arXiv subjects

Benito Marcote

Publications and source records attributed to Benito Marcote.

At least 19 recordsLinked to original sources

arXiv2026

A Galactic microblazar as a potential accelerator of ultra-high-energy particles

Context. Persistent jets from X-ray binaries which are aligned very close to the line of sight could be considered to be Galactic equivalents of blazars, or 'microblazars'. They are also expected to power gamma-ray sources. Aims. We intend to assess a serious candidate apparently fulfilling many of the requirements to be considered a genuine member of this class: IRAS 18293-0941. Methods. An intense multi-wavelength observational and theoretical study has been carried out on our proposed candidate source. Results. With photometric and spectroscopic properties typical of a binary star, this system exhibits clear collimated and one-sided radio emission matching the effects of relativistic motion along a reduced ejection angle. Only fast variability is not observed possibly smoothed by a dense circumstellar envelope. A physical scenario is consistently modeled that also gives credibility to its likely connection with LHAASO J1831-1007u*, an ultra-high-energy source in its immediate vicinity. Conclusions. Our reported identification not only helps to fill a gap in Galactic taxonomy, but also potentially strengthens the role of the microblazar and microquasar families in our understanding of the most energetic Milky Way phenomena.

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arXiv2026

Transforming X-ray Binary Astrophysics with SKA+VLBI

X-ray binaries (XRBs) are unique laboratories where accretion, jets, strong gravity and magnetic fields can be probed on humanly tractable timescales. The phased SKA-Mid operating as a single, ultra-sensitive Very Long Baseline Interferometry (VLBI) element will transform radio studies of XRBs primarily through its time-domain capabilities: substantially improved sensitivity on VLBI baselines that include SKA-Mid in Bands 2 and 5, together with connected-element SKA-Mid imaging extending down to 0.35--1 GHz (Band 1), microarcsecond-precision astrometry for bright systems, high-fidelity polarimetry for the most strongly polarized sources, and rapid target-of-opportunity response. In synergy with global VLBI networks, SKA+VLBI will track the evolution of compact ejecta and compact jets on astronomical unit (AU) scales, measure frequency-dependent core shifts to infer magnetic field strengths and gradients, resolve disk--jet coupling during state transitions in real time, and determine precise distances and natal kicks via parallaxes and proper motions. Joint campaigns with future X-ray and optical telescopes will enable strictly simultaneous, multi-band constraints on accretion--ejection physics and on jet composition. We outline a quantitative program for \aastar\ and AA4, including cadenced, multi-frequency VLBI ``movies'' of jets over the first days of outbursts, an XRB astrometric census, and a core-shift survey, and we provide representative detection rates, magnetic field measurements and distance accuracies. These outcomes will set the microphysical foundation for jet physics across the mass scale from stellar-mass black holes and neutron stars to active galactic nuclei, and will establish SKA+VLBI as the definitive facility for time-domain, high-resolution XRB astrophysics.

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arXiv2026

Gamma-ray Bursts in the Radio Sky: the Role of the SKA-VLBI

Radio observations of $\gamma$-ray bursts (GRBs) employing the very long baseline interferometry (VLBI) technique provide us with fundamental information on the dynamics and the geometry of the GRB blast wave. With its high angular resolution ($\sim$milli-arcsecond), VLBI allows us to measure the apparent superluminal expansion, to characterise the structure of the jet and to constrain the viewing angle and jet opening angle. While this information is crucial to understand these transient events, such studies have been possible only for three GRBs to date, owing to both the poor sensitivity of current radio facilities and the paucity of close and bright GRBs. In this chapter, we estimate the impact that the SKA-Mid will have on these studies, when included in a VLBI network. We performed a series of dedicated simulations of VLBI observations of GRBs, considering five VLBI networks and the SKA-Mid, both in its AA* and AA4 configurations. We show that including the SKA-Mid in a global-VLBI experiment will: (i) allow us to measure the size and the expansion of a GRB up to a redshift $z\simeq 0.25$ (at a confidence level of $3\sigma$); (ii) constrain the size $\gtrsim$2 times better than the current global-VLBI array; (iii) improve the localisation precision in Declination from 4 to 30 times; (iv) detect the apparent proper motion of GRBs seen slightly off-axis with a confidence level 3 times better than current VLBI networks. Ultimately, the SKA-Mid will open a new window on a portion of the GRB population that has been inaccessible so far.

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arXiv2026

The Astrophysics of Fast Radio Bursts

Fast radio bursts (FRBs) provide a glimpse of high-energy astrophysical phenomena in other galaxies. They point the way to extreme conditions that are currently undetectable by any other known means. These coherent radio flashes have timescales of microseconds to milliseconds, and inferred energies that are comparable to those of the most extreme bursts seen from Galactic neutron stars. However, the nature of FRB sources remains an open question in astrophysics. Magnetically powered neutron stars known as `magnetars' are a leading candidate for explaining the FRB phenomenon, but other plausible progenitors include magnetically interacting neutron-star binaries or accreting black holes. The diversity of FRB burst types and their galactic environments hint that multiple mechanisms and progenitor types may be responsible. Here we discuss the ways in which the SKA can uncover the nature of FRBs. In particular, we focus on the key advantages of the SKA: its Southern Hemisphere location and hence overlapping sky coverage with the Vera C. Rubin Observatory, its high sensitivity compared to existing wide-field FRB surveys, its fast search timescales down to tens of $\mu$s, and its broad spectral coverage with bands from 50 MHz to 15 GHz. With these capabilities, the SKA will excel in detecting FRB sources across new frequency ranges and timescales. This will aid in a better understanding of the fundamental astrophysics behind FRBs, which will in turn also contribute to their use as cosmological probes, as explored in companion chapters.

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arXiv2026

Probing Physical Conditions in Classical and Symbiotic Novae with the Square Kilometre Array Observatory

Cataclysmic variables and symbiotic stars are interacting binary systems in which a hot white dwarf (WD) orbits a companion main-sequence or red giant star, respectively. Accumulation of hydrogen-rich material on the WD surface may trigger re-ignition of thermonuclear reactions that, under degenerate conditions, lead to an explosive ejection of the accreted layer mixed with WD material. These explosions, known as classical novae, provide opportunities to study key astrophysical processes such as binary evolution, accretion, ionisation of circumstellar material, mass ejection, jet formation, and thermonuclear burning. Radio emission in these systems arises from both thermal and non-thermal processes, which manifest differently in classical and symbiotic novae. $\gamma$-ray emission has also been detected in several cases, and recent progress, driven by coordinated radio and multiwavelength observations, has greatly advanced our understanding of both types of novae. Multi-frequency, multi-epoch, and multi-scale interferometric observations are powerful probes of the evolving physical conditions following thermonuclear explosions, revealing information from both ionised and relativistic particle populations. The SKAO, particularly its SKA-Mid component, will enable regular monitoring of Galactic novae, multiple times per year for classical novae and every few years for symbiotic systems. It will explore a wide range of conditions, including companion types, WD masses, accretion regimes, and surrounding environments. The VLBI capabilities of the SKAO will target compact shocked regions, while its exceptional sensitivity will also allow characterisation of emission during quiescent phases of the binaries.

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arXiv2026

Extending the SKA Across Africa: The Case for a Continental African VLBI Network

The African continent holds the key to unlocking the full potential of global Very Long Baseline Interferometry (VLBI). Strategic placement of radio telescopes across Africa provides the crucial north-south and intermediate baselines that are currently missing from the global VLBI network. This expansion will dramatically enhance imaging fidelity and resolution. In this chapter, we propose a vision for a continental African VLBI Network (AVN) that will operate in close synergy with SKA-Mid, enabling transformational science across all cosmic scales. While only the Hartebeesthoek Radio Astronomy Observatory (HartRAO) in South Africa and the Ghana Radio Astronomy Observatory (GRAO) are currently operational, several partner countries are in the process of refurbishing or converting existing antennas. Here, we advocate for the expansion of this network through the deployment of a limited number of SKA-Mid-type telescopes across the continent, creating an "African arm" of SKA-VLBI. With a maximum baseline of ~ 9000 km (from Rabat, Morocco to Cassis, Mauritius), the proposed continental facility will surpass for example, the resolution that will be achieved by the next generation Very Large Array (ngVLA) by ~ 10 % at similar observing frequencies and significantly enhance global VLBI coverage. Beyond the scientific and technical gains, the AVN represents a unique opportunity for sustainable growth in human capital, education, and innovation across Africa. Developing and operating a continental VLBI array will train the next generation of engineers, data scientists, and astronomers, stimulate local industry, and inspire public engagement in science and technology. We outline the current status, challenges, and potential roadmap towards realizing this vision, and we highlight how a continental African VLBI network will position Africa at the forefront of global radio astronomy.

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arXiv2026

VLBI Observations of SN 2012au Reveal a Compact Radio Source a Decade Post Explosion

Three leading models have been put forth to justify the observed radio re-brightening associated with stripped-envelope supernovae (SESNe) years post-explosion: radiation from an emerging pulsar wind nebula (PWN), shock interaction with a dense circumstellar medium (CSM), or emission from off-axis, relativistic jets. SN 2012au is a particularly intriguing SESN in this regard as observations obtained $\gtrsim$ 6 years post-explosion have shown both (i) optical emission features consistent with a young PWN and (ii) a radio re-brightening. We present the results of our Very-Long-Baseline-Interferometric (VLBI) observations of SN 2012au performed between 8 to 13 years post core-collapse. Our VLBI observations reveal a luminous, steadily fading radio source that remains compact ($\leq1.4\times10^{17}~\mathrm{cm}$) and stationary ($\leq0.36c$) over the course of our campaign. Overall, we find that our VLBI measurements can be readily explained by a $\sim$decade-old PWN, potentially explained by shock interaction with specific CSM geometries, and are unlikely to be explained by emission from an off-axis, relativistic jet. Assuming a PWN origin, our observations require that the initial spin-down luminosity of the central pulsar be between $10^{36}~\mathrm{erg~s^{-1}}\leq\dot{E}_0\leq {4\times10^{42}}~\mathrm{erg~s^{-1}}$ and radio efficiency factor be $\eta_\mathrm{R}\geq {3\times10^{-7}}$ (both quoted at the $ {99.7\%}$ confidence interval). These results are consistent with independent inferences obtained using optical spectroscopy of SN 2012au, alongside inferences of known Galactic systems. If a PWN origin is confirmed, SN 2012au would represent the first extragalactic PWN emerging from a modern day SN, providing a novel opportunity to study the formation properties of a decade-old pulsar.

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arXiv2025

A milliarcsecond localization associates FRB 20190417A with a compact persistent radio source and an extreme magneto-ionic environment

We report the milliarcsecond localization of a high (1379 pc/cc) dispersion measure (DM) repeating fast radio burst, FRB 20190417A. Combining European VLBI Network detections of five repeat bursts, we confirm the FRB's host to be a low-metallicity, star-forming dwarf galaxy at z = 0.12817, similar to the hosts of FRBs 20121102A, 20190520B and 20240114A. We also confirm that it is associated with a previously reported persistent radio source (PRS), which is compact on milliarcsecond scales. Visibility-domain model fitting constrains the transverse physical size of the PRS to < 23 pc and yields an integrated flux density of 191(39) microJy at 1.4 GHz. Though we do not find significant evidence for DM evolution, FRB 20190417A exhibits a time-variable rotation measure (RM) ranging between +3958(11) and +5061(24) rad/m2 over three years. We find no evidence for intervening galaxy clusters in the FRB's line-of-sight and place a conservative lower limit on the rest-frame host DM contribution of 1228 pc/cc (90% confidence) -- the largest known for any FRB so far. This system strengthens the emerging picture of a rare subclass of repeating FRBs with large and variable RMs, above-average host DMs, and luminous PRS counterparts in metal-poor dwarf galaxies. Our results suggest that these systems are the result of environmental selection, or a distinct engine for FRB emission.

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arXiv2025

Radio study of the colliding wind binary HD93129A near periastron and its surroundings

HD93129A is an O+O stellar system whose CWR has been mapped by high angular resolution observations at cm wavelengths. The synchrotron nature of the radio emission confirms its particle accelerator status. According to astrometric measurements since 1996, the system has an orbital period of ~120 yr and recently went through its periastron passage. We characterize the radio emission during the epoch of periastron passage, when the particle density and the local magnetic energy density in the CWR increase. We monitored HD93129A and surroundings at 2.1, 5.5 and 9 GHz with the ATCA over 17 months, with a ~2-month cadence. Previous ATCA data and data collected using other radio observatories were also included. We obtained radio light curves in subbands per band per epoch. The flux densities show an average rise of a factor four from 2003 to 2018, with the caveat that the 2009-2018 time lapse is devoid of data, and a similar decay between 2018 to 2020. We fit the spectral energy distribution of quasi-simultaneous data at three epochs and find that the magnetic-to-thermal pressure ratio does not remain constant along the orbit, possible suggesting magnetic field amplification close to periastron. In the 2019 epoch, we estimate a magnetic field strength of ~1.1G in the apex of the CWR. The evolution of the SED and spectral index is also presented. By combining ATCA and ASKAP images a spectral index map was obtained in an area of 30' size. The radio emission in the direction of other massive binary systems in the field (WR22, WR25 and HD93250) was measured and briefly discussed. Intensive radio monitoring allows us to track the evolution of physical conditions in the shocks. The general trend of decreasing emission of HD93129A in the high-frequency bands in 2019-2020 suggests that the system is at post-periastron, consistent with model predictions. (Abridged)

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arXiv2024

Dinosaur in a Haystack : X-ray View of the Entrails of SN 2023ixf and the Radio Afterglow of Its Interaction with the Medium Spawned by the Progenitor Star (Paper 1)

We present the results from our extensive hard-to-soft X-ray (NuSTAR, Swift-XRT, XMM-Newton, Chandra) and meter-to-mm wave radio (GMRT, VLA, NOEMA) monitoring campaign of the very nearby (d $=6.9$ Mpc) Type II SN2023ixf spanning $\approx$ 4--165 d post-explosion. This unprecedented dataset enables inferences on the explosion's circumstellar medium (CSM) density and geometry. Specifically, we find that the luminous X-ray emission is well modeled by thermal free-free radiation from the forward shock with rapidly decreasing photo-electric absorption with time. The radio spectrum is dominated by synchrotron radiation from the same shock, and the NOEMA detection of high-frequency radio emission may indicate a new component consistent with the secondary origin. Similar to the X-rays, the level of free-free absorption affecting the radio spectrum rapidly decreases with time as a consequence of the shock propagation into the dense CSM. While the X-ray and the radio modeling independently support the presence of a dense medium corresponding to an \emph{effective} mass-loss rate $\dot{M} \approx 10^{-4}\, \rm M_{\odot}\,yr^{-1}$ at $R = (0.4-14) \times 10^{15}$ (for $v_{\rm w}=\rm 25 \,km\,s^{-1}$), our study points at a complex CSM density structure with asymmetries and clumps. The inferred densities are $\approx$10--100 times those of typical red supergiants, indicating an extreme mass-loss phase of the progenitor in the $\approx$200 years preceding core collapse, which leads to the most X-ray luminous Type II SN and the one with the most delayed emergence of radio emission. These results add to the picture of the complex mass-loss history of massive stars on the verge of collapse and demonstrate the need for panchromatic campaigns to fully map their intricate environments.

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arXiv2024

A Repeating Fast Radio Burst Source in a Low-Luminosity Dwarf Galaxy

We present the localization and host galaxy of FRB 20190208A, a repeating source of fast radio bursts (FRBs) discovered using CHIME/FRB. As part of the PRECISE repeater localization program on the EVN, we monitored FRB 20190208A for 65.6 hours at $\sim1.4$ GHz and detected a single burst, which led to its VLBI localization with 260 mas uncertainty (2$\sigma$). Follow-up optical observations with the MMT Observatory ($i\gtrsim 25.7$ mag (AB)) found no visible host at the FRB position. Subsequent deeper observations with the GTC, however, revealed an extremely faint galaxy ($r=27.32 \pm0.16$ mag), very likely ($99.95 \%$) associated with FRB 20190208A. Given the dispersion measure of the FRB ($\sim580$ pc cm$^{-3}$), even the most conservative redshift estimate ($z_{\mathrm{max}}\sim0.83$) implies that this is the lowest-luminosity FRB host to date ($\lesssim10^8L_{\odot}$), even less luminous than the dwarf host of FRB 20121102A. We investigate how localization precision and the depth of optical imaging affect host association, and discuss the implications of such a low-luminosity dwarf galaxy. Unlike the other repeaters with low-luminosity hosts, FRB 20190208A has a modest Faraday rotation measure of a few tens of rad m$^{-2}$, and EVN plus VLA observations reveal no associated compact persistent radio source. We also monitored FRB 20190208A for 40.4 hours over 2 years as part of the \'ECLAT repeating FRB monitoring campaign on the Nan\c{c}ay Radio Telescope, and detected one burst. Our results demonstrate that, in some cases, the robust association of an FRB with a host galaxy will require both high localization precision, as well as deep optical follow-up.

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arXiv2024

Investigating the Role of Pre-supernova Massive Stars in the Acceleration of Galactic Cosmic Rays

Galactic cosmic rays (GCRs) constitute a significant part of the energy budget of our Galaxy, and the study of their accelerators is of high importance in modern astrophysics. Their main sources are likely supernova remnants (SNRs). These objects are capable to convert a part of their mechanical energy into accelerated charged particles. However, even though the mechanical energy reservoir of SNRs is promising, a conversion rate into particle energy of 10 to 20% is necessary to feed the population of GCRs. Such an efficiency is however not guaranteed. Complementary sources deserve thus to be investigated. This communication aims to address the question of the contribution to the acceleration of GCRs by pre-supernova massive stars in binary or higher multiplicity systems

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arXiv2024

Mapping Obscured Star Formation in the Host Galaxy of FRB 20201124A

We present high-resolution 1.5 $-$ 6 GHz Karl G. Jansky Very Large Array (VLA) and Hubble Space Telescope (HST) optical and infrared observations of the extremely active repeating fast radio burst (FRB) FRB 20201124A and its barred spiral host galaxy. We constrain the location and morphology of star formation in the host and search for a persistent radio source (PRS) coincident with FRB 20201124A. We resolve the morphology of the radio emission across all frequency bands and measure a star formation rate SFR $\approx 8.9\,M_{\odot}$ yr$^{-1}$, approximately $\approx 2.5-6$ times larger than optically-inferred SFRs, demonstrating dust-obscured star formation throughout the host. Compared to a sample of all known FRB hosts with radio emission, the host of FRB 20201124A has the most significantly obscured star formation. While HST observations show the FRB to be offset from the bar or spiral arms, the radio emission extends to the FRB location. We propose that the FRB progenitor could have formed in situ (e.g., a magnetar born from a massive star explosion). It is still plausible, although less likely, that the progenitor of FRB 20201124A migrated from the central bar of the host. We further place a limit on the luminosity of a putative PRS at the FRB position of $L_{\rm 6.0 \ GHz}$ $\lesssim$ 1.8 $\times 10^{27}$ erg s$^{-1}$ Hz$^{-1}$, among the deepest PRS luminosity limits to date. However, this limit is still broadly consistent with both magnetar nebulae and hypernebulae models assuming a constant energy injection rate of the magnetar and an age of $\gtrsim 10^{5}$ yr in each model, respectively.

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arXiv2023

Milliarcsecond Localisation of the Hyperactive Repeating FRB 20220912A

We present very-long-baseline interferometry (VLBI) observations of the hyperactive repeating FRB 20220912A using the European VLBI Network (EVN) with an EVN-Lite setup. We detected 150 bursts from FRB 20220912A over two observing epochs in October 2022. Combining the data of these bursts allows us to localise FRB 20220912A to a precision of a few milliarcseconds, corresponding to a transverse scale of less than 10 pc at the distance of the source. The precision of this localisation shows that FRB 20220912A lies closer to the centre of its host galaxy than previously found, although still significantly offset from the host galaxy's nucleus. On arcsecond scales, FRB 20220912A is coincident with a persistent continuum radio source known from archival observations, however, we find no compact persistent emission on milliarcsecond scales. The persistent radio emission is thus likely to be from star-formation in the host galaxy. This is in contrast to some other active FRBs, such as FRB 20121102A and FRB 20190520B.

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arXiv2023

Constraints on the persistent radio source associated with FRB 20190520B using the European VLBI Network

We present very-long-baseline interferometry (VLBI) observations of a continuum radio source potentially associated with the fast radio burst source FRB 20190520B. Using the European VLBI network (EVN), we find the source to be compact on VLBI scales with an angular size of $<2.3$ mas ($3σ$). This corresponds to a transverse physical size of $<9$ pc (at the $z=0.241$ redshift of the host galaxy), confirming it to be an FRB persistent radio source (PRS) like that associated with the first-known repeater FRB 20121102A. The PRS has a flux density of $201 \pm 34 \rm{μJy}$ at 1.7 GHz and a spectral radio luminosity of $L_{1.7 \rm GHz} = (3.0 \pm 0.5) \times 10^{29}\,\mathrm{erg s^{-1} Hz^{-1}}$ (also similar to the FRB 20121102A PRS). Comparing to previous lower-resolution observations, we find that no flux is resolved out on milliarcsecond scales. We have refined the PRS position, improving its precision by an order of magnitude compared to previous results. We also report the detection of a FRB 20190520B burst at 1.4 GHz and find the burst position to be consistent with the PRS position, at $\lesssim20$ mas. This strongly supports their direct physical association and the hypothesis that a single central engine powers both the bursts and the PRS. We discuss the model of a magnetar in a wind nebula and present an allowed parameter space for its age and the radius of the putative nebula powering the observed PRS emission. Alternatively, we find that an accretion-powered 'hypernebula' model also fits our observational constraints.

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arXiv2022

CASA on the fringe -- Development of VLBI processing capabilities for CASA

New functionality to process Very Long Baseline Interferometry (VLBI) data has been implemented in the CASA package. This includes two new tasks to handle fringe fitting and VLBI-specific amplitude calibration steps. Existing tasks have been adjusted to handle VLBI visibility data and calibration meta-data properly. With these updates, it is now possible to process VLBI continuum and spectral line observations in CASA. This article describes the development and implementation, and presents an outline for the workflow when calibrating European VLBI Network or Very Long Baseline Array data in CASA. Though the CASA VLBI functionality has already been vetted extensively as part of the Event Horizon Telescope data processing, in this paper we compare results for the same dataset processed in CASA and AIPS. We find identical results for the two packages and conclude that CASA in some cases performs better, though it cannot match AIPS for single-core processing time. The new functionality in CASA allows for easy development of pipelines or Jupyter notebooks, and thus contributes to raising VLBI data processing to present day standards for accessibility, reproducibility, and reusability.

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arXiv2021

Cygnus X-1 contains a 21-solar mass black hole -- implications for massive star winds

The evolution of massive stars is influenced by the mass lost to stellar winds over their lifetimes. These winds limit the masses of the stellar remnants (such as black holes) that the stars ultimately produce. We use radio astrometry to refine the distance to the black hole X-ray binary Cygnus X-1, which we find to be $2.22^{+0.18}_{-0.17}$ kiloparsecs. When combined with previous optical data, this implies a black hole mass of $21.2\pm2.2$ solar masses, higher than previous measurements. The formation of such a high-mass black hole in a high-metallicity system constrains wind mass loss from massive stars.

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arXiv2021

The 60 pc Environment of FRB 20180916B

Fast Radio Burst FRB 20180916B in its host galaxy SDSS J015800.28+654253.0 at 149 Mpc is by far the closest-known FRB with a robust host galaxy association. The source also exhibits a 16.35-day period in its bursting. Here we present optical and infrared imaging as well as integral field spectroscopy observations of FRB 20180916B with the WFC3 camera on the Hubble Space Telescope and the MEGARA spectrograph on the 10.4-m Gran Telescopio Canarias. The 60-90 milliarcsecond (mas) resolution of the Hubble imaging, along with the previous 2.3-mas localization of FRB 20180916B, allow us to probe its environment with a 30-60 pc resolution. We constrain any point-like star-formation or HII region at the location of FRB 20180916B to have an H$α$ luminosity $L_\mathrm{Hα} \lesssim 10^{37}\,\mathrm{erg\,s^{-1}}$ and, correspondingly, constrain the local star-formation rate to be $\lesssim10^{-4}\,\mathrm{M_\odot\,yr^{-1}}$. The constraint on H$α$ suggests that possible stellar companions to FRB 20180916B should be of a cooler, less massive spectral type than O6V. FRB 20180916B is 250 pc away (in projected distance) from the brightest pixel of the nearest young stellar clump, which is $\sim380$\,pc in size (full-width at half maximum). With the typical projected velocities of pulsars, magnetars, or neutron stars in binaries (60-750 km s$^{-1}$), FRB 20180916B would need 800 kyr to 7 Myr to traverse the observed distance from its presumed birth site. This timescale is inconsistent with the active ages of magnetars ($\lesssim10$ kyr). Rather, the inferred age and observed separation are compatible with the ages of high-mass X-ray binaries and gamma-ray binaries, and their separations from the nearest OB associations.

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