arXiv subjects

Sergei Trushkin

Publications and source records attributed to Sergei Trushkin.

5 recordsLinked to original sources

arXiv2026

Distinct Jet Properties in the X-Ray-Obscured State of GRS 1915+105

GRS 1915+105 has remained in an X-ray-obscured state since its transition from a long-lasting unobscured state in 2019. We report on 6.7-GHz East Asia VLBI Network observations of GRS 1915+105 obtained during strong radio flares detected at 2.3--11.2 GHz with the RATAN-600 radio telescope in 2025. Our images reveal two contrasting jet morphologies. The first epoch, associated with a flare evolving from an optically thick to an optically thin spectrum, shows a bright radio core accompanied by an extended jet structure. By contrast, the second epoch, observed near the peak of another flare displaying optically thin emission at lower frequencies, is dominated by two bright, symmetric, well-separated jet blobs and shows no detectable radio core. If these jets exhibited the apparent superluminal motions commonly observed prior to 2019, measurable angular shifts would be expected over the five-hour observations. However, no significant jet motion is detected. Combined with our derived jet speed of $βΓ\lesssim 0.40$, these results suggest that the jets launched during the current obscured state are slower than the relativistic jets ($βΓ\gtrsim 1$) observed earlier during the unobscured state. Together with the recently reported large variations in jet orientation, our findings in GRS 1915+105 provide robust support for the emerging paradigm that X-ray binary jets launched in obscured and unobscured states likely exhibit distinct propagation properties.

astro-ph.HE↗

arXiv2026

Discovery of Unusual Jet Orientation Variations in the Microquasar GRS 1915+105

We report large day-timescale variations in the orientation of the southeast--northwest jet in the prototype microquasar GRS 1915+105. These results are based on three-epoch East Asia VLBI Network (EAVN) observations at 6.7 GHz, obtained during giant radio flares in 2025 detected by the RATAN-600 monitoring program. Our observations reveal the smallest position angle (PA) of $118^\circ \pm 7^\circ$ ever measured for the jet in GRS 1915+105, which increases to $152^\circ \pm 2^\circ$ within 37 days. Based on the literature results, we further suggest that the jet orientation has exhibited significant variations over a PA range of $118^\circ$--$188^\circ$ since 2023. This unusual jet orientation behavior in GRS 1915+105 during its current X-ray-obscured state may arise from a warped, precessing inner accretion disk, as implied by recent X-ray spectroscopy. Notably, one image reveals a peculiar morphology in GRS 1915+105, which likely indicates lateral spreading of the approaching southeast jet. Future observations are essential to clarify the issues raised in this work.

astro-ph.HE↗

arXiv2024

X-ray Spectral and Timing Properties of the Black Hole Binary XTE J1859+226 and their Relation to Jets

We compiled the X-ray and soft gamma-ray observations of the Galactic black hole binary XTE J1859+226 in the 1999--2000 outburst from RXTE, ASCA, BeppoSAX and CGRO. Throughout systematic spectral analysis using a two-component model consisting of a multi-temperature accretion disk plus a fraction of its flux convolved with an empirical Comptonized powerlaw component, we found that the innermost radius ($r_{\rm in}$) and temperature (Tin) of the disk are very variable with time in the rising phase of soft X-ray flux where Type-A/B/C low-frequency quasi-periodic oscillations (QPOs) were found. After this phase, $r_{\rm in}$ remains constant at around 60 km assuming a distance of 8 kpc and an inclination angle of 67$^{\circ}$, and Tin smoothly decays with time. The constant $r_{\rm in}$ suggests a presence of the innermost stable circular orbit (ISCO), with $r_{\rm in}$ repeatedly moving closer and farther away from the ISCO in the rising phase. Both disk parameters are remarkably correlated with independently analyzed timing properties such as QPO frequency and rms variability. Type-A/B QPOs are seen only when $r_{\rm in}$ is close to the ISCO, while Type-C are seen when $r_{\rm in}$ is truncated and the frequency changes with a relation of $r^{-1.0}_{\rm in}$, supporting that Type-C QPOs occur at the inner edge of the truncated disk. Accurate determinations of the frequency--$r_{\rm in}$ relation for various objects should be a powerful tool to discriminate plausible Type-C QPO models. Furthermore, we suggest that jet ejection events may occur when $r_{\rm in}$ rapidly approaches to the ISCO, along with rapid changes of the disk flux, the rms variability and the hardness ratio. A rapid shrinkage of $r_{\rm in}$ down to the ISCO can be a useful index as a precursor of radio flares for triggering Target-of-Opportunity observations and would provide constraints on jet launching mechanisms.

astro-ph.HE↗

arXiv2024

Cygnus X-3 revealed as a Galactic ultraluminous X-ray source by IXPE

The accretion of matter by compact objects can be inhibited by radiation pressure if the luminosity exceeds the critical value, known as the Eddington limit. Discovery of ultraluminous X-ray sources has shown that accretion can proceed even when the apparent luminosity significantly exceeds this limit. High apparent luminosity might be produced thanks to geometric beaming of the radiation by an outflow. The outflow half-opening angle, which determines the amplification due to beaming, has never been robustly constrained. Using the Imaging X-ray Polarimetry Explorer, we made the measurement of X-ray polarization in the Galactic X-ray binary Cyg X-3. We find high, over 20%, nearly energy-independent linear polarization, orthogonal to the direction of the radio ejections. These properties unambiguously indicate the presence of a collimating outflow in the X-ray binary Cyg~X-3 and constrain its half-opening angle, <15 degrees. Thus, the source can be used as a laboratory for studying the super-critical accretion regime. This finding underscores the importance of X-ray polarimetry in advancing our understanding of accreting sources.

astro-ph.HE↗

arXiv2011

SS433's accretion disc, wind and jets: before, during and after a major flare

The Galactic microquasar SS433 occasionally exhibits a major flare when the intensity of its emission increases significantly and rapidly. We present an analysis of high-resolution, almost-nightly optical spectra obtained before, during and after a major flare, whose complex emission lines are deconstructed into single gaussians and demonstrate the different modes of mass loss in the SS433 system. During our monitoring, an initial period of quiescence was followed by increased activity which culminated in a radio flare. In the transition period the accretion disc of SS433 became visible in H-alpha and HeI emission lines and remained so until the observations were terminated; the line-of-sight velocity of the centre of the disc lines during this time behaved as though the binary orbit has significant eccentricity rather than being circular, consistent with three recent lines of evidence. After the accretion disc appeared its rotation speed increased steadily from 500 to 700 km/s. The launch speed of the jets first decreased then suddenly increased. At the same time as the jet launch speed increased, the wind from the accretion disc doubled in speed. Two days afterwards, the radio flux exhibited a flare. These data suggest that a massive ejection of material from the companion star loaded the accretion disc and the system responded with mass loss via different modes that together comprise the flare phenomena. We find that archival data reveal similar behaviour, in that when the measured jet launch speed exceeds 0.29c this is invariably simultaneous with, or a few days before, a radio flare. Thus we surmise that a major flare consists of the overloading of the accretion disc, resulting in the speeding up of the H-alpha rotation disc lines, followed by enhanced mass loss not just via its famous jets at higher-than-usual speeds but also directly from its accretion disc's wind.

astro-ph.GA↗