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 Soft X-ray Emission of Quasars

1994 ◽  
Vol 159 ◽  
pp. 373-373
Author(s):  
N. Schartel ◽  
R. Walter ◽  
H.H. Fink
Keyword(s):  
Power Law ◽  
High Redshift ◽  
Spectral Band ◽  
Black Body ◽  
Spectral Slope ◽  
X Ray ◽  
Body Model ◽  
Sky Survey ◽  
Photon Index ◽  
The Mean

From a list of known quasars compiled from various catalogues we selected all sources detected by the PSPC (0.1 – 2.4 keV) aboard ROSAT with more than 80 counts during the all sky survey. A sample of 102 sources resulted. At higher redshifts most of the selected sources are radio-loud. At a redshift smaller than 0.50 we found 54 radio-quiet quasars and 30 radio-loud sources. For this reduced sample the mean spectral index of the radio-quiet sources (< Γ > = 2.53) and that of the radio-loud ones (< Γ > = 2.26) are clearly different with a significance of 3.3 σ.About 2/3 of the bright quasars observed with Einstein also belong to our sample. The spectra observed with ROSAT are sytematically steeper than the ones observed with Einstein yielding a < ΓROSAT – ΓEinstein > of 0.66 ± 0.18 for radio quiet and of 0.68 ± 0.19 for radio-loud sources, respectively.For radio loud quasars, the mean spectral slope decreases from 2.3 to 1.5 when the redshift increases beyond 0.5 (figure 1). The fact that high redshift sources show a photon index of about 1.5, which is similar to the mean index observed with Einstein for radio-loud sources, suggests that this decrease towards higher redshifts can be interpreted by the shift of the soft X-ray excess outside of the ROSAT spectral band when the redshift increases. The solid lines in figure 1 represent theoretical pathes of the photon index as a function of the redshift as derived from simulations assuming a power law plus black body model spectrum for the quasars X-ray emission. In curve No 1 the powerlaw index is fixed to 1.4. To be compatible with the observation the temperature of the blackbody component must range between 50 and 70 eV. Curve No 2 asssumes the same model with a powerlaw index fixed to 1.8 to account for radio quiet sources.

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 The X-ray Emission of Quasars as Observed by Ginga

1994 ◽  
Vol 159 ◽  
pp. 123-125
Author(s):  
A.J. Lawson ◽  
M.J.L. Turner
Keyword(s):  
Spectral Index ◽  
Rest Frame ◽  
Line Emission ◽  
Adequate Description ◽  
Rank Tests ◽  
X Ray ◽  
Spectrum Radio ◽  
Show Evidence ◽  
The Mean ◽  
The Relationship

We present preliminary results on a spectal analysis of quasars observed by the X-ray observatory Ginga. Simple power-law models with fixed Galactic absorbtion provide an adequate description of the spectra for most of the sources in the 2–18 keV band. A small number of sources show evidence for a feature at 6.4 keV (in the source rest frame) due to Fe line emission. Maximum likelihood and Spearman rank tests were used to investigate the relationship between radio loudness and X-ray spectral index in this class of object. These tests showed, respectively, that the mean X-ray spectral index of radio quiet quasars (RQQs) is significantly different from that of flat spectrum radio loud quasars (FRSQs) at the >99% level, and that the dominant relationship with spectral index is radio loudness (not X-ray luminosity or redshift) at >99% significance. This last result has not previously been demonstrated in this band, but agrees with findings in the lower energy Einstein band (0.5–3.5 keV). These results are discussed in the context of current unified models.

scholarly journals X-ray observations of the nova shell IPHASX J210204.7+471015*

2021 ◽  
Author(s):  
J A Toalá ◽  
G Rubio ◽  
E Santamaría ◽  
M A Guerrero ◽  
S Estrada-Dorado ◽  
...  
Keyword(s):  
Time Series ◽  
Binary System ◽  
Binary Star ◽  
Optical Observations ◽  
X Ray ◽  
Imaging Camera ◽  
Nova Shells ◽  
Intermediate Polars ◽  
Time Series Analyses ◽  
Nova Shell

Abstract We present the analysis of XMM-Newton European Photon Imaging Camera (EPIC) observations of the nova shell IPHASX J210204.7+471015. We detect X-ray emission from the progenitor binary star with properties that resemble those of underluminous intermediate polars such as DQ Her: an X-ray-emitting plasma with temperature of TX = (6.4 ± 3.1) × 106 K, a non-thermal X-ray component, and an estimated X-ray luminosity of LX = 1030 erg s−1. Time series analyses unveil the presence of two periods, the dominant with a period of 2.9 ± 0.2 hr, which might be attributed to the spin of the white dwarf, and a secondary of 4.5 ± 0.6 hr that is in line with the orbital period of the binary system derived from optical observations. We do not detect extended X-ray emission as in other nova shells probably due to its relatively old age (130–170 yr) or to its asymmetric disrupted morphology which is suggestive of explosion scenarios different to the symmetric ones assumed in available numerical simulations of nova explosions.

Changes in antibiotic usage and susceptibility in nosocomial Enterobacteriaceae and Pseudomonas isolates following the introduction of ertapenem to hospital formulary

2011 ◽  
Vol 140 (1) ◽  
pp. 115-125 ◽  
Author(s):  
C. J. GRABER ◽  
C. HUTCHINGS ◽  
F. DONG ◽  
W. LEE ◽  
J. K. CHUNG ◽  
...  
Keyword(s):  
Time Series ◽  
Linear Trend ◽  
Interrupted Time Series ◽  
Antibiotic Usage ◽  
Cross Resistance ◽  
Hospital Formulary ◽  
Time Series Analyses ◽  
The Mean ◽  
The Impact ◽  
Change In Mean

SUMMARYThere is concern that widespread usage of ertapenem may promote cross-resistance to other carbapenems. To analyse the impact that adding ertapenem to our hospital formulary had on usage of other broad-spectrum agents and on susceptibilities of nosocomial Enterobacteriaceae and Pseudomonas isolates, we performed interrupted time-series analyses to determine the change in linear trend in antibiotic usage and change in mean proportion and linear trend of susceptibility pre- (March 2004–June 2005) and post- (July 2005–December 2008) ertapenem introduction. Usage of piperacillin-tazobactam (P=0·0013) and ampicillin-sulbactam (P=0·035) declined post-ertapenem introduction. For Enterobacteriaceae, the mean proportion susceptible to ciprofloxacin (P=0·016) and piperacillin-tazobactam (P=0·038) increased, while the linear trend in susceptibility significantly increased for cefepime (P=0·012) but declined for ceftriaxone (P=0·0032). For Pseudomonas, the mean proportion susceptible to cefepime (P=0·011) and piperacillin-tazobactam (P=0·028) increased, as did the linear trend in susceptibility to ciprofloxacin (P=0·028). Notably, no significant changes in carbapenem susceptibility were observed.

Physiological fractals: Visual and statistical evidence across timescales and experimental states

2020 ◽  
Author(s):  
Jeffrey J Kim
Keyword(s):  
Time Series ◽  
Published Data ◽  
Compassion Meditation ◽  
Open Questions ◽  
Mean And Variance ◽  
Time Series Analyses ◽  
The Mean ◽  
Highly Correlated ◽  
Mind Training ◽  
Stable Signal

A marker of engaging in compassion meditation and related processes is an increase in heart-rate variability (HRV), typically interpreted as a marker of parasympathetic nervous response. Whilst insightful, open questions remain. For example, which timescale is best to examine the effects of meditation and related practices on HRV? Furthermore, how might advanced time series analyses – such as stationarity – be able to examine dynamic changes in the mean and variance of the HRV signal across time? Here we apply such methods to previously published data, which measured HRV pre- and post- a two-week compassionate mind training (CMT) intervention. Inspection of these data reveal that a visualization of HRV correlations across resting and compassion meditation states, pre- and post- two-week training, is retained across numerous recording timescales. Here, the fractal-like nature of our data indicate that the accuracy of representing HRV data can exist across timescales, albeit with greater or lesser granularity. Interestingly, inspection of the HRV signal at Time 2 compassion meditation versus Time 1 revealed a more highly correlated (i.e., potentially more stable) signal. We followed up these results with tests of stationarity, which revealed Time 2 had a less stochastic (variable) signal than Time 1, and a measure of distance in the time series, which showed that Time 2 had less of an average difference between rest and meditation than at Time 1. Our results provide novel assessment of visual and statistical markers of HRV change across distinct experimental states.

scholarly journals Evidence for a Common Magnetic Driver for Flares and Quiescent Coronae/Chromospheres

1985 ◽  
Vol 38 (6) ◽  
pp. 971 ◽  
Author(s):  
A Skumanich
Keyword(s):  
High Frequency ◽  
Flare Activity ◽  
Mean Power ◽  
X Ray ◽  
V Band ◽  
The Mean

The mean power and rate of optical flares in dMe stars are found to be correlated with their quiet coronal X-ray luminosity. The mean flare luminosity in the photometric V-band appears to scale linearly with the X-ray luminosity with a slope of 0�04. This coincidence suggests that quiet and flare activity in coronae/chromospheres may be related by one and the same flaring mechanism. We propose that 'quiet' activity is due to microflares-a low yield but high frequency continuation of flares.

scholarly journals The Soft X-ray Excesses Observed by ROSAT

1994 ◽  
Vol 159 ◽  
pp. 338-338
Author(s):  
R. Walter ◽  
H.H. Fink
Keyword(s):  
Power Law ◽  
Spectral Energy Distribution ◽  
Seyfert Galaxies ◽  
High Energy ◽  
Wide Distribution ◽  
Spectral Energy ◽  
Spectral Slope ◽  
X Ray ◽  
Object A ◽  
The Mean

The properties of the soft X-ray excesses of bright Seyfert 1 galaxies and Quasars are described using the observations obtained with the PSPC (0.1–2.4 keV) detector of the XRT telescope aboard ROSAT during the ROSAT all sky survey (RASS). The sample consists of 58 Seyfert 1 type AGN detected with more than 300 counts during the RASS and observed at least once with IUE.The soft X-ray photon indices of our sample members range from 1.6 to 3.4 in a wide distribution (< Γ > = 2.50, σ = 0.48). The width of the distribution is considerably larger than the mean statistical uncertainty on the individual spectral slopes (σ = 0.33). Excepting for IC 4329A and Mrk 766, the mean contribution of absorbing cold matter intrinsic to the Seyfert galaxies of our sample to the absorbing column density is less than 1020cm−2. In IC 4329A and Mrk 766 intrinsic absorbtion is observed at soft X-ray. Both sources are also strongly reddened by dust.An excess of soft X-ray flux is detected in 90% of the sources above the exptrapolation of the hard X-ray power law. It can be shown that the PSPC spectral slope is a measure of the strength of the soft X-ray excess. If the reddened sources are excluded, a correlation appears between the strength of the ultraviolet blue bump and the soft X-ray photon index (figure 1). The ratio of the ultraviolet to infrared fluxes and the ultraviolet spectral slope are also related to the strength of the blue bump. The observations are compatible with a model where most of the spectral variations arising among the sources studied are driven by the strength of the bump component, which varies by a factor of 100 from object to object. A bump model consisting of a power law with a high energy cutoff at 80 eV can fit most of the sources. In any case, the spectral energy distribution of the ultraviolet to soft X-ray bump is characterised by vFv(1375 Å) = (1–5) ∫ε > 150eVFεdε.

scholarly journals Hyperluminous starburst gives up its secrets

2019 ◽  
Vol 489 (1) ◽  
pp. 427-436 ◽  
Author(s):  
R J Ivison ◽  
M J Page ◽  
M Cirasuolo ◽  
C M Harrison ◽  
V Mainieri ◽  
...  
Keyword(s):  
Rest Frame ◽  
Spectral Energy Distribution ◽  
Imaging Spectroscopy ◽  
Far Infrared ◽  
Host Galaxy ◽  
Spectral Energy ◽  
X Ray ◽  
Dusty Galaxies ◽  
Imaging And Spectroscopy ◽  
Ir Emission

Abstract HATLAS J084933.4 + 021443 was identified as a dusty starburst via its rest-frame far-infrared (far-IR) emission. Multifrequency imaging and spectroscopy revealed a cluster of four dusty galaxies at z = 2.41, covering 80 kpc. Here, we use Atacama Large Millimetre Array to confirm a more distant, fifth protocluster member, and present X-ray and rest-frame optical imaging spectroscopy of the brightest, an unlensed hyperluminous IR galaxy (HyLIRG). The data reveal broad Hα and bright [N ii] lines, and bright X-ray emission, characteristics that betray a Type-1 active galactic nucleus (AGN), strengthening evidence that AGN are ubiquitous amongst HyLIRGs. The accreting black hole is supermassive, Mbh ≈ 2 × 109 M⊙, with little intrinsic absorption, NH ≈ 5 × 1021 cm−2. The X-ray properties suggest the accretion luminosity rivals that of the starburst, yet it is not obvious where this emerges in its panchromatic spectral energy distribution. We outline three scenarios that could give rise to the observed characteristics, and how we might distinguish between them. In the first, we see the AGN through the host galaxy because of the cavity it excavates. In the others, the AGN is not cospatial with the starburst, having been ejected via asymmetric gravitational radiation, or having evolved towards the naked quasar phase in an unseen companion.

scholarly journals KASHz: No evidence for ionised outflows instantaneously suppressing star formation in moderate luminosity AGN at z ∼ 1.4–2.6

2020 ◽  
Vol 492 (3) ◽  
pp. 3194-3216 ◽  
Author(s):  
J Scholtz ◽  
C M Harrison ◽  
D J Rosario ◽  
D M Alexander ◽  
C-C Chen ◽  
...  
Keyword(s):  
Star Formation ◽  
Spectroscopic Data ◽  
Rest Frame ◽  
High Redshift ◽  
Host Galaxies ◽  
X Ray ◽  
Spatially Resolved ◽  
Long Time ◽  
Positive And Negative Feedback ◽  
Attenuation Corrected

ABSTRACT As part of our KMOS AGN Survey at High-redshift (KASHz), we present spatially resolved VLT/KMOS and VLT/SINFONI spectroscopic data and ALMA 870 μm continuum imaging of eight z = 1.4–2.6 moderate AGN ($L_{\rm 2-10 \, \rm kev}$ = 1042–1045 ergs s−1). We map [O iii], H α and rest-frame FIR emission to search for any spatial anticorrelation between ionised outflows (traced by the [O  iii] line) and star formation (SF; traced by H α and FIR), that has previously been claimed for some high-z AGN and used as evidence for negative and/or positive AGN feedback. First, we conclude that H α is unreliable to map SF inside our AGN host galaxies based on: (i) SF rates inferred from attenuation-corrected H α can lie below those inferred from FIR; (ii) the FIR continuum is more compact than the H α emission by a factor of ∼2 on average; (iii) in half of our sample, we observe significant spatial offsets between the FIR and H α emission, with an average offset of 1.4 ± 0.6 kpc. Secondly, for the five targets with outflows we find no evidence for a spatial anticorrelation between outflows and SF using either H α or FIR as a tracer. This holds for our re-analysis of a famous z = 1.6 X-ray AGN (‘XID 2028’) where positive and negative feedback has been previously claimed. Based on our results, any impact on SF by ionised outflows must be subtle, either occurring on scales below our resolution, or on long time-scales.

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