ABSTRACT
We present the first sample of tidal disruption events (TDEs) discovered during the SRG all-sky survey. These 13 events were selected among X-ray transients detected in the 0° < l < 180° ...hemisphere by eROSITA during its second sky survey (2020 June 10 to December 14) and confirmed by optical follow-up observations. The most distant event occurred at z = 0.581. One TDE continued to brighten at least 6 months. The X-ray spectra are consistent with nearly critical accretion on to black holes of a few ×103 to $10^8\, \mathrm{ M}_\odot$, although supercritical accretion is possibly taking place. In two TDEs, a spectral hardening is observed 6 months after the discovery. Four TDEs showed an optical brightening apart from the X-ray outburst. The other nine TDEs demonstrate no optical activity. All 13 TDEs are optically faint, with Lg/LX < 0.3 (Lg and LX being the g band and 0.2–6 keV luminosity, respectively). We have constructed a TDE X-ray luminosity function, which can be fit by a power law with a slope of −0.6 ± 0.2, similar to the trend observed for optically selected TDEs. The total rate is estimated at (1.1 ± 0.5) × 10−5 TDEs per galaxy per year, an order of magnitude lower than inferred from optical studies. This suggests that X-ray bright events constitute a minority of TDEs, consistent with models predicting that X-rays can only be observed from directions close to the axis of a thick accretion disc formed from the stellar debris. Our TDE detection threshold can be lowered by a factor of ∼2, which should allow a detection of ∼700 TDEs by the end of the SRG survey.
The MVN (Monitor Vsego Neba, all-sky monitor) experiment onboard the International Space Station for high-accuracy measurement of the cosmic X-ray background by the aperture modulation method being ...planned in 2022–2025 is considered. The technique that allows the measurement error within the MVN experiment to be minimized is described. Simulations of the main results of the experiment have been performed. They have shown that a record accuracy of measuring the cosmic X-ray background can be achieved. The main MVN systems are considered, and the results of the flight and ground-based experiments to measure the parameters of these systems are presented.
The article describes the MVN experiment (MVN – Monitor Vsego Neba in Russian transliteration) – All Sky Monitor onboard the ISS, which will start in 2021. The main scientific task of the experiment ...is to measure the cosmic X-ray background in energy range of 6 – 70 keV with unprecedented high absolute and spectral accuracy (about 1%). To reach this goal, Space Research Institute of the Russian Academy of Sciences has developed scientific payload called MVN. The main instrument of MVN is the SPIN-X1-MVN X-ray monitor, which is equipped with four CdTe based semiconductor detectors. The X-ray monitor will be mounted on the external surface of the ISS with zenith orientation. The structure of the monitor including the key systems (detectors, gears, thermal control system) is considered. Measuring of the cosmic X-ray background is carried out by the aperture modulation method described in detail in this article. Also we describe an optimal algorithm of the obtained in experiment data filtering, which will provide us with highest quality of the CXB measurement.
The Atmospheric Chemistry Suite (ACS) package is an element of the Russian contribution to the ESA-Roscosmos ExoMars 2016 Trace Gas Orbiter (TGO) mission. ACS consists of three separate infrared ...spectrometers, sharing common mechanical, electrical, and thermal interfaces. This ensemble of spectrometers has been designed and developed in response to the Trace Gas Orbiter mission objectives that specifically address the requirement of high sensitivity instruments to enable the unambiguous detection of trace gases of potential geophysical or biological interest. For this reason, ACS embarks a set of instruments achieving simultaneously very high accuracy (ppt level), very high resolving power (>10,000) and large spectral coverage (0.7 to 17 μm—the visible to thermal infrared range). The near-infrared (NIR) channel is a versatile spectrometer covering the 0.7–1.6 μm spectral range with a resolving power of ∼20,000. NIR employs the combination of an echelle grating with an AOTF (Acousto-Optical Tunable Filter) as diffraction order selector. This channel will be mainly operated in solar occultation and nadir, and can also perform limb observations. The scientific goals of NIR are the measurements of water vapor, aerosols, and dayside or night side airglows. The mid-infrared (MIR) channel is a cross-dispersion echelle instrument dedicated to solar occultation measurements in the 2.2–4.4 μm range. MIR achieves a resolving power of >50,000. It has been designed to accomplish the most sensitive measurements ever of the trace gases present in the Martian atmosphere. The thermal-infrared channel (TIRVIM) is a 2-inch double pendulum Fourier-transform spectrometer encompassing the spectral range of 1.7–17 μm with apodized resolution varying from 0.2 to 1.3 cm
−1
. TIRVIM is primarily dedicated to profiling temperature from the surface up to ∼60 km and to monitor aerosol abundance in nadir. TIRVIM also has a limb and solar occultation capability. The technical concept of the instrument, its accommodation on the spacecraft, the optical designs as well as some of the calibrations, and the expected performances for its three channels are described.
The models and results of the experimental studies of the characteristics of objects that are new for domestic instrumentation are presented: an X-ray mirror system and a CdTe strip semiconductor ...detector that are used in the first Russian ART-XC reflecting X-ray telescope. This telescope is a part of the Spektr-RG international space observatory, which started to the L2 libration point in July 2019.
During a 2-year period in 2005–2007, we conducted surveillance of group A rotaviruses and other enteric agents among patients hospitalized with acute gastroenteritis in 8 different cities of the ...Russian Federation. Fecal specimens were gathered from 3208 children (including 2848 children aged <5 years) and 1354 adults who were admitted to hospitals in Moscow, St. Petersburg, Chelyabinsk, Nizhnii Novgorod, Tyumen, Khabarovsk, Makhachkala, and Yakutsk. Polymerase chain reaction was performed to detect rotaviruses of groups A and C, noroviruses of genogroups I and II, astrovirus, sapovirus, and enteric adenoviruses (group F). Group A rotavirus was the most common viral pathogen detected among children aged <5 years (43.6%), followed by norovirus (12.5%), whereas norovirus was the pathogen most commonly detected in adults (11.9%). P and G genotypes were determined for 515 rotavirus specimens, and the most prevalent genotypes were G1P8 (44.9%), G4P8 (40.0%), G2P4 (8.5%), and G3P8 (6.6%). This study is the first multicenter study of rotaviruses in the Russian Federation and documents the important burden of disease caused by this pathogen, which soon may be preventable by vaccination
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.
During accretion-induced outbursts, low-mass X-ray binaries demonstrate a complex behavior accompanied by a rapid change in their spectral and timing characteristics in the entire range of the ...electromagnetic spectrum — from radio to hard X-rays. So far there is no complete, self-consistent model describing all of the observed phenomena, including the rapid changes in visible and near-infrared fluxes and the correlation of these changes with the X-ray emission, while the observed evolution of outbursts is described in terms of the transition between characteristic states. Based on quasi-simultaneous optical, infrared, and X-ray observations, we show that the sharp decline in optical brightness near the low/hard-to-high/soft state transition is accompanied by an increase in the frequency of the observed X-ray quasi-periodic oscillations. This behavior can be explained in terms of the model in which both X-ray and optical emissions are produced by the synchrotron mechanism in a hot flow near a compact object.
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
.
ABSTRACT
We present phase-resolved spectroscopy, photometry, and circular spectropolarimetry of the eclipsing polar UZ Fornacis. Doppler tomography of the strongest emission lines using the ...inside-out projection revealed the presence of three emission regions: from the irradiated face of the secondary star, the ballistic stream and the threading region, and the magnetically confined accretion stream. The total intensity spectrum shows broad emission features and a continuum that rises in the blue. The circularly polarized spectrum shows the presence of three cyclotron emission harmonics at ∼4500, 6000, and 7700 Å, corresponding to harmonic numbers 4, 3, and 2, respectively. These features are dominant before the eclipse and disappear after the eclipse. The harmonics are consistent with a magnetic field strength of ∼57 MG. We also present phase-resolved circular and linear photopolarimetry to complement the spectropolarimetry around the times of eclipse. MeerKAT radio observations show a faint source that has a peak flux density of 30.7 ± 5.4 $\mu$Jy beam−1 at 1.28 GHz at the position of UZ For.
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