.7-1.2+3.4 kpc. The data collected quasi-simultaneously with XMM–Newton and NuSTAR showed the presence of a modulation with a period of 6680 ± 3 s in the X-ray light curves of the source. This unveils that the compact object hosted in this system is a slowly rotating neutron star. The broadband X-ray spectrum showed the presence of a strong absorption (≫1023 cm−2) and prominent emission lines at 6.4 keV, and 7.1 keV. These features are usually found in wind-fed systems, in which the emission lines result from the fluorescence of the X-rays from the accreting compact object on the surrounding stellar wind. The presence of a strong absorption line around ~21 keV in the spectrum suggests a cyclotron origin, thus allowing us to estimate the neutron star magnetic field as ~2.4 × 1012 G. All evidencethus suggests IGR J17329-2731 is a symbiotic X-ray binary. As no X-ray emission was ever observed from the location of IGR J17329-2731 by INTEGRAL (or other X-ray facilities) during the past 15 yr in orbit and considering that symbiotic X-ray binaries are known to be variable but persistent X-ray sources, we concluded that INTEGRAL caught the first detectable X-ray emission from IGR J17329-2731 when the source shined as a symbiotic X-ray binary. The Swift XRT monitoring performed up to ~3 months after the discovery of the source, showed that it maintained a relatively stable X-ray flux and spectral properties.

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.

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