arXiv subjects

James C. A. Miller-Jones

Publications and source records attributed to James C. A. Miller-Jones.

At least 91 records · Page 5Linked to original sources

arXiv2020

Infrared interferometry to spatially and spectrally resolve jets in X-ray binaries

Infrared interferometry is a new frontier for precision ground based observing, with new instrumentation achieving milliarcsecond (mas) spatial resolutions for faint sources, along with astrometry on the order of 10 microarcseconds. This technique has already led to breakthroughs in the observations of the supermassive black hole at the Galactic centre and its orbiting stars, AGN, and exo-planets, and can be employed for studying X-ray binaries (XRBs), microquasars in particular. Beyond constraining the orbital parameters of the system using the centroid wobble and spatially resolving jet discrete ejections on mas scales, we also propose a novel method to discern between the various components contributing to the infrared bands: accretion disk, jets and companion star. We demonstrate that the GRAVITY instrument on the Very Large Telescope Interferometer (VLTI) should be able to detect a centroid shift in a number of sources, opening a new avenue of exploration for the myriad of transients expected to be discovered in the coming decade of radio all-sky surveys. We also present the first proof-of-concept GRAVITY observation of a low-mass X-ray binary transient, MAXI J1820+070, to search for extended jets on mas scales. We place the tightest constraints yet via direct imaging on the size of the infrared emitting region of the compact jet in a hard state XRB.

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arXiv2020

Relativistic X-ray jets from the black hole X-ray binary MAXI J1820+070

The black hole MAXI J1820+070 was discovered during its 2018 outburst and was extensively monitored across the electromagnetic spectrum. Following the detection of relativistic radio jets, we obtained four Chandra X-ray observations taken between 2018 November and 2019 May, along with radio observations conducted with the VLA and MeerKAT arrays. We report the discovery of X-ray sources associated with the radio jets moving at relativistic velocities with a possible deceleration at late times. The broadband spectra of the jets are consistent with synchrotron radiation from particles accelerated up to very high energies (>10 TeV) by shocks produced by the jets interacting with the interstellar medium. The minimal internal energy estimated from the X-ray observations for the jets is $\sim 10^{41}$ erg, significantly larger than the energy calculated from the radio flare alone, suggesting most of the energy is possibly not radiated at small scales but released through late-time interactions.

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arXiv2020

The Rise and Fall of ASASSN-18pg: Following a TDE from Early To Late Times

We present nearly 500 days of observations of the tidal disruption event ASASSN-18pg, spanning from 54 days before peak light to 441 days after peak light. Our dataset includes X-ray, UV, and optical photometry, optical spectroscopy, radio observations, and the first published spectropolarimetric observations of a TDE. ASASSN-18pg was discovered on 2018 July 11 by the All-Sky Automated Survey for Supernovae (ASAS-SN) at a distance of $d=78.6$ Mpc, and with a peak UV magnitude of $m\simeq14$ it is both one of the nearest and brightest TDEs discovered to-date. The photometric data allow us to track both the rise to peak and the long-term evolution of the TDE. ASASSN-18pg peaked at a luminosity of $L\simeq2.2\times10^{44}$ erg s$^{-1}$, and its late-time evolution is shallower than a flux $\propto t^{-5/3}$ power-law model, similar to what has been seen in other TDEs. ASASSN-18pg exhibited Balmer lines and spectroscopic features consistent with Bowen fluorescence prior to peak which remained detectable for roughly 225 days after peak. Analysis of the two-component H$α$ profile indicates that, if they are the result of reprocessing of emission from the accretion disk, the different spectroscopic lines may be coming from regions between $\sim10$ and $\sim60$ light-days from the black hole. No X-ray emission is detected from the TDE and there is no evidence of a jet or strong outflow detected in the radio. Our spectropolarimetric observations give no strong evidence for significant asphericity in the emission region, with the emission region having an axis ratio of at least $\sim0.65$.

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arXiv2020

The MAVERIC survey: A hidden pulsar and a black hole candidate in ATCA radio imaging of the globular cluster NGC 6397

Using a 16.2 hr radio observation by the Australia Telescope Compact Array (ATCA) and archival Chandra data, we found $>5σ$ radio counterparts to 4 known and 3 new X-ray sources within the half-light radius ($r_\mathrm{h}$) of the Galactic globular cluster NGC 6397. The previously suggested millisecond pulsar (MSP) candidate, U18, is a steep-spectrum ($S_ν\propto ν^α$; $α=-2.0^{+0.4}_{-0.5}$) radio source with a 5.5 GHz flux density of $54.7\pm 4.3~\mathrm{μJy}$. We argue that U18 is most likely a "hidden" MSP that is continuously hidden by plasma shocked at the collision between the winds from the pulsar and companion star. The nondetection of radio pulsations so far is probably the result of enhanced scattering in this shocked wind. On the other hand, we observed 5.5 GHz flux of the known MSP PSR J1740-5340 (U12) to decrease by a factor of $>2.8$ during epochs of 1.4 GHz eclipse, indicating that the radio flux is absorbed in its shocked wind. If U18 is indeed a pulsar whose pulsations are scattered, we note the contrast with U12's flux decrease in eclipse, which argues for two different eclipse mechanisms at the same radio frequency. In addition to U12 and U18, we also found radio associations for 5 other Chandra X-ray sources, four of which are likely background galaxies. The last, U97, which shows strong H$α$ variability, is mysterious; it may be either a quiescent black hole low-mass X-ray binary, or something more unusual.

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arXiv2019

Lorentz Factors of compact jets in Black hole X-ray binaries

Compact, continuously launched jets in black hole X-ray binaries (BHXBs) produce radio to optical-infrared synchrotron emission. In most BHXBs, an infrared (IR) excess (above the disc component) is observed when the jet is present in the hard spectral state. We investigate why some BHXBs have prominent IR excesses and some do not, quantified by the amplitude of the IR quenching or recovery over the transition from/to the hard state. We find that the amplitude of the IR excess can be explained by inclination dependent beaming of the jet synchrotron emission, and the projected area of the accretion disc. Furthermore, we see no correlation between the expected and the observed IR excess for Lorentz factor 1, which is strongly supportive of relativistic beaming of the IR emission, confirming that the IR excess is produced by synchrotron emission in a relativistic outflow. Using the amplitude of the jet fade and recovery over state transitions and the known orbital parameters, we constrain for the first time the bulk Lorentz factor range of compact jets in several BHXBs (with all the well-constrained Lorentz factors lying in the range of $Γ$ = 1.3 - 3.5). Under the assumption that the Lorentz factor distribution of BHXB jets is a power-law, we find that N($Γ$) $\propto Γ^{ -1.88^{+0.27}_{-0.34}}$. We also find that the very high amplitude IR fade/recovery seen repeatedly in the BHXB GX 339-4 favors a low inclination angle ($< 15^\circ$) of the jet.

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arXiv2019

An HI absorption distance to the black hole candidate X-ray binary MAXI J1535-571

With the Australian Square Kilometre Array Pathfinder (ASKAP) we monitored the black hole candidate X-ray binary MAXI J1535--571 over seven epochs from 21 September to 2 October 2017. Using ASKAP observations, we studied the HI absorption spectrum from gas clouds along the line-of-sight and thereby constrained the distance to the source. The maximum negative radial velocities measured from the HI absorption spectra for MAXI J1535--571 and an extragalactic source in the same field of view are $-69\pm4$ km s$^{-1}$ and $-89\pm4$ km s$^{-1}$, respectively. This rules out the far kinematic distance ($9.3^{+0.5}_{-0.6}$ kpc), giving a most likely distance of $4.1^{+0.6}_{-0.5}$ kpc, with a strong upper limit of the tangent point at $6.7^{+0.1}_{-0.2}$ kpc. At our preferred distance, the peak unabsorbed luminosity of MAXI J1535--571 was $>78$ per cent of the Eddington luminosity, and shows that the soft-to-hard spectral state transition occurred at the very low luminosity of 1.2 -- 3.4 $\times$ 10$^{-5}$ times the Eddington luminosity. Finally, this study highlights the capabilities of new wide-field radio telescopes to probe Galactic transient outbursts, by allowing us to observe both a target source and a background comparison source in a single telescope pointing.

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arXiv2019

A rapidly-changing jet orientation in the stellar-mass black hole V404 Cygni

Powerful relativistic jets are one of the main ways in which accreting black holes provide kinetic feedback to their surroundings. Jets launched from or redirected by the accretion flow that powers them should be affected by the dynamics of the flow, which in accreting stellar-mass black holes has shown increasing evidence for precession due to frame dragging effects that occur when the black hole spin axis is misaligned with the orbital plane of its companion star. Recently, theoretical simulations have suggested that the jets can exert an additional torque on the accretion flow, although the full interplay between the dynamics of the accretion flow and the launching of the jets is not yet understood. Here we report a rapidly changing jet orientation on a timescale of minutes to hours in the black hole X-ray binary V404 Cygni, detected with very long baseline interferometry during the peak of its 2015 outburst. We show that this can be modelled as Lense-Thirring precession of a vertically-extended slim disk that arises from the super-Eddington accretion rate. Our findings suggest that the dynamics of the precessing inner accretion disk could play a role in either directly launching or redirecting the jets within the inner few hundred gravitational radii. Similar dynamics should be expected in any strongly-accreting black hole whose spin is misaligned with the inflowing gas, both affecting the observational characteristics of the jets, and distributing the black hole feedback more uniformly over the surrounding environment.

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arXiv2019

ALMA observations of A0620-00: fresh clues on the nature of quiescent black hole X-ray binary jets

We report on ALMA continuum observations of the black hole X-ray binary A0620-00, at an X-ray luminosity nine orders of magnitude sub-Eddington. The system was significantly detected at 98 GHz (at $44 \pm 7~μ{\rm Jy}$) and only marginally at 233 GHz ($20 \pm 8~μ{\rm Jy}$), about 40 days later. These results suggest either an optically thin sub-mm synchrotron spectrum, or highly variable sub-mm jet emission on month timescales. Although the latter appears more likely, we note that, at the time of the ALMA observations, A0620-00 was in a somewhat less active optical-IR state than during all published multi-wavelength campaigns when a flat-spectrum, partially self-absorbed jet has been suggested to extend from the radio to the mid-IR regime. Either interpretation is viable in the context of an internal shock model, where the jet's spectral shape and variability are set by the power density spectrum of the shells' Lorentz factor fluctuations. While strictly simultaneous radio-mm-IR observations are necessary to draw definitive conclusions for A0620-00, the data presented here, in combination with recent radio and sub-mm results from higher luminosity systems, demonstrate that jets from black hole X-ray binaries exhibit a high level of variability - either in flux density or intrinsic spectral shape, or both - across a wide spectrum of Eddington ratios. This is not in contrast with expectations from an internal shock model, where lower jet power systems can be expected to exhibit larger fractional variability owing to an overall decrease in synchrotron absorption.

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arXiv2019

Astro2020 Science White Paper: Compact Stellar Jets

This paper outlines the importance of understanding jets from compact binaries for the problem of understanding the broader phenomenology of jet production. Because X-ray binaries are nearby and bright, have well-measured system parameters, and vary by factors of $\sim 10^6$ on $\sim$ year timescales, they provide a unique opportunity to understand how various aspects of the jet physics change in response to changes in the accretion flow, giving the possibility of looking for trends within individual systems and testing their universality with other systems, rather than trying to interpret large samples of objects on a statistical basis.

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arXiv2018

Science with an ngVLA: Accretion and Jets in Local Compact Objects

Despite the prevalence of jets in accreting systems and their impact on the surrounding medium, the fundamental physics of how they are launched and collimated is not fully understood. Radio observations of local compact objects, including accreting stellar mass black holes, neutron stars and white dwarfs, probe their jet emission. Coupled with multi-wavelength observations, this allows us to test the underlying accretion-outflow connection and to establish the relationship between the accretor properties and the jet power, which is necessary to accurately model jets. Compact accretors are nearby, numerous and come in a range of accretor properties, and hence are ideal probes for the underlying jet physics. Despite this there are a number of key outstanding questions regarding accretion-driven outflows in these objects that cannot be answered with current radio observations. The vastly improved sensitivity, polarization capabilities, spatial resolution and high-frequency coverage of the ngVLA will be crucial to answering these, and subsequently determining the fundamental physics behind accretion and jets at all physical scales.

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arXiv2018

A multi-wavelength view of the neutron star binary 1FGL J1417.7--4402: A progenitor to canonical millisecond pulsars

The Fermi $γ$-ray source 1FGL J1417.7--4407 (J1417) is a compact X-ray binary with a neutron star primary and a red giant companion in a $\sim$5.4 day orbit. This initial conclusion, based on optical and X-ray data, was confirmed when a 2.66 ms radio pulsar was found at the same location (and with the same orbital properties) as the optical/X-ray source. However, these initial studies found conflicting evidence about the accretion state and other properties of the binary. We present new optical, radio, and X-ray observations of J1417 that allow us to better understand this unusual system. We show that one of the main pieces of evidence previously put forward for an accretion disk---the complex morphology of the persistent H$α$ emission line---can be better explained by the presence of a strong, magnetically driven stellar wind from the secondary and its interaction with the pulsar wind. The radio spectral index derived from VLA/ATCA observations is broadly consistent with that expected from a millisecond pulsar, further disfavoring an accretion disk scenario. X-ray observations show evidence for a double-peaked orbital light curve, similar to that observed in some redback millisecond pulsar binaries and likely due to an intrabinary shock. Refined optical light curve fitting gives a distance of 3.1$\pm$0.6 kpc, confirmed by a Gaia DR2 parallax measurement. At this distance the X-ray luminosity of J1417 is (1.0$^{+0.4}_{-0.3}$) $\times 10^{33}$ erg s$^{-1}$, which is more luminous than all known redback systems in the rotational-powered pulsar state, perhaps due to the wind from the giant companion. The unusual phenomenology of this system and its differing evolutionary path from redback millisecond pulsar binaries points to a new eclipsing pulsar "spider" subclass that is a possible progenitor of normal field millisecond pulsar binaries.

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arXiv2018

The MAVERIC survey: A transitional millisecond pulsar candidate in Terzan 5

Transitional millisecond pulsars are accreting millisecond pulsars that switch between accreting X-ray binary and millisecond radio pulsar states. Only a handful of these objects have been identified so far. Terzan 5 CX1 is a variable hard X-ray source in the globular cluster Terzan 5. In this paper, we identify a radio counterpart to CX1 in deep Very Large Array radio continuum data. Chandra observations over the last fourteen years indicate that CX1 shows two brightness states: in 2003 and 2016 the source was the brightest X-ray source in the cluster (at L$_X \sim 10^{33}$ erg s$^{-1}$), while in many intermediate observations, its luminosity was almost an order of magnitude lower. We analyze all available X-ray data of CX1, showing that the two states are consistent with the spectral and variability properties observed for the X-ray active and radio pulsar states of known transitional millisecond pulsars. Finally, we discuss the prospects for the detection of CX1 as a radio pulsar in existing timing data.

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arXiv2018

The geometric distance and binary orbit of PSR B1259-63

The pulsar/massive star binary system PSR B1259-63 / LS 2883 is one of the best-studied gamma-ray binaries, a class of systems whose bright gamma-ray flaring can provide important insights into high-energy physics. Using the Australian Long Baseline Array we have conducted very long baseline interferometric observations of PSR B1259-63 over 4.4 years, fully sampling the 3.4-year orbital period. From our measured parallax of $0.38\pm0.05$ mas we use a Bayesian approach to infer a distance of $2.6^{+0.4}_{-0.3}$ kpc. We find that the binary orbit is viewed at an angle of $154\pm3$ degrees to the line of sight, implying that the pulsar moves clockwise around its orbit as viewed on the sky. Taking our findings together with previous results from pulsar timing observations, all seven orbital elements for the system are now fully determined. We use our measurement of the inclination angle to constrain the mass of the stellar companion to lie in the range 15-31$M_{\odot}$. Our measured distance and proper motion are consistent with the system having originated in the Cen OB1 association and receiving a modest natal kick, causing it to have moved $\sim$8 pc from its birthplace over the past $\sim3\times10^5$ years. The orientation of the orbit on the plane of the sky matches the direction of motion of the X-ray synchrotron-emitting knot observed by the Chandra X-ray Observatory to be moving away from the system.

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arXiv2018

The MAVERIC Survey: Still No Evidence for Accreting Intermediate-mass Black Holes in Globular Clusters

We present the results of an ultra-deep, comprehensive radio continuum survey for the accretion signatures of intermediate-mass black holes in globular clusters. The sample, imaged with the Karl G.~Jansky Very Large Array and the Australia Telescope Compact Array, comprises 50 Galactic globular clusters. No compelling evidence for an intermediate-mass black hole is found in any cluster in our sample. In order to achieve the highest sensitivity to low-level emission, we also present the results of an overall stack of our sample, as well as various subsamples, also finding non-detections. These results strengthen the idea that intermediate-mass black holes with masses $\gtrsim 1000 M_{\odot}$ are rare or absent in globular clusters.

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arXiv2018

The Maveric Survey: a Red Straggler Binary with an Invisible Companion in the Galactic Globular Cluster M10

We present the discovery and characterization of a radio-bright binary in the Galactic globular cluster M10. First identified in deep radio continuum data from the Karl G. Jansky Very Large Array, M10-VLA1 has a flux density of $27\pm4$ $μ$Jy at 7.4 GHz and a flat to inverted radio spectrum. Chandra imaging shows an X-ray source with $L_X \approx 10^{31}$ erg s$^{-1}$ matching the location of the radio source. This places M10-VLA1 within the scatter of the radio--X-ray luminosity correlation for quiescent stellar-mass black holes, and a black hole X-ray binary is a viable explanation for this system. The radio and X-ray properties of the source disfavor, though do not rule out, identification as an accreting neutron star or white dwarf system. Optical imaging from the Hubble Space Telescope and spectroscopy from the SOAR telescope show the system has an orbital period of 3.339 d and an unusual "red straggler" component: an evolved star found redward of M10's red giant branch. These data also show UV/optical variability and double-peaked H$α$ emission characteristic of an accretion disk. However, SOAR spectroscopic monitoring reveals that the velocity semi-amplitude of the red straggler is low. We conclude that M10-VLA1 is most likely either a quiescent black hole X-ray binary with a rather face-on ($ i < $ 4$^{\circ}$) orientation or an unusual flaring RS CVn-type active binary, and discuss future observations that could distinguish between these possibilities.

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arXiv2017

Multiwavelength observations of the black hole X-ray binary A0620-00 in quiescence

We present results from simultaneous multiwavelength X-ray, radio, and optical/near-infrared observations of the quiescent black hole X-ray binary A0620-00 performed in 2013 December. We find that the Chandra flux has brightened by a factor of 2 since 2005, and by a factor of 7 since 2000. The spectrum has not changed significantly over this time, being consistent with a power law of $Γ= 2.07\pm 0.13$ and a hydrogen column of $N_H=3.0 \pm 0.5\times 10^{21}\rm{cm}^{-2}$. Very Large Array observations of A0620-00 at three frequencies, over the interval of 5.25--22.0 GHz, have provided us with the first broadband radio spectrum of a quiescent stellar mass black hole system at X-ray luminosities as low as $10^{-8}$ times the Eddington luminosity. Compared to previous observations, the source has moved to lower radio and higher X-ray luminosity, shifting it perpendicular to the standard track of the radio/X-ray correlation for X-ray binaries. The radio spectrum is inverted with a spectral index $α= 0.74 \pm 0.19$ ($S_ν \propto ν^α$). This suggests that the peak of the spectral energy distribution is likely to be between $10^{12}$ and $10^{14}$ Hz, and that the near IR and optical flux contain significant contributions from the star, the accretion flow, and from the outflow. Decomposing these components may be difficult, but holds the promise of revealing the interplay between accretion and jet in low luminosity systems.

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arXiv2017

Simultaneous Chandra and VLA Observations of the Transitional Millisecond Pulsar PSR J1023+0038: Anti-correlated X-ray and Radio Variability

We present coordinated Chandra X-ray Observatory and Karl G. Jansky Very Large Array observations of the transitional millisecond pulsar PSR J1023+0038 in its low-luminosity accreting state. The unprecedented five hours of strictly simultaneous X-ray and radio continuum coverage for the first time unambiguously show a highly reproducible, anti-correlated variability pattern. The characteristic switches from the X-ray high mode into a low mode are always accompanied by a radio brightening with duration that closely matches the X-ray low mode interval. This behavior cannot be explained by a canonical inflow/outflow accretion model where the radiated emission and the jet luminosity are powered by, and positively correlated with, the available accretion energy. We interpret this phenomenology as alternating episodes of low-level accretion onto the neutron star during the X-ray high mode that are interrupted by rapid ejections of plasma by the active rotation-powered pulsar, possibly initiated by a reconfiguration of the pulsar magnetosphere, that cause a transition to a less luminous X-ray mode. The observed anti-correlation between radio and X-ray luminosity has an additional consequence: transitional MSPs can make excursions into a region of the radio/X-ray luminosity plane previously thought to be occupied solely by black hole X-ray binary sources. This complicates the use of this luminosity relation to identify candidate black holes, suggesting the need for additional discriminants when attempting to establish the true nature of the accretor.

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arXiv2017

The Science Case for Simultaneous mm-Wavelength Receivers in Radio Astronomy

This review arose from the European Radio Astronomy Technical Forum (ERATec) meeting held in Firenze, October 2015, and aims to highlight the breadth and depth of the high-impact science that will be aided and assisted by the use of simultaneous mm-wavelength receivers. Recent results and opportunities are presented and discussed from the fields of: continuum VLBI (observations of weak sources, astrometry, observations of AGN cores in spectral index and Faraday rotation), spectral line VLBI (observations of evolved stars and massive star-forming regions) and time domain observations of the flux variations arising in the compact jets of X-ray binaries. Our survey brings together a large range of important science applications, which will greatly benefit from simultaneous observing at mm-wavelengths. Such facilities are essential to allow these applications to become more efficient, more sensitive and more scientifically robust. In some cases without simultaneous receivers the science goals are simply unachievable. Similar benefits would exist in many other high frequency astronomical fields of research.

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