NuSTAR Observations Research Articles

X-ray flashes from the low-mass X-ray binary IGR J17407−2808

IGR J17407−2808 is an enigmatic and poorly studied X-ray binary that was recently observed quasi-simultaneously with NuSTAR and XMM-Newton. In this paper we report the results of this observational campaign. During the first 60 ks of observation, the source was caught in a relatively low emission state characterised by a modest variability and an average flux of ∼8.3 × 10−13 erg cm−2 s−1 (4−60 keV). Subsequently, IGR J17407−2808 entered a significantly more active emission state that persisted for the remaining ∼40 ks of the NuSTAR observation. During this state, IGR J17407−2808 displayed several fast X-ray flares of ∼1 − 100 s in duration and featuring profiles with either single or multiple peaks. The source flux in the flaring state reached values as high as ∼2 × 10−9 erg cm−2 s−1 (4−60 keV), leading to a measured dynamic range during the NuSTAR and XMM-Newton campaign of ≳103. We also analysed available archival photometric near-infrared data for IGR J17407−2808 in order to improve the constraints available so far on the nature of the donor star hosted in this system. Our analysis shows that the donor star can be either a rare K or M-type sub-subgiant, a K-type main sequence or subgiant star. Our findings support the classification of IGR J17407−2808 as a low-mass X-ray binary. We discuss the X-ray behaviour of the source as recorded by NuSTAR and XMM-Newton in view of this revised classification.

Broadband X-Ray Spectral Analysis of the ULX NGC 1313 X-1 Using JeTCAF: Origin of the ULX Bubble

NGC 1313 X-1 is a mysterious ultraluminous X-ray (ULX) source whose X-ray-powering mechanism and bubble-like structure surrounding the source are topics of intense study. Here, we perform an X-ray spectroscopic study of the source using joint XMM-Newton and NuSTAR observations taken during 2012–2017. The combined spectra cover the energy band 0.3–20 keV. We use the accretion–ejection-based JeTCAF model for spectral analysis. The model-fitted disk mass accretion rate varies from 4.6 to 9.6 and the halo mass accretion rate varies from 4.0 to 6.1 with a dynamic Comptonizing corona of average size of ∼15 r g . The data fitting is carried out for different black hole (BH) mass values. The goodness of the fit and uncertainties in model parameters improve while using higher BH masses, with the most probable mass of the compact object being 133 ± 33 M ⊙. We have estimated the mass outflow rate, its velocity and power, and the age of the inflated bubble surrounding the source. Our estimated bubble morphology is in accordance with the observed optical bubble and winds found through high-resolution X-ray spectroscopy, suggesting that the bubble was expanded by the outflows originating from the central source. Finally, we conclude that the super-Eddington accretion onto a nearly intermediate-mass BH may power a ULX when the accretion efficiency is low, though their efficiency increases when the jet/outflow is taken into account, in agreement with numerical simulations in the literature.

The Low-temperature Corona in ESO 511−G030 Revealed by NuSTAR and XMM-Newton

We present the results from a coordinated XMM-Newton + NuSTAR observation of the Seyfert 1 galaxy ESO 511−G030. With this joint monitoring program, we conduct a detailed variability and spectral analysis. The source remained in a low flux and very stable state throughout the observation period, although there are slight fluctuations of flux over long timescales. The broadband (0.3–78 keV) spectrum shows the presence of a power-law continuum with a soft excess below 2 keV, a relatively narrow iron Kα emission (∼6.4 keV), and an obvious cutoff at high energies. We find that the soft excess can be modeled by two different possible scenarios: a warm (kT e ∼ 0.19 keV) and optically thick (τ = 18–25) Comptonizing corona or a relativistic reflection from a high-density () inner disk. All models require a low temperature (kT e ∼ 13 keV) for the hot corona.

Nustar observation of the binary system 4U 0114 + 65

ABSTRACT The high-mass X-ray binary system 4U 0114 + 65 was observed by Nustar in October 2019 and by XMM-Newton in August 2015. Here we performed spectral and timing analysis of the Nustar observation and carry out timing analysis on the XMM-Newton data. We measured the spin period of the neutron star from both observations and found a spin-up rate $\dot{p}$ = 1.54 ± 0.38 × 10−6$\mathrm{s\, s}^{-1}$ . During the Nustar observation, two flares occurred, one shortly after the start of the observation and the other near the end separated by a long period of low/quiescent state. The large and sudden flares mostly resulted from accretion of corotating interaction region (CIR) material. A common spectral model to high mass X-ray binaries (HMXBs), powerlaw with high energy cutoff and absorption at low energy, gave a good fit to both flaring and quiescent states. A fluorescent iron line was not required in fitting any of the states. On the other hand, very tentative evidence of Cyclotron Resonant Scattering Feature (CRSF) at ∼17 keV was found during fitting using cyclabs model; however, fitting improvement was not significant enough to confirm its detection, plus a very narrow width (<1 keV) was obtained for the line and its first harmonic. Visual inspection of the spectra showed a deficiency of emission near the expected first and second harmonic. Another important feature visually noticed in the spectra is the presence of hard tail above 50 keV. This could be explained by the shocked material bounding the CIR.

Relativistic X-ray reflection and photoionized absorption in the neutron star low-mass X-ray binary GX 13+1

ABSTRACT We analysed a dedicated NuSTAR observation of the neutron star low-mass X-ray binary Z-source GX 13+1 to study the timing and spectral properties of the source. From the colour–colour diagram, we conclude that during that observation the source transitioned from the normal branch to the flaring branch. We fitted the spectra of the source in each branch with a model consisting of an accretion disc, a Comptonized blackbody, relativistic reflection (relxillNS), and photoionized absorption (warmabs). Thanks to the combination of the large effective area and good energy resolution of NuSTAR at high energies, we found evidence of relativistic reflection in both the Fe K line profile and the Compton hump present in the 10–25 keV energy range. The inner disc radius is Rin ≲ 9.6 rg , which allowed us to further constrain the magnetic field strength to B ≲ 1.8 × 108 G. We also found evidence for the presence of a hot wind leading to photoionized absorption of Fe and Ni, with a Ni overabundance of ∼6 times solar. From the spectral fits, we find that the distance between the ionizing source and the slab of ionized absorbing material is ∼4–40 × 105 km. We also found that the width of the boundary layer extends ∼3 km above the surface of a neutron star, which yielded a neutron star radius RNS ≲ 16 km. The scenario inferred from the spectral modelling becomes self-consistent only for high electron densities in the accretion disc, ne ∼ 1022 − 1023 cm−3, as expected for a Shakura–Sunyaev disc, and significantly above the densities provided by relxillNS models. These results have implications for our understanding of the physical conditions in GX 13+1.

Unravelling optical and X-ray properties of the disc-dominated intermediate polar IGR J15094-6649

ABSTRACT We present analyses of an Intermediate Polar, IGR J15094-6649, based on the archival optical data obtained from the Transiting Exoplanet Survey Satellite (TESS) and X-ray data obtained from the Suzaku, NuSTAR, and Neil Gehrels Swift Observatory (Swift). Present analysis confirms and refines the previously reported spin period of IGR J15094-6649 as 809.49584 ± 0.00075 s. Clear evidence of a beat period of 841.67376 ± 0.00082 s is found during the long-term TESS optical observations, which was not evident in the earlier studies. The dominance of X-ray and optical spin pulse unveils the disc-fed dominance accretion, however, the presence of an additional beat frequency indicates that part of the accreting material also flows along the magnetic field lines. The energy-dependent spin pulsations in the low (<10 keV) energy band are due to the photoelectric absorption in the accretion flow. However, the complex absorbers may be responsible to produce low amplitude spin modulations via Compton scattering in the hard (>10 keV) energy band and indicate that the height of the X-ray emitting region may be negligible. The observed double-humped X-ray profiles with a pronounced dip are indicative of the photoelectric absorption in the intervening accretion stream. Analysis of the X-ray spectra reveals the complexity of the X-ray emission, being composed of multitemperature plasma components with a soft excess, reflection, and suffers from strong absorption.

The multiwavelength view of shocks in the fastest nova V1674 Her

ABSTRACT Classical novae are shock-powered multiwavelength transients triggered by a thermonuclear runaway on an accreting white dwarf. V1674 Her is the fastest nova ever recorded (time to declined by two magnitudes is t2 = 1.1 d) that challenges our understanding of shock formation in novae. We investigate the physical mechanisms behind nova emission from GeV γ-rays to cm-band radio using coordinated Fermi-LAT, NuSTAR, Swift, and VLA observations supported by optical photometry. Fermi-LAT detected short-lived (18 h) 0.1–100 GeV emission from V1674 Her that appeared 6 h after the eruption began; this was at a level of (1.6 ± 0.4) × 10−6 photons cm−2 s−1. Eleven days later, simultaneous NuSTAR and Swift X-ray observations revealed optically thin thermal plasma shock-heated to kTshock = 4 keV. The lack of a detectable 6.7 keV Fe Kα emission suggests super-solar CNO abundances. The radio emission from V1674 Her was consistent with thermal emission at early times and synchrotron at late times. The radio spectrum steeply rising with frequency may be a result of either free-free absorption of synchrotron and thermal emission by unshocked outer regions of the nova shell or the Razin–Tsytovich effect attenuating synchrotron emission in dense plasma. The development of the shock inside the ejecta is unaffected by the extraordinarily rapid evolution and the intermediate polar host of this nova.

Investigation of a small X-ray flaring event in NLS1 galaxy NGC 4051

ABSTRACT We performed a detailed broad-band spectral and timing analysis of a small flaring event of ∼120 ks in the narrow-line Seyfert 1 galaxy NGC 4051 using simultaneous XMM–Newton and NuSTAR observations. The ∼300 ks long NuSTAR observation and the overlapping XMM–Newton exposure were segregated into pre-flare, flare, and post-flare segments. During the flare, the NuSTAR count rate peaked at 2.5 times the mean count rate before the flare. Using various physical and phenomenological models, we examined the 0.3–50 keV X-ray spectrum, which consists of a primary continuum, reprocessed emission, warm absorber and ultrafast outflows at different time-scales. The mass of the central black hole is estimated to be ≥1.32 × 105 M⊙ from spectral analysis. The absence of correlation between the flux in the 6–7 keV and 10–50 keV bands suggests different origins of the iron emission line and the Compton hump. From the spectral analysis, we found that the reflection fraction drops significantly during the flare, accompanied by an increase in the coronal height above the disc. The spectrum became soft during the flare, supporting the ‘softer when brighter’ nature of the source. After the alleviation of the flare, the coronal height drops and the corona heats up. This indicates that there could be inflation of the corona during the flare. We found no significant change in the inner accretion disc or the seed photon temperature. These results suggest that the flaring event occurred due to a change in coronal properties rather than any notable change in the accretion disc.

Hot accretion flows in low-luminosity active galactic nuclei in NGC 4258 and NGC 7213

ABSTRACT We study the high energy emission of two active galactic nuclei (AGNs), NGC 4258 and NGC 7213. We directly apply the general-relativistic hot flow model, kerrflow, to the archival BeppoSAX, NuSTAR, and Suzaku observations of these objects. Most of these data sets indicate that about 10–20 per cent of the accretion power is used for the direct heating of electrons; however, we find also indications for significant changes of the electron heating efficiency in some cases. Furthermore, all these X-ray data sets indicate rather strongly magnetized flows, with the magnetic field close to the equipartition with the gas pressure. Comparison of the model prediction with the Fermi/LAT data for NGC 7213 allows us to constrain the content of non-thermal protons to at most 10 per cent.

Clumpy Wind Studies and the Nondetection of a Cyclotron Line in OAO 1657–415

Winds of massive stars are suspected to be inhomogeneous (or clumpy), which biases the measures of their mass-loss rates. In high-mass X-ray binaries (HMXBs), the compact object can be used as an orbiting X-ray point source to probe the wind and constrain its clumpiness. We perform a spectrotiming analysis of the HMXB OAO 1657–415 with nonsimultaneous NuSTAR and NICER observations. We compute the hardness ratio from the energy-resolved light curves, and, using an adaptive rebinning technique, we thus select appropriate time segments to search for rapid spectral variations on timescales of a few hundred to thousands of seconds. The column density and intensity of the iron Kα line were strongly correlated, and the recorded spectral variations were consistent with accretion from a clumpy wind. We also illustrate a novel framework to measure clump sizes and masses in HMXBs more accurately based on the absorption measurements and orbital parameters of the source. We then discuss the limitations posed by current X-ray spacecraft in such measurements and present prospects with future X-ray missions. We find that the source pulse profiles show a moderate dependence on energy. We identify a previously undetected dip in the pulse profile visible throughout the NuSTAR observation near spin phase 0.15 possibly caused by intrinsic changes in accretion geometry close to the neutron star. We do not find any evidence for the debated cyclotron line at ∼36 keV in the time-averaged or phase-resolved spectra with NuSTAR.

A Broadband X-Ray Study of the Rabbit Pulsar Wind Nebula Powered by PSR J1418-6058

We report on broadband X-ray properties of the Rabbit pulsar wind nebula (PWN) associated with the pulsar PSR J1418−6058 using archival Chandra and XMM-Newton data, as well as a new NuSTAR observation. NuSTAR data above 10 keV allowed us to detect the 110 ms spin period of the pulsar, characterize its hard X-ray pulse profile, and resolve hard X-ray emission from the PWN after removing contamination from the pulsar and other overlapping point sources. The extended PWN was detected up to ∼20 keV and is described well by a power-law model with a photon index Γ ≈ 2. The PWN shape does not vary significantly with energy, and its X-ray spectrum shows no clear evidence of softening away from the pulsar. We modeled the spatial profile of X-ray spectra and broadband spectral energy distribution in the radio to TeV band to infer the physical properties of the PWN. We found that a model with low magnetic field strength (B ∼ 10 μG) and efficient diffusion (D ∼ 1027 cm2 s−1) fits the PWN data well. The extended hard X-ray and TeV emission, associated respectively with synchrotron radiation and inverse Compton scattering by relativistic electrons, suggest that particles are accelerated to very high energies (≳500 TeV), indicating that the Rabbit PWN is a Galactic PeVatron candidate.

Capturing the lowest luminosity state of the supergiant fast X-ray transient XTE J1739−302

Here, we report the results of our analysis of recent Chandra, XMM-Newton, and NuSTAR observations of the supergiant fast X-ray transient XTE J1739−302. The source was caught in a low X-ray luminosity state, from a few 1031–1034 erg s−1 (0.5–10 keV). A very low X-ray luminosity was captured during an XMM-Newton observation performed in October 2022, at a few 1031 erg s−1 (0.5–10 keV), which had never been observed before in XTE J1739−302. The XMM-Newton spectrum could be well fitted either by an absorbed, steep power-law model (photon index of 3.5) or by a collisionally ionized diffuse gas with a temperature of 0.7 keV that would very likely have been produced by shocks in the supergiant donor wind. These observations covered different orbital phases, but they all appear compatible with the low luminosity level expected from the orbital INTEGRAL light curve. The absorbing column density is variable in the range between 1022 and 1023 cm−2. The broadband X-ray spectrum was feasibly investigated at 1034 erg s−1 (0.5–30 keV) for the first time in XTE J1739−302 with non-simultaneous (albeit at similar orbital phases) Chandra and NuSTAR data, showing a power-law spectral shape with a photon index of ∼2.2 and an absorbing column density of ∼1023 cm−2. Remarkably, owing to the XMM-Newton observation, the amplitude of the X-ray variability now exceeds five orders of magnitude, making XTE J1739−302 one of the most extreme SFXTs.

Supercritical accretion of BeXRB SXP 15.3

ABSTRACTWe have studied the temporal and spectral properties of SXP 15.3, observed by NuSTAR in the hard energy range 3–79 keV during late 2018. Timing analysis of the NuSTAR observations predicts coherent pulsation at $15.2388\,\,\pm \,\,0.0002\, \mathrm{s}$. The pulse profiles in different energy bands demonstrate energy dependence. The shape of the pulse profile was generally suggestive of a fan-beam-dominated pattern, which, when combined with the measured luminosity, predicts that the source may be accreting in the supercritical regime. A non-monotonic increase in pulse fraction with energy was observed. The NuSTAR observations show that the pulse period of the source has spun up at a rate of −0.0176 s yr−1 compared with the previous analysis by the same observatory more than 1 year ago. The source flux in the present NuSTAR study in the 3–79 keV energy range is ${\sim }1.36\,\,\times \,\,10^{-10}\, \mathrm{erg\, cm}^{-2}\, \mathrm{s}^{-1}$, which corresponds to a luminosity of ${\sim }6\,\,\times \,\,10^{37}\, \mathrm{erg\, s}^{-1}$. Cyclotron line energy of the source is detected at ∼5 keV. Pulse-phase-resolved spectroscopy shows that the cyclotron line energy varies significantly with pulse phase and the photon index becomes softer with increasing flux. In addition, we have studied the evolution of the luminosity with time using 2017 and 2018 Swift/XRT observations. Analysis of the Swift/XRT data reveals that the photon index is positively correlated with the source luminosity, which is a characteristic of supercritical accretion phenomena.

Revisiting the Galactic X-Ray Binary MAXI J1631–479: Implications for High Inclination and a Massive Black Hole

X-ray spectroscopy of Galactic black hole binaries serves as a powerful tool to gain an overall understanding of the system. Not only can the properties of the accretion disk be studied in detail, the fundamental properties of the black hole such as spin and mass can also be measured. In this work we carry out a comprehensive spectral analysis of the X-ray binary MAXI J1631–479 using data from NICER and NuSTAR observatories. We trace the evolution of the accretion disk properties, such as density, ionization, and Fe abundance, as the source transitions from a disk-dominated soft state to a power-law-dominated hard intermediate state. As expected the disc ionization increased with hardness while the density and abundance (at solar values) remained unchanged. We provide strong constraints on the spin of the black hole (a > 0.996) and the inclination of the inner disk (50°–70°). We also use the soft-state NICER observations to constrain the black hole mass using distance estimates from optical observations. We find the probable mass of the black hole to be much higher than its X-ray binary counterparts with a conservative lower limit of 15 at 4.5 kpc.

Orbital- and Spin-phase Variability in the X-Ray Emission from the Accreting Pulsar Centaurus X-3

We present a time-resolved analysis using 39 ks NuSTAR observation data of the X-ray pulsar Centaurus X-3, covering an orbital-phase interval of Φ = 0.199–0.414. The orbital- and spin-phase variabilities are investigated through time-resolved spectra, light curves, and pulse profiles. The orbital-phase variability was due to the mixture of two comparable effects: intrinsic flux variability of ∼10% and obscuration by the clumpy stellar wind. The typical size and number density of the clumps are ∼9 × 1010 cm and ∼3 × 1012 cm−3, respectively. In the spin-phase-resolved analysis, we detected variations in the spectral features of the continuum, the Fe line, and the cyclotron resonance scattering feature (CRSF). The photon index ranged from 0.72 to 1.06, corresponding to the difference in the Comptonization optical depth by a factor of ∼1.6. The equivalent width and intensity of the Fe line had negative correlations with the continuum flux. The central energy and the strength of the CRSF increased at the pulse maximum. The former ranged from 26.0 to 28.7 keV, while the latter varied by a factor of ∼1.9. The pulse profile was double-peaked in the low-energy band, and it gradually shifted to being single-peaked with energy, indicating the existence of two distinct emission patterns, corresponding to the pencil and fan beams. Finally, we found that the pulse profiles were highly stable along the orbital phase, within a variation degree of ∼20%, which provides evidence of the highly stable accretion stream of the binary system.

The outburst of the changing-look AGN IRAS 23226-3843 in 2019

Aims. IRAS 23226-3843 has previously been classified as a changing-look active galactic nucleus (AGN) based on observations taken in the 1990s in comparison to X-ray data (Swift, XMM-Newton, and NuSTAR) and optical spectra taken after a very strong X-ray decline in 2017. In 2019, Swift observations revealed a strong rebrightening in X-ray and UV fluxes. We aimed to study this outburst in greater detail. Methods. We took follow-up Swift, XMM-Newton, and NuSTAR observations of IRAS 23226-3843 together with optical spectra (SALT and SAAO 1.9 m telescope) from 2019 until 2021. Results. IRAS 23226-3843 showed a strong X-ray and optical outburst in 2019. It varied in the X-ray continuum by a factor of 5 and in the optical continuum by a factor of 1.6 within two months. This corresponds to a factor of 3 after correction for the host galaxy contribution. The Balmer and Fe II emission-line intensities showed comparable variability amplitudes during the outburst in 2019. The Hα emission-line profiles of IRAS 23226-3843 changed from a blue-peaked profile in the years 1997 and 1999 to a broad double-peaked profile in 2017 and 2019. However, there were no major profile variations in the extremely broad double-peaked profiles despite the strong intensity variations in 2019. One year after the outburst, IRAS 23226-3843 changed its optical spectral type and became a Seyfert type 2 object in 2020. Blue outflow components are present in the optical Balmer lines and in the Fe band in the X-rays. A deep broadband XMM-Newton/NuSTAR spectrum was taken during IRAS 23226-3843’s maximum state in 2019. This spectrum is qualitatively very similar to a spectrum taken in 2017, but by a factor of 10 higher. The soft X-ray band appears featureless. The soft excess is well modeled with a Comptonization model. A broadband fit with a power-law continuum, Comptonized soft excess, and Galactic absorption gives a good fit to the combined EPIC-pn and NuSTAR spectrum. In addition, we see a complex and broadened Fe K emission-line profile in the X-rays. The changing-look character in IRAS 23226-3843 is most probably caused by changes in the accretion rate – based on the short-term variations on timescales of weeks to months.

NuSTAR Observes Two Bulgeless Galaxies: No Hard X-Ray AGN Detected in NGC 4178 or J0851+3926

The discovery over the last several decades of low- and moderate-luminosity active galactic nuclei (AGNs) in disk-dominated galaxies—which show no “classical” bulges—suggests that secular mechanisms represent an important growth pathway for supermassive black holes in these systems. We present new follow-up NuSTAR observations of the optically elusive AGNs in two bulgeless galaxies, NGC 4178 and J0851+3926. Galaxy NGC 4178 was originally reported as hosting an AGN based on the detection of [Ne v] mid-infrared emission detected by Spitzer, and based on Chandra X-ray imaging, it has since been argued to host either a heavily obscured AGN or a supernova remnant. Galaxy J0851+3926 was originally identified as an AGN based on its Wide-Field Infrared Survey Explorer mid-IR colors, and follow-up near-infrared spectroscopy previously revealed a hidden broad-line region, offering compelling evidence for an optically elusive AGN. Neither AGN is detected within the new NuSTAR imaging, and we derive upper limits on the hard X-ray 10–24 keV fluxes of <7.41 × 10−14 and <9.40 × 10−14 erg cm−2 s−1 for the AGNs in NGC 4178 and J0851+3926, respectively. If these nondetections are due to large absorbing columns along the line of sight, the nondetections in NGC 4178 and J0851+3926 could be explained with column densities of log(N H/cm2) > 24.2 and 24.1, respectively. The nature of the nuclear activity in NGC 4178 remains inconclusive; it is plausible that the [Ne v] traces a period of higher activity in the past, but that the AGN is relatively quiescent now. The nondetection in J0851+3926 and multiwavelength properties are consistent with the AGN being heavily obscured.

Wideband study of the brightest black hole X-ray binary 4U 1543−47 in the 2021 outburst: signature of disc-wind regulated accretion

ABSTRACT A comprehensive wideband spectral analysis of the brightest black hole X-ray binary 4U 1543−47 during its 2021 outburst is carried out for the first time using NICER, NuSTAR, and AstroSat observations by phenomenological and reflection modelling. The source attains a super-Eddington peak luminosity and remains in the soft state, with a small fraction ($\lt 3{{\ \rm per\ cent}}$) of the inverse-Comptonized photons. The spectral modelling reveals a steep photon index (Γ ∼ 2–2.6) and relatively high inner disc temperature (Tin ∼ 0.9–1.27 keV). The line-of-sight column density varies between (0.45–0.54) × 1022 cm−2. Reflection modelling using the RELXILL model suggests that 4U 1543−47 is a low-inclination system (θ ∼ 32°–40°). The accretion disc is highly ionized (log ξ &amp;gt; 3) and has super solar abundance (3.6–10 AFe,⊙) over the entire period of study. We detected a prominent dynamic absorption feature between ∼8 and 11 keV in the spectra throughout the outburst. This detection is the first of its kind for X-ray binaries. We infer that the absorption of the primary X-ray photons by the highly ionized, fast-moving disc winds can produce the observed absorption feature. The phenomenological spectral modelling also shows the presence of a neutral absorption feature ∼7.1–7.4 keV, and both ionized and neutral absorption components follow each other with a delay of a typical viscous time-scale of 10–15 d.

A NuSTAR view of SS433

Context. SS433 is a Galactic microquasar with powerful outflows (double jet, accretion disk and winds) with a well-known orbital, precessional, and nutational period. Aims. In this work we characterise different outflow parameters throughout the precessional cycle of the system. Methods. We analysed ten NuSTAR (3–70 keV) observations of ∼30 ks that span ∼1.5 precessional cycles. We extracted averaged spectra and modelled them using a combination of a double thermal jet model (bjet) and pure neutral and relativistic reflection (xillverCp and relxilllpCp) over an accretion disk. Results. We find an average jet bulk velocity of β = v/c ∼ 0.29 with an opening angle of ≲6 deg. Eastern jet kinetic power ranges from 1 to 1039 erg s−1, with base ‘coronal’ temperatures To ranging from between 14 and 18 keV. Nickel-to-iron abundances remain constant at ∼9 (within 1σ). The western to eastern jet-flux ratio becomes ∼1 on intermediate phases, which is about 35% of the total precessional orbit. The 3–70 keV total unabsorbed luminosity of the jet and disk ranges from 2 to 20 × 1037 erg s−1, with the disk reflection component mainly contributing to the hard 20–30 keV excess and the stationary 6.7 keV ionised Fe line complex. Conclusions. At low opening angles Θ, we find that the jet expands sideways following an adiabatic expansion of a gas with temperature To. Finally, the central source and lower parts of the jet could be hidden by an optically thick region of τ &gt; 0.1 and size R ∼ NH/ne0 ∼ 1.5 × 109 cm ∼ 1700 rg for MBH = 3 M⊙.

Broadband study and the discovery of pulsations from the Be/X-ray binary eRASSU J052914.9−662446 in the Large Magellanic Cloud

Context.The Magellanic Clouds are our nearest star-forming galaxies. While the population of high-mass X-ray binaries (HMXBs) in the Small Magellanic Cloud is relatively well studied, our knowledge about the Large Magellanic Cloud (LMC) is far from complete given its large angular extent and the insufficient coverage with X-ray observations.Aims.We conducted a search for new HMXBs in the LMC using data from eROSITA, the soft X-ray instrument on board the Spektrum-Roentgen-Gamma satellite.Methods.After confirming the nature of eRASSU J052914.9−662446 as a hard X-ray source that is positionally coincident with an early-type star, we followed it up with optical spectroscopic observations from the South African Large Telescope (SALT) and a dedicatedNuSTARobservation.Results.We study the broadband timing and spectral behaviour of the newly discovered HMXB eRASSU J052914.9−662446 through eROSITA,Swift, andNuSTARdata in X-rays and the Optical Gravitational Lensing Experiment (OGLE) and SALT RSS data at the optical wavelength. We report the detection of a spin period at 1412 s and suggest that the orbital period of the system is ∼151 days. We thereby establish that eRASSU J052914.9−662446 is an accreting pulsar. Furthermore, through optical spectroscopic observations and the detection of Hαemission, the source is identified as a Be X-ray binary pulsar in the LMC. We also investigated the variability of the source in the optical and X-ray regime over the past decades and provide estimates of the possible magnetic field strength of the neutron star.