'Bursts, beats, and beyond': uncovering the landscape from accretion to ignition of 4U 1728–34 using AstroSat.
Saved in:
| Title: | 'Bursts, beats, and beyond': uncovering the landscape from accretion to ignition of 4U 1728–34 using AstroSat. |
|---|---|
| Authors: | Salgundi, Anirudh1 (AUTHOR) anirudhsalgundi@gmail.com, Bala, Suman1,2 (AUTHOR), Raman, Gayathri3 (AUTHOR), Pathak, Utkarsh1 (AUTHOR), Bhalerao, Varun1 (AUTHOR) |
| Source: | Journal of Astrophysics & Astronomy. 4/4/2026, Vol. 47 Issue 1, p1-19. 19p. |
| Subjects: | X-ray bursts, Neutron stars, Oscillations, Accretion disks, Space astronomy, X-ray binaries |
| Abstract: | A comprehensive study on persistent and thermonuclear burst emission of 4U 1728–34, commonly known as 'Slow Burster', is performed using seven archival observations of AstroSat spanning from 2016 to 2019. The burst-free persistent spectra can be well fitted with a blackbody (bbody) and a powerlaw (powerlaw) components, with a powerlaw photon index (Γ) found to be ∼ 2, indicating the source was in 'high/soft' banana state or intermediate state. The time-averaged power density spectrum reveals the presence of twin kilohertz Quasi Periodic Oscillations (kHz QPOs) with centroid frequencies 619 ± 10 and 965 ± 6 Hz with a maximum fractional root mean squared amplitude of 6.24 ± 1.31 % at ∼ 16 keV. From the upper kHz QPO, we infer the magnetospheric disk radius to be ∼ 17 km, corresponding to a magnetic field strength of 0.35– 1.27 × 10 7 G. The burst spectral evolution indicates Photospheric Radius Expansion (PRE) in five bursts, yielding a touchdown radius of 3.1–5.47 km. These bursts reached near-Eddington luminosities, through which the distance of the source was calculated to be 5.18–5.21 kpc. Two of the bursts show coherent oscillations at 362.81–363.93 Hz. The presence of twin kHz QPOs and coherent Burst Oscillations allows us to provide two different estimates for the spin frequency of the Neutron Star in the system, for the first time using AstroSat. [ABSTRACT FROM AUTHOR] |
| Copyright of Journal of Astrophysics & Astronomy is the property of Springer Nature and its content may not be copied or emailed to multiple sites without the copyright holder's express written permission. Additionally, content may not be used with any artificial intelligence tools or machine learning technologies. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.) | |
| Database: | Engineering Source |
|
Full text is not displayed to guests.
Login for full access.
|
|
| Abstract: | A comprehensive study on persistent and thermonuclear burst emission of 4U 1728–34, commonly known as 'Slow Burster', is performed using seven archival observations of AstroSat spanning from 2016 to 2019. The burst-free persistent spectra can be well fitted with a blackbody (bbody) and a powerlaw (powerlaw) components, with a powerlaw photon index (Γ) found to be ∼ 2, indicating the source was in 'high/soft' banana state or intermediate state. The time-averaged power density spectrum reveals the presence of twin kilohertz Quasi Periodic Oscillations (kHz QPOs) with centroid frequencies 619 ± 10 and 965 ± 6 Hz with a maximum fractional root mean squared amplitude of 6.24 ± 1.31 % at ∼ 16 keV. From the upper kHz QPO, we infer the magnetospheric disk radius to be ∼ 17 km, corresponding to a magnetic field strength of 0.35– 1.27 × 10 7 G. The burst spectral evolution indicates Photospheric Radius Expansion (PRE) in five bursts, yielding a touchdown radius of 3.1–5.47 km. These bursts reached near-Eddington luminosities, through which the distance of the source was calculated to be 5.18–5.21 kpc. Two of the bursts show coherent oscillations at 362.81–363.93 Hz. The presence of twin kHz QPOs and coherent Burst Oscillations allows us to provide two different estimates for the spin frequency of the Neutron Star in the system, for the first time using AstroSat. [ABSTRACT FROM AUTHOR] |
|---|---|
| ISSN: | 02506335 |
| DOI: | 10.1007/s12036-025-10124-1 |
