What the study found
MAXI J1752–457 was observed with NuSTAR after a superburst, and the source was confirmed to match the previously seen Einstein Probe source EP240809a. The hard X-ray emission was consistent with a spherical blackbody component plus a steep nonthermal power-law component.
Why the authors say this matters
The authors conclude that the source had entered an accretion-powered flux state. The findings also suggest ongoing evolution of the electron energy distribution responsible for the power-law component several days after the superburst, although the abstract says a conclusive physical interpretation is not possible.
What the researchers tested
The researchers analyzed two NuSTAR observations taken after a superburst detected by MAXI/Gas Slit Camera in 2024 November. They performed spectral analysis and energy-resolved timing analysis of the source during both observations.
What worked and what didn't
At about 79 hours after the superburst began, they measured a blackbody temperature of kT_bb = 0.60 ± 0.1 keV and a blackbody radius to distance ratio R_bb/D_8 = 6.0 with uncertainties of -0.3 and +0.4 km, without corrections for scattering in the neutron star atmosphere. The blackbody temperature did not change significantly over the 1-day interval between observations, and the timing analysis showed variability dominated by red noise in the power-law component, which the authors associate with coupling with an accretion disk. They also measured a photon index of about 4, which is steeper than typically observed during accretion onto neutron stars at similar luminosities.
What to keep in mind
The source distance is not yet known, and the radius estimate depends on D_8, the distance in units of 8 kpc. The abstract also notes that there were no hard X-ray observations prior to and throughout the superburst, which limits interpretation.
Key points
- NuSTAR follow-up confirmed MAXI J1752–457 is the same source as EP240809a.
- The hard X-ray spectrum fit a spherical blackbody plus a steep nonthermal power-law component.
- About 79 hours after the superburst, the blackbody temperature was 0.60 ± 0.1 keV.
- The measured photon index was about 4, steeper than usually seen in similar neutron-star accretion states.
- The authors say the source had entered an accretion-powered flux state.
- The source distance is unknown, limiting the radius estimate.
Disclosure
- Research title:
- NuSTAR sees a hard X-ray state after MAXI J1752–457 superburst
- Authors:
- Sean N. Pike, H. Negoro, D. J. K. Buisson, Benjamin M. Coughenour, J. Gerber, A. W. Shaw, M. Sugizaki, John A. Tomsick
- Institutions:
- Netherlands Institute for Radio Astronomy, Surugadai Nihon University Hospital, Utah Valley University, Butler University, Kanazawa University, University of California, Berkeley
- Publication date:
- 2026-04-23
- OpenAlex record:
- View
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