arXiv subjects

Maksat Satybaldiev

Publications and source records attributed to Maksat Satybaldiev.

4 recordsLinked to original sources

arXiv2026

Optical Follow-Up of Two Spider Pulsar Candidates: An Irradiated Redback and a Possible Double Giant Impostor

Compact binary millisecond pulsars (nicknamed "spiders") are a growing class of neutron stars: more than 100 systems are known in the Galactic field, including more than 30 candidates where pulsations have not been detected. Here we report the results of an optical follow-up of two spider pulsar candidates: 2FGL J0846.0+2820 (J0846, a huntsman candidate in an 8.1 d orbit) and 4FGL J0935.3+0901 (J0935, with a 2.4 h orbital period and proposed as a spider of either the transitional, black widow or redback sub-class). We also analyzed their multi-wavelength properties (infrared, X-ray and $γ$-ray bands), in order to assess their nature and current state. The optical orbital light curves of J0846 change from double-peaked in 2023 to single-peaked in 2024, but we argue they are not consistent with either irradiation-driven or ellipsoidal orbital modulation. Its spectral energy distribution shows evidence for two blackbody-like components with similar temperatures ($T$) and radii ($R$), which dominate the optical ($T_2\simeq6000$ K, $R_2\simeq1.8$ R$_\odot$) and infrared ($T_1\simeq3400$ K, $R_1\simeq5.2$ R$_\odot$) bands. Based on this, we argue that J0846 is not a bona fide pulsar candidate and propose an alternative identification: a detached double red giant. In J0935, we find a light curve with one flux maximum around superior conjunction of the companion, where the colors and inferred temperature increase, suggesting prominent irradiation from the pulsar. We place constraints on its companion base temperature ($4000\!-\!4600$ K), which support one of the three classifications proposed for J0935: a redback spider in the pulsar state.

astro-ph.HE↗

arXiv2026

Gamma-ray Modes in a Transitional Pulsar

Transitional millisecond pulsars (tMSPs) exhibit a unique sub-luminous disk state, at the cross-roads between accretion and rotation power, where they switch between two distinct X-ray modes. We present the discovery of gamma-ray modes in PSR J1023+0038, the first confirmed tMSP, from stacking Fermi-LAT data during the modes (which we identify using simultaneous X-ray observations). Surprisingly, we find that gamma-rays and X-rays are anti-correlated during this mode switching: the gamma-ray flux is higher in the X-ray low mode, and vice versa. This contradicts the state-of-the-art model, which predicts bright gamma-rays from the interaction between the pulsar wind and surrounding disk via synchrotron and inverse Compton processes. Because the pulsar wind is likely absent in the gamma-ray high (X-ray low) mode, which is also brighter in the radio band, we suggest that jet emission is dominant in GeV gamma-rays.

astro-ph.HE↗

arXiv2026

Gamma-ray Orbital Modulation in Spider Pulsars: Three Discoveries and a Universal Modulated Fraction

Compact binary millisecond pulsars (also known as spiders) allow us to probe pulsar winds in their innermost regions, between the light cylinder (radius $\sim10^{7}$ cm) and the companion star (at $\sim10^{11}$ cm). Their flux is known to vary along the orbit, from radio to X-rays. During the past decade, gamma-ray orbital modulation (GOM) has been discovered in a handful of spiders, but its origin remains largely unknown. We present the results of a systematic search for GOM among 43 systems, selecting pulsed 0.1-1 GeV photons and using spin and orbital ephemeris from Fermi's Third Pulsar Catalog. We discover GOM from three spiders - PSR J1124-3653, PSR J1946-5403 and PSR J2215+5135 - and confirm four previous detections. In all seven cases so far, the GOM peaks near the pulsar's superior conjunction. The X-ray orbital light curves are usually in antiphase, peaking when the pulsar is at inferior conjunction, but we find one case where both gamma-rays and X-rays peak around superior conjunction: PSR J1946-5403. We measure the modulated fractions of the GOM and find consistent values for all seven spiders, with an average $22.0\pm2.6\%$. Including eclipsing systems seen edge-on, we find no clear dependence of the modulated fraction on the orbital inclination (within $\simeq$45-90$^\circ$). Our results challenge previous models proposed to explain GOM in spiders, based on inverse Compton and synchrotron emission close to the companion, since these predict a clear dependence on orbital inclination (stronger modulation at high inclinations). We nearly double the number of GOM detections in spiders, showing that it is more common than previously thought.

astro-ph.HE↗

arXiv2023

Spectral and temporal analysis of the Supergiant Fast X-ray Transient IGR J16195-4945 with SRG/ART-XC

We present the results of the analysis of the SRG/ART-XC observation of the Supergiant Fast X-ray Transient IGR J16195-4545 performed on March 3, 2021. Six bright flares are present in the light curve, with no significant change in hardness occuring during these flares. The spectrum is described with an absorbed power law model with a high energy exponential cutoff showing heavy absorption, with $N_H=(12\pm2)\times 10^{22}\text{ cm}^{-2}$ and $Γ=0.56\pm 0.15$, $E_{cut}=13\pm 2$ keV. Adopting the Bayesian block decomposition of the light curve, we measured the properties of the observed flares (duration, rise time, waiting time, released energy and pre-flare luminosity), which are consistent with the quasi-spherical subsonic accretion model. The stellar wind velocity of the supergiant is estimated to be $v_{w} \approx 500$ km s$^{-1}$. Additionally, the system was found to have an unusual near-IR variability.

astro-ph.HE↗