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Search Results: 1 - 10 of 407079 matches for " Jon M. Miller "
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The Masses and Spins of Neutron Stars and Stellar-Mass Black Holes
M. Coleman Miller,Jon M. Miller
Physics , 2014, DOI: 10.1016/j.physrep.2014.09.003
Abstract: Stellar-mass black holes and neutron stars represent extremes in gravity, density, and magnetic fields. They therefore serve as key objects in the study of multiple frontiers of physics. In addition, their origin (mainly in core-collapse supernovae) and evolution (via accretion or, for neutron stars, magnetic spindown and reconfiguration) touch upon multiple open issues in astrophysics. In this review, we discuss current mass and spin measurements and their reliability for neutron stars and stellar-mass black holes, as well as the overall importance of spins and masses for compact object astrophysics. Current masses are obtained primarily through electromagnetic observations of binaries, although future microlensing observations promise to enhance our understanding substantially. The spins of neutron stars are straightforward to measure for pulsars, but the birth spins of neutron stars are more difficult to determine. In contrast, even the current spins of stellar-mass black holes are challenging to measure. As we discuss, major inroads have been made in black hole spin estimates via analysis of iron lines and continuum emission, with reasonable agreement when both types of estimate are possible for individual objects, and future X-ray polarization measurements may provide additional independent information. We conclude by exploring the exciting prospects for mass and spin measurements from future gravitational wave detections, which are expected to revolutionize our understanding of strong gravity and compact objects.
The new X-ray transient SAX J1711.6-3808: decoupling between its 3-20 keV luminosity and its state transitions
Rudy Wijnands,Jon M. Miller
Physics , 2001, DOI: 10.1086/324329
Abstract: We present a study of the correlated spectral and timing behavior of the new X-ray transient SAX J1711.6-3808 during its 2001 outburst using data obtained with the RXTE. We also investigate the correlations between those source properties and the 3-20 keV X-ray luminosity. The behavior of the source during the observations can be divided into two distinct state types. During the hard state, the energy spectra are relatively hard and can be described by only a power-law component, and the characteristic frequencies (i.e., the frequency of the 1-7 Hz QPOs observed for the first time in this source) in the power spectra are low. However, during the ``soft'' state, the spectra are considerably softer (in addition to the power-law component, a soft component is necessary to fit the spectra) and the frequencies are the highest observed. Remarkably, this distinction into two separate states cannot be extrapolated to also include the 3-20 keV X-ray luminosity. Except for one observation, this luminosity steadily decreased but the hard state was observed both at the highest and lowest observed luminosities. In contrast, the soft state occurred only at intermediate luminosities. This clearly demonstrates that the state behavior of SAX J1711.6-3808 is decoupled from its X-ray luminosity and that if the X-ray luminosity traces the accretion rate in SAX J1711.6-3808, then the state transitions are not good accretion rate indicators, or vice versa. The data of SAX J1711.6-3808 does not allow us to conclusively determine its exact nature. The source resembles both neutron star and black hole systems when they have low luminosities. We discuss our results with respect to the correlated timing and spectral behavior observed in other LMXBs and the implications of our results on the modeling of the outburst light curves of X-ray transients.
Observable Consequences of Merger-Driven Gaps and Holes in Black Hole Accretion Disks
Kayhan Gultekin,Jon M. Miller
Physics , 2012, DOI: 10.1088/0004-637X/761/2/90
Abstract: We calculate the observable signature of a black hole accretion disk with a gap or hole created by a secondary black hole embedded in the disk. We find that for an interesting range of parameters of black hole masses (~10^6 to 10^9 solar masses), orbital separation (~1 AU to ~0.1 pc), and gap width (10 to 190 disk scale heights), the missing thermal emission from a gap manifests itself in an observable decrement in the spectral energy distribution. We present observational diagnostics in terms of power-law forms that can be fit to line-free regions in AGN spectra or in fluxes from sequences of broad filters. Most interestingly, the change in slope in the broken power-law is almost entirely dependent on the width of gap in the accretion disk, which in turn is uniquely determined by mass ratio of the black holes, such that it scales roughly as q^(5/12). Thus one can use spectral observations of the continuum of bright active galactic nuclei to infer not only the presence of a closely separated black hole binary but also the mass ratio. When the black hole merger opens an entire hole (or cavity) in the inner disk, the broad band SED of the AGN or quasar may serve as a diagnostic. Such sources should be especially luminous in optical bands but intrinsically faint in X-rays (i.e., not merely obscured). We briefly note that viable candidates may have already been identified, though extant detailed modeling of those with high quality data have not yet revealed an inner cavity.
Broad iron lines in neutrons stars: dynamical broadening or wind scattering?
Edward M. Cackett,Jon M. Miller
Physics , 2013, DOI: 10.1088/0004-637X/777/1/47
Abstract: Broad iron emission lines are observed in many accreting systems from black holes in AGN and X-ray binaries to neutron star low-mass X-ray binaries. The origin of the line broadening is often interpreted as due to dynamical broadening and relativistic effects. However, alternative interpretations have been proposed, included broadening due to Compton scattering in a wind or accretion disk atmosphere. Here we explore the observational signatures expected from broadening in a wind, in particular that the iron line width should increase with an increase in the column density of the absorber (due to an increase in the number of scatterings). We study the data from three neutron star low-mass X-ray binaries where both a broad iron emission line and absorption lines are seen simultaneously, and show that there is no significant correlation between line width and column density. This favors an inner disk origin for the line broadening rather than scattering in a wind.
Chandra grating spectroscopy of the Be/X-ray binary 1A 0535+262
Mark T. Reynolds,Jon M. Miller
Physics , 2010, DOI: 10.1088/0004-637X/723/2/1799
Abstract: We present Chandra HETGS spectroscopy of the Be/X-ray binary 1A 0535+262 obtained during the 2009/2010 giant outburst. These are the first CCD grating spectra of this type of system during a giant outburst. Our spectra reveal a number of lines including a narrow Fe K_alpha emission line with a FWHM of ~ 5000 km s^-1. For the first time, we detect the presence of a highly ionized outflow in a Be/X-ray binary. Assuming that the line is He-like Fe XXV, fits with a simple Gaussian imply an outflow velocity of ~ 1500 km s^-1. However, self-consistent photoionization modeling with XSTAR suggests that Fe XXIII-XXIV must also contribute. In this case, an outflow velocity of ~ 3000 km s^-1 is implied. These results are discussed in the context of the accretion flow in Be-star, neutron star, and black hole X-ray binaries.
A detailed study of the 5 Hz quasi-periodic oscillations in the bright X-ray transient and black-hole candidate GRS 1739-278
Rudy Wijnands,Mariano Mendez,Jon M. Miller,Jeroen Homan
Physics , 2001, DOI: 10.1046/j.1365-8711.2001.04871.x
Abstract: We present a detailed study of the 5 Hz quasi-periodic oscillation (QPO) recently discovered in the bright X-ray transient and black-hole candidate GRS 1739-278 (Borozdin & Trudolyubov 2000) during a Rossi X-ray Timing Explorer observation taken on 1996 March 31. In total 6.6 ksec of on-source data were obtained, divided in two data sets of 3.4 and 3.2 ksec which were separated by 2.6 ksec. The 5 Hz QPO was only present during the second data set. The QPO increased in strength from below 2% rms amplitude for photon energies below 4 keV to ~5% rms amplitude for energies above 10 keV. The soft QPO photons (below 5 keV) lagged the hard ones (above 10 keV) by almost 1.5 radian. Besides the QPO fundamental, its first overtone was detected. The strength of the overtone increased with photon energy (from <2% rms below 5 keV to ~8% rms above 10 keV). Although the limited statistics did not allow for an accurate determination of the lags of the first overtone, indications are that also for this QPO the soft photons lagged the hard ones. When the 5 Hz QPO was not detected (i.e., during the first part of the observation), a broad noise component was found for photon energies below 10 keV but it became almost a true QPO (with a Q value of ~1.9) above that energy, with a frequency of ~3 Hz. Its hard photons preceded the soft ones in a way reminiscent of the 5 Hz QPO, strongly suggesting that both features are physically related. We discuss our finding in the frame work of low-frequency QPOs and their properties in BHCs.
4U 1957+11: a persistent low-mass X-ray binary and black-hole candidate in the high state?
Rudy Wijnands,Jon M. Miller,Michiel van der Klis
Physics , 2001, DOI: 10.1046/j.1365-8711.2002.05137.x
Abstract: We report on several pointed Rossi X-ray Timing Explorer observations of the enigmatic low-mass X-ray binary (LMXB) 4U 1957+11 at different X-ray luminosities. The luminosity of the source varied by more than a factor of four on time scales of months to years. The spectrum of the source tends to get harder when its luminosity increases. Only very weak (1%-2% rms amplitude; 0.001-10 Hz; 2-60 keV) rapid X-ray variability was observed during the observations. A comparison of the spectral and temporal behaviour of 4U1957+11 with other X-ray binary systems, in particular LMC X-3, indicates that 4U 1957+11 is likely to be a persistent LMXB harboring a black hole and which is persistently in the black-hole high state. If confirmed, it would be the only such system known.
A Jet Model for the Broadband Spectrum of the Seyfert-1 Galaxy NGC 4051
Dipankar Maitra,Jon M. Miller,Sera Markoff,Ashley King
Physics , 2011, DOI: 10.1088/0004-637X/735/2/107
Abstract: Recent radio VLBI observations of the ~parsec-scale nuclear region of the narrow line Seyfert 1 galaxy NGC 4051 hint toward the presence of outflowing plasma. From available literature we have collected high-quality, high-resolution broadband spectral energy distribution data of the nuclear region of NGC 4051 spanning from radio through X-rays, to test whether the broadband SED can be explained within the framework of a relativistically outflowing jet model. We show that once the contribution from the host galaxy is taken into account, the broadband emission from the active galactic nucleus of NGC 4051 can be well described by the jet model. Contributions from dust and ongoing star-formation in the nuclear region tend to dominate the IR emission even at the highest resolutions. In the framework of the jet model, the correlated high variability of the extreme ultraviolet and X-rays compared to other wavelengths suggests that the emission at these wavelengths is optically thin synchrotron originating in the particle acceleration site(s) in the jet very close (few $r_g=GM_{BH}/c^2$) to the central supermassive black hole of mass M_{BH}. Our conclusions support the hypothesis that narrow line Seyfert 1 galaxies (which NGC 4051 is a member of) harbor a "jetted" outflow with properties similar to what has already been seen in low-luminosity AGNs and stellar mass black holes in hard X-ray state.
Warm Absorbers and Outflows in the Seyfert-1 Galaxy NGC 4051
Ashley L. King,Jon M. Miller,John Raymond
Physics , 2011, DOI: 10.1088/0004-637X/746/1/2
Abstract: We present both phenomenological and more physical photoionization models of the Chandra HETG spectra of the Seyfert-1 AGN NGC 4051. We detect 40 absorption and emission lines, encompassing highly ionized charge states from O, Ne, Mg, Si, S and the Fe L-shell and K-shell. Two independent photoionization packages, XSTAR and Cloudy, were both used to self-consistently model the continuum and line spectra. These fits detected three absorbing regions in this system with densities ranging from 10^{10} to 10^{11} cm^{-3}. In particular, our XSTAR models require three components that have ionization parameters of log \xi = 4.5, 3.3, & 1.0, and are located within the BLR at 70, 300, and 13,000 R_g, respectively, assuming a constant wind density. Larger radii are inferred for density profiles which decline with radius. The Cloudy models give a similar set of parameters with ionization parameters of log \xi = 5.0, 3.6, & 2.2 located at 40, 200, and 3,300 R_g. We demonstrate that these regions are out-flowing from the system, and carry a small fraction of material out of the system relative to the implied mass accretion rate. The data suggest that magnetic fields may be an important driving mechanism.
The Fundamental Plane of Accretion Onto Black Holes with Dynamical Masses
Kayhan Gultekin,Edward M. Cackett,Jon M. Miller,Tiziana Di Matteo,Sera Markoff,Douglas O. Richstone
Physics , 2009, DOI: 10.1088/0004-637X/706/1/404
Abstract: Black hole accretion and jet production are areas of intensive study in astrophysics. Recent work has found a relation between radio luminosity, X-ray luminosity, and black hole mass. With the assumption that radio and X-ray luminosity are suitable proxies for jet power and accretion power, respectively, a broad fundamental connection between accretion and jet production is implied. In an effort to refine these links and enhance their power, we have explored the above relations exclusively among black holes with direct, dynamical mass-measurements. This approach not only eliminates systematic errors incurred through the use of secondary mass measurements, but also effectively restricts the range of distances considered to a volume-limited sample. Further, we have exclusively used archival data from the Chandra X-ray Observatory to best isolate nuclear sources. We find log(L_R) = (4.80 +/- 0.24) + (0.78 +/- 0.27) log(M_BH) + (0.67 +/- 0.12) log(L_X), in broad agreement with prior efforts. Owing to the nature of our sample, the plane can be turned into an effective mass predictor. When the full sample is considered, masses are predicted less accurately than with the well-known M-sigma relation. If obscured AGN are excluded, the plane is potentially a better predictor than other scaling measures.
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