Broadband X-ray spectral and timing properties of the accreting millisecond X-ray pulsar IGR J17498−2921 during the 2023 outburst

We report on the broadband spectral and timing properties of the accreting millisecond X-ray pulsar during its April 2023 outburst. We used data from (1--10 keV) nustar \ (3--79 keV) (2--150 keV), and (30--150 keV). We detected significant 401 Hz pulsations across the 0. 5--150 keV band. The pulse fraction increases from sim 2 at 1 keV to sim 13 at 66 keV. We detected five type-I X-ray bursts, including three photospheric radius expansion bursts, with a rise time of sim 2 s and an exponential decay time of sim 5 s. The recurrence time is sim 9. 1 h, which can be explained by unstable thermonuclear burning of hydrogen-deficient material on the neutron star surface. The quasi-simultaneous 1--150 keV broadband spectra from nustar \ and can be aptly fitted by an absorbed reflection model relxillCp and a Gaussian line of instrumental origin. The Comptonized emission from the hot corona is characterized by a photon index Gamma of sim 1. 8 and an electron temperature kT_ e of sim 40 keV. We obtained a low inclination angle i The accretion disk shows properties of strong ionization, erg cm over-solar abundance Fe 7. 7, and high density, e 19. 5. However, a lower disk density with normal abundance and ionization could also be possible. Based on the inner disk radius of in =1. 67R_ ISCO and the long-term spin-down rate of -3. 1 (2) Hz, we were able to constrain the magnetic field of to the range of (0. 9-2. 4) G.