208 research outputs found
First Detection of Mid-Infrared Variability from an Ultraluminous X-Ray Source Holmberg II X-1
We present mid-infrared (IR) light curves of the Ultraluminous X-ray Source
(ULX) Holmberg II X-1 from observations taken between 2014 January 13 and 2017
January 5 with the \textit{Spitzer Space Telescope} at 3.6 and 4.5 m in
the \textit{Spitzer} Infrared Intensive Transients Survey (SPIRITS). The mid-IR
light curves, which reveal the first detection of mid-IR variability from a
ULX, is determined to arise primarily from dust emission rather than from a jet
or an accretion disk outflow. We derived the evolution of the dust temperature
( K), IR luminosity (
), mass (
), and equilibrium temperature radius
( AU). A comparison of X-1 with a sample
spectroscopically identified massive stars in the Large Magellanic Cloud on a
mid-IR color-magnitude diagram suggests that the mass donor in X-1 is a
supergiant (sg) B[e]-star. The sgB[e]-interpretation is consistent with the
derived dust properties and the presence of the [Fe II] (
m) emission line revealed from previous near-IR studies of X-1. We
attribute the mid-IR variability of X-1 to increased heating of dust located in
a circumbinary torus. It is unclear what physical processes are responsible for
the increased dust heating; however, it does not appear to be associated with
the X-ray flux from the ULX given the constant X-ray luminosities provided by
serendipitous, near-contemporaneous X-ray observations around the first mid-IR
variability event in 2014. Our results highlight the importance of mid-IR
observations of luminous X-ray sources traditionally studied at X-ray and radio
wavelengths.Comment: 9 page, 4 figures, 1 table, Accepted to ApJ Letter
The Ultra-Fast Outflow of WKK 4438: Suzaku and NuSTAR X-ray Spectral Analysis
Previous X-ray spectral analysis has revealed an increasing number of AGNs
with high accretion rates where an outflow with a mildly relativistic velocity
originates from the inner accretion disk. Here we report the detection of a new
ultra-fast outflow (UFO) with a velocity of in addition to a relativistic disk reflection
component in a poorly studied NLS1 WKK~4438, based on archival \nustar and
\suzaku observations. The spectra of both \suzaku and \nustar observations show
an Fe~\textsc{xxvi} absorption feature and the \suzaku data also show evidence
for an Ar~\textsc{xviii} with the same blueshift. A super-solar argon abundance
() and a slight iron over-abundance
() are found in our spectral
modelling. Based on Monte-Carlo simulations, the detection of the UFO is
estimated to be around at 3 significance. The fast wind most likely
arises from a radius of away from the central black hole. The disk
is accreting at a high Eddington ratio (). The
mass outflow rate of the UFO is comparable with the disk mass inflow rate
(), assuming a maximum covering factor.
The kinetic power of the wind might not be high enough to have influence in AGN
feedback () due to a relatively
small column density (~cm). However note that
both the inferred velocity and the column density could be lower limits owing
to the low viewing angle ().Comment: 7 pages, 3 figures, accepted by MNRA
A Rapidly Spinning Black Hole Powers the Einstein Cross
Observations over the past 20 years have revealed a strong relationship
between the properties of the supermassive black hole (SMBH) lying at the
center of a galaxy and the host galaxy itself. The magnitude of the spin of the
black hole will play a key role in determining the nature of this relationship.
To date, direct estimates of black hole spin have been restricted to the local
Universe. Herein, we present the results of an analysis of 0.5 Ms of
archival Chandra observations of the gravitationally lensed quasar Q 2237+305
(aka the "Einstein-cross"), lying at a redshift of z = 1.695. The boost in flux
provided by the gravitational lens allows constraints to be placed on the spin
of a black hole at such high redshift for the first time. Utilizing state of
the art relativistic disk reflection models, the black hole is found to have a
spin of at the 90% confidence level. Placing a
lower limit on the spin, we find (4). The high value of
the spin for the black hole in Q 2237+305 lends
further support to the coherent accretion scenario for black hole growth. This
is the most distant black hole for which the spin has been directly constrained
to date.Comment: 5 pages, 3 figures, 1 table, formatted using emulateapj.cls. Accepted
for publication in ApJ
Bright radio emission from an ultraluminous stellar-mass microquasar in M 31
A subset of ultraluminous X-ray sources (those with luminosities of less than 10^(40 ) erg s^(−1); ref. 1) are thought to be powered by the accretion of gas onto black holes with masses of ~5–20 M_⊙ , probably by means of an accretion disk. The X-ray and radio emission are coupled in such Galactic sources; the radio emission originates in a relativistic jet thought to be launched from the innermost regions near the black hole, with the most powerful emission occurring when the rate of infalling matter approaches a theoretical maximum (the Eddington limit). Only four such maximal sources are known in the Milky Way, and the absorption of soft X-rays in the interstellar medium hinders the determination of the causal sequence of events that leads to the ejection of the jet. Here we report radio and X-ray observations of a bright new X-ray source in the nearby galaxy M 31, whose peak luminosity exceeded 10^(39) erg s^(−1). The radio luminosity is extremely high and shows variability on a timescale of tens of minutes, arguing that the source is highly compact and powered by accretion close to the Eddington limit onto a black hole of stellar mass. Continued radio and X-ray monitoring of such sources should reveal the causal relationship between the accretion flow and the powerful jet emission
The Broadband X-Ray Spectrum of the X-Ray-obscured Type 1 AGN 2MASX J193013.80+341049.5
We present results from modeling the broadband X-ray spectrum of the Type 1 active galactic nucleus (AGN) 2MASX J193013.80+341049.5 using NuSTAR, Swift, and archival XMM-Newton observations. We find this source to be highly X-ray obscured, with column densities exceeding 10²³ cm⁻² across all epochs of X-ray observations, spanning an 8 yr period. However, the source exhibits prominent broad optical emission lines, consistent with an unobscured Type 1 AGN classification. We fit the X-ray spectra with both phenomenological reflection models and physically motivated torus models to model the X-ray absorption. We examine the spectral energy distribution of this source and investigate some possible scenarios to explain the mismatch between X-ray and optical classifications. We compare the ratio of reddening to X-ray absorbing column density (E_(B−V)/N_H) and find that 2MASX J193013.80+341049.5 likely has a much lower dust-to-gas ratio relative to the Galactic interstellar medium, suggesting that the broad line region itself could provide the source of extra X-ray obscuration, being composed of low-ionization, dust-free gas
What is on Tap? The Role of Spin in Compact Objects and Relativistic Jets
We examine the role of spin in launching jets from compact objects across the
mass scale. Our work includes a total of 37 Seyferts, 11 stellar-mass black
holes, and 13 neutron stars. We find that when the Seyfert reflection lines are
modeled with Gaussian line features (a crude proxy for inner disk radius and
therefore spin), only a slight inverse correlation is found between the
Doppler-corrected radio luminosity at 5 GHz (a proxy for jet power) and line
width. When the Seyfert reflection features are fit with
relativistically-blurred disk reflection models that measure spin, there is a
tentative positive correlation between the Doppler-corrected radio luminosity
and the spin measurement. Further, when we include stellar-mass black holes in
the sample, to examine the effects across the mass scale, we find a slightly
stronger correlation with radio luminosity per unit mass and spin, at a
marginal significance (2.3 sigma confidence level). Finally, when we include
neutron stars, in order to probe lower spin values, we find a positive
correlation (3.3 sigma confidence level) between radio luminosity per unit mass
and spin. Although tentative, these results suggest that spin may have a role
in determining the jet luminosity. In addition, we find a slightly more
significant correlation (4.4 sigma confidence level) between radio luminosity
per Bolometric luminosity and spin, using our entire sample of black holes and
neutrons stars. Again, although tentative, these relations point to the
possibility that the mass accretion rate, i.e. Bolometric luminosity, is also
important in determining the jet luminosity, in addition to spin. Our analysis
suggests that mass accretion rate and disk or coronal magnetic field strength
may be the "throttle" in these compact systems, to which the Eddington limit
and spin may set the maximum jet luminosity that can be achieved.Comment: 14 pages, 13 Figures, ApJ Accepte
Spectral and temporal properties of the ultra-luminous X-ray pulsar in M82 from 15 years of Chandra observations and analysis of the pulsed emission using NuSTAR
The recent discovery by Bachetti et al. (2014) of a pulsar in M82 that can
reach luminosities of up to 10^40 ergs s^-1, a factor of ~100 the Eddington
luminosity for a 1.4 Msol compact object, poses a challenge for accretion
physics. In order to better understand the nature of this source and its duty
cycle, and in the light of several physical models that have been subsequently
published, we conduct a spectral and temporal analysis of the 0.5-8 keV X-ray
emission from this source from 15 years of Chandra observations. We fit the
Chandra spectra of the pulsar with a power-law model and a disk black body
model, subjected to interstellar absorption in M82. We carefully assess for the
effect of pile-up in our observations, where 4/19 observations have a pile-up
fraction >10%, which we account for during spectral modeling with a convolution
model. When fitted with a power-law model, the average photon index when the
source is at high luminosity (L_X>10^39 ergs s^-1) is Gamma=1.33+/-0.15. For
the disk black body model, the average temperature is T=3.24+/-0.65 keV,
consistent with other luminous X-ray pulsars. We also investigated the
inclusion of a soft excess component and spectral break, finding that the
spectra are also consistent with these features common to luminous X-ray
pulsars. In addition, we present spectral analysis from NuSTAR over the 3-50
keV range where we have isolated the pulsed component. We find that the pulsed
emission in this band is best fit by a power-law with a high-energy cut-off,
where Gamma=0.6+/-0.3 and E_C=14^{+5}_{-3} keV. While the pulsar has previously
been identified as a transient, we find from our longer-baseline study that it
has been remarkably active over the 15-year period, where for 9/19 (47%)
observations that we analyzed, the pulsar appears to be emitting at a
luminosity in excess of 10^39 ergs s^-1, greater than 10 times its Eddington
limit.Comment: Accepted for publication by Ap
A new, clean catalogue of extragalactic non-nuclear X-ray sources in nearby galaxies
We have created a new, clean catalogue of extragalactic non-nuclear X-ray sources by correlating the 3XMM-DR4 data release of the XMM-Newton Serendipitous Source Catalogue with the Third Reference Catalogue of Bright Galaxies and the Catalogue of Neighbouring Galaxies, using an improved version of the method presented in Walton et al. Our catalogue contains 1314 sources, of which 384 are candidate ultraluminous X-ray sources (ULXs). The resulting catalogue improves upon previous catalogues in its handling of spurious detections by taking into account XMM-Newton quality flags. We estimate the contamination of ULXs by background sources to be 24 per cent. We define a 'complete' subsample as those ULXs in galaxies for which the sensitivity limit is below 10 39 erg s -1 and use it to examine the hardness ratio properties between ULX and non-ULX sources, and ULXs in different classes of host galaxy. We find that ULXs have a similar hardness ratio distribution to lower luminosity sources, consistent with previous studies. We also find that ULXs in spiral and elliptical host galaxies have similar distributions to each other independent of host galaxy morphology, however, our results do support previous indications that the population of ULXs is more luminous in star-forming host galaxies than in non-star-forming galaxies. Our catalogue contains further interesting subpopulations for future study, including Eddington Threshold sources and highly variable ULXs. We also examine the highest luminosity (L X > 5 × 10 40 erg s -1) ULXs in our catalogue in search of intermediate-mass black hole candidates, and find nine new possible candidates.We gratefully acknowledge support from the Science and Technology Facilities Council (HPE through grant ST/K501979/1, TPR through ST/P000541/1). HPE acknowledges support under National Aeronautics and Space Administration contract NNG08FD60C. MJM and DJW acknowledge support from STFC Ernest Rutherford fellowships. SM acknowledges financial support by the Spanish Ministry of Economy and Competitiveness through grant AYA2016-76730-P (MINECO/FEDER)
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