arXiv subjects

Dilda Berdikhan

Publications and source records attributed to Dilda Berdikhan.

3 recordsLinked to original sources

arXiv2026

Hub-filament systems and the growth of massive stars: episodic accretion, clustered environments, and projection effects

The processes controlling the early mass growth of future massive stars remain poorly understood, particularly the connection of this growth to star clustering and hub-filament systems (HFSs). This connection is difficult to establish observationally, because projection effects and line-of-sight confusion in position-position-velocity (PPV) data can distort the information about the intrinsic filamentary structure. To investigate this connection, we used a three-dimensional magnetohydrodynamic (MHD) simulation of star formation, where stars are represented by accreting sink particles. We identify clustered stellar environments, reconstruct time-dependent accretion histories, and investigate the relation between enhanced-accretion episodes and the locations of HFSs. We also use line radiative transfer modeling to produce synthetic molecular-line observations and examine how the same structures appear in projected PPV data. In our simulation, we find that 80% of future massive stars are associated with clustered environments. Their growth is also highly episodic: typically, about 40% of the accreted mass is gained during periods of enhanced accretion that occupy only about 10% of the total growth time. Periods of enhanced accretion occur slightly closer to three-dimensional HFS proxies, suggesting a possible link between HFS morphology and episodic accretion in future massive stars. Overall, our results suggest that the early growth of future massive stars is connected to both their clustered environment and the HFS structure of the surrounding gas, and projection effects must be considered when interpreting HFS in PPV data.

astro-ph.GA↗

arXiv2026

A fast X-ray transient with chromatic flares: signatures of violent collisions induced by late-time central engine reactivation

Extragalactic Fast X-ray Transients (EFXTs) represent an emerging class of high-energy phenomena characterized by X-ray outbursts lasting from tens to hundreds of seconds. However, for more than half of the EFXTs, their physical origins remain elusive. In this Letter, we report the discovery of EP250302a, a luminous EFXT detected by the Einstein Probe (EP) at a redshift of $z = 1.131$. The multi-wavelength light curves of EP250302a reveal remarkable temporal features that distinguish it from the previously known EP-detected EFXT population, most notably a needle-like X-ray flare accompanied by smooth optical rebrightening during the afterglow phase. We suggest that the distinct X-ray and optical behaviors constitute the first observed instance of late-time violent collision of two relativistic shells in an EFXT. Drawing on insights from GRB studies, such a collision process strongly indicates the reactivation of a central engine, making EP250302a-like transients a unique laboratory for probing the late-time activity and jet physics of EFXT central engines.

astro-ph.HE↗

arXiv2025

Cloud-cloud collision and star formation in G013.313+0.193

We study the G013.313+0.193 G013.313 region, a complex environment characterized by molecular cloud interactions indicative of cloud-cloud collision (CCC). Observations of the NH3(1,1) and (2,2) inversion transitions were obtained using the Nanshan 26 m radio telescope, while HCO+ (1-0), 12CO, 13CO, and C18O(1-0) transitions from the Purple Mountain Observatory Delingha 14 m telescope. Archival data are also included. We identified key observational signatures of CCC, including complementary spatial distributions, U-shaped structures, bridge features, and V-shaped velocity distributions. The position-velocity diagrams (P-V) reveal clear indications of gas interaction between two velocity components, suggesting an ongoing collision at an estimated angle of approximately 45 degree to the line of sight. The estimated collision timescale is 0.35-1.03 Myr, aligned with the inferred ages of young stellar objects (YSOs) in the region, supporting the hypothesis of collision-induced star formation. Hub-filament system (HFS) are identified in the compressed gas region, where filaments converge toward a dense hub, suggesting the CCC as a potential driver of HFS formation and massive star formation. The high column density suggests favorable conditions for the formation of massive stars. Although alternative kinematic drivers such as longitudinal collapse and shear motion are considered, CCC remains the most plausible explanation for the observed features. Our findings contribute to our understanding of the mechanisms of cloud dynamics and massive star formation in turbulent molecular environments.

astro-ph.GA↗