We present results of the spectral and timing analysis of the X-ray pulsar LMC X-4 with the NuSTAR observatory in the broad energy range 3-79 keV. Along with the detailed analysis of the averaged source spectrum, the high-precision pulse phased-resolved spectra were obtained for the first time. It has been shown that the comptonization model gives the best approximation of the obtained spectra. The evolution of its parameters was traced depending on the pulse phase as well. The search for the possible cyclotron absorption line was performed for all energy spectra in the 5-55 keV energy range. The obtained upper limit for the depth of the cyclotron absorption line $τ\simeq0.15$ ($3σ$) indicates no cyclotron absorption line in this energy range, which provides an estimate of the magnitude of the magnetic field on the surface of the neutron star: $B < 3 \times 10^{11}$ G or $B > 6.5 \times 10^{12}$ G. The latter one is agree with the estimate of the magnetic field obtained from the analysis of the power spectrum of the pulsar: $B \sim 3 \times 10^{13}$ G. Based on results of the pulse phase-resolved spectroscopy we revealed a delay between maxima of the source emission and the equivalent width of the fluorescent iron line. This delay can be apparently associated with the travel time of photons between the emitting regions in the vicinity of the neutron star and the relatively cold regions where this emission is reflected (presumably, at the inflowing stream or at the place of an interaction of the stream and the outer edge of the accretion disk).
We present the results obtained from detailed spectral and timing studies of extra-galactic black hole X-ray binaries LMC~X--1 and LMC~X--3, using simultaneous observations with {\it Nuclear Spectroscopic Telescope Array (NuSTAR)} and {\it Neil Gehrels Swift} observatories. The combined spectra in the $0.5-30$~keV energy range, obtained between 2014 and 2019, are investigated for both sources. We do not find any noticeable variability in $0.5-30$~keV light curves, with $0.1-10$~Hz fractional rms estimated to be $<2$\%. No evidence of quasi-periodic oscillations is found in the power density sp…
We present results of the analysis of super-Eddington flares registered from the X-ray pulsar LMC X-4 by the NuSTAR observatory in the broad energy range 3-79 keV. The pulsar spectrum is well described by the thermal comptonization model both in a quiescent state and during flares, when the peak luminosity reaches values $L_{\rm x} \sim (2-4)\times10^{39}$ erg s$^{-1}$. An important feature, found for the first time, is that the order of magnitude increase in the luminosity during flares is observed primarily at energies below 25-30 keV, whereas at higher energies (30-70 keV) the shape of the …
We present a broad-band X-ray study of the effect of superorbital periods on X-ray spectra and pulse profiles in the neutron star X-ray binaries LMC X-4 and SMC X-1. These two sources display periodic or quasi-periodic variations in luminosity on the order of tens of days which are known to be superorbital, and are attributed to warped, precessing accretion disks. Using joint NuSTAR and XMM-Newton observations that span a complete superorbital cycle, we examine the broad-band spectra of these sources and find the shape to be well described by an absorbed power law with a soft blackbody compone…
We report results of the first detailed spectral and temporal studies of the recently discovered Be/X-ray binary eRASSU J050810.4$-$660653 in LMC based on the data from the SRG/ART-XC, NuSTAR and Swift/XRT instruments obtained in December 2021 - May 2022 in a wide energy range of 0.5-79 keV. Pulsations with the period of $40.5781 \pm 0.0004$ s were found in the source light curve with the pulsed fraction monotonically increasing with the energy. An estimate of the orbital period of $\sim38$ days was obtained based on the long-term monitoring of the system. The source spectrum can be well appro…
We have studied the Be/X-ray binary (BeXRB) pulsar eRASSU J050810.4-660653 recently discovered in the Large Magellanic Cloud (LMC). Timing and spectral features of the source have been discussed in detail using NuSTAR \& XMM-Newton observations. Coherent pulsation of the source was detected at $\sim 40.578\;\pm\;0.001$ s using NuSTAR observation. We analyzed pulse profiles of the source in different energy bands using NuSTAR \& XMM-Newton data. The pulse-profile evolved with time but was generally suggestive of a pencil-beam dominated pattern, which combined with the measured luminosity, indic…
We present results of long NuSTAR (200 ks) and XMM-Newton (100 ks) observations of the Arches stellar cluster, a source of bright thermal (kT~2 keV) X-rays with prominent Fe XXV K_alpha 6.7 keV line emission and a nearby molecular cloud, characterized by an extended non-thermal hard X-ray continuum and fluorescent Fe K_alpha 6.4 keV line of a neutral or low ionization state material around the cluster. Our analysis demonstrates that the non-thermal emission of the Arches cloud underwent a dramatic change, with its homogeneous morphology, traced by fluorescent Fe K_alpha line emission, vanishin…
Extragalactic black hole X-ray binaries LMC X-1 and LMC X-3 are the persistent sources, usually found in soft spectral state. We present the results from spectral and timing study of these sources using MAXI, NICER, NuSTAR and AstroSat observations carried out during 2014-2020. Study of long-term MAXI lightcurve shows that the fractional variability of flux in 2-10keV is moderate ($\sim$20%) in LMCX-1 and high ($\sim$50%) in LMCX-3. The energy spectra of both sources are characterized by a disc blackbody and a Comptonization component with LMCX-1 having an additional Fe-line emission feature. …
The cold disk/torus gas surrounding active galactic nuclei (AGN) emits fluorescent lines when irradiated by hard X-ray photons. The fluorescent lines of elements other than Fe and Ni are rarely detected due to their relative faintness. We report the detection of K$α$ lines of neutral Si, S, Ar, Ca, Cr, and Mn, along with the prominent Fe K$α$, Fe K$β$, and Ni K$α$ lines, from the deep Chandra observation of the low-luminosity Compton-thick AGN in M51. The Si K$α$ line at 1.74 keV is detected at $\sim3σ$, the other fluorescent lines have a significance between 2 and 2.5 $σ$, while the Cr line h…
We report on a \textit{NuSTAR} and \textit{Swift}/XRT observation of the newly discovered X-ray transient MAXI J1820+070. \textit{Swift}/XRT and \textit{NuSTAR} have concurrently observed the newly detected source on 14 March 2018. We have simultaneously fitted the broad-band spectra obtained from \textit{Swift}/XRT and \textit{NuSTAR}. The observed joint spectra in the energy range 0.6--78.0 keV are well modeled with a weak disk black-body emission, dominant thermal Comptonization and relativistic reflection fraction. We have detected a fluorescent Iron-K$α$ line relativistically broadened, a…
We present the first high-resolution X-ray study of emission line variability with superorbital phase in the neutron star binary LMC X-4. Our analysis provides new evidence from X-ray spectroscopy confirming accretion disk precession as the origin of the superorbital period. The spectra, obtained with the Chandra High-Energy Transmission Grating Spectrometer (HETGS) and the XMM-Newton Reflection Grating Spectrometer (RGS), contain a number of emission features, including lines from hydrogen-like and helium-like species of N, O, Ne, and Fe, a narrow O VII RRC, and fluorescent emission from cold…
We studied the spectral changes of the high-mass X-ray binary system LMC X-4 to understand the origin and mechanisms beyond its super-orbital modulation (30.4 days). To this aim, we obtained a monitoring campaign with Swift/XRT (0.3-10 keV) and complemented these data with the years-long Swift/BAT survey data (15-60 keV). We found a self-consistent, physically motivated, description of the broadband X-ray spectrum using a Swift/XRT and a NuSTAR observation at the epoch of maximum flux. We decomposed the spectrum into the sum of a bulk+thermal Comptonization, a disk-reflection component and a s…
In this work, we present a spectral and temporal analysis of {\it Swift}/XRT and {\it NuSTAR} observations of GRS 1716--249 during its recent 2016--2017 outburst. This low mass X-ray binary underwent an extraordinary outburst after a long quiescence of 23 years, since its last major outburst in 1993. The source was observed over two different epochs during 2017 April, 07 and 10. The best fit joint spectral fitting in the energy range 0.5 $-$ 79.0 keV indicates that the spectrum is best described by relatively cold, weak disk blackbody emission, dominant thermal Comptonization emission, and a r…
Two \textit{NuSTAR} observations of the luminous X-ray pulsar LMC X-4 in October and November 2015 captured several bright accretion flares from this source, which has a long history of stable pulse and superorbital behavior. We present a timing analysis of these data in which we detect a rapid pulse turn-on in association with the accretion flares, during which the source reaches super-Eddington luminosities. Pulsations, which are normally seen from this source, are found to only occur for approximately one hour before and during the bright flares. Beyond one hour before and after the flares,…
We present simultaneous XMM-Newton and NuSTAR observations spanning 3-78 keV of the nearest radio galaxy, Centaurus A (Cen A). The accretion geometry around the central engine in Cen A is still debated, and we investigate possible configurations using detailed X-ray spectral modeling. NuSTAR imaged the central region of Cen A with sub-arcminute resolution at X-ray energies above 10 keV for the first time, but finds no evidence for an extended source or other off-nuclear point-sources. The XMM-Newton and NuSTAR spectra agree well and can be described with an absorbed power-law with a photon ind…
We present results from ${\it NuSTAR}$ and ${\it SWIFT}$/XRT joint spectral analysis of V4641 Sgr during a disk dominated or soft state as well as a powerlaw dominated or hard state. The soft state spectrum is well modeled by a relativistically blurred disk emission, a powerlaw, a broad Iron line, two narrow emission lines and two edges. The Markov Chain Monte Carlo simulation technique and the relativistic effects seen in the disk and broad Iron line allow us to self-consistently constrain the inner disk radius, disk inclination angle and distance to the source at 2.43$^{+0.39}_{-0.17}$ R$_g$…
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 (SMC) is relatively well studied, our knowledge about the Large Magellanic Cloud (LMC) is far from complete given its large angular extent and 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 (SRG) satellite. Methods. After confirming the nature of eRASSU J052914.9-662446 as a hard X-ray source position…
We report on the timing and spectral analysis of two Suzaku observations with different flux levels of the high-mass X-ray binary KS 1947+300 during its 2013 outburst. In agreement with simultaneous NuSTAR observations, the continuum is well described by an absorbed power law with a cut-off and an additional black body component. In addition we find fluorescent emission from neutral, He-like, and even H-like iron. We determine a pulse period of ~18.8 s with the source showing a spin-up between the two observations. Both Suzaku observations show a very similar behavior of the pulse profile, whi…
[Abridged] We investigated the X-ray characteristics of the Class I YSO Elias 29 with joint XMM-Newton and NuSTAR observations of 300 ks and 450 ks, respectively. These are the first observations of a very young (<1 Myr) stellar object in a band encompassing simultaneously both soft and hard X-rays. In addition to the hot Fe complex at 6.7 keV, we observed fluorescent emission from Fe at $\sim6.4$ keV, confirming the previous findings. The line at 6.4 keV is detected during quiescent and flaring states and its flux is variable. The equivalent width is found varying in the $\approx 0.15--0.5$ k…
Using X-ray observations from the NuSTAR and Swift satellites, we present temporal and spectral properties of an intermediate polar (IP) IGR J16547-1916. A persistent X-ray period at ~ 546 s confirming the optical spin period obtained from previous observations is detected. The detection of a strong X-ray spin pulse reinforces the classification of this system as an intermediate polar. The lack of orbital or side-band periodicities in the X-rays implies that the system is accreting predominantly via a disk. A variable covering absorber appears to be responsible for the spin pulsations in the l…
The fundamental parameters describing the coronal spectrum of an accreting black hole are the slope $Γ$ of the power-law continuum and the energy $E_{cut}$ at which it rolls over. Remarkably, this parameter can be accurately measured for values as high as 1 MeV by modeling the spectrum of X-rays reflected from a black hole accretion disk at energies below 100 keV. This is possible because the details in the reflection spectrum, rich in fluorescent lines and other atomic features, are very sensitive to the spectral shape of the hardest coronal radiation illuminating the disk. We show that fitti…
The Be X-ray pulsar SMC X-3 underwent an extra long and ultraluminous giant outburst from 2016 August to 2017 March. The peak X-ray luminosity is up to $\sim 10^{39}$ erg/s, suggesting a mildly super-Eddington accretion onto the strongly magnetized neutron star. It therefore bridges the gap between the Galactic Be/X-ray binaries ($L_{\rm X}^{\rm peak} \leq 10^{38}$ erg/s) and the ultraluminous X-ray pulsars ($L_{\rm X}^{\rm peak} \geq 10^{40}$ erg/s) found in nearby galaxies. A number of observations were carried out to observe the outburst. In this paper, we perform a comprehensive phase-reso…
Complex Nuclear Structure in Seyfert 2 Galaxy NGC 4388 Revealed by XRISM Observation
Kyoto University（京都大学）；Institute of Space and Astronautical Science (ISAS), Japan Aerospace Exploration Agency (JAXA)（日本宇宙航空研究开发机构宇宙科学研究所）；University of Michigan（密歇根大学）；NASA Goddard Space Flight Center (GSFC)（美国国家航空航天局戈达德太空飞行中心）；Osaka University（大阪大学）；Max-Planck-Institut für Extraterrestrische Physik（马克斯·普朗克地外物理研究所）；Saint Mary’s University（圣玛丽大学）；University of Teacher Education Fukuoka（福冈教育大学）
In intermediate polars (IPs), the intrinsic thermal emissions from white dwarfs (WDs) have typically been studied. Few reports have analyzed X-ray reflections from WDs. We recently developed an elaborate IP-reflection spectral model. Herein, we report the first application of a reflection model with an IP thermal model to the spectra of the brightest typical IP V1223 Sagittarii observed by the Suzaku and NuSTAR satellites. The model reasonably reproduces the spectra within the range of 5-78 keV and estimates the WD mass as 0.92$\pm$0.02 $M_\odot$. The WD mass estimated by the proposed model is…
Classification of IGR J20084+3221 as an Intermediate Polar using X-ray and Optical Observations
University of California, San Diego（加州大学圣迭戈分校）；NASA Goddard Space Flight Center（美国宇航局戈达德太空飞行中心）；Center for Research and Exploration in Space Science and Technology, NASA/GSFC（NASA/GSFC空间科学与技术研究探索中心）；The Catholic University of America（美利坚天主教大学）；Jet Propulsion Laboratory, California Institute of Technology（加州理工学院喷气推进实验室）；Butler University（巴特勒大学）
