Abstract
We present the first joint NuSTAR and NICER observations of the ultracompact X-ray binary (UCXB) 4U 1543−624 obtained in 2020 April. The source was at a luminosity of
L
0.5−50 keV
= 4.9(
D
.../7 kpc)
2
× 10
36
erg s
−1
and showed evidence of reflected emission in the form of an O
viii
line, Fe K line, and Compton hump within the spectrum. We used a full reflection model, known as
xillverCO
, that is tailored for the atypical abundances found in UCXBs, to account for the reflected emission. We tested the emission radii of the O and Fe line components and conclude that they originate from a common disk radius in the innermost region of the accretion disk (
R
in
≤ 1.07
R
ISCO
). Assuming that the compact accretor is a neutron star (NS) and the position of the inner disk is the Alfvén radius, we placed an upper limit on the magnetic field strength to be
B
≤ 0.7(
D
/7 kpc) × 10
8
G at the poles. Given the lack of pulsations detected and position of
R
in
, it was likely that a boundary layer region had formed between the NS surface and inner edge of the accretion disk with an extent of 1.2 km. This implies a maximum radius of the neutron star accretor of
R
NS
≤ 12.1 km when assuming a canonical NS mass of 1.4
M
⊙
.
Aims. Most of our knowledge of the circumnuclear matter in Seyfert galaxies is based on the X-ray spectra of the brightest Compton-thick Seyfert 2 galaxies. The complete obscuration of the nuclear ...radiation in these sources allows us to study all the components arising from reprocessing of the primary continuum in the circumnuclear matter in detail, while they are heavily diluted in unobscured sources, often down to invisibility. Methods. We present the XMM-Newton RGS and EPIC pn spectra of a long (≃100 ks) observation of one of the soft X-ray brightest Compton-thick Seyfert 2 galaxies, NGC 424. As a first step, we performed a phenomenological analysis of the data to derive the properties of all the spectral components. On the basis of these results, we fitted the spectra with self-consistent photoionisation models, produced with cloudy. Results. The high-energy part of the spectrum is dominated by a pure neutral Compton reflection component and a neutral iron Kα line, together with Kα emission from neutral Ni, suggesting a significant Ni/Fe overabundance. The soft X-ray RGS spectrum comes mostly from line emission from H-like and He-like C, N, O, and Ne, as well as from the Fe L-shell. The presence of narrow RRC from O viii, O vii, and C vi, the last two with resolved widths corresponding to temperatures around 5–10 eV, is a strong indication of a gas in photoionisation equilibrium, as confirmed by the prevalence of the forbidden component in the O vii triplet. Two gas phases with different ionisation parameters are needed to reproduce the spectrum with a self-consistent photoionisation model, any contribution from a gas in collisional equilibrium being no more than 10% of the total flux in the 0.35–1.55 keV band. When this self-consistent model is applied to the 0.5–10 keV band of the EPIC pn spectrum, a third photoionised phase is needed to account for emission lines with higher ionisation potential, although Kα emission from S xv and Fe xxvi remains under-predicted.
Using the 4 Ms Chandra Deep Field-South (CDF-S) survey, we have identified a sample of 6845 X-ray-undetected galaxies that dominates the unresolved 20%-25% of the 6-8 keV cosmic X-ray background ...(XRB). This sample was constructed by applying mass and color cuts to sources from a parent catalog based on GOODS-South Hubble Space Telescope z-band imaging of the central 6'radius area of the 4 Ms CDF-S. The stacked 6-8 keV detection is significant at the 3.9sigma level, but the stacked emission was not detected in the 4-6 keV band, which indicates the existence of an underlying population of highly obscured active galactic nuclei (AGNs). Further examinations of these 6845 galaxies indicate that the galaxies on the top of the blue cloud and with redshifts of 1 <, ~ z <, ~ 3, magnitudes of 25 <, ~ z sub(850) <, ~ 28, and stellar masses of 2 x 10 super(8) <, ~ Mlow */M sub(middot in circle) <, ~ 2 x 10 super(9) make the majority contributions to the unresolved 6-8 keV XRB. Such a population is seemingly surprising given that the majority of the X-ray-detected AGNs reside in massive (> ~10 super(10) M sub(middot in circle)) galaxies. We discuss constraints upon this underlying AGN population, supporting evidence for relatively low mass galaxies hosting highly obscured AGNs, and prospects for further boosting the stacked signal.
We have observed the hard X-ray selected Narrow-Line Seyfert 1 galaxy SWIFT J2127.4+5654 with Suzaku. We report the detection of a broad relativistic iron emission line from the inner accretion disc. ...Partial covering by either neutral or partially ionized gas cannot reproduce the spectral shape and, even if its presence is assumed, it does not significantly change the inferred broad-line parameters. By assuming that the inner edge of the accretion disc corresponds to the innermost stable circular orbit of the black hole space–time, the line profile enables us to measure a black hole spin a= 0.6 ± 0.2. However, a non-rotating Schwarzschild space–time is excluded at just above the 3σ level, while a maximally spinning Kerr black hole is excluded at the ∼5σ level. The intermediate spin we measure may indicate a recent merger, or that accretion-driven black hole growth in this source proceeds through short-lived episodes with chaotic angular momentum alignment between the disc and the hole rather than via prolonged accretion. The measured steep emissivity index (q≃ 5) constrains the irradiating X-ray source to be very centrally concentrated. Light bending may help focus the primary emission towards the innermost accretion disc, thus steepening the irradiation profile. On the other hand, steep profiles can also be reached if magnetic extraction of the hole rotational energy is at work. If this is the case, the interplay between accretion (spinning up the black hole) and rotational energy extraction (spinning it down) forces the hole to reach an equilibrium spin value which, under standard assumptions, is remarkably consistent with our measurement. Rotational energy extraction would then be able to simultaneously account for the intermediate spin and steep emissivity profile we infer from our spectral analysis without the need to invoke chaotic accretion episodes. We also report tentative evidence for short time-scale line profile variability. The relatively low statistical significance of the variability (about 98 per cent confidence level) prevents us from drawing any firm conclusions which must be deferred to future observations.
ABSTRACT We present an analysis of ionized X-ray disk winds found in the Fe K band of four stellar-mass black holes observed with Chandra, including 4U 1630−47, GRO J1655−40, H 1743−322, and GRS ...1915+105. High-resolution photoionization grids were generated in order to model the data. Third-order gratings spectra were used to resolve complex absorption profiles into atomic effects and multiple velocity components. The Fe xxv line is found to be shaped by contributions from the intercombination line (in absorption), and the Fe xxvi line is detected as a spin-orbit doublet. The data require 2-3 absorption zones, depending on the source. The fastest components have velocities approaching or exceeding increasing mass outflow rates and wind kinetic power by orders of magnitude over prior single-zone models. The first-order spectra require re-emission from the wind, broadened by a degree that is loosely consistent with Keplerian orbital velocities at the photoionization radius. This suggests that disk winds are rotating with the orbital velocity of the underlying disk, and provides a new means of estimating launching radii-crucial to understanding wind driving mechanisms. Some aspects of the wind velocities and radii correspond well to the broad-line region in active galactic nuclei (AGNs), suggesting a physical connection. We discuss these results in terms of prevalent models for disk wind production and disk accretion itself, and implications for massive black holes in AGNs.
The narrow-line Seyfert 1 Galaxy 1H 0707−495 went into a low state from 2010 December to 2011 February, discovered by a monitoring campaign using the X-Ray Telescope on the Swift satellite. We ...triggered a 100 ks XMM-Newton observation of the source in 2011 January, revealing the source to have dropped by a factor of 10 in the soft band, below 1 keV, and a factor of 2 at 5 keV, compared with a long observation in 2008. The sharp spectral drop in the source usually seen around 7 keV now extends to lower energies, below 6 keV in our frame. The 2011 spectrum is well fitted by a relativistically blurred reflection spectrum similar to that which fits the 2008 data, except that the emission is now concentrated solely to the central part of the accretion disc. The irradiating source must lie within 1 gravitational radius of the event horizon of the black hole, which spins rapidly. Alternative models are briefly considered, but none has any simple physical interpretation.
We perform a detailed spatially resolved, spectroscopic, analysis of the core of the Centaurus cluster of galaxies using a deep Chandra X-ray observation and XMM–Newton data. The Centaurus cluster ...core has particularly high metallicity, up to twice the solar values, and we measure the abundances of Fe, O, Ne, Mg, Si, S, Ar, Ca and Ni. We map the distribution of these elements in many spatial regions, and create radial profiles to the east and west of the centre. The ratios of the most robustly determined elements to iron are consistent with solar ratios, indicating that there has been enrichment by both Type Ia and Type II supernovae. For a normal initial stellar mass function, the metallicity peak represents the products of about 4 × 1010 M⊙ of star formation. This star formation can have occurred continuously at a rate of 5 M⊙ yr−1 for the past 8 Gyr or more, or was part of the formation of the central galaxy at earlier times. Either conclusion requires that the inner core of the Centaurus cluster has not suffered a major disruption within the past 8 Gyr, or even longer.
Exposure to gasoline fumes through inhalation or accidental ingestion has been associated with chronic inflammatory reactions leading to oxidative stress, oxidative DNA damage and increased risk of ...chronic lung conditions and cancer. This study assessed the peak expiratory flow rate (PEFR) and biomarkers of oxidative stress (total antioxidant capacity (TAC), total plasma peroxides (TPP), oxidative stress index (OSI)), oxidative DNA damage (8-hydroxy-2-deoxyguanosine (8-OHdG)), 1-hydroxypyrene and urine creatinine in Gasoline Station Attendants. A total of 100 consenting adults, aged 18-60 years, comprising 50 gasoline station attendants and 50 non-gasoline station attendants (controls) were enrolled into this comparative cross-sectional study. The PEFR was determined using the peak flow meter, TAC, TPP and creatinine by colorimetry, 8-OHdG by enzyme linked immunosorbent assay (ELISA), 1-hydroxypyrene (1-HOP) by high performance liquid chromatography and OSI by calculation. Data was analysed using unpaired Student t-test and Pearson's correlation analysis at p<0.05.
The body mass index, TPP, OSI and 8-OHdG levels were significantly higher and TAC and PEFR lower in gasoline pump attendants compared to the control groups (p<0.05). Positive correlations were observed between TPP and years at work (r=0.638, p=0.000), between TPP and OSI (r=0.282, p=0.047) and negative correlation between TAC and OSI (r=-0.555, p=0.000) only in gasoline station attendants. Exposure to gasoline is associated with increased lipid peroxidation and oxidative DNA damage, reduced lung function and depletion of antioxidants which may result in oxidative stress and increased risk for the development of chronic lung conditions in gasoline station attendants.
We present integral field spectroscopic observations of six emission-line nebulae that surround the central galaxy of cool core clusters. Qualitatively similar nebulae are observed in cool core ...clusters even when the dynamics and possibly formation and excitation source are different. Evidence for a nearby secondary galaxy disturbing a nebula, as well as active galactic nucleus- and starburst-driven outflows are presented as possible formation mechanisms. One nebula has a rotational velocity of the same amplitude as the underlying molecular reservoir, which implies that the excitation or formation of a nebula does not require any disturbance of the molecular reservoir within the central galaxy. Bulk flows and velocity shears of a few hundred km s−1 are seen across all nebulae. The majority lack any ordered rotation, their configurations are not stable so the nebulae must be constantly reshaping, dispersing and reforming. The dimmer nebulae are cospatial with dust features whilst the more luminous are not. Significant variation in the ionization state of the gas is seen in all nebulae through the non-uniform N ii/Hα ratio. There is no correlation between the line ratio and Hα surface brightness, but regions with excess blue or ultraviolet (UV) light have lower line ratios. This implies that UV from massive, young stars act in combination with an underlying heating source that produces the observed low-ionization spectra.
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