| Name: Aromal P |
| Affiliation: Indian Institute of Technology Indore |
| Conference ID: ASI2026_348 |
| Title: The 2024 outburst of the neutron star LMXB EXO 0748–676: An investigation of bursts and eclipses with AstroSat |
| Abstract Type: Poster |
| Abstract Category: High Energy Phenomena, Fundamental Physics and Astronomy |
| Author(s) and Co-Author(s) with Affiliation: Aromal P(Indian Institute of Technology, Indore - 453552, India), Unnati Kashyap(Texas Tech University, Lubbock - 79409-1051, USA), Manoneeta Chakraborty(Indian Institute of Technology, Indore - 453552, India), Sudip Bhattacharyya(Tata Institute of Fundamental Research, Mumbai, 400005 - India), Thomas J. Maccarone(Texas Tech University, Lubbock - 79409-1051, USA), Vijay Choudhary(Indian Institute of Technology, Indore - 453552, India) |
| Abstract: We present a detailed analysis of the Type-I (thermonuclear) X-ray bursts and eclipses observed during the 2024 outburst of the neutron star low-mass X-ray binary EXO 0748–676, utilizing multi-instrument data from the AstroSat mission (Aromal et al. 2025). Discovered in 1985, the source underwent a 24-year outburst before entering quiescence in 2008; the 2024 activity represents only its second recorded outburst after a 16-year quiescent phase. Our analysis of data from the Large Area X-ray Proportional Counter (LAXPC) identified three thermonuclear bursts, two of which were observed simultaneously with the Soft X-ray Telescope (SXT). Our time-resolved spectroscopy characterizes two of these as photospheric radius expansion (PRE) events, and from their peak flux, we estimate a source distance of 7.42+/-0.53 kpc. Furthermore, we report the first-ever simultaneous observation of a thermonuclear burst with the Ultra-Violet Imaging Telescope (UVIT), providing evidence of X-ray burst reprocessing in the accretion disk. Notably, one burst exhibited a secondary peak approximately 30 s after the primary. This secondary feature, more prominent in the soft X-ray energies, correlates with the evolution of the hotspot radius and exhibits no temperature variations. The burst energetics and ignition conditions suggest a fuel composition of mixed H/He. Furthermore, a detected soft excess during one burst likely results from the interaction of the burst photons with the accretion environment. Finally, we characterize the energy dependence and temporal evolution of the orbital eclipses to probe the local binary environment. These results provide critical insights into the physics of thermonuclear ignition, flame propagation, the burst-accretion interaction, and the evolution of LMXBs. |
