Aims. X 1822-371 is an eclipsing binary system with a period close to 5.57 h and an orbital period derivative Porb of 1.42(3) × 10-10 s s-1. The extremely high value of its Porb is compatible with a super-Eddington mass transfer rate from the companion star and, consequently, an intrinsic luminosity at the Eddington limit. The source is also an X-ray pulsar, it shows a spin frequency of 1.69 Hz and is in a spin-up phase with a spin frequency derivative of 7.4 × 10-12 Hz s-1. Assuming a luminosity at the Eddington limit, a neutron star magnetic field strength of B=8 × 1010 G is estimated. However, a direct measure of B could be obtained observing a CRSF in the energy spectrum. Analysis of XMM-Newton data suggested the presence of a cyclotron line at 0.73 keV, with an estimated magnetic field strength of B=(8.8 ± 0.3)× 1010 G. Methods. Here we analyze the 0.3-50 keV broadband spectrum of X 1822-371 combining a 0.3-10 keV NICER spectrum and a 4.5-50 keV NuSTAR spectrum to investigate the presence of a cyclotron absorption line and the complex continuum emission spectrum. Results. The NICER spectrum confirms the presence of a cyclotron line at 0.66 keV. The continuum emission is modeled with a Comptonized component, a thermal component associated with the presence of an accretion disk truncated at the magnetospheric radius of 105 km and a reflection component from the disk blurred by relativistic effects. Conclusions. We confirm the presence of a cyclotron line at 0.66 keV inferring a NS magnetic field of B=(7.9 ± 0.5)× 1010 G and suggesting that the Comptonized component originates in the accretion columns.

Iaria R., Di Salvo T., Anitra A., Miceli C., Barra F., Leone W., et al. (2024). Confirmation of the presence of a CRSF in the NICER spectrum of X 1822-371. ASTRONOMY & ASTROPHYSICS, 683, 79 [10.1051/0004-6361/202345888].

Confirmation of the presence of a CRSF in the NICER spectrum of X 1822-371

Iaria R.
Primo
;
Di Salvo T.;Anitra A.;Miceli C.;Barra F.;
2024-03-01

Abstract

Aims. X 1822-371 is an eclipsing binary system with a period close to 5.57 h and an orbital period derivative Porb of 1.42(3) × 10-10 s s-1. The extremely high value of its Porb is compatible with a super-Eddington mass transfer rate from the companion star and, consequently, an intrinsic luminosity at the Eddington limit. The source is also an X-ray pulsar, it shows a spin frequency of 1.69 Hz and is in a spin-up phase with a spin frequency derivative of 7.4 × 10-12 Hz s-1. Assuming a luminosity at the Eddington limit, a neutron star magnetic field strength of B=8 × 1010 G is estimated. However, a direct measure of B could be obtained observing a CRSF in the energy spectrum. Analysis of XMM-Newton data suggested the presence of a cyclotron line at 0.73 keV, with an estimated magnetic field strength of B=(8.8 ± 0.3)× 1010 G. Methods. Here we analyze the 0.3-50 keV broadband spectrum of X 1822-371 combining a 0.3-10 keV NICER spectrum and a 4.5-50 keV NuSTAR spectrum to investigate the presence of a cyclotron absorption line and the complex continuum emission spectrum. Results. The NICER spectrum confirms the presence of a cyclotron line at 0.66 keV. The continuum emission is modeled with a Comptonized component, a thermal component associated with the presence of an accretion disk truncated at the magnetospheric radius of 105 km and a reflection component from the disk blurred by relativistic effects. Conclusions. We confirm the presence of a cyclotron line at 0.66 keV inferring a NS magnetic field of B=(7.9 ± 0.5)× 1010 G and suggesting that the Comptonized component originates in the accretion columns.
mar-2024
Settore FIS/05 - Astronomia E Astrofisica
Iaria R., Di Salvo T., Anitra A., Miceli C., Barra F., Leone W., et al. (2024). Confirmation of the presence of a CRSF in the NICER spectrum of X 1822-371. ASTRONOMY & ASTROPHYSICS, 683, 79 [10.1051/0004-6361/202345888].
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Utilizza questo identificativo per citare o creare un link a questo documento: https://hdl.handle.net/10447/638059
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