X-ray Jet Research Articles

Superluminal Proper Motion in the X-Ray Jet of Centaurus A

The structure of the jet in Cen A is likely better revealed in X-rays than in the radio band, which is usually used to investigate jet proper motions. In this paper, we analyze Chandra Advanced CCD Imaging Spectrometer observations of Cen A from 2000 to 2022 and develop an algorithm for systematically fitting the proper motions of its X-ray jet knots. Most of the knots had an apparent proper motion below the detection limit. However, one knot at a transverse distance of 520 pc had an apparent superluminal proper motion of 2.7 ± 0.4c. This constrains the inclination of the jet to be i < 41° ± 6° and the velocity of this knot to be β > 0.94 ± 0.02. This agrees well with the inclination measured in the inner jet by the Event Horizon Telescope but contradicts previous estimates based on jet and counterjet brightness. It also disagrees with the proper motion of the corresponding radio knot, of 0.8 ± 0.1c, which further indicates that the X-ray and radio bands trace distinct structures in the jet. There are four prominent X-ray jet knots closer to the nucleus, but only one of these is inconsistent with being stationary. A few jet knots also have a significant proper-motion component in the nonradial direction. This component is typically larger closer to the center of the jet. We also detect brightness and morphology variations at a transverse distance of 100 pc from the nucleus.

Minimalist model of the W50/SS433 extended X-ray jet: Anisotropic wind with recollimation shocks

W50 is a radio nebula around the hyperaccreting Galactic microquasar SS433. We focus on one peculiar feature of W50, that is, on a pair of so-called extended X-ray jets (EXJs). These jets have a size of ∼20 pc and a sharp inner boundary, and their spectra are well represented by a featureless X-ray continuum. We argue that EXJs could be an outcome of a powerful anisotropic wind produced by a supercritical accretion disk. In the simplest version of this model, the wind itself consists of two components. The first component is a nearly isotropic outflow that subtends most of the solid angle as seen from the compact source and creates the quasi-spherical part of the W50 nebula. The second component is a more collimated wind that is aligned with the rotation axis of the binary system (polar wind). The isotropic outflow passes through the termination shock, and its increased thermal pressure creates a sequence of recollimation shocks in the polar wind, giving it the appearance of an extended X-ray structure. In this model, the EXJ continuum spectrum is due to synchrotron emission of electrons that are accelerated at the shocks that arise in the polar wind. At variance with many other studies, the EXJ structures in this model are not directly related to the highly collimated and precessing 0.26 c baryonic jets. Instead, the EXJ and the ears of W50 are produced by the part of the wind whose Eddington-level kinetic luminosity is confined to a half-opening angle of 5–10 degrees. This is not necessarily a recollimated version of the 0.26 c jets.

Chandra Study of the Proper Motion of HST-1 in the Jet of M87

The radio galaxy M87 is well known for its jet, which features a series of bright knots observable from radio to X-ray wavelengths. We analyze the X-ray image and flux variability of the knot HST-1 in the jet. Our analysis includes all 112 available Chandra ACIS-S observations from 2000 to 2021, with a total exposure time of ∼884 ks. We use deconvolved images to study the brightness profile of the X-ray jet and measure the relative separation between the core and HST-1. From 2003 to 2005 (which coincides with a bright flare from HST-1), we find a correlation between the flux of HST-1 and its offset from the core. In subsequent data, we find a steady increase in this offset, which implies a bulk superluminal motion for HST-1 of 6.6 ± 0.9 c (2.0 ± 0.3 pc yr−1), in keeping with prior results. We discuss models for the flux–offset correlation that feature either two or four emission regions separated by tens of parsecs. We attribute these results to moving shocks in the jet, which allow us to measure the internal structure of the jet.

The On-axis Jetted Tidal Disruption Event AT2022cmc: X-Ray Observations and Broadband Spectral Modeling

AT2022cmc was recently reported as the first on-axis jetted tidal disruption event (TDE) discovered in the last decade, and the fourth on-axis jetted TDE candidate known so far. In this work, we present NuSTAR hard X-ray (3–30 keV) observations of AT2022cmc, as well as soft X-ray (0.3–6 keV) observations obtained by NICER, Swift, and XMM-Newton. Our analysis reveals that the broadband X-ray spectra can be well described by a broken power law with f ν ∝ ν −0.5 (f ν ∝ ν −1) below (above) the rest-frame break energy of E bk ∼ 10 keV at the observer frame t obs = 7.8 and 17.6 days since discovery. At t obs = 36.2 days, the X-ray spectrum is consistent with either a single power law or a broken power law. By modeling the spectral energy distribution from radio to hard X-ray across the three NuSTAR observing epochs, we find that the submillimeter/radio emission originates from external shocks at large distances ≳1017 cm from the black hole, the UV/optical light comes from a thermal envelope with radius ∼1015 cm, and the X-ray emission is consistent with synchrotron radiation powered by energy dissipation at intermediate radii within the (likely magnetically dominated) jet. We constrain the bulk Lorentz factor of the jet to be of the order 10–100. Our interpretation differs from the model proposed by Pasham et al. where both the radio and X-rays come from the same emitting zone in a matter-dominated jet. Our model for the jet X-ray emission has broad implications on the nature of relativistic jets in other sources such as gamma-ray bursts.

Revisiting a Core–Jet Laboratory at High Redshift: Analysis of the Radio Jet in the Quasar PKS 2215+020 at z = 3.572

The prominent radio quasar PKS 2215+020 (J2217+0220) was once labelled as a new laboratory for core–jet physics at redshift z=3.572 because of its exceptionally extended jet structure traceable with very long baseline interferometric (VLBI) observations up to a ∼600 pc projected distance from the compact core and a hint of an arcsec-scale radio and an X-ray jet. While the presence of an X-ray jet could not be confirmed later, this active galactic nucleus is still unique at high redshift with its long VLBI jet. Here, we analyse archival multi-epoch VLBI imaging data at five frequency bands from 1.7 to 15.4 GHz covering a period of more than 25 years from 1995 to 2020. We constrain apparent proper motions of jet components in PKS 2215+020 for the first time. Brightness distribution modeling at 8 GHz reveals a nearly 0.02 mas yr−1 proper motion (moderately superluminal with apparently two times the speed of light), and provides δ=11.5 for the Doppler-boosting factor in the inner relativistic jet that is inclined within 2∘ to the line of sight and has a Γ=6 bulk Lorentz factor. These values qualify PKS 2215+020 as a blazar, with rather typical jet properties in a small sample of only about 20 objects at z&gt;3.5 that have similar measurements to date. According to the 2-GHz VLBI data, the diffuse and extended outer emission feature at ∼60 mas from the core, probably a place where the jet interacts with and decelerated by the ambient galactic medium, is consistent with being stationary, albeit slow motion cannot be excluded based on the presently available data.

The extremely X-ray luminous radio-loud quasar CFHQS J142952 + 544717 at z = 6.18 under Chandra high-angular resolution lens

ABSTRACT We present the first X-ray observation at sub-arcsecond resolution of the high-redshift (z = 6.18) radio-loud quasar CFHQS J142952 + 544717 (J1429). The ∼100 net-count 0.3–7 keV spectrum obtained from ∼30 ks Chandra exposure is best fit by a single power-law model with a photon index Γ = 2.0 ± 0.2 and no indication of an intrinsic absorber, implying a 3.6–72 keV rest-frame luminosity $L_{\rm X}=(2.3^{+0.6}_{-0.5})\times 10^{46}$ erg s−1. We identify a second X-ray source at 30″ distance from J1429 position, with a soft (Γ ≃ 2.8) and absorbed (equivalent hydrogen column density NH &amp;lt; 13.4 × 1020 cm−2) spectrum, which likely contaminated J1429 spectra obtained in lower angular resolution observations. Based on the analysis of the Chandra image, the bulk of the X-ray luminosity is produced within the central ∼3 kpc region, either by the disc/corona system, or by a moderately aligned jet. In this context, we discuss the source properties in comparison with samples of low- and high-redshift quasars. We find indication of a possible excess of counts over the expectations for a point-like source in a 0.5″–1.5″ (∼3−8 kpc) annular region. The corresponding X-ray luminosity at J1429 redshift is 4 × 1045 erg s−1. If confirmed, this emission could be related to either a large-scale X-ray jet, or a separate X-ray source.

Multithermal Jet Formation Triggered by Flux Emergence

Flux emergence is responsible for various solar eruptions. Combining observation and simulations, we investigate the influence of flux emergence at one footpoint of an arcade on coronal rain as well as induced eruptions. The emergence changes the pressure in the loops, and the internal coronal rain all moves to the other side. The emerging flux reconnects with the overlying magnetic field, forming a current sheet and magnetic islands. The plasma is ejected outwards and heated, forming a cool jet ∼6000 K and a hot X-ray jet ∼4 million Kelvin (MK) simultaneously. The jet dynamical properties agree very well between observation and simulation. In the simulation, the jet also displays transverse oscillations with a period of 8 minutes, in a so-called whiplike motion. The movement of the jet and dense plasmoids changes the configuration of the local magnetic field, facilitating the occurrence of the Kelvin–Helmholtz instability, and vortex-like structures form at the boundary of the jet. Our simulation clearly demonstrates the effect of emergence on coronal rain, the dynamical details of reconnecting plasmoid chains, the formation of multithermal jets, and the cycling of cool mass between the chromosphere and the corona.

Offsets between X-Ray and Radio Components in X-Ray Jets: The AtlasX

The X-ray emission mechanism of powerful extragalactic jets—which has important implications for their environmental impacts—is poorly understood. The X-ray/radio positional offsets in the individual features of jets provide important clues. Extending previous work in Reddy et al., we present a detailed comparison between X-ray maps, deconvolved using the Low-count Image Reconstruction and Analysis tool, and radio maps of 164 components from 77 Chandra-detected X-ray jets. We detect 94 offsets (57%), with 58 new detections. In FR II–type jet knots, the X-rays peak and decay before the radio in about half the cases, disagreeing with the predictions of one-zone models. While a similar number of knots lack statistically significant offsets, we argue that projection and distance effects result in offsets below the detection level. Similar deprojected offsets imply that X-rays could be more compact than radio for most knots, and we qualitatively reproduce this finding with a “moving-knot” model. The bulk Lorentz factor (Γ) derived for knots under this model is consistent with previous radio-based estimates, suggesting that kiloparsec-scale jets are only mildly relativistic. An analysis of the X-ray/radio flux ratio distributions does not support the commonly invoked mechanism of X-ray production from inverse Compton scattering of the cosmic microwave background, but does show a marginally significant trend of declining flux ratio as a function of the distance from the core. Our results imply the need for multi-zone models to explain the X-ray emission from powerful jets. We provide an interactive list of our X-ray jet sample at http://astro.umbc.edu/Atlas-X.

Advancements in Liquid Jet Technology and X-ray Spectroscopy for Understanding Energy Conversion Materials during Operation.

ConspectusWater splitting is intensively studied for sustainable and effective energy storage in green/alternative energy harvesting-storage-release cycles. In this work, we present our recent developments for combining liquid jet microtechnology with different types of soft X-ray spectroscopy at high-flux X-ray sources, in particular developed for studying the oxygen evolution reaction (OER). We are particularly interested in the development of in situ photon-in/photon-out techniques, such as in situ resonant inelastic X-ray scattering (RIXS) techniques at high-repetition-frequency X-ray sources, pointing toward operando capabilities. The pilot catalytic systems we use are perovskites having the general structure ABO3 with lanthanides or group II elements at the A sites and transition metals at the B sites. Depending on the chemical substitutions of ABO3, their catalytic activity for OER can be tuned by varying the composition.In this work, we present our in situ RIXS studies of the manganese L-edge of perovskites during OER. We have developed various X-ray spectroscopy approaches like transmission zone plate-, reflection zone plate-, and grating-based emission spectroscopy techniques. Combined with tunable incident X-ray energies, we yield complementary information about changing (inverse) X-ray absorption features of the perovskites, allowing us to deduce element- and oxidation-state-specific chemical monitoring of the catalyst. Adding liquid jet technology, we monitor element- and oxidation-state-specific interactions of the catalyst with water adsorbate during OER. By comparing the different technical spectroscopy approaches combined with high-repetition-frequency experiments at synchrotrons and free-electron lasers, we conclude that the combination of liquid jet with low-resolution zone-plate-based X-ray spectroscopy is sufficient for element- and oxidation-state-specific chemical monitoring during OER and easy to handle.For an in-depth study of OER mechanisms, however, including the characterization of catalyst-water adsorbate in terms of their charge transfer properties and especially valence intermediates formed during OER, high-resolution spectroscopy tools based on a combination of liquid jets with gratings bear bigger potential since they allow resolution of otherwise-overlapping X-ray spectroscopy transitions. Common for all of these experimental approaches is the conclusion that without the versatile developments of liquid jets and liquid beam technologies, elaborate experiments such as high-repetition experiments at high-flux X-ray sources (like synchrotrons or free-electron lasers) would hardly be possible. Such experiments allow sample refreshment for every single X-ray shot for repetition frequencies of up to 5 MHz, so that it is possible (a) to study X-ray-radiation-sensitive samples and also (b) to utilize novel types of flux-hungry X-ray spectroscopy tools like photon-in/photon-out X-ray spectroscopy to study the OER.

Inconspicuous Solar Polar Coronal X-Ray Jets as the Source of Conspicuous Hinode/EUV Imaging Spectrometer Doppler Outflows

We examine in greater detail five events previously identified as being sources of strong transient coronal outflows in a solar polar region in Hinode/Extreme Ultraviolet (EUV) Imaging Spectrometer (EIS) Doppler data. Although relatively compact or faint and inconspicuous in Hinode/X-ray Telescope (XRT) soft-X-ray (SXR) images and in Solar Dynamics Observatory (SDO)/Atmospheric Imaging Assembly (AIA) EUV images, we find that all of these events are consistent with being faint coronal X-ray jets. The evidence for this is that the events result from eruption of minifilaments of projected sizes spanning 5000–14,000 km and with erupting velocities spanning 19–46 km s−1, which are in the range of values observed in cases of confirmed X-ray polar coronal hole jets. In SXR images, and in some EUV images, all five events show base brightenings, and faint indications of a jet spire that (in four of five cases where determinable) moves away from the brightest base brightening; these properties are common to more obvious X-ray jets. For a comparatively low-latitude event, the minifilament erupts from near (≲few arcsec) a location of near-eruption-time opposite-polarity magnetic-flux-patch convergence, which again is consistent with many observed coronal jets. Thus, although too faint to be identified as jets a priori, otherwise all five events are identical to typical coronal jets. This suggests that jets may be more numerous than recognized in previous studies, and might contribute substantially to solar wind outflow, and to the population of magnetic switchbacks observed in Parker Solar Probe (PSP) data.

A multiwavelength study of multiple spectral component jets in AGN: testing the IC/CMB model for the large-scale-jet X-ray emission

ABSTRACT Over ∼150 resolved, kpc-scale X-ray jets hosted by active galactic nuclei have been discovered with the Chandra X-ray Observatory. A significant fraction of these jets have an X-ray spectrum either too high in flux or too hard to be consistent with the high-energy extension of the radio-to-optical synchrotron spectrum, a subtype we identify as Multiple Spectral Component (MSC) X-ray jets. A leading hypothesis for the origin of the X-rays is the inverse-Compton scattering of the cosmic microwave background by the same electron population producing the radio-to-optical synchrotron spectrum (known as the IC/CMB model). In this work, we test the IC/CMB model in 45 extragalactic X-ray jets using observations from the Fermi Large Area Telescope to look for the expected high level of gamma-ray emission, utilizing observations from the Atacama Large Millimeter/submillimeter Array (ALMA) and the Hubble Space Telescope (HST) when possible to best constrain the predicted gamma-ray flux. Including this and previous works, we now find the IC/CMB model to be ruled out in a total of 24/45 MSC X-ray jets due to its over-prediction for the observed MeV-to-GeV gamma-ray flux. We present additional evidence against the IC/CMB model, including the relative X-ray-to-radio relativistic beaming in these sources, and the general mismatch between radio and X-ray spectral indexes. Finally, we present upper limits on the large-scale bulk-flow Lorentz factors for all jets based on the Fermi upper limits, which suggest that these jets are at most mildly relativistic.

Investigating the Origin of X-Ray Jets: A Case Study of Four Hybrid Morphology MOJAVE Blazars

We carried out Chandra, Hubble Space Telescope (HST), and Very Large Array observations of four MOJAVE blazars that have previously been classified as hybrid (FR I/II) blazars in terms of radio morphology but not total radio power. The motivation of this study is to determine the X-ray emission mechanism in jets, these being different in FR I and FR II jets. We detected X-ray jet emission with sufficient signal to noise in two blazars, viz. PKS 0215+015 and TXS 0730+504. We carried out spectral energy distribution modeling of the broadband emission from the jet regions in these sources and found that a single synchrotron emission model is ruled out due to the deep upper limits obtained from HST optical and IR data. The inverse Compton-cosmic microwave background model can reproduce the X-ray jet emission in both sources although the model requires extreme jet parameters. Both our sources possess FR II-like radio powers and our results are consistent with previous studies suggesting that radio power is more important than FR morphology in determining the emission mechanism of X-ray jets.

X-Ray Jets in the High-redshift Quasars J1405+0415 and J1610+1811

We investigate Chandra X-ray observations of the radio-loud quasars J1405+0415 and J1610+1811 at redshifts z = 3.215 and z = 3.122, respectively, for evidence of extended X-ray emission. Observations totalling 95 ks per target are combined, and X-ray jets that are spatially coincident with known radio features are detected at a greater than 4σ significance. Hardness ratios and emission spectra are determined for all X-ray features, and X-ray fluxes and luminosities are measured. Jet-to-core X-ray flux ratios are estimated for each system, and the ratios are consistent with those observed for nearby and more distant jet systems, although the spread in the parameter is large. These results suggest that to first order the X-ray jet emission mechanisms are redshift invariant. In addition to the extended emission analysis, incorporating also archival data from Swift, we examined the properties of a decline in the Chandra flux from the active galactic nucleus (AGN) of J1610+1811 observed between 2018 and 2021. We conclude that the variability is most likely due to a flaring event that occurred between the years 2017 and 2018 and originated from either the AGN or the inner jet region.

The Forward and Reverse Shock Dynamics of Cassiopeia A

Abstract We report on proper motion measurements of the forward- and reverse shock regions of the supernova remnant Cassiopeia A (Cas A), including deceleration/acceleration measurements of the forward shock. The measurements combine 19 yr of observations with the Chandra X-ray Observatory, using the 4.2–6 keV continuum band, preferentially targeting X-ray synchrotron radiation. The average expansion rate is 0.218 ± 0.029% yr−1 for the forward shock, corresponding to a velocity of ≈5800 km s−1. The time derivative of the proper motions indicates deceleration in the east, and an acceleration up to 1.1 × 10−4 yr−2 in the western part. The reverse shock moves outward in the east, but in the west it moves toward the center with an expansion rate of −0.0225 ± 0.0007 % yr−1, corresponding to −1884 ± 17 km s−1. In the west, the reverse shock velocity in the ejecta frame is ≳3000 km s−1, peaking at ∼8000 km s−1, explaining the presence of X-ray synchrotron emitting filaments there. The backward motion of the reverse shock can be explained by either a scenario in which the forward shock encountered a partial, dense, wind shell, or one in which the shock transgressed initially through a lopsided cavity, created during a brief Wolf–Rayet star phase. Both scenarios are consistent with the local acceleration of the forward shock. Finally we report on the proper motion of the northeastern jet, using both the X-ray continuum band, and the Si xiii K-line emission band. We find expansion rates of, respectively, 0.21% and 0.24% yr−1, corresponding to velocities at the tip of the X-ray jet of 7830–9200 km s−1.

Further Evidence for the Minifilament-eruption Scenario for Solar Polar Coronal Jets

Abstract We examine a sampling of 23 polar-coronal-hole jets. We first identified the jets in soft X-ray (SXR) images from the X-ray telescope (XRT) on the Hinode spacecraft, over 2014–2016. During this period, frequently the polar holes were small or largely obscured by foreground coronal haze, often making jets difficult to see. We selected 23 jets among those adequately visible during this period, and examined them further using Solar Dynamics Observatory’s (SDO) Atmospheric Imaging Assembly (AIA) 171, 193, 211, and 304 Å images. In SXRs, we track the lateral drift of the jet spire relative to the jet base’s jet bright point (JBP). In 22 of 23 jets, the spire either moves away from (18 cases) or is stationary relative to (4 cases) the JBP. The one exception where the spire moved toward the JBP may be a consequence of line-of-sight projection effects at the limb. From the AIA images, we clearly identify an erupting minifilament in 20 of the 23 jets, while the remainder are consistent with such an eruption having taken place. We also confirm that some jets can trigger the onset of nearby “sympathetic” jets, likely because eruption of the minifilament field of the first jet removes magnetic constraints on the base-field region of the second jet. The propensity for spire drift away from the JBP, the identification of the erupting minifilament in the majority of jets, and the magnetic-field topological changes that lead to sympathetic jets, all support or are consistent with the minifilament-eruption model for jets.

Direct observation of an extended X-ray jet at z = 6.1

We report on the direct observation of an extended X-ray jet in the z = 6.1 radio-loud active galactic nucleus PSO J030947.49+271757.31 from a deep Chandra X-ray observation (128 ksec). This detection represents the most distant kiloparsec-scale off-nuclear emission resolved in X-rays to date. The angular distance of the emission is ∼4″ (corresponding to ∼20 kpc at z = 6.1), along the same direction of the jet observed at parsec scales in previous VLBA high-resolution radio observations. Moreover, the 0.5–7.0 keV isophotes coincide with the extended radio emission as imaged by the VLA Sky Survey at 3 GHz. The rest-frame 2–10 keV luminosity of the extended component is L2 − 10 keV = 5.9 × 1044 erg s−1, about 8% of the core: this makes it one of the most luminous jets resolved in X-rays so far. Through spectral energy distribution modelling we find that this emission can be explained by the inverse Compton interaction with the photons of the cosmic microwave background, assuming that the jet’s physical parameters are similar to those in the local Universe. At the same time, we find that the radiation produced by a putative population of high-energy electrons through the synchrotron process observed at low redshift is quenched at high redshift, hence becoming negligible.

Discovery of a bright extended X-ray jet in RGB J1512+020A

ABSTRACTWe report the discovery of a bright, extended X-ray jet in the quasar RGB J1512+020A (z = 0.22). Chandra observations show the X-ray core and 13 arcsec (∼45 kpc projected) extended emission coincident with the radio jet. The jet stands out as one of brightest X-ray jets (LX ∼ 7 × 1043 erg s−1) at low redshift (z &amp;lt; 0.5) discovered so far, with remarkably large X-ray to radio luminosity ratios (LX/Lr up to ∼50). We identified four main components, two unresolved knots and two extended structures, one being the jet brightest feature (JBF). All jet features are also detected in ALMA archival observations. The radio, sub-mm to X-ray spectra of the two knots can be modelled with a single synchrotron component. For the two resolved structures, the ALMA data unveil a turnover of the low-energy continuum at ∼460 GHz. External Comptonization of cosmic microwave background photons can account for the observed X-ray emission if the jet speed remains highly relativistic, with bulk motion Γbulk &amp;gt; 15, up to tens of kiloparsec from the core. However, the comparison with the spectral energy distribution of similar X-ray detected jets shows that the alternative hypothesis of synchrotron emission from an additional population of ultra-high-energy electrons is also possible. We report a tentative (≳2σ) optical detection of the JBF in images of the Dark Energy Camera Legacy Survey. If confirmed, the optical emission should be either the low-energy tail of the radiative component responsible for the X-ray emission or a third, separate component.

Discovery of stable titanium at the northeastern jet of Cassiopeia A: Need for a weak jet mechanism?

Abstract The origin of the jet-like structures observed in Cassiopeia A is still unclear, although it seems to be related to its explosion mechanism. X-ray observations of the characteristic structures could provide us useful information on the explosive nucleosynthesis via the observation of elements, which is a unique approach to understand its origin. We here report the discovery of shocked stable Ti, which is produced only at the inner region of exploding stars, in the northeast jet of Cassiopeia A using the 1 Ms deep observation with the Chandra X-ray observatory. The observed Ti coexists with other intermediate-mass elements (e.g., Si, S, Ar, Ca) and Fe at the tip of the X-ray jet structure. We found that its elemental composition is explained well with the production by the incomplete Si burning regime, indicating that the formation process of the jet structure was sub-energetic at the explosion (the peak temperature during the nuclear burning must be ≲5 × 109 K at most). Thus, we conclude that the energy source that formed the jet structure was not the primary engine for the supernova explosion. Our results are useful to limit the power of the jet-structure formation process, and a weak jet mechanism with low temperature may be needed to explain it.

State-of-the-art energetic and morphological modelling of the launching site of the M87 jet

M87 has been the target of numerous astronomical observations across the electromagnetic spectrum, and very long baseline interferometry has resolved an edge-brightened jet1–4. However, the origin and formation of its jets remain unclear. In our current understanding, black holes (BH) are the driving engine of jet formation5, and indeed the recent Event Horizon Telescope observations revealed a ring-like structure in agreement with theoretical models of accretion onto a rotating Kerr BH6. In addition to the spin of the BH being a potential source of energy for the launching mechanism, magnetic fields are believed to play a key role in the formation of relativistic jets7,8. A priori, the spin, a⋆, of the BH in M87⋆ is unknown; however, when accounting for the estimates of the X-ray luminosity and jet power, values of $$\left|{a}_{\star }\right|\gtrsim 0.5$$ appear favoured6. Besides the properties of the accretion flow and the BH spin, the radiation microphysics including the particle distribution (thermal6 and non-thermal9,10) as well as the particle acceleration mechanism11 play a crucial role. We show that general relativistic magnetohydrodynamic simulations and general relativistic radiative transfer calculations can reproduce the broadband spectrum from the radio to the near-infrared regime and simultaneously match the observed collimation profile of M87, thus allowing us to set rough constraints on the dimensionless spin of M87* to be 0.5 ≲ a⋆ ≲ 1.0, with higher spins being possibly favoured. General relativistic magnetohydrodynamic simulations with general relativistic radiative transfer reproduce remarkably well the broadband spectrum and morphology of the innermost jet of M87, allowing some first rough constraints on the spin of M87*.

Relation of Microstreams in the Polar Solar Wind to Switchbacks and Coronal X-Ray Jets

Abstract Ulysses data obtained at high solar latitudes during periods of minimum solar activity in 1994 and 2007 are examined to determine the relation between velocity structures called microstreams and folds in the magnetic field called switchbacks. A high correlation is found. The possibility of velocity peaks in microstreams originating from coronal X-ray jets is reexamined; we now suggest that microstreams are the consequence of the alternation of patches of switchbacks and quiet periods, where the switchbacks could be generated by minifilament/flux rope eruptions that cause coronal jets.