Temporal and spectral X-ray properties of magnetar SGR 1900+14 derived from observations with NuSTAR and XMM-Newton

Abstract

X-ray observations play a crucial role in understanding the emission mechanism and relevant physical phenomena of magnetars. We report X-ray observations of a young magnetar SGR 1900+14 made in 2016, which is famous for a giant flare in 1998 August. Simultaneous observations were conducted with XMM-Newton and NuSTAR on 2016 October 20 with 23 and 123 ks exposures, respectively. The NuSTAR hard X-ray coverage enabled us to detect the source up to 70 keV. The 1-10 keV and 15-60 keV fluxes were $3.11(3)\times 10^{-12}\mathrm{erg}{\mathrm{s}}^{-1}\mathrm{c}{\mathrm{m}}^{-2}$ and $6.8(3)\times 10^{-12}\mathrm{erg}{\mathrm{s}}^{-1}\mathrm{c}{\mathrm{m}}^{-2}$, respectively. The 1-70 keV spectra were well fitted by a blackbody plus power-law model with a surface temperature of $kT=0.52(2)\mathrm{keV}$, a photon index of the hard power-law of $\Gamma =1.21(6)$, and a column density of $N_{\mathrm{H}}=1.96(11)\times 10^{22}\mathrm{c}{\mathrm{m}}^{-2}$. Compared with previous observations with Suzaku in 2006 and 2009, the 1-10 keV flux showed a decrease by 25-40%, while the spectral shape did not show any significant change with differences of $kT$ and $N_{\mathrm{H}}$ being within 10% of each other. Through timing analysis, we found that the rotation period of SGR 1900+14 on 2016 October 20 was $5.22669(3)\mathrm{s}$. The long-term evolution of the rotation period shows a monotonic decrease in the spin-down rate $\dot{P}$ lasting for more than 15 years. We also found a characteristic behavior of the hard-tail power-law component of SGR 1900+14. The energy-dependent pulse profiles vary in morphology with a boundary of 10 keV. The phase-resolved spectra show the differences between photon indices ($\Gamma =1.02$-$1.44$) as a function of the pulse phase. Furthermore, the photon index is positively correlated with the X-ray flux of the hard power-law component, which could not be resolved by the previous hard X-ray observations.

arXiv comment13 pages, 11 figures, accepted for publication in PASJ

References in corpus (39)

• The European Photon Imaging Camera on XMM-Newton: The MOS Cameras
• The Nuclear Spectroscopic Telescope Array (NuSTAR) Mission
• Atomic Data for Astrophysics. II. New Analytic Fits for Photoionization Cross Sections of Atoms and Ions
• Magnetars
• Physics of Strongly Magnetized Neutron Stars
• The McGill Magnetar Catalog
• Electrodynamics of Magnetars: Implications for the Persistent X-ray Emission and Spindown of the Soft Gamma Repeaters and Anomalous X-ray Pulsars
• A giant, periodic flare from the soft gamma repeater SGR1900+14
• Magnetars: the physics behind observations
• Discovery of a magnetar associated with the Soft Gamma Repeater SGR 1900+14
• Untwisting magnetospheres of neutron stars
• Systematic study of magnetar outbursts
• The Giant Flare of 1998 August 27 from SGR 1900+14: I. An Interpretive Study of BeppoSAX and Ulysses Observations
• Photon Splitting and Pair Creation in Highly Magnetized Pulsars
• Magnetars as persistent hard X-ray sources: INTEGRAL discovery of a hard tail in SGR 1900+14
• IACHEC Cross-Calibration of Chandra, NuSTAR, Swift, Suzaku, and XMM-Newton with 3C 273 and PKS 2155-304
• Cross-calibration of the X-ray Instruments onboard the Chandra, INTEGRAL, RXTE, Suzaku, Swift, and XMM-Newton Observatories using G21.5-0.9
• Imaging X-ray, Optical, and Infrared Observations of the Transient Anomalous X-ray Pulsar XTE J1810-197
• The progenitor mass of the magnetar SGR1900+14
• Broad-band study with Suzaku of the magnetar class
• Magnetar Broadband X-ray Spectra Correlated with Magnetic Fields: Suzaku Archive of SGRs and AXPs Combined with NuSTAR, Swift, and RXTE
• The first XMM-Newton observations of the Soft Gamma-ray Repeater SGR 1900+14
• Multi-wavelength Observations of the Radio Magnetar PSR J1622-4950 and Discovery of its Possibly Associated Supernova Remnant
• The X-ray outburst of the Galactic Centre magnetar SGR J1745-2900 during the first 1.5 year
• Is SGR 1900+14 a Magnetar?
• In Orbit Timing Calibration of the Hard X-Ray Detector on Board Suzaku
• An Energetic Magnetar in HESS J1713-381/CTB 37B
• Deep NuSTAR and Swift Monitoring Observations of the Magnetar 1E 1841-045
• Chandra monitoring of the Galactic Centre magnetar SGR J1745-2900 during the initial 3.5 years of outburst decay
• The Sleeping Monster: NuSTAR observations of SGR 1806-20, 11 years after the Giant Flare
• Long-term X-ray changes in the emission from the anomalous X-ray pulsar 4U 0142+61
• Spin-down evolution and radio disappearance of the magnetar PSR J1622$-$4950
• XMM-Newton observations of SGR 1806-20 over seven years following the 2004 Giant Flare
• The variable spin-down rate of the transient magnetar XTE J1810--197
• Phase-resolved NuSTAR and Swift-XRT Observations of Magnetar 4U 0142+61
• Five years of SGR 1900+14 observations with BeppoSAX
• The 2001 April Burst Activation of SGR 1900+14: Pulse Properties and Torque
• Photon splitting and Compton scattering in strongly magnetized hot plasma
• The timing behavior of magnetar Swift J1822.3-1606: timing noise or a decreasing period derivative?

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• Magnetars and Axion-like Particles: Probes with the Hard X-ray Spectrum
• Discovery of 40.5 ks Hard X-ray Pulse-Phase Modulations from SGR 1900+14
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• X-ray Monitoring of the Magnetar CXOU J171405.7-381031 in SNR CTB 37B
• Magnetar Hard X-Ray Emission from Axion-like Particle Conversion
• Unveiling the nature of the unidentified gamma-ray sources 4FGL J1908.6+0915e, HESS J1907+089/HOTS J1907+091, and 3HWC J1907+085 in the sky region of the magnetar SGR 1900+14
• About the observational check of the mechanism of gamma radiation in Soft Gamma Repeaters (SGR)