An X-ray survey of the Galactic center region with a radius of ~20◦ has been performed using the data obtained with the JEM-X telescope onboard the INTEGRAL observatory over ~10 years of observations ...(2003–2013). The exposure at the field center directly toward the Galactic center has reached 4.8 Ms. We have constructed sky maps in the 5–10 and 10–25 keV energy bands and compiled a catalog of detected sources. Together with 83 sources revealed on the integral sky maps, it includes 22 transients that are absent on them but are confidently detected during outbursts with a duration of several days. One of the persistent sources, IGR J17452-2909, has never been observed previously. In contrast to the catalog of sources detected in the harder energy band by the IBIS/ISGRI telescope onboard the INTEGRAL observatory, most of the sources in this catalog are low-mass X-ray binaries (73 of the 105 sources) and only 18 + 3 are high-mass X-ray binaries and cataclysmic variables. Out of the Galactic sources, there are also the black hole candidate XTE J1652-453, the peculiar X-ray burster XMMJ174457-2850.3, and the soft gamma repeater SGR 1806–20 in the catalog; out of the extragalactic sources, there are three active galactic nuclei and a galaxy cluster (Oph CL). The nature of four sources, including the newly discovered one, still remains unknown. We have constructed the luminosity function for the low-mass X-ray binaries from the catalog and considered other statistical properties of their sample.
We report the discovery of low-frequency quasi-periodic oscillations (QPOs) in the power spectrum of the X-ray nova MAXI J1535-571 at the initial stage of its outburst in September 2017. Based on ...data from the SWIFT and INTEGRAL instruments, we have traced the evolution of the QPO parameters (primarily their frequency) with time and their correlation with changes in the X-ray spectrum of the source (changes in the emission flux and hardness). We place constraints on the theoretical QPO generation models.
The discovery of a type I X-ray burst from the faint unidentified transient source IGR J17445-2747 in the Galactic bulge by the JEM-X telescope onboard the INTEGRAL observatory is reported. Type I ...bursts are believed to be associated with thermonuclear explosions of accreted matter on the surface of a neutron star with a weak magnetic field in a low-mass X-ray binary. Thus, this observation allows the nature of this source to be established.
We present the first results of the SRG observation of the pulsar 4U 1538–52 based on ARC-XC and eROSITA data. An extended emission in the form of a halo is detected around the source in the 0.5–8 ...keV energy band. Our simulation has shown that its surface brightness distribution can be described by a two-component model composed of a flat disk
in radius and a
-model with a characteristic size
. We have constructed a broadband spectrum of 4U 1538–52 in the energy range 0.5–30 keV, which can be fitted by a weakly absorbed (
cm
) power law with a high-energy cutoff. In addition, iron emission lines are detected in the pulsar spectrum at 6–7 keV. We show that the observed halo spectrum is considerably softer (a power-law index
) than the pulsar spectrum (a power-law index
), consistent with the predictions of theoretical models for the X-ray scattering by dust.
The source SXP 1323 is a peculiar high-mass X-ray binary located in the Small Magellanic Cloud. It is renowned for its rapid spin-up. We investigate for the first time broadband X-ray properties of ...SXP 1323 as observed by the
Mikhail Pavlinsky
ART-XC and eROSITA telescopes on board the Spectrum-Roentgen-Gamma observatory. Using ART-XC and eROSITA data, we produced a first broadband 1−20 keV X-ray spectrum and estimated the pulsed fraction box 8 keV. With the addition of archival
XMM-Newton
observations, we traced the evolution of the spin period of SXP 1323 over the last five years and found that after 2016, the source switched to a linear spin-up with a rate of −29.9 s yr
−1
. The broadband X-ray spectrum is typical for accreting X-ray pulsars. It has a steep power-law index (Γ = −0.15) and an exponential cutoff energy of 5.1 keV. No significant difference between spectra obtained in states with and without pulsations were found.
The dependence of the spin frequency derivative
ν
˙
of accreting neutron stars with a strongmagnetic field (X-ray pulsars) on the mass accretion rate (bolometric luminosity,
L
bol
) has been ...investigated for eight transient pulsars in binary systems with Be stars. Using data from the Fermi/GBM and Swift/BAT telescopes, we have shown that for seven of the eight systems the dependence
ν
˙
(
L
bol
) can be fitted by the model of angular momentum transfer through an accretion disk, which predicts the relation
ν
˙
∼
L
6/7
bol
. Hysteresis in the dependence
ν
˙
(
L
bol
) has been confirmed in the system V 0332+53 and has been detected for the first time in the systems KS 1947+300, GRO J1008-57, and 1A 0535+26. Estimates for the radius of the neutron star magnetosphere in all of the investigated systems have been obtained. We show that this quantity varies from pulsar to pulsar and depends strongly on the analytical model and the estimates for the neutron star and binary system parameters.
We present an analysis of the X-ray data obtained in the period of flaring activity of SS 433 in July and August 2018, during which the brightest radio flares over the entire history of its ...observations were detected at frequencies 2–5 GHz based on data from the RATAN-600 radio telescope. The Swift/XRT and NICER space observatory data were obtained immediately during the radio flares within the program of Target of Opportunity (ToO) observations. The Chandra/HETGS observations and the additional quasi-simultaneous NICER calibration observations were carried out in the active phase of the system between the radio intensity peaks. We show that during the peak radio fluxes the emission lines of the relativistic jets are detected with confidence in the X-ray spectrum, while their basic parameters remain stable, which can serve as evidence for the absence of significant violations in the jet collimation and acceleration mechanisms. At the same time, the X-ray intensity of the jets at these moments drops by a factor of 4–5 and is restored to its normal values within
days. Anomalous deviations of the jet line positions from the predictions of the kinematic model were found in the period of activity and during the radio flares. Our modeling of the Chandra spectra using the emission model of baryonic jets in SS 433 point to rapid changes in the structure of the wind from the supercritical disk that partially blocks the emission from the hottest regions of the jets. The set of these factors points to a possible connection of the emergence of radio flares and active states of SS 433 with perturbations in the rate of mass transfer and outflow in the system.
Close binary systems consisting of two neutron stars (BNS) emit gravitational waves, that allow them to merge on timescales shorter than Hubble time. It is widely believed, that NS–NS mergers in such ...systems power short gamma-ray bursts (GRB). Several mechanisms which could lead to electromagnetic energy release prior to a merger have been proposed. We estimate the ability to observe the possible pre-burst emission with telescopes of Spectrum–Roentgen–Gamma. We also investigate first such event, GRB210919A, which fell into the field of view of the SRG telescopes less than two days before the burst.
We present a catalog of sources detected by the Mikhail Pavlinsky ART-XC telescope onboard the SRG space observatory during the observations of the Galactic plane region near a longitude
(L20 field) ...in October 2019. The L20 field was observed four times in the scanning mode, which provided a uniform coverage of the sky region with a total area of
with a median sensitivity of
erg s
cm
(at 50
detection completeness) in the 4–12 keV energy band. As a result, we have detected 29 X-ray sources at a statistically significant level, 11 of which have not been detected previously by other X-ray observatories. Preliminary estimates show that four of them can presumably be extragalactic in nature. We also show that the source SRGA J183220.1
103508 (CXOGSG J183220.8
103510) is most likely a galaxy cluster containing a bright radio galaxy at redshift
.
Based on long-term SWIFT, RXTE, and MAXI observations of the X-ray novae H 1743-322 (IGR J17464-3213) and GX 339-4, we have investigated the morphology and classified the light curves of their X-ray ...outbursts. In particular, we have confirmed the existence of two radically different types of outbursts, soft (S) and hard (H), in both sources and revealed their varieties, ultrabright (U) and intermediate (I). The properties and origin of the differences in the light curves of these outbursts are discussed in terms of the truncated accretion disk model.
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