Observed X-ray Luminosity Research Articles

AT2021lwx: Another Neutrino-coincident Tidal Disruption Event with a Strong Dust Echo?

We discuss the possible association of an astrophysical neutrino (IC220405B) with the recently reported, extremely energetic tidal disruption event (TDE) candidate AT2021lwx (ZTF20abrbeie, aka “Scary Barbie”) at redshift z = 0.995. Although the TDE is about 2.°6 off the direction of the reconstructed neutrino event (outside the 90% confidence level localization region), the TDE candidate shares some important characteristics with so-far-reported neutrino–TDE associations: a strong infrared dust echo, high bolometric luminosity, a neutrino time delay with respect to the peak mass accretion rate of the order of a hundred days, and a high observed X-ray luminosity. We interpret this new association using an isotropic emission model, where neutrinos are produced by the collision of accelerated protons with infrared photons. After accounting for the high redshift of AT2021lwx (by interpreting the data in the supermassive black hole (SMBH) frame), we find that the expected neutrino fluences and neutrino time delays are qualitatively comparable to the other TDEs. Since data are only available up to 300 days postpeak in the SMBH frame, significant uncertainties exist in the dust echo interpretation, and therefore in the predicted number of neutrinos detected, Nν≃3.0×10−3−0.012 . We recommend further follow-up of this object for an extended period and suggest refining the reconstruction of the neutrino arrival direction in this particular case.

X-ray study on the core collapse supernova 2008ax using XMM-Newton and Swift/XRT

We studied the x-ray evolution of the core collapse, Type IIb, supernova SN 2008ax. In addition to the four Swift/XRT observations previously published, we included, for the first time, two observations from XMM-NEWTON to our analysis that have not been published before. By focusing on the early observations of the SN 2008ax, we were able to explore the time evolution of both x-ray luminosity (Lx) and temperature (Tx) during the radiative phase. The analysis showed that the evolution of Lx and Tx can be expressed as a power law as Lx ∝ t −0.87 and Tx ∝ t −0.46, respectively. Based on the observed x-ray luminosity, we estimated the mass-loss rate ( Ṁ ) for the progenitor star to be approximately 0.64 ± 0.15 × 10−5 M⊙ yr −1, for a wind velocity of 10 km s−1. This finding is in good agreement with the previous studies.

On the lack of X-ray pulsation in most neutron star low-mass X-ray binaries

ABSTRACT We have investigated whether the lack of X-ray pulsations from most neutron star (NS) low-mass X-ray binaries (LMXBs) could be due to the extension of their inner disc to the NS surface. To estimate the inner disc radii, we have employed the model, recently proposed to account for the torque reversals of LMXBs. In this model, the inner disc radius depends on the spin period as well as the dipole moment and the mass inflow rate of the disc. Our model results indicate that most LMXBs have mass accretion rates above the minimum critical rates required for the inner disc to reach down to the NS surface and thereby quench the pulsed X-ray emission. For most sources X-ray pulsations are allowed when the period decreases below a certain critical value. For the same parameters, the model is also consistent with the observed X-ray luminosity ranges of the individual accreting millisecond X-ray pulsars (AMXPs). The paucity of AMXPs compared to the majority population of non-pulsing LMXBs is explained, as well as the fact that AMXPs are transient sources.

The High-mass X-Ray Binary Luminosity Functions of Dwarf Galaxies

Drawing from the Chandra archive and using a carefully selected set of nearby dwarf galaxies, we present a calibrated high-mass X-ray binary (HMXB) luminosity function in the low-mass galaxy regime and search for an already hinted at dependence on metallicity. Our study introduces a new sample of local dwarf galaxies (D < 12.5 Mpc and M * < 5 × 109 M ⊙), expanding the specific star formation rates (sSFR) and gas-phase metallicities probed in previous investigations. Our analysis of the observed X-ray luminosity function indicates a shallower power-law slope for the dwarf galaxy HMXB population. In our study, we focus on dwarf galaxies that are more representative in terms of sSFR compared to prior work. In this regime, the HMXB luminosity function exhibits significant stochastic sampling at high luminosities. This likely accounts for the pronounced scatter observed in the galaxy-integrated HMXB population’s L X/SFR versus metallicity for our galaxy sample. Our calibration is necessary to understand the active galactic nuclei content of low-mass galaxies identified in current and future X-ray survey fields and has implications for binary population synthesis models, as well as X-ray-driven cosmic heating in the early Universe.

Rotating Massive Strangeon Stars and X-Ray Plateau of Short GRBs

Strangeon stars, which are proposed to describe the nature of pulsar-like compact stars, have passed various observational tests. The maximum mass of a non-rotating strangeon star could be high, which implies that the remnants of binary strangeon star mergers could even be long-lived massive strangeon stars. We study rigidly rotating strangeon stars in the slowly rotating approximation, using the Lennard-Jones model for the equation of state. Rotation can significantly increase the maximum mass of strangeon stars with unchanged baryon numbers, enlarging the mass-range of long-lived strangeon stars. During spin-down after merger, the decrease of radius of the remnant will lead to the release of gravitational energy. Taking into account the efficiency of converting the gravitational energy luminosity to the observed X-ray luminosity, we find that the gravitational energy could provide an alternative energy source for the plateau emission of X-ray afterglow. The fitting results of X-ray plateau emission of some short gamma-ray bursts suggest that the magnetic dipole field strength of the remnants can be much smaller than that of expected when the plateau emission is powered only by spin-down luminosity of magnetars.

An Optically Discovered Outburst from XTE J1859+226

Using the Zwicky Transient Facility, in 2021 February we identified the first known outburst of the black hole X-ray transient XTE J1859+226 since its discovery in 1999. The outburst was visible at X-ray, UV, and optical wavelengths for less than 20 days, substantially shorter than its full outburst of 320 days in 1999, and the observed peak luminosity was 2 orders of magnitude lower. Its peak bolometric luminosity was only 2 × 1035 erg s−1, implying an Eddington fraction of about 3 × 10−4. The source remained in the hard spectral state throughout the outburst. From optical spectroscopy measurements we estimate an outer disk radius of 1011 cm. The low observed X-ray luminosity is not sufficient to irradiate the entire disk, but we observe a surprising exponential decline in the X-ray light curve. These observations highlight the potential of optical and infrared synoptic surveys to discover low-luminosity activity from X-ray transients.

The X-ray view of optically selected dual AGN

ABSTRACT We present a study of optically selected dual Active Galactic Nuclei (AGN) with projected separations of 3–97 kpc. Using multiwavelength (MWL) information (optical, X-ray, mid-IR), we characterized the intrinsic nuclear properties of this sample and compared them with those of isolated systems. Among the 124 X-ray-detected AGN candidates, 52 appear in pairs and 72 as single X-ray sources. Through MWL analysis, we confirmed the presence of the AGN in &amp;gt;80 per cent of the detected targets in pairs (42 out of 52). X-ray spectral analysis confirms the trend of increasing AGN luminosity with decreasing separation, suggesting that mergers may have contributed to triggering more luminous AGN. Through X-ray/mid-IR ratio versus X-ray colours, we estimated a fraction of Compton-thin AGN (with 1022 cm−2 &amp;lt; NH &amp;lt; 1024 cm−2) of about 80 per cent, while about 16 per cent are Compton-thick sources (with NH &amp;gt; 1024 cm−2). These fractions of obscured sources are larger than those found in samples of isolated AGN, confirming that pairs of AGN show higher obscuration. This trend is further confirmed by comparing the de-reddened [O iii] emission with the observed X-ray luminosity. However, the derived fraction of Compton-thick sources in this sample at the early stages of merging is lower than that reported for late-merging dual-AGN samples. Comparing NH from X-rays with that derived from E(B − V) from narrow-line regions, we found that the absorbing material is likely to be associated with the torus or broad-line regions. We also explored the X-ray detection efficiency of dual-AGN candidates, finding that, when observed properly (at on-axis positions and with long exposures), X-ray data represent a powerful way to confirm and investigate dual-AGN systems.

New insights into the Triangulum Australis supercluster of galaxies

The Triangulum Australis cluster is one of about a dozen nearby massive cluster systems which contribute to the gravitational pull behind the so-called Great Attractor that is dominated by the nearby Shapley Supercluster mass, which conforms the galaxy velocity flows observed in that general direction. Here, we study the structure and dynamical mass of the Triangulum Australis cluster together with the neighbouring cluster AS0794. We present a set of 131 velocities collected in the regions of the two clusters with the 2.5 m Du Pont telescope at Las Campanas Observatory (Chile). For the Triangulum Australis cluster we find a dynamical mass of about Mv = 4.2 (±1.3) × 1015 M⊙ and for AS0794 a value of about Mv = 1.7 (±1.3) × 1013 M⊙. These values are consistent with the observed X-ray luminosities of these clusters. Combined with velocities already known we reanalyse the structure and dynamics of this general region, finding that both clusters, together with at least eight other ones, form a large supercluster, centered on TriAus (which dominates in terms of mass). We find that this supercluster is part of a large-scale structure filament linked to the Shapley supercluster (SSC). Uncertainties remain on the richness and detailed structure of this filament and the TriAus supercluster because parts of it remain hidden behind the Galaxy disk.

Phase-resolved spectroscopic analysis of the eclipsing black hole X-ray binary M33 X-7: System properties, accretion, and evolution

M33 X-7 is the only known eclipsing black hole high mass X-ray binary. The system is reported to contain a very massive O supergiant donor and a massive black hole in a short orbit. The high X-ray luminosity and its location in the metal-poor galaxy M33 make it a unique laboratory for studying the winds of metal-poor donor stars with black hole companions and it helps us to understand the potential progenitors of black hole mergers. Using phase-resolved simultaneous HST- and XMM-Newton-observations, we traced the interaction of the stellar wind with the black hole. We observed a strong Hatchett-McCray effect in M33 X-7 for the full range of wind velocities. Our comprehensive spectroscopic investigation of the donor star (X-ray+UV+optical) yields new stellar and wind parameters for the system that differ significantly from previous estimates. In particular, the masses of the components are considerably reduced to ≈38 M⊙ for the O-star donor and ≈11.4 M⊙ for the black hole. The O giant is overfilling its Roche lobe and shows surface He enrichment. The donor shows a densely clumped wind with a mass-loss rate that matches theoretical predictions. An extended ionization zone is even present during the eclipse due to scattered X-ray photons. The X-ray ionization zone extends close to the photosphere of the donor during inferior conjunction. We investigated the wind-driving contributions from different ions and the changes in the ionization structure due to X-ray illumination. Toward the black hole, the wind is strongly quenched due to strong X-ray illumination. For this system, the standard wind-fed accretion scenario alone cannot explain the observed X-ray luminosity, pointing toward an additional mass overflow, which is in line with our acceleration calculations. The X-ray photoionization creates an He II emission region around the system emitting ∼1047 ph s−1. We computed binary evolutionary tracks for the system using MESA. Currently, the system is transitioning toward an unstable mass transfer phase, possibly resulting in a common envelope of the black hole and the O-star donor. Since the mass ratio is q ≳ 3.3 and the period is short, the system is unlikely to survive the common envelope, but will rather merge.

X-ray illuminated accretion discs and quasar microlensing disc sizes

Aims. We study the half-light radius versus black hole mass as well as the luminosity versus black hole mass relations in active galactic nuclei (AGN) when the disc is illuminated by the X-ray corona. Methods. We used KYNSED, a recently developed spectral model for studying broadband spectral energy distribution in AGN. We considered non-illuminated Novikov-Thorne discs and X-ray illuminated discs based on a Novikov-Thorne temperature radial profile. We also considered the case where the temperature profile is modified by a colour-correction factor. In the case of X-ray illumination, we assumed that the X-ray luminosity is equal to the accretion power that is dissipated to the disc below a transition radius and we computed the half-light radius and the disc luminosity for many black hole masses, as well as a wide range of accretion rates, black hole spins, X-ray luminosities and heights of the corona. Results. The half-light radius of X-ray illuminated radii can be up to ∼3.5 times greater than the radius of a standard disc, even for a non-spinning black hole, based on a wide range of model parameters – as long as the transition radius is larger than three times the radius of the innermost stable circular orbit and the coronal height is greater than ∼40 Rg. This result is due to the fact that the absorbed X-rays act as a secondary source of energy, increasing the disc temperature, and mainly at large radii. Non-illuminated discs are consistent with observations, but only at the 2.5σ level. On the other hand, X-ray illuminated discs can explain both the half-light radius-black hole mass as well as the luminosity-black hole mass relation in AGN, for a wide range of physical parameters. The range of the parameter space is broader in the case where we consider the colour-correction factor. X-ray illuminated discs can explain the data when we observe gravitationally lensed quasars mainly face-on, but also if the mean inclination angle is 60°. In addition, we show that the observed X-ray luminosity of the gravitationally lensed quasars is fully consistent with the X-ray luminosity that is necessary for heating the disc. Conclusions. X-ray disc illumination was proposed many years ago to explain various features that are commonly observed in the X-ray spectra of AGN. Recently, we showed that X-ray illumination of the accretion disc can also explain the observed UV/optical time-lags in AGN, while in this work, we show that the same model can also account for the quasar micro-lensing disc size problem. These results support the hypothesis of the disc X-ray illumination in AGN.

Unveiling the Interplay between the GASP Jellyfish Galaxy JO194 and Its Environment with Chandra

X-ray studies of jellyfish galaxies opened a window into the physics of the interplay between the intracluster medium (ICM) and interstellar medium (ISM). In this paper, we present the study of an archival Chandra observation of the GASP jellyfish galaxy JO194. We observe X-ray emission extending from the stellar disk to the unwinding spiral arms with an average temperature of kT = 0.79 ± 0.03 keV. To investigate the origin of the X-ray emission, we compare the observed X-ray luminosities with those expected from the star formation rates (SFRs) obtained from Hα emission. We estimate an X-ray luminosity excess of a factor ∼2–4 with respect to the SF; therefore, we conclude that SF is not the main event responsible for the extended X-ray emission of JO194. The metallicity in the spiral arms () is consistent with that of the ICM around JO194 (Z = 0.35 ± 0.07); thus, we suggest that ICM radiative cooling dominates the X-ray emission of the arms. We speculate that the X-ray plasma results from the ISM‒ICM interplay, although the nature of this interplay is still mostly unknown. Finally, we observe that the X-ray properties of JO194 are consistent with those of two other GASP galaxies with different stellar mass, phase-space conditions in their hosting clusters, and local ICM conditions. We suggest that the conditions required to induce extended X-ray emission in jellyfish galaxies are established at the beginning of the stripping, and they can persist on long timescales so that galaxies in different clusters and evolutionary stages can present a similar extended X-ray emission.

Evolution of X-Ray Activity in

Measuring the evolution of X-ray emission from pre-main-sequence (PMS) stars gives insight into two issues: the response of magnetic dynamo processes to changes in the interior structure, and the effects of high-energy radiation on protoplanetary disks and primordial planetary atmospheres. We present a sample of 6003 stars with ages 7–25 Myr in 10 nearby open clusters from Chandra X-ray and Gaia-EDR3 surveys. Combined with previous results in large samples of younger (≲5 Myr) stars in MYStIX and SFiNCs star-forming regions, mass-stratified activity-age relations are derived for the early phases of stellar evolution. X-ray luminosity (L X ) is constant during the first few Myr, possibly due to the presence of extended X-ray coronas insensitive to temporal changes in stellar size. L X then decays during the 7–25 Myr period, more rapidly as stellar mass increases. This decay is interpreted as decreasing efficiency of the α 2 dynamo as radiative cores grow and a solar-type αΩ dynamo emerges. For more massive 3.5–7 M ⊙ fully radiative stars, the X-ray emission plummets—indicating the lack of an effective magnetic dynamo. The findings provide improved measurements of high-energy radiation effects on circumstellar material, first for the protoplanetary disk and then for the atmospheres of young planets. The observed X-ray luminosities can be so high that an inner Earth-mass rocky, unmagnetized planet around a solar-mass PMS star might lose its primary and secondary atmospheres within a few (several) million years. PMS X-ray emission may thus have a significant impact on the evolution of early-planetary atmospheres and the conditions promoting the rise of habitability.

X-ray pulsar HD 49798: a contracting white dwarf with a debris disk?

HD 49798/RX J0648.0C4418 is a peculiar binary including a hot subdwarf of O spectral type and a compact companion in a 1.55 day orbit. Based on the steady spin period derivative Ṗ = (−2.17 ± 0.01) × 10−15 s s−1 , the compact object was thought to be a contracting young white dwarf (WD). However, the X-ray luminosity produced by the wind accretion of the massive WD is one order of magnitude smaller than the observed value. In this work, we propose an alternative model to account for the observed X-ray luminosity. If the WD were surrounded by a debris disk, the accretion from the debris disk could produce the observed X-ray luminosity and X-ray pulses. Based on the time-varying accretion rate model, the current mass of the debris disk is constrained to 3.9 × 10−6 M⊙. The accretion torque exerted by such a debris disk can only influence the spin evolution of the WD in the early stages, and its affect is obviously smaller than that caused by the contraction of the WD in the current stage. According to accretion theory, the magnetic field of the WD is constrained to ∼(0.7−7) × 104 G. The calculated conventional polar cap radius of the WD is larger than the observed emitting-zone radius, which probably originates from the existence of strong and small-scale local magnetic field in the polar cap surface. We expect that further multiband observations of this source could help us to confirm or rule out the existence of a debris disk.

X-ray and optical emission from large superbubbles including the stellar photoionization

ABSTRACT N70 is a giant superbubble (SB) produced by the stellar cluster LH 114. The dynamic of the stellar SB can be explained with hydrodynamic simulations. However, the explanation of the observed X-ray luminosity is still a matter of debate. Observations show that this kind of superbubbles exhibits X-ray luminosities of the order of 1035 erg s−1, which cannot be explained by only considering the mechanical luminosity of the stellar components. Instead, theoretical models predict luminosities one order of magnitude lower. In this work, we attempt to answer this discrepancy by including a core-collapse supernova explosion (SN) and the photons emitted by each of the stars involved. We find that a core-collapse SN, with an initial mass of 10 M⊙, can explain the missing X-ray emission, lasting approximately 1000 yr. Also, the radiation produces an enhancement of the filamentary superbubble morphology and it increases the SB radius by $\sim 23{{\ \rm per\ cent}}$ with respect to the pure hydrodynamic case.

X-ray evolution of the nova V959 Mon suggests a delayed ejection and a non-radiative shock

ABSTRACT X-ray observations of shocked gas in novae can provide a useful probe of the dynamics of the ejecta. Here we report on X-ray observations of the nova V959 Mon, which was also detected in GeV gamma-rays with the Fermi satellite. We find that the X-ray spectra are consistent with a two-temperature plasma model with non-solar abundances. We interpret the X-rays as due to shock interaction between the slow equatorial torus and the fast polar outflow that were inferred from radio observations of V959 Mon. We further propose that the hotter component, responsible for most of the flux, is from the reverse shock driven into the fast outflow. We find a systematic drop in the column density of the absorber between days 60 and 140, consistent with the expectations for such a picture. We present intriguing evidence for a delay of around 40 d in the expulsion of the ejecta from the central binary. Moreover, we infer a relatively small (a few times 10−6 M⊙) ejecta mass ahead of the shock, considerably lower than the mass of 104 K gas inferred from radio observations. Finally, we infer that the dominant X-ray shock was likely not radiative at the time of our observations, and that the shock power was considerably higher than the observed X-ray luminosity. It is unclear why high X-ray luminosity, closer to the inferred shock power, is never seen in novae at early times, when the shock is expected to have high enough density to be radiative.

GJ 357 b

Aims. In this paper we present a deep X-ray observation of the nearby M dwarf GJ 357 and use it to put constraints on the atmospheric evolution of its planet, GJ 357 b. We also analyse the systematic errors in the stellar parameters of GJ 357 in order to see how they affect the perceived planetary properties. Methods. By comparing the observed X-ray luminosity of its host star, we estimate the age of GJ 357 b as derived from a recent XMM-Newton observation (log Lx [erg s−1] = 25.73), with Lx− age relations for M dwarfs. We find that GJ 357 presents one of the lowest X-ray activity levels ever measured for an M dwarf, and we put a lower limit on its age of 5 Gyr. Using this age limit, we performed a backwards reconstruction of the original primordial atmospheric reservoir. Furthermore, by considering the systematic errors in the stellar parameters, we find a range of possible planetary masses, radii, and densities. Results. From the backwards reconstruction of the irradiation history of GJ 357 b’s we find that the upper limit of its initial primordial atmospheric mass is ~38 M⊕. An initial atmospheric reservoir significantly larger than this may have survived through the X-ray and ultraviolet irradiation history, which would not be consistent with current observations that suggest a telluric composition. However, given the relatively small mass of GJ 357 b, even accreting a primordial envelope ≳10 M⊕ would have been improbable as an unusually low protoplanetary disc opacity, large-scale migration, and a weak interior luminosity would have been required. For this reason, we discard the possibility that GJ 357 b was born as a Neptunian- or Jovian-sized body. In spite of the unlikelihood of a currently existing primordial envelope, volcanism and outgassing may have contributed to a secondary atmosphere. Under this assumption, we present three different synthetic IR spectra for GJ 357 b that one might expect, consisting of 100% CO2, 100% SO2, and 75% N2, 24% CO2 and 1% H2O, respectively. Future observations with space-based IR spectroscopy missions will be able to test these models. Finally, we show that the uncertainties in the stellar and planetary quantities do not have a significant effect on the estimated mass or radius of GJ 357 b.

How Do Supernovae Impact the Circumgalactic Medium? I. Large-scale Fountains around a Milky Way–like Galaxy

Abstract Feedback is indispensable in galaxy formation. However, lacking resolutions, cosmological simulations often use ad hoc feedback parameters. Conversely, small-box simulations, while they better resolve the feedback, cannot capture gas evolution beyond the simulation domain. We aim to bridge the gap by implementing small-box results of supernovae-driven outflows into dark matter halo-scale simulations and studying their impact on large scales. Galactic outflows are multiphase, but small-box simulations show that the hot phase (T ≈ 106–7 K) carries the majority of energy and metals. We implement hot outflows in idealized simulations of the Milky Way halo, and examine how they impact the circumgalactic medium. In this paper, we discuss the case when the star formation surface density is low and therefore the emerging hot outflows are gravitationally bound by the halo. We find that outflows form a large-scale, metal-enriched atmosphere with fountain motions. As hot gas accumulates, the inner atmosphere becomes “saturated.” Cool gas condenses, with a rate balancing the injection of the hot outflows. This balance leads to a universal density profile of the hot atmosphere, independent of mass outflow rate. The atmosphere has a radially decreasing temperature, naturally producing the observed X-ray luminosity and column densities of O vi, O vii, and O viii. The self-regulated atmosphere has a baryon and a metal mass of (0.5–1.2) × 1010 M ⊙ and (0.6–1.4) × 108 M ⊙, respectively, small compared to the “missing” baryons and metals from the halo. We conjecture that the missing materials reside at even larger radii, ejected by more powerful outflows in the past.

NuSTAR observations of four nearby X-ray faint AGNs: low luminosity or heavy obscuration?

ABSTRACT We present NuSTAR (Nuclear Spectroscopic Telescope Array) observations of four active galactic nuclei (AGNs) located within 15 Mpc. These AGNs, namely ESO 121-G6, NGC 660, NGC 3486, and NGC 5195, have observed X-ray luminosities of L2–10 keV,obs ≲ 1039 erg s−1, classifying them as low-luminosity AGN (LLAGN). We perform broad-band X-ray spectral analysis for the AGN by combining our NuSTAR data with Chandra or XMM–Newton observations to directly measure their column densities (NH) and infer their intrinsic power. We complement our X-ray data with archival and new high-angular resolution mid-infrared (mid-IR) data for all objects, except NGC 5195. Based on our X-ray spectral analysis, we found that both ESO 121-G6 and NGC 660 are heavily obscured (NH &amp;gt; 1023 cm−2; L2–10 keV,int ∼ 1041 erg s−1), and NGC 660 may be Compton thick. We also note that the X-ray flux and spectral slope for ESO 121-G6 have significantly changed over the last decade, indicating significant changes in the obscuration and potentially accretion rate. On the other hand, NGC 3486 and NGC 5195 appear to be unobscured and just mildly obscured, respectively, with L2–10 keV,int &amp;lt; 1039 erg s−1, i.e. genuine LLAGN. Both of the heavily obscured AGNs have Lbol &amp;gt; 1041 erg s−1 and λEdd ≳ 10−3, and are detected in high-angular resolution mid-IR imaging, indicating the presence of obscuring dust on nuclear scale. NGC 3486, however, is undetected in high-resolution mid-IR imaging, and the current data do not provide stringent constraints on the presence or absence of obscuring nuclear dust in the AGN.

Early neutron star evolution in high-mass X-ray binaries

ABSTRACT The application of standard accretion theory to observations of X-ray binaries provides valuable insights into neutron star (NS) properties, such as their spin period and magnetic field. However, most studies concentrate on relatively old systems, where the NS is in its late propeller, accretor, or nearly spin equilibrium phase. Here, we use an analytic model from standard accretion theory to illustrate the evolution of high-mass X-ray binaries (HMXBs) early in their life. We show that a young NS is unlikely to be an accretor because of the long duration of ejector and propeller phases. We apply the model to the recently discovered ∼4000 yr old HMXB XMMU J051342.6−672412 and find that the system’s NS, with a tentative spin period of 4.4 s, cannot be in the accretor phase and has a magnetic field B &amp;gt; a few × 1013 G, which is comparable to the magnetic field of many older HMXBs and is much higher than the spin equilibrium inferred value of a few × 1011 G. The observed X-ray luminosity could be the result of thermal emission from a young cooling magnetic NS or a small amount of accretion that can occur in the propeller phase.

X-ray signatures of black hole feedback: hot galactic atmospheres in IllustrisTNG and X-ray observations

ABSTRACT Hot gaseous atmospheres that permeate galaxies and extend far beyond their stellar distribution, where they are commonly referred to as the circumgalactic medium, imprint important information about feedback processes powered by the stellar populations of galaxies and their central supermassive black holes (SMBHs). In this work, we study the properties of this hot X-ray emitting medium using the IllustrisTNG cosmological simulations. We analyse their mock X-ray spectra, obtained from the diffuse and metal-enriched gas in TNG100 and TNG50, and compare the results with X-ray observations of nearby early-type galaxies. The simulations reproduce the observed X-ray luminosities (LX) and temperature (TX) at small (&amp;lt;Re) and intermediate (&amp;lt;5Re) radii reasonably well. We find that the X-ray properties of lower mass galaxies depend on their star formation rates. In particular, in the magnitude range where the star-forming and quenched populations overlap, $M_{\rm K}\sim -24\ (M_*\sim 10^{10.7}\, \mathrm{M}_\odot)$, we find that the X-ray luminosities of star-forming galaxies are on average about an order of magnitude higher than those of their quenched counterparts. We show that this diversity in LX is a direct manifestation of the quenching mechanism in the simulations, where the galaxies are quenched due to gas expulsion driven by SMBH kinetic feedback. The observed dichotomy in LX is thus an important observable prediction for the SMBH feedback-based quenching mechanisms implemented in state-of-the-art cosmological simulations. While the current X-ray observations of star-forming galaxies are broadly consistent with the predictions of the simulations, the observed samples are small and more decisive tests are expected from the sensitive all-sky X-ray survey with eROSITA.